All Physics and Chemistry Biology Brief Notes
Physics Important Notes
Chemistry Important Notes
Biology Important Notes
Nutrition in Plants
All organisms take food and utilise it to get energy for the growth and maintenance of their bodies.
Green plants synthesise their food themselves by the process ofphotosynthesis.
They are autotrophs. Plants use simple chemical substances like carbon dioxide, water and minerals for the synthesis of food.Chlorophyll and sunlight are the essential requirements for photosynthesis.
Complex chemical substances such as carbohydrates are the products of photosynthesis.
Solar energy is stored in the form of food in the leaves with the help of chlorophyll.
Oxygen is produced during photosynthesis.
Oxygen released in photosynthesis is utilised by living organisms for their survival.
Fungi derive nutrition from dead, decaying matter. They are saprotrophs.
Plants like Cuscuta are parasites. They take food from the host plant.
A few plants and all animals are dependent on others for their nutrition
and are called heterotrophs.
Animal nutrition includes nutrient requirement, mode of intake of food
and its utilisation in the body.
All organisms take food and utilise it to get energy for the growth and maintenance of their bodies.
Green plants synthesise their food themselves by the process ofphotosynthesis.
They are autotrophs. Plants use simple chemical substances like carbon dioxide, water and minerals for the synthesis of food.Chlorophyll and sunlight are the essential requirements for photosynthesis.
Complex chemical substances such as carbohydrates are the products of photosynthesis.
Solar energy is stored in the form of food in the leaves with the help of chlorophyll.
Oxygen is produced during photosynthesis.
Oxygen released in photosynthesis is utilised by living organisms for their survival.
Fungi derive nutrition from dead, decaying matter. They are saprotrophs.
Plants like Cuscuta are parasites. They take food from the host plant.
A few plants and all animals are dependent on others for their nutrition
and are called heterotrophs.
Animal nutrition includes nutrient requirement, mode of intake of food
and its utilisation in the body.
Digestive system
The human digestive system consists of the alimentary canal and secretory glands. It consists of the (i) buccal cavity, (ii) oesophagus,(iii) stomach, (iv) small intestine, (v) large intestine ending in rectumand (vi) anus. The main digestive glands which secrete digestive juices are (i) the salivary glands, (ii) the liver and (iii) the pancreas.
The stomach wall and the wall of the small intestine also secrete digestive juices.
The modes of feeding vary in different organisms._ Nutrition is a complex process involving: (i) ingestion, (ii) digestion,(iii) Absorption, (iv) assimilation and (v) egestion.
Digestion of carbohydrates, like starch, begins in the buccal cavity. The
digestion of protein starts in the stomach.
The bile secreted from theliver, the pancreatic juice from the pancreas and the digestive juice from
the intestinal wall complete the digestion of all components of food in the small intestine.
The digested food is absorbed in the blood vessels from the small intestine.
The absorbed substances are transported to different parts of the body.
Water and some salts are absorbed from the undigested food in the large intestine.
The undigested and unabsorbed residues are expelled out of the body as faeces through the anus.
The grazing animals like cows, buffaloes and deer are known as ruminants. They quickly ingest, swallow their leafy food and store it in the rumen. Later, the food returns to the mouth and the animal chews it peacefully.
Amoeba ingests its food with the help of its false feet or pseudopodia.
The food is digested in the food vacuole.
The human digestive system consists of the alimentary canal and secretory glands. It consists of the (i) buccal cavity, (ii) oesophagus,(iii) stomach, (iv) small intestine, (v) large intestine ending in rectumand (vi) anus. The main digestive glands which secrete digestive juices are (i) the salivary glands, (ii) the liver and (iii) the pancreas.
The stomach wall and the wall of the small intestine also secrete digestive juices.
The modes of feeding vary in different organisms._ Nutrition is a complex process involving: (i) ingestion, (ii) digestion,(iii) Absorption, (iv) assimilation and (v) egestion.
Digestion of carbohydrates, like starch, begins in the buccal cavity. The
digestion of protein starts in the stomach.
The bile secreted from theliver, the pancreatic juice from the pancreas and the digestive juice from
the intestinal wall complete the digestion of all components of food in the small intestine.
The digested food is absorbed in the blood vessels from the small intestine.
The absorbed substances are transported to different parts of the body.
Water and some salts are absorbed from the undigested food in the large intestine.
The undigested and unabsorbed residues are expelled out of the body as faeces through the anus.
The grazing animals like cows, buffaloes and deer are known as ruminants. They quickly ingest, swallow their leafy food and store it in the rumen. Later, the food returns to the mouth and the animal chews it peacefully.
Amoeba ingests its food with the help of its false feet or pseudopodia.
The food is digested in the food vacuole.
Fibre to Fabric
Silk comes from silkworms and wool is obtained from sheep, goat and
yak. Hence silk and wool are animal fibres.
The hairs of camel, llama and alpaca are also processed to yield wool.
In India, mostly sheep are reared for getting wool.
Sheep hair is sheared off from the body, scoured, sorted, dried, dyed,spun and woven to yield wool.
Silkworms are caterpillars of silk moth.
During their life cycle, the worms spin cocoons of silk fibres.
Silk fibres are made of a protein.
Silk fibres from cocoons are separated out and reeled into silk threads.
Weavers weave silk threads into silk cloth.
Weather, Climate and Adaptations of Animals to Climate
The day-to-day condition of the atmosphere at a place with respect to the temperature, humidity, rainfall, wind-speed, etc., is called the weather at that place.
The weather is generally not the same on any two days and week after week.
The maximum temperature of the day occurs generally in the afternoon while the minimum temperature occurs in the early morning.
The times of sunrise and sunset also change during the year.
All the changes in the weather are driven by the sun.
The average weather pattern taken over a long time, say 25 years, is called the climate of the place
The tropical and the polar regions are the two regions of the earth, which have severe climatic conditions.
Animals are adapted to the conditions in which they live.
The polar regions are very cold throughout the year. The sun does not set for six months in a year and in the other six months it does not rise.
Animals in the polar region are adapted to the extremely cold climate by having some special characteristics such as white fur, strong sense of smell, a layer of fat under the skin, wide and large paws for swimming and walking, etc.
Migration is another means to escape the harsh, cold conditions.
Because of the hospitable climatic conditions huge populations of plants and animals are found in the tropical rainforests.
Animals in the tropical rainforests are adapted such that they eat different kinds of food to overcome the competition for food and shelter.
Some adaptations of animals living in the tropical rainforests include living on the trees, development of strong tails, long and large beaks, bright colours, sharp patterns, loud voice, diet of fruits, sensitive hearing,sharp eyesight, thick skin, ability to camouflage in order to protect
themselves from predators, etc.
Respiration in Organisms
Respiration is essential for survival of living organisms.
It releases energy from the food.
The oxygen we inhale is used to breakdown glucose into
carbon dioxide and water. Energy is released in the process.
The breakdown of glucose occurs in the cells of an organism
(cellular respiration).
If the food is broken down with the use of oxygen, it is
called aerobic respiration.
If the breakdown occurs without the use of oxygen, the respiration
is called anaerobic respiration.
During heavy exercise when the supply of oxygen to our
muscle cells is insufficient, food breakdown is by anaerobic respiration.
Breathing is a part of the process of respiration during
which an organism takes in the oxygen-rich air and gives out air rich in carbon
dioxide.
The respiratory organs for the exchange of gases vary in
different organisms.
During inhalation,
our lungs expand and then come back to the original state as the air moves out
during exhalation.
Increased physical
activity enhances the rate of breathing.
In animals like cow,
buffalo, dog and cat the respiratory organs and the process of breathing are
similar to those in humans.
In earthworm, the
exchange of gases occurs through the moist skin. In fishes it takes place
through gills and in insects through the tracheae.
In a plant the roots
take in air present in the soil.
Leaves have tiny pores called stomata through which they
exchange gases.
The breakdown of glucose in the plant cells is similar to
that in other living beings.
Transportation in Animals and Plants In most animals the blood that circulates in
the body distributes food and oxygen to different cells of the body. It also
carries waste products to different parts of the body for excretion.
Circulatory system
consists of the heart and blood vessels.
In humans, blood
flows through arteries and veins and the heart acts as a pumping organ.
Blood consists of
plasma, RBC, WBC and platelets. Blood is red due to the presence of a red
pigment, haemoglobin.
The human heart beats
about 70ñ80 times per minute in an adult person. This is called heart rate.
Arteries carry blood
from the heart to all parts of the body.
Veins carry blood
from all parts of the body back to the heart.
Removal of waste products from the body is called excretion.
Excretory system of humans consists of two kidneys, two
ureters, a urinary bladder, and urethra.
Salts and urea are
removed along with water as sweat.
Fish excrete waste substances such as ammonia which directly
dissolve in water.
Birds, insects and lizard excrete uric acid in semi-solid
form.
Water and mineral nutrients are absorbed by roots from the
soil.
Nutrients are transported along with water to the entire
plant via the vascular tissue called xylem.
The vascular tissue
for the transport of food to the various parts of the plant is phloem.
A lot of water is
lost by plants in the form of vapour through stomata during transpiration.
Transpiration generates a force which pulls up water
absorbed by the roots from the soil, to reach the stem and leaves.
Reproduction in Plants
All organisms multiply or reproduce their own kind.
In plants there are
two modes of reproduction, asexual and sexual.
