BIOLOGY

THE FUNDAMENTAL UNIT OF LIFE

∙ The cell is the basic structural and fundamental unit of life.

I. Who Discovered Cell and How?

∙ Cell was discovered by Robert Hooke in 1665, he observed the thin slice of cork (the bark of a tree) and found

little rooms in the structure of a honeycomb. Later on, they were known as cells.

∙ Cell theory was proposed by J.M. Schleiden and T. Schwann in 1838-39.

∙ The cell theory was further expanded by R. Virchow (1855) by stating, “Omnis Cellula e Callula” which means all

cells arise from pre-existing cells.

∙ Purkinje in 1839 coined the term for the fluid substance of the cell, “protoplasm”.

∙ The scientist Robert Brown discovered the nucleus of the cell.

II. Classification of organisms:

On the basis of number of cells present in organisms, they are classified into two categories.
1. Unicellular Organisms: The organisms which are made up of single cells and perform all the essential
activities of life. A single cell may form a whole organism as in Amoeba, Paramecium, Chlamydomonas and
Bacteria, etc.
2. Multicellular Organisms: The organisms which are made of a group of cells and perform different function
to sustain the life organism is called multicellular organisms. Fungi, plants, and animals are multicellular
organisms.

III. Types of cells:

A. Various cells of the human body vary in structure according to their function. Based on origin and cellular
structure, there are two types of cells.
1. Prokaryotic cells
2. Eukaryotic cells

S.no Features Eukaryotic cell Prokaryotic cell

(i) Size Generally large(5-100µm) Generally small (1-10µm)

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 (ii) Nucleus They have a well-defined nucleus. A well-defined nucleus is absent.
They have nuclear material called
nucleiod.
(iv) Cell wall Present in plant and fungal cells, It is made up of peptidoglycan.
while absent in animal cells.
(v) Cell organelles Membrane-bround cell organelles are Membrane-bound cell organelles are
present. absent.
(vi) Chromosomes Single or multiple chromosomes are A single chromosome is present.
present
B. The differences between plant cells and animal cells are listed below:

Plant cell Animal cell

1. A plant cell is surrounded by a rigid cell wall. 1. An animal cell does not have a cell wall.
It is made up of cellulose.
2. The presence of a large vacuole is seen in 2. Whereas there are very small vacuoles as
plant cells. compared to plant cells are seen in animal cells.
3. Larger in size. 3. Smaller in size.
4. Plant cells have plastids. 4. Animal cells do not have plastids.
5. Centrosomes are absent in plant cells 5. Animal cells have centrosomes.
6. Plant cells do not have cilia. 6. Animal cells have cilia.
7. Lysosomes are very rare in plant cells. 7. Animal cells have lysosomes.

IV. The Shape of the Cell

∙ The shape and size of cells are related to the specific function they perform. Some cells like Amoeba have

changing shapes while in some cases, cell shape could be more or less fixed. For example: nerve cells.

∙ Every cell has a certain specific component within it known as a cell organelle. These organelles carry out some

very important functions in cells, e.g. making new cell organelle, clearing up waste material from cells, and so on.

V. The Structure of Cell: Each cell is divided into three functional regions –
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(i) Plasma/cell membrane
(ii) Nucleus
(iii) Cytoplasm.
All activities inside and outside of the cell are possible due to these features.

(i) Plasma Membrane:

∙ It is the outermost covering of the cell.

∙ It permits the entry and exit of some materials so it is called a selectively permeable membrane.

∙ It helps in osmosis and diffusion.

∙ It is made up of lipids and proteins.

Transport of substances:
Transport of substances across the plasma membrane can vary depending upon the requirement of cellular energy.
Types of transport are below:

♦ Diffusion: It is the movement of substances from high concentration to low concentration. For instance, exchange

of gases through stomata some substances like carbon dioxide or oxygen can move across the cell membrane
by diffusion.

♦ Osmosis: It is the movement of water molecules from a region of higher concentration to a lower concentration

through a semipermeable membrane. The movement of water molecules by osmosis is a special case of
diffusion. It could be endosmosis or exosmosis.

Endosmosis: Endosmosis is the movement of solvent into the cell.

Exosmosis: Exosmosis is the movement of solvent out of the cell.

