BIO(Ecosystems)

                   Ecosystems

         Let us discuss these questions

What is a habitat?

Is a tree habitat only for a crow?

In what way an ecosystem is different

from habitat?

We found that there were differences

between the ecosystems of land and water

and different ecosystems on land and water

as well. We can see differences within

ecosystems in very small areas as well.

We have studied in the chapter 'habitat' about 

the variations in the living

communities, as well as organisms

present at different levels, in the pond

ecosystem and the tree. In this chapter we

will see how organisms have started

inhabiting certain areas, what needs they

have and how they acquire different

conditions from their surroundings to meet

them.

                   Mangroves

To adjust themselves to diverse and

distinct changes in ecosystems, organisms

have to adapt different means for better

survival. For example, some trees such as

Mangroves like Avicennia have evolved a

curious way to deal with the problems of

growing in a wet and salty place. They have

evolved to have curious looking

These “knees” (aerial roots) develop

from the lateral roots that are growing near

the surface, and protrude up to 12 inches

out of the soil or sediment. The precise

function of these “knees” is not definitely

known, but there is general agreement that

they aid the plants in maintaining adequate

root respiration in a watery environment.

We do not find such structures in plants

growing around us.

All such ways and means that organisms

adopt or develop over a certain period of

time in different conditions for better

survival are adaptations of organisms. We

may also say that adaptation is a feature that

is common in any population because it

provides some improvements for better

survival.

Activity-1:

Take a  Aloevera and a

Balsam plant in two separate pots. Water

each of them with two tablespoons of water.

Do not water them for a week. Observe

the condition of the plants after a week.

Which plant showed growth?

Which plant dried first? Why?

Activity-2:

Collect an aquatic plant out of a water

body( Eg. Duck weed, Hydrilla, Vallisneria

etc. either floating at the surface or

propping out of it). Carry it back home and

plant it in a pot and water it.

What do you observe? Compare

your observation with that of

activity1 and write a note on what

you find.

From the above activity we see that

some plants dry up without water very

quickly, while others can grow even with

very little water. Each of these plants are

adapted to the conditions in their

surroundings on the basis of need of water.

What is meant by adaptations?

Describe your opinion.

Organisms in nature create adaptable

situations around them on the basis of their

needs. They also adapt to situations

specifically. For example in Opuntia, the

leaves are reduced to spines so that

transpiration loss is checked and water is

stored in the tissues of the stem (succulent

stems). This helps the plant to live in

conditions of water scarcity as we come

across, in deserts. Aloe vera are found in

our surroundings these days as well but you

may have heard that they are generally called

as desert plants (xerophytes).

                Opuntia

                  Baobab

                 Cactus

Though these are called Living stones they are not stones. The

swollen leaves are adapted to desert conditions, minimizing water

loss and storingwater. These are also called Pebble Plants . Each pebble is actually a leaf with a cut window that lets in light. The stone like appearance deceives the animals and saves it from being eaten. Now a days, many Xerophytes aregrown as ornamental plants in pots at homes. Some plants as a whole seem to be flowers. Some with thorns, some have flowers with bright colour petals. Now a

days these kind of plants are used as gifts for Birthdays and other occasions also.

     

             Pebble plant

Adaptations in some more desert animals

The Side-Winder adder snake crawls

sideways with only a small amount of its

body pressed against the hot sand. This

technique helps it to keep itself cool. The

Golden Mole escapes the heat of the sun

by swimming through the sand just below

the surface. It rarely emerges out as it finds

all the needs below the ground

Some animals show extraordinary

ability to survive in the desert. The

Kangaroo Rat of western North American

desert can live without drinking water

through out its life. Because its body

synthesizes little water in the process of

digestion. The desert bird the Sand grouse

flies long distances to an oasis in search

of water, which it carries back in its crop

for its nestlings.

The furry soles of Fennec Fox helps it

walk on hot sand and loses heat through its

ears. When the sand becomes too hot the

sand diving lizard holds its feet in the air to

cool down.

            Rattle snake

              Sandgrouse

 

Adaptations in Aquatic ecosystems:

We shall study two different types of

ecosystems in water (aquatic ecosystems)

and some conditions in the environment that

influence adaptations.