There are several methods of asexual reproduction such as fragmentation,
budding, spore formation and vegetative propagation.
Sexual reproduction
involves the fusion of male and female gametes.
In vegetative
propagation new plants are produced from different vegetative parts such as
leaves, stems and roots.
Flower is the
reproductive part of a plant.
A flower may be
unisexual with either the male or the female reproductive parts.
A bisexual flower has
both the male and the female reproductive parts.
The male gametes are
found inside the pollen grains and female gametes are found in the ovule.
Pollination is the
process of transfer of pollen grains from the anther of one flower to the
stigma of the same or another flower.
Pollination is of two types, self-pollination and
cross-pollination. In self-pollination, pollen grains are transferred from the
anther to the stigma of the same flower. In cross-pollination, pollen grains
are transferred from the anther of one flower to the stigma of another flower of
the same kind.
Pollination takes place in plants with the help of wind,
water and insects.
The fusion of male and female gametes is called
fertilisation.
Fertilised egg is
called zygote. Zygote develops into an embryo.
Fruit is the mature
ovary whereas ovule develops into a seed, which contains the developing embryo.
Seed dispersal is
aided by wind, water and animals.
Seed dispersal helps the plants to (i) prevent overcrowding,
(ii) avoid competition for sunlight, water and minerals and (iii) invade new
habitats.
Water: A Precious Resource
Water is essential for all living beings. There can be no
life without it.
Water exists in three
forms: solid, liquid and vapour.
Though water is maintained by the water cycle, yet there is
an acute scarcity of water in many parts of the globe.
There is an uneven distribution of water. Much of it has
resulted from human activities.
Rapid growth of industries,
increasing population, growing irrigation requirements and mismanagement are
some of the causes for water shortage.
We need to be worried about the wastage during the supply of
water through pipes, the leaking taps in buildings and other places.
Unnecessary use of water and overdrawing from groundwater
should be avoided. Recharge of water to the ground should be increased.
The need of the hour is that every individual uses water
economically.
Plants wilt and
ultimately dry-up if they are not watered for a few days.
Forests: Our Lifeline
We get various products from the forests surrounding us.
Forest is a system comprising various plants, animals and micro-organisms.
In a forest, trees
form the uppermost layer, followed by shrubs. The herbs form the lowest layer
of vegetation.
Different layers of
vegetation provide food and shelter for animals, birds and insects.
The various components of the forest are interdependent on
one another.
The forest keeps on growing and changing, and can
regenerate.
In the forest, there
is interaction between soil, water, air and living organisms.
Forests protect the
soil from erosion.
Soil helps forests to grow and regenerate.
Forests are the
lifeline for the forest-dwelling communities.
Forests influence
climate, water cycle and air quality
Waste water Story
Used water is wastewater. Wastewater could be reused.
Wastewater is
generated in homes, industries, agricultural fields and in other human
activities. This is called sewage.
Sewage is a liquid
waste which causes water and soil pollution.
Wastewater is treated in a sewage treatment plant.
Treatment plants reduce pollutants in wastewater to a level
where nature can take care of it.
Where underground sewerage systems and refuse disposal
systems are not available, the low cost on-site sanitation system can be
adopted.
By-products of wastewater treatment are sludge and biogas.
Open drain system is
a breeding place for flies, mosquitoes and organisms which cause diseases.
We should not
defecate in the open. It is possible to have safe disposal of excreta by low
cost methods.
CROP PRODUCTION AND MANAGEMENT
In order to provide food to our growing population, we need
to adopt certain agricultural practices.
Same kinds of plants
grown and cultivated at a place constitute a crop.
In India, crops can
be broadly categorised into two types based on seasons - rabi and kharif crops.
It is necessary to
prepare soil by tilling and levelling. Ploughs and levellers are used for this
purpose.
Sowing of seeds at
appropriate depths and distances gives good yield. Good variety of seeds are
sown after selection of healthy seeds.
Sowing is done by seed drills.
Soil needs replenishment and enrichment through the use of organic
manure and fertilisers. Use of chemical fertilisers has increased tremendously
with the introduction of new crop varieties.
Supply of water to crops at appropriate intervals is called
irrigation.
Weeding involves
removal of unwanted and uncultivated plants called weeds.
Harvesting is the
cutting of the mature crop manually or by machines.
Separation of the grains from the chaff is called threshing.
Proper storage of
grains is necessary to protect them from pests and microorganisms.
Food is also obtained from animals for which animals are
reared. This is called animal husbandry.
MICRO-ORGANISMS
Microorganisms are too small and are not visible to the
unaided eye.
They can live in all kinds of environment, ranging from ice
cold climate to hot springs and deserts to marshy lands.
Microorganisms are
found in air, water and in the bodies of plants and animals.
They may be
unicellular or multicellular.
Microorganisms include bacteria, fungi, protozoa and some
algae. Viruses, though different from the above mentioned living organisms, are
considered microbes.
Viruses are quite different from other microorganisms. They
reproduce only inside the host organism; bacterium, plant or animal cell.
Some microorganisms
are useful for commercial production of medicines and alcohol.
Some microorganisms
decompose the organic waste and dead plants and animals into simple substances
and clean up the environment.
Protozoans cause
serious diseases like dysentery and malaria.
Some of the microorganisms grow on our food and cause food
poisoning.
Some microorganisms reside in the root nodules of leguminous
plants. They can fix nitrogen from air into soil and increase the soil
fertility.
Some bacteria and blue green algae present in the soil fix
nitrogen from the atmosphere and convert into nitrogenous compounds.
Certain bacteria
convert compounds of nitrogen present in the soil into nitrogen gas which is
released to the atmosphere.
CONSERVATION OF PLANTS AND ANIMALS
Wildlife
sanctuary, national park and biosphere reserve are names given to the areas meant
for conservation and preservation of forest and wild animals.
Biodiversity
refers to the variety of living organisms in a specific area.
Plants and animals of a particular area are known
as the flora and fauna of that area.
Endemic species are found only in a particular
area.
Endangered
species are those which are facing the danger of extinction.
Red Data Book contains a record of endangered
species.
Migration is
the phenomenon of movement of a species from its own habitat to some other habitat
for a particular time period every year for a specific purpose like breeding.
We should
save, reuse and recycle paper to save trees, energy and water.
Reforestation is the restocking of destroyed forests
by planting new trees.
CELL -STRUCTURE AND FUNCTIONS
All organisms are made of smaller parts called organs.
Organs are made of still smaller parts. The smallest living
part of an organism is a ‘cell’.
Cells were first observed in cork by Robert Hooke in 1665.
Cells exhibit variety
of shapes and sizes.
Number of cells also varies from organism to organism.
Some cells are big
enough to be seen with the unaided eye. Hen’s egg is an example.
Some organisms are
single-celled, while others contain large number of cells.
The single cell of
unicellular organisms performs all the basic functions performed by a variety
of cells in multi cellular organisms.
The cell has three
main parts, (i) the cell membrane, (ii) cytoplasm which contains smaller
components called organelles, and (iii) the nucleus.
Nucleus is separated from cytoplasm by a nuclear membrane.
Cells without well
organised nucleus, i.e. lacking nuclear membrane, are called prokaryotic cells.
Plant cells differ from animal cells in having an additional
layer around the cell membrane termed cell wall.
Coloured bodies called plastids are found in the plant cells
only. Green plastids containing chlorophyll are called chloroplasts.
Plant cell has a big
central vacuole unlike a number of small vacuoles in animal cells.
REPRODUCTION IN ANIMALS
There are two modes by which animals reproduce. These are:
(i) Sexual reproduction, and (ii) Asexual reproduction.
Reproduction
resulting from the fusion of male and female gametes is called sexual reproduction.
The reproductive
organs in the female include ovaries, oviducts and uterus.
The reproductive organs in male include testes, sperm ducts
and penis.
The ovary produces female gametes called ova and the testes
produce male gametes called sperms.
The fusion of ovum and sperm is called fertilization. The
fertilized egg is called a zygote.
Fertilization that
takes place inside the female body is called internal fertilization. This is observed
in human beings and other animals such as hens, cows and dogs.
Fertilization that
takes place outside the female body is called external fertilization. This is observed
in frogs, fish, starfish, etc.
The zygote divides repeatedly to give rise to an embryo.
The embryo gets embedded in the wall of the uterus for
further development.
The stage of the
embryo in which all the body parts are identifiable is called fetus.
Animals such as human beings, cows and dogs which give birth
to young ones are called viviparous animals.
Animals such as hen, frog, lizard and butterfly which lay
eggs are called oviparous animals.
The transformation of
the larva into adult through drastic changes is called metamorphosis.
The type of reproduction in which only a single parent is
involved is called asexual reproduction.
In hydra, new individuals develop from buds.
This method of asexual reproduction is called budding.
Amoeba reproduces by
dividing itself into two.
This type of asexual reproduction is called binary fission.
REACHING THE AGE OF ADOLESCENCE
Humans become capable of reproduction after puberty sets in.
Between the ages of 11 years and 19 years children are called adolescents.
The onset of puberty brings about growth of the reproductive
organs. Hair grow at various places on the body. Breasts develop in girls and
facial hair (moustache and beard) appear in boys. Voice of boys becomes hoarse
as voice box enlarges during adolescence.
Children gain height
during adolescence.
The onset of puberty
and maturity of reproductive parts are controlled by hormones.