Endoosmosis and exosmosis processes take place on the basis of a concentration gradient.
There are three types of solution on the basis of concentration:

(i) Isotonic solution (ii) Hypotonic solution (iii) Hypertonic solution

If a cell is placed in a medium If a cell is placed in a medium If a cell is placed in a medium
that has exactly the same water surrounding the cell that has a that has a lower concentration of
concentration as the cell, there higher water concentration than water than the cell, then the water
will be no net movement of water the cell, i.e. the outside solution is will move outside and the cell
across the cell membrane. Such a very dilute, and then the water will lose water by exosmosis.
solution is known as an isotonic enters the cell from the external Such a solution is known as a
solution. Water crosses the cell solution by endosmosis. Such a hypertonic solution.
membrane in both directions, but solution is known as a hypotonic In this, the cell will shrink.
the amount going in is the same solution.

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 as the amount going out, so there In this, the cell is likely to swell
is no overall movement of water. up.
The cell will stay the same size.

♦ In addition to the plasma membrane, plants have another rigid outer covering called a cell wall.

It is made up of cellulose. In fungus, it is made up of chitin.

(ii) Nucleus: It has a double-layered nuclear membrane having nuclear pores for the transfer of material and
chromosomes. The chromosomes contain information for the inheritance of features from parents to the next
generation in the form of DNA and protein molecules.
The functional segments of DNA are called genes.

(iii) Cytoplasm: It is a fluid content inside the plasma membrane. It contains many special cell organelles. The
nucleus and cytoplasm are together called protoplasm. It stores important chemicals such as amino acids,
glucose, vitamins, and iron, etc.

VI. Cell organelle:

To keep the cells alive and functional, a different part of the cell carries different functions. These parts are said to
be cell organelles.

∙ Various cell organelles are as follows :

(i) Endoplasmic Reticulum (ER): ER is a large network of membrane-bound tubular structures scattered in the
cytoplasm. It is often termed as a system of the membrane. There are two types of Endoplasmic Reticulum –
Rough or Smooth. RER has ribosomes on its surface. It helps in protein synthesis. SER helps in the
manufacturing of fat molecules or lipids.

(ii) Golgi Apparatus: It was first designed by Camillo Golgi. It consists of membrane-bound, fluid-filled vesicles
arranged parallel to each other in stacks called cisterns.
It helps in the storage modification and packaging of products in vesicles. It is also involved in the formation of
lysosomes.

(iii) Lysosomes: These are membrane-bound sacs filled with digestive enzymes. It helps in removing any dead or
old worn-out cell organelles by digesting them and making space for new organelles. During the disturbance in
cellular metabolism, e.g. when the cells get damaged, lysosomes may burst and release the powerful digestive
enzymes which digest their own cell. Lysosomes are called suicide bags of cells.

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 (iv) Mitochondria: It is known as the powerhouse of the cell. The energy required for various chemical activities
needed for life is released by mitochondria in the form of ATP molecules.
Mitochondria have double membranes called the outer and inner membranes. Mitochondria have their own DNA
and ribosomes.

(v) Plastids: Plastids are found only in plant cells. These are of two types –
(a) Chromoplast (coloured) and (b) Leucoplast (colourless).
The most important chromoplasts are chloroplast which contain green pigment called chlorophyll.
It helps in the synthesis of food in plants by photosynthesis.
Plastids also have their own DNA and ribosomes.

(vi) Vacuoles: These are fluid or solid-filled membrane-bound sacs in the cytoplasm. In animal cells, they are
small but in plant cells, a single, prominent large vacuole is present.
Many important substances for the life of plants are stored in vacuoles.
It is helpful in expelling excess water.

VII. Cell Division:

There are two types of cell division – Mitosis and Meiosis.
The process in which most of the cells divide for growth is called mitosis.

The process that produces four new cells instead of just two, is called meiosis.

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 Class-9

SHORT NOTE
TISSUES
● A group of cells that are similar in structure and/or work together to achieve a particular function forms a tissue.
● Study of tissues: Histology
● Types of tissues: 1. Plant tissues 2. Animal tissues

PLANT TISSUES ANIMAL TISSUES

Dead and supportive living

Based on the dividing capacity of tissues, various Cell growth in animals is more uniform. So, there
plants can be classified as growing or meristematic is no such demarcation of dividing and nondividing
tissue and permanent tissue. regions in animals.