Aquatic ecosystems are mainly

classified into two different types as Fresh

water and Marine ecosystems.

Ponds, Lakes, Rivers are the examples

of Fresh water Ecosystems

Seas, Oceans are the examples of

Marine Ecosystems

As the living conditions are different

we come across various adaptations in

several organisms living in these ecosystems.

General aquatic adaptation as can be

seen structurally (in body structure) are

like presence of some special air spaces

inside bodies or presence of such

substances that help organisms to swim and

float in water to inhabit different levels in

the water body, or bear specialized

structures to swim like flippers as in Turtles

and fins in fishes. Fishes, Dolphins etc have

floaters in their body (special structures of

their digestive canals) to be able to inhabit

particular levels in the water body.

Microscopic photosynthetic organisms

like planktons have droplets of oil in their

cells that keeps them float. Larger plants 

have long tough leaves and flexible stems.

Marine ecosystem:

Over the last 2,000 million years, plant

and animal life on earth has continuously

evolved from its simple beginnings in the

oceans to the complex existence on land

today. It is no accident that protoplasm, a

substance found in every living cell,

strongly resembles seawater. Although

some animals emerged from the sea

millions of years ago to fill all available

places on land, some remained in the ocean

and evolved and adapted to life beneath the

surface.

The ocean covers a larger part of the

planet, yet it remains a little understood

place as scientists have limited scope for

the study of habitats that lack physical

boundaries and a span of thousands of

miles.

Adaptations on the basis of light

penetration:

Euphotic zone

The organisms living in this zone are

mostly floaters and swimmers. Animals in

this zone usually have shiny bodies

reflecting light away to merge with shiny

water surface are transparent. These usually

have very sharp vision. Plants are mostly

green and photosynthetic activity is

maximum in this zone. Some flora and

fauna of this zone are trouts, herrings,

dolphins, jelly fishes, different type of coral

colonies which are extremely colourful,

different types of algae & sea grasses

(emergent plant species: rooted to the

sides, in marine ecosystems these are

rooted in the continental shelf area)

diatoms etc. Nearly 80% of marine flora

and fauna are found in this zone.

        Coral colonies

Bathyal zone:

Most of the plants found in this zone

are the red and brown kelps, sponges, corals

even animals with tubular bodies like

squids and large animals like whales etc.

Some of these have a flat body like the ray

fishes. They may have big eyes sensitive to

very dim light

                Ray fish

Abyssal zone:

These zones are

dark and cold

throughout the year.

Photosynthetic activity

is absent. Deep sea

animals are mostly

predators and

scavengers. The larger

forms have wide

mouths and huge curved teeth which prevent

escape of any prey. Absence of skeleton,

flattened bodies are some other

characteristics observed. Some also have

special structures that produce light on their

bellies, around their eyes(which are usually

nonfunctional that is, the organisms are

blind) and at the sides of their bodies, some

animals glow (shows bio luminiscence) in

the darkness of deep waters

              Angular fish

               Brittle Star

Freshwater Ecosystems:

Fresh water ecosystems are stagnant water types as well as running water types. They may vary in size from as small as a puddle and pond to a large lake, river etc. Just like the marine ecosystems, to

study environmental conditions in lakes, some zones are marked. The Littoral zone, Limnetic zone and Profundal zones on the

basis of light penetration. Based on availability of light different kinds of organisms are found in these zones. Different factors like light, salt content, food, oxygen affect the organisms and their

populations in different ways.

Littoral zone: The shallow zone near

the shore is also called as littoral zone. The

water near the shore is usually muddy or

turbid. This topmost and warmest zone at

the edge of a water body is home to Snails,

Clams, Insects, several Crustaceans, Fishes

and Amphibians and the eggs and larvae of

Dragonflies etc.

Several organisms in this zone have

well developed sight, usually have dull and

greyish bodies and are fast swimmers.

Plants like Mosses, Water lily, Vallisneria,

Hydrilla etc are found here along with

several types of algae. High photosynthetic

activity occurs in this zone. Predators of

this zone are Tortoise, Snakes and Ducks.