Hormones are
secretions of endocrine glands which pour them directly into the blood stream.
Pituitary gland
secretes hormones which include growth hormone and hormones that make other
glands such as the testes, ovaries ,thyroids and adrenals, secrete hormones.
Pancreas secretes insulin, thyroid produces thyroxine and
adrenals produce adrenalin.
Testosterone is the male hormone and estrogen, the female
hormone. The uterine wall in females prepares itself to receive the developing
fertilised egg. In case there is no fertilisation, the thickened ining of the
uterine wall breaks down and goes out of the body along with blood. This is
called menstruation.
Sex of the unborn
child depends on whether the zygote has XX or XY chromosomes.
It is important to
eat balanced food and maintain personal hygiene during adolescence.
THE FUNDAMENTAL UNIT OF LIFE
The fundamental organizational unit of life is the cell.
Cells are enclosed by a plasma membrane composed of lipids and
proteins.
The cell membrane is an active part of the cell. It
regulates the movement of materials between the ordered interior of the cell and
the outer environment.
In plant cells, a
cell wall composed mainly of cellulose is located outside the cell membrane.
The presence of the
cell wall enables the cells of plants, fungi and bacteria to exist in hypotonic
media without bursting.
The nucleus in
eukaryotes is separated from the cytoplasm by double-layered membrane and it
directs the life processes of the cell.
The ER functions both
as a passageway for intracellular transport and as a manufacturing surface.
The Golgi apparatus consists of stacks of membrane-bound vesicles
that function in the storage, odification and packaging of substances
manufactured in the cell.
Most plant cells have large membranous organelles called plastids,
which are of two types – hromoplasts and leucoplasts.
Chromoplasts that
contain chlorophyll are called chloroplasts and they perform photosynthesis.
The primary function of leucoplasts is storage.
Most mature plant
cells have a large central vacuole that helps to maintain the turgidity of the
cell and stores important substances including wastes.
Prokaryotic cells have no membrane-bound organelles, their chromosomes
are composed of only nucleic acid, and they have only very small ribosomes as
organelles.
TISSUES
Tissue is a group of cells similar in structure and
function.
Plant tissues are of
two main types – meristematic and permanent.
Meristematic tissue is the dividing tissue present in the
growing regions of the plant.
Permanent tissues are derived from meristematic tissue once they
lose the ability to divide. They are classified as simple and complex tissues.
Parenchyma,
collenchyma and sclerenchyma are three types of simple tissues. Xylem and
phloem are types of complex tissues.
Animal tissues can be epithelial, connective, muscular and nervous
tissue.
Depending on shape and function, epithelial tissue is
classified as squamous, cuboidal, columnar, iliated and glandular.
The different types of connective tissues in our body
include areolar tissue, adipose tissue, one,tendon, ligament, cartilage and
blood.
Striated, unstriated and cardiac are three types of muscle tissues.
Nervous tissue is made of neurons that receive and conduct impulses.
DIVERSITY IN LIVING ORGANISMS
Classification helps us in exploring the diversity of life
forms.
The major characteristics considered for classifying all organisms
into five major kingdoms are:
(a) whether they are made of prokaryotic or eukaryotic cells
(b) whether the cells are living singly or organised into
multicellular and thus complex organisms
(c) whether the cells have a cell-wall and whether they
prepare their own food.
All living organisms are divided on the above bases into
five kingdoms, namely Monera, Protista, Fungi, Plantae and Animalia.
The classification of
life forms is related to their evolution.
Plantae and Animalia are further divided into subdivisions on
the basis of increasing complexity of body organisation.
Plants are divided into five groups: Thallophytes,
Bryophytes, Pteridophytes, Gymnosperms and Angiosperms.
Animals are divided into ten groups: Porifera, Coelenterata,Platyhelminthes,
Nematoda, Annelida,
Arthropoda, Mollusca, Echinodermata, Protochordata and
Vertebrata.
The binomial
nomenclature makes for a uniform way of identification of the vast diversity of
life around us.
The binomial nomenclature is made up of two words – a
generic name and a specific name.
WHY DO WE FALL ILL
Health is a state of physical, mental and social well-being.
The health of an individual is dependent on his/her physical
surroundings and his/her economic status.
Diseases are classified as acute or chronic, depending on
their duration.
Disease may be due to
infectious or non-infectious causes.
Infectious agents
belong to different categories of organisms and may be unicellular and
microscopic or multicellular.
The category to which a disease-causing organism belongs decides
the type of treatment.
Infectious agents are
spread through air, water, physical contact or vectors.
Prevention of disease
is more desirable than its successful treatment.
Infectious diseases
can be prevented by public health hygiene measures that reduce exposure to
infectious agents.
Infectious diseases can also be prevented by using immunisation.
Effective prevention
of infectious diseases in the community requires that everyone should have
access to public hygiene and immunisation.
Life Processes
Movement of various types can be taken as an indication of
life.
The maintenance of life requires processes like nutrition,
respiration, transport of materials within the body and excretion of waste
products.
Autotrophic nutrition
involves the intake of simple inorganic materials from the environment and
using an external energy source like the Sun to synthesise complex high-energy
organic material.
Heterotrophic nutrition involves the intake of complex
material prepared by other organisms.
In human beings, the
food eaten is broken down by various steps along the alimentary canal and the
digested food is absorbed in the small intestine to be sent to all cells in the
body.
During the process of
respiration, complex organic compounds such as glucose are broken down to
provide energy in the form of ATP. ATP is used to provide energy for other
reactions in the cell.
Respiration may be
aerobic or anaerobic. Aerobic respiration makes more energy available to the
organism.
In human beings, the
transport of materials such as oxygen, carbon dioxide, food and excretory
products is a function of the circulatory system. The circulatory system
consists of the heart, blood and blood vessels.
In highly
differentiated plants, transport of water, minerals, food and other materials is
a function of the vascular tissue which consists of xylem and phloem. In human
beings, excretory products in the form of soluble nitrogen compounds are
removed by the nephrons in the kidneys.
Plants use a variety of techniques to get rid of waste
material. For example, waste material may be stored in the cell-vacuoles or as
gum and resin, removed in the falling leaves, or excreted into the surrounding
soil.
Control and Coordination
Control and coordination are the functions of the nervous
system and hormones in our bodies.
The responses of the
nervous system can be classified as reflex action, voluntary action or
involuntary action.
The nervous system
uses electrical impulses to transmit messages.
The nervous system gets information from our sense organs
and acts through our muscles.
Chemical coordination
is seen in both plants and animals.
Hormones produced in one part of an organism move to another
part to achieve the desired effect.
A feedback mechanism regulates the action of the hormones.
How do Organisms Reproduce
Reproduction, unlike other life processes, is not essential
to maintain the life of an individual organism.
Reproduction involves
creation of a DNA copy and additional cellular apparatus by the cell involved
in the process.
Various organisms use
different modes of reproduction depending on their body design.
In fission, many
bacteria and protozoa simply divide into two or more daughter cells.
Organisms such as hydra can regenerate if they are broken
into pieces. They can also give out buds which mature into new individuals.
Roots, stems and leaves of some plants develop into new
plants through vegetative propagation.
These are examples of
asexual reproduction where new generations are created from a single
individual.
Sexual reproduction
involves two individuals for the creation of a new individual.
DNA copying
mechanisms creates variations which are useful for ensuring the survival of the
species. Modes of sexual reproduction allow for greater variation to be
generated.
Reproduction in flowering plants involves transfer of pollen
grains from the anther to the stigma
which is referred to as pollination. This
is followed by fertilisation.
Changes in the body at puberty, such as increase in breast
size in girls and new facial hair growth in boys, are signs of sexual
maturation.
The male reproductive
system in human beings consists of testes which produce sperms, vas deferens,
seminal vesicles, prostate gland, urethra and penis.
The female reproductive system in human beings consists of
ovaries, fallopian tubes, uterus and vagina.
Sexual reproduction in human beings involves the
introduction of sperm in the
Heredity and Evolution
Variations arising during the process of reproduction can be
inherited.
These variations may
lead to increased survival of the individuals.
Sexually reproducing
individuals have two copies of genes for the same trait. If the copies are not
identical, the trait that gets expressed is called the dominant trait and the
other is called the recessive trait. Traits in one individual may be inherited
separately, giving rise to new combinations of traits in the offspring of
sexual reproduction.
Sex is determined by
different factors in various species. In human beings, the sex of the child
depends on whether the paternal chromosome is X (for girls) or Y (for boys).
Variations in the
species may confer survival advantages or merely contribute to the genetic
drift.
Changes in the non-reproductive tissues caused by
environmental factors are not inheritable.
Speciation may take place when variation is combined with
geographical isolation.
Evolutionary relationships are traced in the classification of
organisms.
Tracing common ancestors back in time leads us to the idea
that at some point of time, non-living material must have given rise to life.
Evolution can be worked out by the study of not just living
species, but also fossils.
Complex organs may have evolved because of the survival
advantage of even the intermediate stages.
Organs or features may be adapted to new functions during
the course of evolution.
For example, feathers are thought to have been initially
evolved for warmth and later adapted for flight.
Evolution cannot be said to ‘progress’ from ‘lower’ forms to
‘higher’ forms. Rather, evolution seems to have given rise to more complex body
designs even while the simpler body designs continue to flourish.
Study of the evolution of human beings indicates that all of
us belong to a single species that evolved in Africa and spread across the
world in stages.