PLANT TISSUES:
On the basis of the dividing capacity, plant tissues are of two types:
1. Meristematic tissues
2. Permanent tissues

● Meristematic tissues: Consist of actively-dividing cells present on certain specific regions.

Depending on the region where they are present, meristematic tissues are classified as:

1. Apical meristem: Present at the growing tips of stems and roots.

Function: To increase the length of stems and roots.
2. Lateral meristem: Present at the base of leaves or internodes.
Function: For the longitudinal growth of plants.
3. Intercalary meristem: Present on the lateral sides of the stems and roots.
Function: To increase the thickness of stems and roots.

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● Permanent tissues: Meristematic tissues take up a specific role and lose the ability to divide and form permanent
tissues.
● This process of taking up a permanent shape, size, and a function is called differentiation
Permanent tissues are of two types:
1. SIMPLE PERMANENT TISSUES: Consist of only one type of cell.
● Simple permanent tissues are of three types:

PARENCHYMA COLLENCHYMA SCLERENCHYMA

Most common and living cells. Composed of living and elongated Composed of dead cells
cells,present in leaf stalks below the
epidermis.

Unspecialised cells with thin cell cell walls irregularly thickened at the long, narrow, and thick-walled
walls. comers. cell due to presence of lignin.

Large intercellular spaces. No intercellular space. no intercellular spaces.

generally stores food. mechanical support and flexibility in ● present in stems, around
plants vascular bundles, in the
veins of leaves and in the
hard covering of seeds and
nuts.
● It provides strength to the
plant parts.

2. COMPLEX PERMANENT TISSUES: Made up of more than one type of cells (Conducting tissues).
● Types of complex permanent tissues:
1. Xylem: Conducts water and minerals from the roots to the different parts of the plant.
● consists of tracheids, vessels, xylem parenchyma and xylem fibres.
● Tracheids and vessels have thick walls, and many are dead cells when mature.
● Tracheids and vessels are tubular structures. This allows them to transport water and minerals vertically.
● The parenchyma stores food.
● Xylem fibres are mainly supportive in function.

2. Phloem: Conducts food material from the leaves to the different parts of the plant.
● Phloem is made up of five types of cells: sieve cells, sieve tubes, companion cells, phloem fibres and the phloem
parenchyma.
● Sieve tubes are tubular cells with perforated walls
● Except phloem fibres, other phloem cells are living cells.

ANIMAL TISSUES:
Animal tissues are classified into four types based on the functions they perform:
1. Epithelial tissue 2. Connective tissue 3. Muscular tissue 4. Nervous tissue

1. EPITHELIAL TISSUE: Form the covering of the external surfaces, internal cavities and organs of the animal body.
● Epithelial tissue cells are tightly packed and form a continuous sheet.
● Various types of epithelial tissues are:
1. Simple squamous epithelium: Single layer of flat cells.
Location in the human body: Lining of the mouth, oesophagus, lung, alveoli, etc.
2. Cuboidal epithelium: Consists of cube like cells.
Location in the human body: Lining of the kidney tubules and ducts of the salivary glands.
Function: secretion and absorption.
3. Columnar epithelium: Consists of elongated or column-like cells.
Location in the human body: Inner lining of the intestine and gut. Function: secretion and absorption.
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2. CONNECTIVE TISSUE: Specialised to connect various body organs.
● Areolar tissue: Found in the skin and muscles, around the blood vessels, nerves, etc.
● Adipose tissue: Acts as the storage site of fats; found between the internal organs and below the skin; acts as an
insulator for the body.
● Dense regular connective tissue: Main components are tendons and ligaments; tendons connect muscles to bones,
while ligaments connect two bones together.
● Skeletal tissue: Main components of skeletal tissues are cartilage and bone.
● Fluid tissue: Blood is the vascular tissue present in animals.

3. MUSCULAR TISSUE: consists of elongated cells, also called muscle fibres.

● responsible for movement in our body.
● Muscles contain special proteins called contractile proteins, which contract and relax to cause movement.

● Three types of muscles fibres are there namely:

SKELETAL/STRIATED MUSCLE SMOOTH/UNSTRIATED CARDIAC MUSCLE
MUSCLE

mostly attached to bones and help in body Cells are long, spindle-shaped and The muscles of the heart
movement. possess a single nucleus. show rhythmic
contraction and relaxation
throughout life.