The limnetic zone is the open water

zone at the top of the water body and

consequently receives a good deal of light.

This zone contains a variety of freshwater

fish with bright shiny, greyish or silver

black scales that help them to merge with

the surroundings. Transparent or whitish

bodied crustaceans like Daphnia, Cyclops,

small Shrimps are also found in this zone.

There are different types of floating plants

like Water hyacinth, Wolffia, Pistia along

with a variety of algae. 

The profundal zone is dimly lit and

cold. Mostly heterotrophs (saprochytes -

microbes that decompose dead organisms)

are found in this region. Most of the

animals, the so called bottom dwellers, that

live here are mostly scavengers and

predators, for example Crustaceans, Crabs,

Fishes like Eels and Glossogobius (isika

dondu), Snails, Turtles etc. They adapt

themselves by feeding on dead animals that

settle down. Many kinds of bacteria

(detritus) thrive here that help in

decomposing the dead organisms. Mud of

the bottom floor, tiny particles of dead and

decaying matter of plants and animal bodies

make the water very turbid. Hence the

bottom dwellers , rely mostly on smell and

auditory (related to hearing) senses rather

than vision to aquire their food.

Adaptations in some aquatic plants

Partially submerged plants have

numerous air spaces inside the stems

,leaves ,roots that aid in gaseous exchange

and buoyancy. Leaf bases of Water Hyacinth

(Eichhornia crassipes) form air filled

structures to keep them afloat. In water

lilies leaves are flat, have an oily surface

with stomata present on the upper surface

of the leaf, while incompletely submerged

plants like Hydrilla, stomata are absent,

leaves are thin, stems are highly flexible.

The main adaptations that give Hydrilla an

advantage over other native plants are: it

can grow at low light intensities, it is better

at absorbing carbon dioxide from the water

(diffuses into leaves), it is able to store

nutrients for later use, it can tolerate a wide

range of water quality conditions for

example salinity(can grow in saline waters

as well), and it can propagate sexually and

asexually.

Other examples of adaptations

Adaptation to temperature in plants

The effect of temperature on plants of terrestrial ecosystem can be seen in different ways. Do all plants shed their leaves at

same time in a year throughout the world. Some plants in

temperate regions shed their leaves before the winter starts. This is to minimize transpiration loss as well as reduce photosynthetic and other metabolic activities, as low temperature renders several chemicals inactive for some time. In tropical regions some plants

shed their leaves before the start of summer. Plants growing in hot climates, usually keep the stomata closed during the day to reduce transpiration loss. High temperatures also lead to adaptations like reduced leaf. Let us recall why xerophytic plants have modified stems and leaves.

          Adaptive Radiation in Galapagos Finches

Try to guess if there is any relation between type of food taken and the structure of beak. The seed eaters had thick and heavy

beaks. The fruit eaters had stubby beaks. The insect eaters had sharp and long beaks. . Darwin observed that these birds had adapted to their immediate surrounding for food and shelter and showed a lot of

variation even within the same species, especially with respect to the form of beaks. He made a sketch of the same as shown in the above. Thus he concluded that adaptation was something that an organism is undergoing continuously, even within very closely related forms in a particularly geographically separated area.

BIO(Agricultural Production)

                   Agricultural Production

                 

        How to increase the food

production?

        We know that the cultivated land is very limited. If we make use of plenty of land for cultivation some forests may be destroyed. This leads to environmental problems. So we need to think of another

solution. Observe the following solutions.

1. Increasing the area of cultivated land.

2. Increasing production in the existing

land.

3. Developing high yielding varieties.

4. Crop rotation

5. Cultivating Mixed crops.

6. Cultivating short term crops like Rabi.

       Which of the above option do you think

is more meaningful?

You have already learnt about long term

and short term crops or Kharif and Rabi

crops in your classes. Short term varieties

produce grains more than long term

varieties.

Alternating of crops preserve the soil

fertility. Mixed crop system helps the

farmers to produce variety of crops as well

as increase in the production.

To get high yield 3 types of methods

are being used.