Management of Natural Resources
Our resources like forests, wild life, water, coal and
petroleum need to be used in a Sustainable manner.
We can reduce pressure on the environment by sincerely
applying the maxim of ‘Reduce, Reuse and Recycle’ in our lives.
Management of forest
resources has to take into account the interests of various stakeholders.
The harnessing of
water resources by building dams has social, economic and environmental
implications. Alternatives to large dams exist. These are locale-specific and
may be developed so as to give local people control over their local resources.
The fossil fuels, coal and petroleum, will ultimately be
exhausted. Because of this and because their combustion pollutes our
environment, we need to use these resources judiciously.
BIOTECHNOLOGY : PRINCIPLES AND PROCESSES
Biotechnology deals with large scale production and
marketing of products and processes using live organisms, cells or enzymes.
Modern biotechnology using genetically modified organisms
was made possible only when man learnt to alter the chemistry of DNA and
construct recombinant DNA. This key process is called recombinant DNA
technology or genetic engineering. This process involves the use of restriction
endonucleases, DNA ligase, appropriate plasmid or viral vectors to isolate and
ferry the foreign DNA into host organisms, xpression of the foreign gene, purification of
the gene product, i.e., the functional protein and finally making a suitable
formulation for marketing. Large scale production involves use of bioreactors.
Biotechnology has given to humans several useful products by
using microbes, plant, animals and their metabolic machinery. Recombinant DNA
technology has made it possible to engineer microbes, plants and animals such
that they have novel capabilities. Genetically Modified Organisms have been
created by using methods other than natural methods to transfer one or more
genes from one organism to another, generally using techniques such as
recombinant DNA technology.
GM plants have been useful in increasing crop yields, reduce
postharvest losses and make crops more tolerant of stresses. There are several
GM crop plants with improved nutritional value of foods and reduced the
reliance on chemical pesticides (pest-resistant crops).
Recombinant DNA technological processes have made immense impact
in the area of healthcare by enabling mass production of safe and more
effective therapeutics. Since the recombinant therapeutics are identical to
human proteins, they do not induce unwanted immunological responses and are
free from risk of infection as was observed in case of similar products
isolated from non-human sources.
Human insulin is made in bacteria yet its structure is
absolutely identical to that of the natural molecule.
Transgenic animals are also used to understand how genes contribute
to the development of a disease by serving as models for human diseases, such
as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer’s.
Gene therapy is the insertion of genes into an individual’s
cells and tissues to treat diseases especially hereditary diseases. It does so
by replacing a defective mutant allele with a functional one or gene targeting
which involves gene amplification. Viruses that attack their hosts and
introduce their genetic material into the host cell as part of their
replication cycle are used as vectors to transfer healthy genes or more recently
portions of genes.
The current interest in the manipulation of microbes,
plants, and animals has raised serious ethical questions.
BIODIVERSITY AND CONSERVATION
Since life originated on earth nearly 3.8 billion years ago,
there had been enormous diversification of life forms on earth. Biodiversity
refers to the sum total of diversity that exists at all levels of biological organisation.
Of particular importance is the diversity at genetic, species and ecosystem
levels and conservation efforts are aimed at protecting diversity at all these
levels. More than 1.5 million species have been recorded in the world, but there
might still be nearly 6 million species on earth waiting to be discovered and
named. Of the named species, > 70 per cent are animals, of which 70 per cent
are insects. The group Fungi has more species
than all the vertebrate species combined. India, with about 45,000 species
of plants and twice as many species of animals, is one of the 12 mega diversity
countries of the world.
Species diversity on earth is not uniformly distributed but
shows interesting patterns. It is generally highest in the tropics and
decreases towards the poles. Important explanations for the species richness of
the tropics are: Tropics had more evolutionary time; they provide a relatively
constant environment and, they receive more solar energy which contributes to
greater productivity. Species richness is also function of the area of a
region; the species-area relationship is generally a rectangular hyperbolic
function. It is believed that communities with high diversity tend to be less variable,
more productive and more resistant to biological invasions. Earth’s fossil
history reveals incidence of mass extinctions in the past, but the present
rates of extinction, largely attributed to human activities, are 100 to 1000
times higher. Nearly 700 species have become extinct in recent times and more
than 15,500 species (of which > 650 are from India currently face the threat
of extinction. The causes of high extinction rates at present include habitat
(particularly forests) loss and fragmentation, over -exploitation, biological
invasions and co-extinctions.
Earth’s rich biodiversity is vital for the very survival of
mankind.
The reasons for conserving biodiversity are narrowly
utilitarian, broadly utilitarian and ethical.
Besides the direct benefits
(food, fibre, firewood,pharmaceuticals, etc.), there are many indirect benefits
we receive through ecosystem services such as pollination, pest control,
climate moderation and flood control. We also have a moral responsibility to take
good care of earth’s biodiversity and pass it on in good order to our next
generation.
Biodiversity conservation may be in situ as well as ex situ.
In in situ conservation, the endangered species are protected in their natural habitat
so that the entire ecosystem is protected. Recently, 34 ‘biodiversity hotspots’
in the world have been proposed for intensive conservation efforts. Of these,
three (Western Ghats-Sri Lanka, Himalaya and Indo-Burma) cover India’s rich
biodiversity regions. Our country’s in situ conservation efforts are reflected
in its 14 biosphere reserves, 90 national parks, > 450 wildlife sanctuaries
and many sacred groves. Ex situ conservation methods include protective maintenance of threatened species in
zoological parks and botanical gardens, in vitro fertilisation, tissue culture
propagation and cryo preservation .
ECOSYSTEM
An ecosystem is a functional unit of nature and comprises
abiotic and biotic components. Abiotic components are inorganic materials- air,water
and soil, whereas biotic components are producers, consumers and decomposers.
Each ecosystem has characteristic physical structure resulting from interaction
amongst abiotic and biotic components. Species composition and stratification
are the two main structural features of an ecosystem. Based on source of
nutrition every organism occupies a place in an ecosystem.
Productivity, decomposition, energy flow, and nutrient
cycling are the four important components of an ecosystem. Primary productivity
is the rate of capture of solar energy or biomass production of the producers.
It is divided into two types: gross primary productivity (GPP) and net primary
productivity (NPP). Rate of capture of solar energy or total production of
organic matter is called as GPP. NPP is the remaining biomass or the energy
left after utilisation of producers. Secondary productivity is the rate of
assimilation of food energy by the consumers. In decomposition, complex organic
compounds of detritus are converted to carbon dioxide, water and inorganic
nutrients by the decomposers.
Decomposition involves three processes, namely
fragmentation of detritus, leaching and catabolism.
Energy flow is unidirectional. First, plants capture solar
energy and then, food is transferred from the producers to decomposers.
Organisms of different trophic levels in nature are
connected to each other for food or energy relationship forming a food chain.
The storage and movement of nutrient elements through the various components of
the ecosystem is called nutrient cycling; nutrients are repeatedly used through
this process. Nutrient cycling is of two types. Gaseous and sedimentary.
Atmosphere or hydrosphere is the reservoir for the gaseous type of cycle
(carbon), whereas Earth’s crust is the reservoir for sedimentary type
(phosphorus). Products of ecosystem processes are named as ecosystem services,
e.g., purification of air and water by forests.
The biotic community is dynamic and undergoes changes with
the passage of time. These changes are sequentially ordered and constitute ecological
succession. Succession begins with invasion of a bare lifeless area by pioneers
which later pave way for successors and ultimately a stable climax community is
formed. The climax community remains stable as long as the environment remains
unchanged.
ENVIRONMENTAL ISSUES
Major issues relating to environmental pollution and
depletion of valuable natural resources vary in dimension from local, regional
to global levels. Air pollution primarily results from burning of fossil fuel, e.g.,
coal and petroleum, in industries and in automobiles. They are harmful to
humans, animals and plants, and therefore must be removed to keep our air
clean. Domestic sewage, the most common source of pollution of water bodies,
reduces dissolved oxygen but increases biochemical oxygen demand of receiving
water. Domestic sewage is rich in nutrients, especially, nitrogen and
phosphorus,
which cause eutrophication and nuisance algal blooms. Industrial
waste waters are often rich in toxic chemicals, especially heavy metals and organic
compounds. Industrial waste waters harm living organisms. Municipal solid
wastes also create problems and must be disposed of in landfills. Disposal of
hazardous wastes like defunct ships, radioactive wastes and e-wastes requires
additional efforts.
Soil pollution primarily results from agricultural
chemicals (e.g., pesticides) and leachates from solid wastes deposited over it.Two
major environmental issues of global nature are increasing greenhouse effect,
which is warming Earth, and depletion of ozone in the stratosphere. Enhanced
greenhouse effect is mainly due to increased emission of carbon dioxide,
methane, nitrous oxide and CFCs., and also due to deforestation. It may
drastically change rainfall pattern, global temperature, besides deleteriously affecting living organisms.
Ozone in the stratosphere, which protects us from harmful
effects of ultraviolet radiation, is depleting fast due to emission of CFCs
thus increasing the risks of skin cancer, mutation and other disorders.
MOLECULAR BASIS OF INHERITANCE
Nucleic acids are long polymers of nucleotides. While DNA
stores genetic information, RNA mostly helps in transfer and expression of
information.
Though DNA and RNA both function as genetic material, but
DNA being chemically and structurally more stable is a better genetic material.