Striations present Striations absent. Striations present.

long, cylindrical, unbranched and found in the iris of the eye, in ureters cylindrical, branched and
multinucleate (having many nuclei) and in the bronchi of the lungs uninucleate.

Voluntary Involuntary Involuntary

4. NERVOUS TISSUE:

● Neuron is the structural and functional unit of the nervous system.

● cells of the nervous tissue are highly specialised for being stimulated and then transmitting the stimulus very rapidly
from one place to another within the body.
● A neuron consists of a cell body with a nucleus and cytoplasm, from which long thin hair-like parts arise.
● Usually each neuron has a single long part (process), called the axon, and many short, branched parts called
dendrites.
● The signal that passes along the nerve fibre is called a nerve impulse.
● The functional combination of nerve and muscle tissue is fundamental to most animals.
● This combination enables animals to move rapidly in response to stimuli.

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 Class 9th

BIOLOGY
IMPROVEMENT IN FOOD RESOURCES
IMPROVEMENT IN FOOD RESOURCES
(i) Food is the basic necessity of all living organisms. Food supplies proteins , carbohydrates, fats, vitamins and
minerals, all of which are required for body development, growth and health. The major sources of our food are
plants and animals.
(ii) Agriculture and animal husbandry provide us with all our animal and plant food.
(iii) Agriculture is the practice of growing of plants in an organised way for obtaining food.
(iv) To feed the ever growing population in India more food is required to be produced.This can be done by farming
on more land. But India is already intensively cultivated. As a result, we do not have any major scope for
increasing the area of land under cultivation. Therefore, it is necessary to increase our production efficiency for
both crops and livestock.
(v) The green revolution has contributed in creasing the food grain production, the white revolution has led to better
availability of milk.

IMPROVEMENT IN CROP YIELDS

(i) Food crops give us carbohydrates, proteins, fats, vitamins and minerals.
(ii) Pulses like gram, pea, pigeon pea, lentil, provides with proteins.
(iii) Oil seeds including soybean, groundnut, sesame, castor, mustard, linseed and sunflower provide us with
necessary fats.
(iv) Vegetables, spices and fruits provide a range of vitamins and minerals in addition to small amounts of proteins,
carbohydrates and fats.
(v) Fodder crops like berseem and oats are raised as food for the livestock.
(vi) The optimum requirement of temperature, water, sunlight, and other conditions varies for different crops for
growth and completion of their life cycle.
(vii) Activities like crop variety improvement, crop production improvement and crop protection and management
help to increase the crop yields.

Crop Variety Improvement

• The main aim of this practice is to find a variety of crops which can withstand different environmental conditions
like high soil salinity, water availability etc., and can give a good yield.

• Hybridisation and genetic modification techniques introduce the useful or desired characters into the crop plants.
This helps the plants to survive and give good yields in different climatic conditions and areas.

Hybridisation refers to crossing between genetically dissimilar plants to produce new type (hybrid) or high yielding
varieties. This crossing may be intervarietal (between different varieties), interspecific (between two different species
of the same genus) or intergeneric (between different genera).

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Genetic modification involves the introduction of a gene (i.e., DNA fragment) that would provide the desired
characteristic. This results in genetically modified crops.
(i) Increased yield
(ii) Improved quality
(iii) Resistance to biotic and abiotic factors, especially those harming the plant.
(iv) Reduction in duration of plant maturity.
(v) Broad range adaptability of the crop plant from various environmental conditions.
(vi) Desired agronomic characteristics particular to a plant.

Variety improvement may be done for one or several of these characteristics.

Crop production management
Production of crops can be improved by practising different cropping patterns, by adding nutrients and manure
required for growth and by proper irrigation of crops.

Cropping patterns
(i) High yields from farms can be obtained by undertaking scientific management practices like mixed farming,
intercropping and crop rotation.
(ii) In mixed cropping, two or more crops are grown together on the same field. For example, wheat+ gram,
groundnut + sunflower. This reduces risk and gives some insurance against failure of one of the crops.
(iii) In intercropping, two or more crops with different nutritional requirements are grown in different rows on the
same farm in a definite row pattern (1:1, 1:2 and 1:3). So as to utilise maximum nutrients and prevent spread of
diseases and pests. For example, soybean + maize, bajra + cowpea.