1. Developing high yielding varieties.

2. Using high yield management methods.

(Crop production management)

3. Crop protection management.

Improving high yielding crop varieties:

Observe the size and colour of maize in your kitchen. (if not, ask your mother why she doesnot purchase maize as a food material) Some seeds are small with yellow colour and some are large with white colour. The white coloured large ones are hybrid variety. They give high yield. Refer annexure for more information.

   

High yielding crop management methods:

(A) Irrigation:

An experiment was conducted to find out how irrigation affected the production of a crop. In the experiment, crops were grown in two fields. One field was irrigated while the other wasn’t. The same amount of nutrients, like nitrogen, was applied to both the fields.

What does a plant do with water?

We learned in the chapter ‘Nutrition in

plants’  that a plant absorbs water 

from the soil. What does it do with this

water? We know that the plant combines

water and carbon dioxide with the help of

sunlight to produce carbohydrates. Starch

is one such carbohydrate. Different types

of sugars and cellulose are also

carbohydrates. A chemical analysis will

show that 100 grams of water reacts with

260 grams of carbon dioxide to form 180

grams of carbohydrates.

But the plant roots do not use all the

water they absorb to produce

carbohydrates. Actually, most of this water evaporates into the air.

  Activity:

Take a polythene bag. Cover the bag on

leaves and tie it. Keep it 4-5 hours. You

observe it. What did you find in the

polythene bag? Where did they come from?

Do this experiment during day time and

night time separately. Note the differences

in your note book

If you tie a plastic bag over a leaf, you

will be able to see how much water a plant

releases into the air. It is estimated that a

plant uses only 0.1 percent of the water it

absorbs to form carbohydrate.

Water evaporates through these stomata.

We know that more water evaporates when

the weather is hot. In such a situation, the

stomata begin to close. This lessens the

amount of water that evaporates from the

leaves

We learned in the chapter ‘Nutrition in

Plants’ of that plants absorb

carbon dioxide. The carbon dioxide also

enters the leaves through the stomata.

When the weather is hot and the stomata

close, what effect would this have on

the absorption of carbon dioxide by the

plant?

What effect would a change in the

amount of carbon dioxide absorbed

have on the growth of the plant?

If the plant does not get water at this

time, what effect would this have on its

growth? Discuss in your class and find

out reasons.

Plants cannot absorb nutrients directly

from soil. Only the nutrient that dissolves

in water is absorbed by the roots of the

plant. We discussed about transportation of

substances in the chapter, “Transportation

of material across the cell membrane” and

in the chapter “Plant Cell”. Try to think of

how xylem and phloem are useful in

transportation.

Water is essential for Agriculture.

What are the main water sources in your

village for agriculture? How farmers

utilize them?

Paddy require more quantity of water.

Can you give such examples?

Cultivation of paddy, wheat and sugar cane

are suitable where places have rich water

resources. If we cultivate such crops by

irrigating them with water from wells and

bore wells what will happen?

Most of the farmers of our state

cultivate crops like paddy, sugar cane

irrespective of proper availability of water,

only because of supporting price and

marketing facility. So farmers invest more

on irrigation of water, electricity bills,

pesticides and fertilizers. Agriculture

Officers advise to cultivate dry land crops

(Aruthadi Pantalu) in less water areas and

follow different water management

practices.

Make a list of crops which require

less amount of water.

Drip irrigation is a good practice in

agriculture to prevent water wastage. In drip

irrigation, water is supplied through small

pipes. These pipes have small holes through

which water passes drop by drop.

 Soil Nutrients:

Nutrients present in the soil are

consumed by plants and are replenished or

returned to the soil in many different ways.

In nature the continuous process of death

and decay add nutrients to the soil and the

process is too slow to be commercially

useful. Rotating crops, adding organic

manure or chemical fertilizers etc. are man

made processes.

Crop rotation:

Usually, farmers do not grow only one

crop in a field. Different crops are grown

in different seasons. It has been seen that

cereal crops take a lot of nutrients from

the soil. Legumes are different. While they

do take nutrients from the soil, they also

provide some nutrients to it. Growing

leguminous crops result in an increase in

the quantity of nitrogenous salts in the soil.