However, RNA is the first to evolve and DNA was derived from
RNA. The hallmark of the double stranded helical structure of DNA is the
hydrogen bonding between the bases from opposite strands. The rule is that Adenine
pairs with Thymine through two H-bonds, and Guanine with Cytosine through three
H-bonds. This makes one strand complementary to the other. The DNA replicates
semi onservatively, the process is guided by the complementary H-bonding. A
segment of DNA that codes for RNA may in a simplistic term can be referred as gene.
During transcription also, one of the strands of DNA acts a template to direct
the synthesis of complementary RNA. In bacteria, the transcribed mRNA is
functional, hence can directly be translated.
In eukaryotes, the gene is split. The coding sequences,
exons, are interrupted by non-coding sequences, introns. Introns are removed and
exons are joined to produce functional RNA by splicing. The messenger RNA
contains the base sequences that are read in a combination of three (to make
triplet genetic code) to code for an amino acid. The genetic code is read again
on the principle of complementarity by tRNA that acts as an adapter molecule.
There are specific tRNAs for every amino acid. The tRNA binds to specific amino
acid at one end and pairs through H-bonding with codes on mRNA through its anticodons.
The site of translation (protein synthesis) is ribosomes, which bind to mRNA
and provide platform for joining of amino acids. One of the rRNA acts as a
catalyst for peptide bond formation, which is an example of RNA enzyme
(ribozyme). Translation is a process that has evolved around RNA, indicating
that life began around RNA. Since, transcription and translation are
energetically very expensive processes,
these have to be tightly regulated.
Regulation of transcription is the primary
step for regulation of gene expression.
In bacteria, more than one gene is arranged together and regulated in units
called as operons. Lac operon is the prototype operon in bacteria, which codes for
genes responsible for metabolism of
lactose. The operon is regulated by the amount of lactose in the medium where
the bacteria are grown.
Therefore, this regulation can also be viewed as regulation
of enzyme synthesis by its substrate.
Human genome project was a mega project that aimed to
sequence every base in human genome.
This project has yielded much new information.
Many new areas and avenues have opened up as a consequence of the project. DNA
Fingerprinting is a technique to find out variations in individuals of a
population at DNA level. It works on the principle of polymorphism in DNA
sequences. It has immense applications in the field of forensic science, genetic
biodiversity and evolutionary biology.
Silk comes from silkworms and wool is obtained from sheep, goat and
yak. Hence silk and wool are animal fibres.
The hairs of camel, llama and alpaca are also processed to yield wool.
In India, mostly sheep are reared for getting wool.
Sheep hair is sheared off from the body, scoured, sorted, dried, dyed,spun and woven to yield wool.
Silkworms are caterpillars of silk moth.
During their life cycle, the worms spin cocoons of silk fibres.
Silk fibres are made of a protein.
Silk fibres from cocoons are separated out and reeled into silk threads.
Weavers weave silk threads into silk cloth.
Weather, Climate and Adaptations of Animals to Climate
The day-to-day condition of the atmosphere at a place with respect to the temperature, humidity, rainfall, wind-speed, etc., is called the weather at that place.
The weather is generally not the same on any two days and week after week.
The maximum temperature of the day occurs generally in the afternoon while the minimum temperature occurs in the early morning.
The times of sunrise and sunset also change during the year.
All the changes in the weather are driven by the sun.
The average weather pattern taken over a long time, say 25 years, is called the climate of the place
The tropical and the polar regions are the two regions of the earth, which have severe climatic conditions.
Animals are adapted to the conditions in which they live.
The polar regions are very cold throughout the year. The sun does not set for six months in a year and in the other six months it does not rise.
Animals in the polar region are adapted to the extremely cold climate by having some special characteristics such as white fur, strong sense of smell, a layer of fat under the skin, wide and large paws for swimming and walking, etc.
Migration is another means to escape the harsh, cold conditions.
Because of the hospitable climatic conditions huge populations of plants and animals are found in the tropical rainforests.
Animals in the tropical rainforests are adapted such that they eat different kinds of food to overcome the competition for food and shelter.
Some adaptations of animals living in the tropical rainforests include living on the trees, development of strong tails, long and large beaks, bright colours, sharp patterns, loud voice, diet of fruits, sensitive hearing,sharp eyesight, thick skin, ability to camouflage in order to protect
themselves from predators, etc.
Respiration in Organisms
Respiration is essential for survival of living organisms.
It releases energy from the food.
The oxygen we inhale is used to breakdown glucose into
carbon dioxide and water. Energy is released in the process.
The breakdown of glucose occurs in the cells of an organism
(cellular respiration).
If the food is broken down with the use of oxygen, it is
called aerobic respiration.
If the breakdown occurs without the use of oxygen, the respiration
is called anaerobic respiration.
During heavy exercise when the supply of oxygen to our
muscle cells is insufficient, food breakdown is by anaerobic respiration.
Breathing is a part of the process of respiration during
which an organism takes in the oxygen-rich air and gives out air rich in carbon
dioxide.
The respiratory organs for the exchange of gases vary in
different organisms.
During inhalation,
our lungs expand and then come back to the original state as the air moves out
during exhalation.
Increased physical
activity enhances the rate of breathing.
In animals like cow,
buffalo, dog and cat the respiratory organs and the process of breathing are
similar to those in humans.
In earthworm, the
exchange of gases occurs through the moist skin. In fishes it takes place
through gills and in insects through the tracheae.
In a plant the roots
take in air present in the soil.
Leaves have tiny pores called stomata through which they
exchange gases.
The breakdown of glucose in the plant cells is similar to
that in other living beings.
Transportation in Animals and Plants In most animals the blood that circulates in
the body distributes food and oxygen to different cells of the body. It also
carries waste products to different parts of the body for excretion.
Circulatory system
consists of the heart and blood vessels.
In humans, blood
flows through arteries and veins and the heart acts as a pumping organ.
Blood consists of
plasma, RBC, WBC and platelets. Blood is red due to the presence of a red
pigment, haemoglobin.
The human heart beats
about 70ñ80 times per minute in an adult person. This is called heart rate.
Arteries carry blood
from the heart to all parts of the body.
Veins carry blood
from all parts of the body back to the heart.
Removal of waste products from the body is called excretion.
Excretory system of humans consists of two kidneys, two
ureters, a urinary bladder, and urethra.
Salts and urea are
removed along with water as sweat.
Fish excrete waste substances such as ammonia which directly
dissolve in water.
Birds, insects and lizard excrete uric acid in semi-solid
form.
Water and mineral nutrients are absorbed by roots from the
soil.
Nutrients are transported along with water to the entire
plant via the vascular tissue called xylem.
The vascular tissue
for the transport of food to the various parts of the plant is phloem.
A lot of water is
lost by plants in the form of vapour through stomata during transpiration.
Transpiration generates a force which pulls up water
absorbed by the roots from the soil, to reach the stem and leaves.
Reproduction in Plants
All organisms multiply or reproduce their own kind.
In plants there are
two modes of reproduction, asexual and sexual.
There are several methods of asexual reproduction such as fragmentation,
budding, spore formation and vegetative propagation.
Sexual reproduction
involves the fusion of male and female gametes.
In vegetative
propagation new plants are produced from different vegetative parts such as
leaves, stems and roots.
Flower is the
reproductive part of a plant.
A flower may be
unisexual with either the male or the female reproductive parts.
A bisexual flower has
both the male and the female reproductive parts.
The male gametes are
found inside the pollen grains and female gametes are found in the ovule.
Pollination is the
process of transfer of pollen grains from the anther of one flower to the
stigma of the same or another flower.
Pollination is of two types, self-pollination and
cross-pollination. In self-pollination, pollen grains are transferred from the
anther to the stigma of the same flower. In cross-pollination, pollen grains
are transferred from the anther of one flower to the stigma of another flower of
the same kind.
Pollination takes place in plants with the help of wind,
water and insects.
The fusion of male and female gametes is called
fertilisation.
Fertilised egg is
called zygote. Zygote develops into an embryo.
Fruit is the mature
ovary whereas ovule develops into a seed, which contains the developing embryo.
Seed dispersal is
aided by wind, water and animals.
Seed dispersal helps the plants to (i) prevent overcrowding,
(ii) avoid competition for sunlight, water and minerals and (iii) invade new
habitats.
Water: A Precious Resource
Water is essential for all living beings. There can be no
life without it.
Water exists in three
forms: solid, liquid and vapour.
Though water is maintained by the water cycle, yet there is
an acute scarcity of water in many parts of the globe.
There is an uneven distribution of water. Much of it has
resulted from human activities.
Rapid growth of industries,
increasing population, growing irrigation requirements and mismanagement are
some of the causes for water shortage.
We need to be worried about the wastage during the supply of
water through pipes, the leaking taps in buildings and other places.
Unnecessary use of water and overdrawing from groundwater
should be avoided. Recharge of water to the ground should be increased.
The need of the hour is that every individual uses water
economically.
Plants wilt and
ultimately dry-up if they are not watered for a few days.
Forests: Our Lifeline
We get various products from the forests surrounding us.
Forest is a system comprising various plants, animals and micro-organisms.
In a forest, trees
form the uppermost layer, followed by shrubs. The herbs form the lowest layer
of vegetation.
Different layers of
vegetation provide food and shelter for animals, birds and insects.