(iv) In crop rotation, different crop combinations are grown on the same field in a pre-planned succession so as to
get maximum returns.

Nutrients
Nutrients are important for the growth of plants which are supplied to them by air, water and soil.
Macro-nutrients Micro-nutrients

They are needed in large amount by the plants They are required in small quantities such as iron,
which include carbon, hydrogen, oxygen, nitrogen manganese, boron, copper, molybdenum, chlorine
phosphorus, potassium, calcium, magnesium and and nickel
sulphur.

Manures
It is obtained from decaying plant matter such as straw, animal dung etc, by the action of microorganisms present in
the soil.
It is classified into three categories on the basis of types of biological materials used which are as follows:

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 Green manure Compost Vermi-composting

(i) Before sowing seeds of (i) It includes farm wastes (i) The process by which
crops, some plants like like livestock excreta (cow compost is prepared by the
leguminous and non- dung), leftover vegetable, decomposition of plant
leguminous plants are - domestic waste, sewage and animal refuse with the
grown. waste, straw, eradicated help of earthworm is called
(ii) They are then mulched by weeds, etc. vermi-composting.
ploughing into the soil. (ii) These substances are (ii) The compost is ingested by
These plants thus turn into decomposed in pits and the the earthworms and then
green manure which helps process of decomposition excreted out which makes
in enriching the soil in is called composting. the compost rich in
nitrogen and phosphorus (iii) The compost is rich in nutrients.
content. organic matter and nutrients

Advantages and disadvantages of manure

Advantages Disadvantages

(i) It helps in enriching the soil with nutrients. (i) The amount of nutrients present in manures
(ii) It consists of humus that restores the texture is less which is not sufficient to fulfill the
of soil for better retention of water. requirement of the crops.
(iii) It is eco-friendly. (ii) Their storage and transportation is not
convenient because of their billy nature.

FERTILIZERS
It is a chemical which consists of salt and other organic compound necessary for plant growth.
Advantages Disadvantages

(i) Plants absorb them as they are water soluble (i) It can lead to soil and water pollution as
and nutrient specific. through rain it seeps deep into the soil.
(ii) Its transportation and storage is easy as it is (ii) Long term use of fertilizers can reduce the
required in small quantities. fertility of soil by changing its texture.

Irrigation is the process of supplying water to crop plants, in fields by different means of irrigation system.
Wells, canals, rivers and tanks are some important irrigation systems in our country.

(i) Wells: There are two types of wells, namely dug wells and tube wells. In a dug well, water is collected from water
bearing strata. Tube wells can tap water from the deeper strata. From these wells, water is lifted by pumps for
irrigation.

(ii) Canals: This is usually an elaborate and extensive irrigation system. In this system, canals receive water from one or
more reservoirs or from rivers. The main canal is divided into branch canals having further distributaries to irrigate
fields.

(iii) River Lift Systems: In areas where canal flow is insufficient or irregular due to inadequate reservoir release, the lift
system is more rational. Water is directly drawn from the rivers for supplementing irrigation in areas close to rivers.

(iv) Tanks: These are small storage reservoirs, which intercept and store the run-off of smaller catchment areas.

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CROP PROTECTION MANAGEMENT
It includes methods to reduce the different kinds of infestation caused by weeds, pests and insects.
Weeds, pests and disease can destroy large amounts of crop plants.
Weeds removal from the crop fields is essential since they use up the requirements of crop plants like food, space,
light etc.
Insect pests and plant pathogens attack different parts of the plant in three different ways and thus, reduce crop yield.
(i) They cut the root, stem and leaf.
(ii) They suck the cell sap from various parts of the plant.
(iii) They bore into stem and fruits and reduce yields.
→ Diseases in plants are caused by pathogens such as bacteria, fungi and viruses. These pathogens can be
transmitted through the soil, water and air.

Weeds, insects and diseases can be controlled by various methods:

• One of the most commonly used methods is the use of pesticides which include herbicides, insecticides and
fungicides. They are used to control weeds, insects and diseases, but they should be used only as much as needed
to avoid environmental pollution and health hazards.
• Weed control methods also include mechanical removal.
• Preventive methods such as proper seedbed preparation, timely sowing of crops, intercropping and crop rotation
also help in weed control.
• Some other preventive measures against pests are the use of resistant varieties, and summer ploughing, in which
fields are ploughed deep in summer to destroy weeds and pests.