Thus to grow a leguminous crop between

cereal crops is beneficial either by

crop rotation or by mixed cropping.

Nitrogen, Phosphorus and Potassium

are the important nutrients.

To avoid nutrient deficiency in the soil, farmers cultivate alternate crops. A farmer cultivated sugar cane in his land for the last five years. Another farmer cultivated sugarcane in the first year and soya bean in the second year and sugarcane in third year. In which case do you think has the land lost most of its nutrients? Crop rotation is the process in which one crop is followed by another crop on an

agricultural field. Some best combinations for crop rotation are given below. After cultivation of paddy, pulses/ groundnut has to be grown, followed by paddy again for cycle to continue. After cultivation of tobacco, mirchi has to be grown for the cycle to go on.

After cultivation of redgram, maize/ paddy has to be grown for the cycle to go on.

What is the benefit of crop rotation?

When cereals are cultivated more

nutrients are utilized. If legumes are grown

in the soil, less nutrients are utilized. Not

only this, they synthesize some nutrients

into the soil. Do you find any crop rotation

methods in your village? What are they?

Ask your village elders and collect the

information about it.

Cultivating mixed crops:

Have you ever seen two types of crops

in the same field?

Which crops are grown in this way?

What are the uses of cultivating mixed

crops?

Discuss in groups and display your

writings in your classroom.

If more than one crop is cultivated in

the same field then it is called mixed crop.

Because of mixed crop cultivation, the soil

becomes fertile. The nutrients which are

used by one crop will be regained by

cultivating another crop.

Which crops can be cultivated as mixed

crops? Observe the following...

Soya grown along with Pea

Pea grown along with Green gram

Corn grown along with Black gram

Groundnut grown along with Sunflower

Groundnut grown along with Red gram

Sorghum grown along with Pea.

         Haldi Plantation

                    Red Gram

      

 

      Peanuts and groundnuts

Is betel a mixed crop?

How can you justify your answer?
Can you name some leguminous crops?
Leguminous crops usually have many small
nodules on their roots. Several different
kinds of bacteria live in these nodules.
These bacteria absorb nitrogen from the air
and convert it into a form that can be used
by the plant. You will learn more about
nitrogen fixation in Bio-Geo-chemical
cycles.
Ask your teacher about names of the
nitrogen fixing bacteria.
You could uproot a Soya bean plant or
a Bengal gram plant to see the nodules on
their roots.

Root nodules in legume plants:

The microorganisms in the nodules use

some of the nitrogen for their own purpose.

Some nitrogen is used by the leguminous

plant itself. But after the crop is harvested,

the roots remain in the soil. So the soil gets

some nitrogen in this way.

Experiments have shown that a

leguminous crop gives about 50 kg to 150

kg of nitrogen per hectare. The crop grown

after the leguminous crop can take

advantage of the availability of more

nitrogen in the soil.

Nowadays a bacterial culture is also

available. This is mixed with the seeds.

When the seeds are sown, the plants are able

to produce more nodules on their roots.

Apart from this, there are various kinds

of blue-green algae that add nitrogen to the

soil. Blue-green algae culture is also

available. It is applied in rice fields.

So if a leguminous crop is rotated with

a cereal crop, the leguminous crop

replenishes, to some extent, the nitrogen

taken from the soil by the cereal crop. But

Potassium, Phosphorus and other nutrient

elements cannot be replenished in this way.

Organic manure:

Do you ever saw a herd of goats in a

vacant field? Why shepherds make

arrangements to stay their goats and sheeps

in the field.

The organic (natural) manure is

produced by decaying the plant and animal

wastes! The manure produced from

decomposed plant and animal products has

more organic material. This gives good

nutrients to the soil. It makes the soil

fertile. Because of humus, the natural

manure, water holding capacity of soil is

increases.

Natural organic manures are generally

divided into two types. One is Concentrated

organic manures and the other is Macro

organic manure.

Groundnut, Gingelly, Castor, Coconut,

Neem, Jatropa seed powders are the

examples of Concentrated organic

manures. These are also used as fodder for

cattle and poultry.

Animal excreta, compost, deep litter

are the examples of Macro organic manure.