The various components of the forest are interdependent on
one another.
The forest keeps on growing and changing, and can
regenerate.
In the forest, there
is interaction between soil, water, air and living organisms.
Forests protect the
soil from erosion.
Soil helps forests to grow and regenerate.
Forests are the
lifeline for the forest-dwelling communities.
Forests influence
climate, water cycle and air quality
Waste water Story
Used water is wastewater. Wastewater could be reused.
Wastewater is
generated in homes, industries, agricultural fields and in other human
activities. This is called sewage.
Sewage is a liquid
waste which causes water and soil pollution.
Wastewater is treated in a sewage treatment plant.
Treatment plants reduce pollutants in wastewater to a level
where nature can take care of it.
Where underground sewerage systems and refuse disposal
systems are not available, the low cost on-site sanitation system can be
adopted.
By-products of wastewater treatment are sludge and biogas.
Open drain system is
a breeding place for flies, mosquitoes and organisms which cause diseases.
We should not
defecate in the open. It is possible to have safe disposal of excreta by low
cost methods.
CROP PRODUCTION AND MANAGEMENT
In order to provide food to our growing population, we need
to adopt certain agricultural practices.
Same kinds of plants
grown and cultivated at a place constitute a crop.
In India, crops can
be broadly categorised into two types based on seasons - rabi and kharif crops.
It is necessary to
prepare soil by tilling and levelling. Ploughs and levellers are used for this
purpose.
Sowing of seeds at
appropriate depths and distances gives good yield. Good variety of seeds are
sown after selection of healthy seeds.
Sowing is done by seed drills.
Soil needs replenishment and enrichment through the use of organic
manure and fertilisers. Use of chemical fertilisers has increased tremendously
with the introduction of new crop varieties.
Supply of water to crops at appropriate intervals is called
irrigation.
Weeding involves
removal of unwanted and uncultivated plants called weeds.
Harvesting is the
cutting of the mature crop manually or by machines.
Separation of the grains from the chaff is called threshing.
Proper storage of
grains is necessary to protect them from pests and microorganisms.
Food is also obtained from animals for which animals are
reared. This is called animal husbandry.
MICRO-ORGANISMS
Microorganisms are too small and are not visible to the
unaided eye.
They can live in all kinds of environment, ranging from ice
cold climate to hot springs and deserts to marshy lands.
Microorganisms are
found in air, water and in the bodies of plants and animals.
They may be
unicellular or multicellular.
Microorganisms include bacteria, fungi, protozoa and some
algae. Viruses, though different from the above mentioned living organisms, are
considered microbes.
Viruses are quite different from other microorganisms. They
reproduce only inside the host organism; bacterium, plant or animal cell.
Some microorganisms
are useful for commercial production of medicines and alcohol.
Some microorganisms
decompose the organic waste and dead plants and animals into simple substances
and clean up the environment.
Protozoans cause
serious diseases like dysentery and malaria.
Some of the microorganisms grow on our food and cause food
poisoning.
Some microorganisms reside in the root nodules of leguminous
plants. They can fix nitrogen from air into soil and increase the soil
fertility.
Some bacteria and blue green algae present in the soil fix
nitrogen from the atmosphere and convert into nitrogenous compounds.
Certain bacteria
convert compounds of nitrogen present in the soil into nitrogen gas which is
released to the atmosphere.
CONSERVATION OF PLANTS AND ANIMALS
Wildlife
sanctuary, national park and biosphere reserve are names given to the areas meant
for conservation and preservation of forest and wild animals.
Biodiversity
refers to the variety of living organisms in a specific area.
Plants and animals of a particular area are known
as the flora and fauna of that area.
Endemic species are found only in a particular
area.
Endangered
species are those which are facing the danger of extinction.
Red Data Book contains a record of endangered
species.
Migration is
the phenomenon of movement of a species from its own habitat to some other habitat
for a particular time period every year for a specific purpose like breeding.
We should
save, reuse and recycle paper to save trees, energy and water.
Reforestation is the restocking of destroyed forests
by planting new trees.
CELL -STRUCTURE AND FUNCTIONS
All organisms are made of smaller parts called organs.
Organs are made of still smaller parts. The smallest living
part of an organism is a ‘cell’.
Cells were first observed in cork by Robert Hooke in 1665.
Cells exhibit variety
of shapes and sizes.
Number of cells also varies from organism to organism.
Some cells are big
enough to be seen with the unaided eye. Hen’s egg is an example.
Some organisms are
single-celled, while others contain large number of cells.
The single cell of
unicellular organisms performs all the basic functions performed by a variety
of cells in multi cellular organisms.
The cell has three
main parts, (i) the cell membrane, (ii) cytoplasm which contains smaller
components called organelles, and (iii) the nucleus.
Nucleus is separated from cytoplasm by a nuclear membrane.
Cells without well
organised nucleus, i.e. lacking nuclear membrane, are called prokaryotic cells.
Plant cells differ from animal cells in having an additional
layer around the cell membrane termed cell wall.
Coloured bodies called plastids are found in the plant cells
only. Green plastids containing chlorophyll are called chloroplasts.
Plant cell has a big
central vacuole unlike a number of small vacuoles in animal cells.
REPRODUCTION IN ANIMALS
There are two modes by which animals reproduce. These are:
(i) Sexual reproduction, and (ii) Asexual reproduction.
Reproduction
resulting from the fusion of male and female gametes is called sexual reproduction.
The reproductive
organs in the female include ovaries, oviducts and uterus.
The reproductive organs in male include testes, sperm ducts
and penis.
The ovary produces female gametes called ova and the testes
produce male gametes called sperms.
The fusion of ovum and sperm is called fertilization. The
fertilized egg is called a zygote.
Fertilization that
takes place inside the female body is called internal fertilization. This is observed
in human beings and other animals such as hens, cows and dogs.
Fertilization that
takes place outside the female body is called external fertilization. This is observed
in frogs, fish, starfish, etc.
The zygote divides repeatedly to give rise to an embryo.
The embryo gets embedded in the wall of the uterus for
further development.
The stage of the
embryo in which all the body parts are identifiable is called fetus.
Animals such as human beings, cows and dogs which give birth
to young ones are called viviparous animals.
Animals such as hen, frog, lizard and butterfly which lay
eggs are called oviparous animals.
The transformation of
the larva into adult through drastic changes is called metamorphosis.
The type of reproduction in which only a single parent is
involved is called asexual reproduction.
In hydra, new individuals develop from buds.
This method of asexual reproduction is called budding.
Amoeba reproduces by
dividing itself into two.
This type of asexual reproduction is called binary fission.
REACHING THE AGE OF ADOLESCENCE
Humans become capable of reproduction after puberty sets in.
Between the ages of 11 years and 19 years children are called adolescents.
The onset of puberty brings about growth of the reproductive
organs. Hair grow at various places on the body. Breasts develop in girls and
facial hair (moustache and beard) appear in boys. Voice of boys becomes hoarse
as voice box enlarges during adolescence.
Children gain height
during adolescence.
The onset of puberty
and maturity of reproductive parts are controlled by hormones.
Hormones are
secretions of endocrine glands which pour them directly into the blood stream.
Pituitary gland
secretes hormones which include growth hormone and hormones that make other
glands such as the testes, ovaries ,thyroids and adrenals, secrete hormones.
Pancreas secretes insulin, thyroid produces thyroxine and
adrenals produce adrenalin.
Testosterone is the male hormone and estrogen, the female
hormone. The uterine wall in females prepares itself to receive the developing
fertilised egg. In case there is no fertilisation, the thickened ining of the
uterine wall breaks down and goes out of the body along with blood. This is
called menstruation.
Sex of the unborn
child depends on whether the zygote has XX or XY chromosomes.
It is important to
eat balanced food and maintain personal hygiene during adolescence.
THE FUNDAMENTAL UNIT OF LIFE
The fundamental organizational unit of life is the cell.
Cells are enclosed by a plasma membrane composed of lipids and
proteins.
The cell membrane is an active part of the cell. It
regulates the movement of materials between the ordered interior of the cell and
the outer environment.
In plant cells, a
cell wall composed mainly of cellulose is located outside the cell membrane.
The presence of the
cell wall enables the cells of plants, fungi and bacteria to exist in hypotonic
media without bursting.
The nucleus in
eukaryotes is separated from the cytoplasm by double-layered membrane and it
directs the life processes of the cell.
The ER functions both
as a passageway for intracellular transport and as a manufacturing surface.
The Golgi apparatus consists of stacks of membrane-bound vesicles
that function in the storage, odification and packaging of substances
manufactured in the cell.
Most plant cells have large membranous organelles called plastids,
which are of two types – hromoplasts and leucoplasts.
Chromoplasts that
contain chlorophyll are called chloroplasts and they perform photosynthesis.
The primary function of leucoplasts is storage.
Most mature plant
cells have a large central vacuole that helps to maintain the turgidity of the
cell and stores important substances including wastes.
Prokaryotic cells have no membrane-bound organelles, their chromosomes
are composed of only nucleic acid, and they have only very small ribosomes as
organelles.
TISSUES
Tissue is a group of cells similar in structure and
function.
Plant tissues are of
two main types – meristematic and permanent.
Meristematic tissue is the dividing tissue present in the
growing regions of the plant.
Permanent tissues are derived from meristematic tissue once they
lose the ability to divide. They are classified as simple and complex tissues.