ANIMAL HUSBANDRY
1. It is the scientific management of animal livestock. It is animal based farming of cattle, goat, sheep, poultry and fish
farming.

2. Management of livestock includes various aspects such as animal’s shelter, feeding, breeding, health and disease
control.

CATTLE FARMING
It is mainly done for two purposes.
(i) For obtaining milk from dairy animals.
(ii) For using draught animals in agriculture and transport purposes.
Milk production depends on lactation period and thus, long lactation period is a desirable quality to consider during
cattle farming. Hence, exotic breeds ( e.g., Jersey, Brown Swiss) showing long lactation periods are crossed with
local breeds(e.g., Red Sindhi, Sahiwal) showing resistance to disease to obtain high quality breeds.
In cattle farming, the cattle shelter should be well ventilated, hygienic and dry.
Cattle food should include roughage and concentrate in balanced amounts.

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 Cattle suffer from a number of diseases. These diseases are caused by bacteria, virus, and parasites. This affects the
health of the cattle and also affects the milk production.

Poultry farming
It includes housing, rearing, sanitation, disease-control and marketing of poultry birds.
This type of farming targets egg production from layers( egg laying poultry) and meat production from broilers(
poultry reared for obtaining meat).

Cross-breeding is done between the Indian or indigenous (e.g., Aseel) and foreign (e.g., Leghorn) breeds of poultry
to obtain a large number of improved varieties of poultry containing desirable traits such as tolerance to high
temperature, dwarf broiler parent, low maintenance requirements and reduction in size of the layers.

Broilers chickens are fed with vitamin-rich supplementary feed (vitamin A and K) for good growth rate and better
feed efficiency.

Poultry birds are needed to be protected from various disease caused by bacteria, fungi, viruses, parasites or due to
nutritional deficiencies, through proper treatment, sanitation and vaccination.

Fish production
It refers to capturing and culturing of fish as a source of edible animal protein for us. It is a cheap source of animal
protein.
There are two ways of obtaining fish. One is from natural resources, which is called capture fishing. The other way
is by fish farming, which is called culture fishery.

Fish culture can be done either in marine or in freshwater ecosystems.

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Types of fisheries
(i) Marine
These are caught using modern as well as traditional methods. Traditional methods include the use of nets and gears
while modern methods include use of satellites to locate the fishes.
It includes sardines, Mackerel, Hilsa, Tuna, pomfret, mussels, prawns, oysters, salmon, mullets, seaweed etc.

(ii) Inland
When fishing is done in freshwater bodies, like lakes, ponds, rivers, and tanks it is called fisheries.
Common varieties cultivated are Rohu, Catla, Grass carp, Common carp etc.

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Composite culture
Intensive fish farming can be done in composite fish culture system. Both local and imported fish species are used in
such systems. In this systems, five to six species can be cultured in a single fishpond. The species that are selected
has different food habits so that they do not compete for food among themselves. Catlas are surface feeders, Rohu
feeds in the middle zone of the pond, Mrigal and common carps are bottom feeders and grass Carps feed on the
aquatic weeds.
Advantages Disadvantages

(i) The fishes do not compete for food. (i) It is difficult to recognize which seed belongs
(ii) The food available in all the part of the pond to which species.
is used. (ii) Some fishes rear only during monsoon.
(iii) Five to six different types of fishes are reared (iii) Lack of availability of good quality seeds.
together.
(iv) This method increase the yield.

Bee-keeping
(i) The practise of bee-keeping is known as apiculture. It is low investment activity which involves rearing, care
and management of honey bee for obtaining honey, wax etc. For commercial honey production, apiaries or bee
farms are established.

(ii) Indigenous bee varieties are Apis cerana indica(Indian bees), Apis dorsata ( rock bee) and Apis florea ( little
bee) whereas Apis mellifera is an Italian variety used for commercial production of honey.

(iii) The availability of sufficient amount of pasturage as well as the type of flowers available to the bees for nectar
and pollen collection determines the quality and taste of the honey.

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