Parenchyma,
collenchyma and sclerenchyma are three types of simple tissues. Xylem and
phloem are types of complex tissues.
Animal tissues can be epithelial, connective, muscular and nervous
tissue.
Depending on shape and function, epithelial tissue is
classified as squamous, cuboidal, columnar, iliated and glandular.
The different types of connective tissues in our body
include areolar tissue, adipose tissue, one,tendon, ligament, cartilage and
blood.
Striated, unstriated and cardiac are three types of muscle tissues.
Nervous tissue is made of neurons that receive and conduct impulses.
DIVERSITY IN LIVING ORGANISMS
Classification helps us in exploring the diversity of life
forms.
The major characteristics considered for classifying all organisms
into five major kingdoms are:
(a) whether they are made of prokaryotic or eukaryotic cells
(b) whether the cells are living singly or organised into
multicellular and thus complex organisms
(c) whether the cells have a cell-wall and whether they
prepare their own food.
All living organisms are divided on the above bases into
five kingdoms, namely Monera, Protista, Fungi, Plantae and Animalia.
The classification of
life forms is related to their evolution.
Plantae and Animalia are further divided into subdivisions on
the basis of increasing complexity of body organisation.
Plants are divided into five groups: Thallophytes,
Bryophytes, Pteridophytes, Gymnosperms and Angiosperms.
Animals are divided into ten groups: Porifera, Coelenterata,Platyhelminthes,
Nematoda, Annelida,
Arthropoda, Mollusca, Echinodermata, Protochordata and
Vertebrata.
The binomial
nomenclature makes for a uniform way of identification of the vast diversity of
life around us.
The binomial nomenclature is made up of two words – a
generic name and a specific name.
WHY DO WE FALL ILL
Health is a state of physical, mental and social well-being.
The health of an individual is dependent on his/her physical
surroundings and his/her economic status.
Diseases are classified as acute or chronic, depending on
their duration.
Disease may be due to
infectious or non-infectious causes.
Infectious agents
belong to different categories of organisms and may be unicellular and
microscopic or multicellular.
The category to which a disease-causing organism belongs decides
the type of treatment.
Infectious agents are
spread through air, water, physical contact or vectors.
Prevention of disease
is more desirable than its successful treatment.
Infectious diseases
can be prevented by public health hygiene measures that reduce exposure to
infectious agents.
Infectious diseases can also be prevented by using immunisation.
Effective prevention
of infectious diseases in the community requires that everyone should have
access to public hygiene and immunisation.
Life Processes
Movement of various types can be taken as an indication of
life.
The maintenance of life requires processes like nutrition,
respiration, transport of materials within the body and excretion of waste
products.
Autotrophic nutrition
involves the intake of simple inorganic materials from the environment and
using an external energy source like the Sun to synthesise complex high-energy
organic material.
Heterotrophic nutrition involves the intake of complex
material prepared by other organisms.
In human beings, the
food eaten is broken down by various steps along the alimentary canal and the
digested food is absorbed in the small intestine to be sent to all cells in the
body.
During the process of
respiration, complex organic compounds such as glucose are broken down to
provide energy in the form of ATP. ATP is used to provide energy for other
reactions in the cell.
Respiration may be
aerobic or anaerobic. Aerobic respiration makes more energy available to the
organism.
In human beings, the
transport of materials such as oxygen, carbon dioxide, food and excretory
products is a function of the circulatory system. The circulatory system
consists of the heart, blood and blood vessels.
In highly
differentiated plants, transport of water, minerals, food and other materials is
a function of the vascular tissue which consists of xylem and phloem. In human
beings, excretory products in the form of soluble nitrogen compounds are
removed by the nephrons in the kidneys.
Plants use a variety of techniques to get rid of waste
material. For example, waste material may be stored in the cell-vacuoles or as
gum and resin, removed in the falling leaves, or excreted into the surrounding
soil.
Control and Coordination
Control and coordination are the functions of the nervous
system and hormones in our bodies.
The responses of the
nervous system can be classified as reflex action, voluntary action or
involuntary action.
The nervous system
uses electrical impulses to transmit messages.
The nervous system gets information from our sense organs
and acts through our muscles.
Chemical coordination
is seen in both plants and animals.
Hormones produced in one part of an organism move to another
part to achieve the desired effect.
A feedback mechanism regulates the action of the hormones.
How do Organisms Reproduce
Reproduction, unlike other life processes, is not essential
to maintain the life of an individual organism.
Reproduction involves
creation of a DNA copy and additional cellular apparatus by the cell involved
in the process.
Various organisms use
different modes of reproduction depending on their body design.
In fission, many
bacteria and protozoa simply divide into two or more daughter cells.
Organisms such as hydra can regenerate if they are broken
into pieces. They can also give out buds which mature into new individuals.
Roots, stems and leaves of some plants develop into new
plants through vegetative propagation.
These are examples of
asexual reproduction where new generations are created from a single
individual.
Sexual reproduction
involves two individuals for the creation of a new individual.
DNA copying
mechanisms creates variations which are useful for ensuring the survival of the
species. Modes of sexual reproduction allow for greater variation to be
generated.
Reproduction in flowering plants involves transfer of pollen
grains from the anther to the stigma
which is referred to as pollination. This
is followed by fertilisation.
Changes in the body at puberty, such as increase in breast
size in girls and new facial hair growth in boys, are signs of sexual
maturation.
The male reproductive
system in human beings consists of testes which produce sperms, vas deferens,
seminal vesicles, prostate gland, urethra and penis.
The female reproductive system in human beings consists of
ovaries, fallopian tubes, uterus and vagina.
Sexual reproduction in human beings involves the
introduction of sperm in the
Heredity and Evolution
Variations arising during the process of reproduction can be
inherited.
These variations may
lead to increased survival of the individuals.
Sexually reproducing
individuals have two copies of genes for the same trait. If the copies are not
identical, the trait that gets expressed is called the dominant trait and the
other is called the recessive trait. Traits in one individual may be inherited
separately, giving rise to new combinations of traits in the offspring of
sexual reproduction.
Sex is determined by
different factors in various species. In human beings, the sex of the child
depends on whether the paternal chromosome is X (for girls) or Y (for boys).
Variations in the
species may confer survival advantages or merely contribute to the genetic
drift.
Changes in the non-reproductive tissues caused by
environmental factors are not inheritable.
Speciation may take place when variation is combined with
geographical isolation.
Evolutionary relationships are traced in the classification of
organisms.
Tracing common ancestors back in time leads us to the idea
that at some point of time, non-living material must have given rise to life.
Evolution can be worked out by the study of not just living
species, but also fossils.
Complex organs may have evolved because of the survival
advantage of even the intermediate stages.
Organs or features may be adapted to new functions during
the course of evolution.
For example, feathers are thought to have been initially
evolved for warmth and later adapted for flight.
Evolution cannot be said to ‘progress’ from ‘lower’ forms to
‘higher’ forms. Rather, evolution seems to have given rise to more complex body
designs even while the simpler body designs continue to flourish.
Study of the evolution of human beings indicates that all of
us belong to a single species that evolved in Africa and spread across the
world in stages.
Management of Natural Resources
Our resources like forests, wild life, water, coal and
petroleum need to be used in a Sustainable manner.
We can reduce pressure on the environment by sincerely
applying the maxim of ‘Reduce, Reuse and Recycle’ in our lives.
Management of forest
resources has to take into account the interests of various stakeholders.
The harnessing of
water resources by building dams has social, economic and environmental
implications. Alternatives to large dams exist. These are locale-specific and
may be developed so as to give local people control over their local resources.
The fossil fuels, coal and petroleum, will ultimately be
exhausted. Because of this and because their combustion pollutes our
environment, we need to use these resources judiciously.
BIOTECHNOLOGY : PRINCIPLES AND PROCESSES
Biotechnology deals with large scale production and
marketing of products and processes using live organisms, cells or enzymes.
Modern biotechnology using genetically modified organisms
was made possible only when man learnt to alter the chemistry of DNA and
construct recombinant DNA. This key process is called recombinant DNA
technology or genetic engineering. This process involves the use of restriction
endonucleases, DNA ligase, appropriate plasmid or viral vectors to isolate and
ferry the foreign DNA into host organisms, xpression of the foreign gene, purification of
the gene product, i.e., the functional protein and finally making a suitable
formulation for marketing. Large scale production involves use of bioreactors.
Biotechnology has given to humans several useful products by
using microbes, plant, animals and their metabolic machinery. Recombinant DNA
technology has made it possible to engineer microbes, plants and animals such
that they have novel capabilities. Genetically Modified Organisms have been
created by using methods other than natural methods to transfer one or more
genes from one organism to another, generally using techniques such as
recombinant DNA technology.
GM plants have been useful in increasing crop yields, reduce
postharvest losses and make crops more tolerant of stresses. There are several
GM crop plants with improved nutritional value of foods and reduced the
reliance on chemical pesticides (pest-resistant crops).
Recombinant DNA technological processes have made immense impact
in the area of healthcare by enabling mass production of safe and more
effective therapeutics. Since the recombinant therapeutics are identical to
human proteins, they do not induce unwanted immunological responses and are
free from risk of infection as was observed in case of similar products
isolated from non-human sources.
Human insulin is made in bacteria yet its structure is
absolutely identical to that of the natural molecule.
Transgenic animals are also used to understand how genes contribute
to the development of a disease by serving as models for human diseases, such
as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer’s.
Gene therapy is the insertion of genes into an individual’s
cells and tissues to treat diseases especially hereditary diseases. It does so
by replacing a defective mutant allele with a functional one or gene targeting
which involves gene amplification. Viruses that attack their hosts and
introduce their genetic material into the host cell as part of their
replication cycle are used as vectors to transfer healthy genes or more recently
portions of genes.
The current interest in the manipulation of microbes,
plants, and animals has raised serious ethical questions.
BIODIVERSITY AND CONSERVATION
Since life originated on earth nearly 3.8 billion years ago,
there had been enormous diversification of life forms on earth. Biodiversity
refers to the sum total of diversity that exists at all levels of biological organisation.
Of particular importance is the diversity at genetic, species and ecosystem
levels and conservation efforts are aimed at protecting diversity at all these
levels. More than 1.5 million species have been recorded in the world, but there
might still be nearly 6 million species on earth waiting to be discovered and
named. Of the named species, > 70 per cent are animals, of which 70 per cent
are insects. The group Fungi has more species
than all the vertebrate species combined. India, with about 45,000 species
of plants and twice as many species of animals, is one of the 12 mega diversity
countries of the world.
Species diversity on earth is not uniformly distributed but
shows interesting patterns. It is generally highest in the tropics and
decreases towards the poles. Important explanations for the species richness of
the tropics are: Tropics had more evolutionary time; they provide a relatively
constant environment and, they receive more solar energy which contributes to
greater productivity. Species richness is also function of the area of a
region; the species-area relationship is generally a rectangular hyperbolic
function. It is believed that communities with high diversity tend to be less variable,
more productive and more resistant to biological invasions. Earth’s fossil
history reveals incidence of mass extinctions in the past, but the present
rates of extinction, largely attributed to human activities, are 100 to 1000
times higher. Nearly 700 species have become extinct in recent times and more
than 15,500 species (of which > 650 are from India currently face the threat
of extinction. The causes of high extinction rates at present include habitat
(particularly forests) loss and fragmentation, over -exploitation, biological
invasions and co-extinctions.
Earth’s rich biodiversity is vital for the very survival of
mankind.
The reasons for conserving biodiversity are narrowly
utilitarian, broadly utilitarian and ethical.
Besides the direct benefits
(food, fibre, firewood,pharmaceuticals, etc.), there are many indirect benefits
we receive through ecosystem services such as pollination, pest control,
climate moderation and flood control. We also have a moral responsibility to take
good care of earth’s biodiversity and pass it on in good order to our next
generation.
Biodiversity conservation may be in situ as well as ex situ.
In in situ conservation, the endangered species are protected in their natural habitat
so that the entire ecosystem is protected. Recently, 34 ‘biodiversity hotspots’
in the world have been proposed for intensive conservation efforts. Of these,
three (Western Ghats-Sri Lanka, Himalaya and Indo-Burma) cover India’s rich
biodiversity regions. Our country’s in situ conservation efforts are reflected
in its 14 biosphere reserves, 90 national parks, > 450 wildlife sanctuaries
and many sacred groves. Ex situ conservation methods include protective maintenance of threatened species in
zoological parks and botanical gardens, in vitro fertilisation, tissue culture
propagation and cryo preservation .
ECOSYSTEM
An ecosystem is a functional unit of nature and comprises
abiotic and biotic components. Abiotic components are inorganic materials- air,water
and soil, whereas biotic components are producers, consumers and decomposers.
Each ecosystem has characteristic physical structure resulting from interaction
amongst abiotic and biotic components. Species composition and stratification
are the two main structural features of an ecosystem. Based on source of
nutrition every organism occupies a place in an ecosystem.
Productivity, decomposition, energy flow, and nutrient
cycling are the four important components of an ecosystem. Primary productivity
is the rate of capture of solar energy or biomass production of the producers.
It is divided into two types: gross primary productivity (GPP) and net primary
productivity (NPP). Rate of capture of solar energy or total production of
organic matter is called as GPP. NPP is the remaining biomass or the energy
left after utilisation of producers. Secondary productivity is the rate of
assimilation of food energy by the consumers. In decomposition, complex organic
compounds of detritus are converted to carbon dioxide, water and inorganic
nutrients by the decomposers.
Decomposition involves three processes, namely
fragmentation of detritus, leaching and catabolism.
Energy flow is unidirectional. First, plants capture solar
energy and then, food is transferred from the producers to decomposers.
Organisms of different trophic levels in nature are
connected to each other for food or energy relationship forming a food chain.
The storage and movement of nutrient elements through the various components of
the ecosystem is called nutrient cycling; nutrients are repeatedly used through
this process. Nutrient cycling is of two types. Gaseous and sedimentary.
Atmosphere or hydrosphere is the reservoir for the gaseous type of cycle
(carbon), whereas Earth’s crust is the reservoir for sedimentary type
(phosphorus). Products of ecosystem processes are named as ecosystem services,
e.g., purification of air and water by forests.
The biotic community is dynamic and undergoes changes with
the passage of time. These changes are sequentially ordered and constitute ecological
succession. Succession begins with invasion of a bare lifeless area by pioneers
which later pave way for successors and ultimately a stable climax community is
formed. The climax community remains stable as long as the environment remains
unchanged.
ENVIRONMENTAL ISSUES
Major issues relating to environmental pollution and
depletion of valuable natural resources vary in dimension from local, regional
to global levels. Air pollution primarily results from burning of fossil fuel, e.g.,
coal and petroleum, in industries and in automobiles. They are harmful to
humans, animals and plants, and therefore must be removed to keep our air
clean. Domestic sewage, the most common source of pollution of water bodies,
reduces dissolved oxygen but increases biochemical oxygen demand of receiving
water. Domestic sewage is rich in nutrients, especially, nitrogen and
phosphorus,
which cause eutrophication and nuisance algal blooms. Industrial
waste waters are often rich in toxic chemicals, especially heavy metals and organic
compounds. Industrial waste waters harm living organisms. Municipal solid
wastes also create problems and must be disposed of in landfills. Disposal of
hazardous wastes like defunct ships, radioactive wastes and e-wastes requires
additional efforts.
Soil pollution primarily results from agricultural
chemicals (e.g., pesticides) and leachates from solid wastes deposited over it.Two
major environmental issues of global nature are increasing greenhouse effect,
which is warming Earth, and depletion of ozone in the stratosphere. Enhanced
greenhouse effect is mainly due to increased emission of carbon dioxide,
methane, nitrous oxide and CFCs., and also due to deforestation. It may
drastically change rainfall pattern, global temperature, besides deleteriously affecting living organisms.
Ozone in the stratosphere, which protects us from harmful
effects of ultraviolet radiation, is depleting fast due to emission of CFCs
thus increasing the risks of skin cancer, mutation and other disorders.
MOLECULAR BASIS OF INHERITANCE
Nucleic acids are long polymers of nucleotides. While DNA
stores genetic information, RNA mostly helps in transfer and expression of
information.
Though DNA and RNA both function as genetic material, but
DNA being chemically and structurally more stable is a better genetic material.
However, RNA is the first to evolve and DNA was derived from
RNA. The hallmark of the double stranded helical structure of DNA is the
hydrogen bonding between the bases from opposite strands. The rule is that Adenine
pairs with Thymine through two H-bonds, and Guanine with Cytosine through three
H-bonds. This makes one strand complementary to the other. The DNA replicates
semi onservatively, the process is guided by the complementary H-bonding. A
segment of DNA that codes for RNA may in a simplistic term can be referred as gene.
During transcription also, one of the strands of DNA acts a template to direct
the synthesis of complementary RNA. In bacteria, the transcribed mRNA is
functional, hence can directly be translated.
In eukaryotes, the gene is split. The coding sequences,
exons, are interrupted by non-coding sequences, introns. Introns are removed and
exons are joined to produce functional RNA by splicing. The messenger RNA
contains the base sequences that are read in a combination of three (to make
triplet genetic code) to code for an amino acid. The genetic code is read again
on the principle of complementarity by tRNA that acts as an adapter molecule.
There are specific tRNAs for every amino acid. The tRNA binds to specific amino
acid at one end and pairs through H-bonding with codes on mRNA through its anticodons.
The site of translation (protein synthesis) is ribosomes, which bind to mRNA
and provide platform for joining of amino acids. One of the rRNA acts as a
catalyst for peptide bond formation, which is an example of RNA enzyme
(ribozyme). Translation is a process that has evolved around RNA, indicating
that life began around RNA. Since, transcription and translation are
energetically very expensive processes,
these have to be tightly regulated.
Regulation of transcription is the primary
step for regulation of gene expression.
In bacteria, more than one gene is arranged together and regulated in units
called as operons. Lac operon is the prototype operon in bacteria, which codes for
genes responsible for metabolism of
lactose. The operon is regulated by the amount of lactose in the medium where
the bacteria are grown.
Therefore, this regulation can also be viewed as regulation
of enzyme synthesis by its substrate.
Human genome project was a mega project that aimed to
sequence every base in human genome.
This project has yielded much new information.
Many new areas and avenues have opened up as a consequence of the project. DNA
Fingerprinting is a technique to find out variations in individuals of a
population at DNA level. It works on the principle of polymorphism in DNA
sequences. It has immense applications in the field of forensic science, genetic
biodiversity and evolutionary biology.
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