Nutrients are rich in the concentrated

organic manures than in macro organic

manure.

         Green Manure

Soil testing:

How do farmers know what type of

crop needs to be cultivated? What types

of crops are suitable for the soil in their

fields? Farmers, who are experienced, are

able to make out from the colour and

texture of the soil.

You had also studied about the same in

your earlier class. Ask a farmer to find

out about crops that can be grown in

different types of soil.

Nowadays, Agricultural officer and the

Soil Testing Technologist are available in

every area. They observe the field and

suggest what to do.

Have you ever heard about Soil Testing Centre?

At these centers the soil technologist collect soil samples from fields and tests the fertility levels of soil. They give us knowledge about the soil. The testing centers are situated in division and district levels. If you send the sample of soil from your field, they send you a report after testing it.

Organic farming:

By using chemical fertilizers, we can

get high yield for only 20 to 30 years. After

that soil becomes reluctant to plant growth.

These chemicals damage soil fertility. If

the soil health is proper, then only the soil

responds to fertilizers. Otherwise, usage

of fertilizers become mere waste.

Long term high yielding capacity of

soil (soil productivity) depends on both

availability of nutrients in the soil (soil

fertility) and suitable physical, chemical

and biological characters of soil (soil

health).

BIO(Animanl Behaviour)

                      Animanl Behaviour

        

     What do we mean by Animal

    Behaviour?

       Animal Behaviour is the scientific study of the interaction of   animals  with each other, with other living beings, and with the   environment. It explores how animals relate to their physical

environment as well as to other organisms, and includes topics such as how animals find and defend resources, avoid predators, choose

mates, reproduce, and care for their young ones. The study of animal behaviour begins with understanding how an animal’s Physiology and Anatomy are integrated with its behaviour. Both external and internal stimuli prompt behaviours External stimuli includes the sounds, smells, threats from other animals and weather. Internal stimuli includes hunger and fear. Scientists are drawn to the study

of animal behaviour for varied reasons and the field is extremely broad, ranging from research on feeding behaviour and habitat

selection to mating behaviour and social organizations.

Different types of Animal Behaviour:

There are several types of behaviours in humans and other animals that have been described and investigated by researchers.

The following types have been studied so far

1. Instinct

2. Imprinting

3. Conditioning

4. Imitation

Instinct:

Instinctual behaviours are the

behaviours that need not be learned. They

can be complex like making nest by birds,

choose mates and forming into groups for

protection etc.

What is going on in the figure?

Will you consider spinning the web

by spider as an instinct behaviour?

Why or why not?

If your hand touches something hot or

sharpened object, accidentally it

automatically moves away. This is because

of reflex action. Reflexes are also a type

of instinct behaviour. We do not have to

learn them.

Imprinting:

You might have observed this type of

situations. Chickens and ducklings are able

to walk almost immediately after hatching

from the egg. Duckling can even swim after

a few days. They recognise their mother

because of a behaviour type called

imprinting.

Ducklings will follow the first moving

object they meet after hatching. They

become socially attached to this object and

treat it as their mother. Imprinting lets

young animals recognise their mother from

a young age. They can follow her for food

and protection. Imprinting is useful if the first moving

object they see really is their mother. But

ducklings will imprint on people, balls and

even cardboard boxes if these happen to be

the first things they see.

Imitation

Imitation is a type of behaviour where

one animal copies another animal. Humans

often imitate each other, often without

realising it. When people talk to each other,

they may stand or sit in a similar way, and

copy each other’s movements. Scientists

think that this happens so that the speakers

feel more at ease with other.

Some scientists think that humans are

the only animals that copy each other. Other

scientists have observed chimpanzees and

other primates imitating each other. For

example Kohler observed that, chimpanzees

can use sticks to spear juicy grubs to eat.

Other chimpanzees copy this behaviour. In

this way they learn new skills. Do you ever

heard monkey imitate us. Read and discuss

about the story 'Monkey and Hat merchant.

Instinct

Humans have instincts, but it is

possible for us to overcome natural urges

to follow certain behaviour. For example,

hungry persons might start eating

immediately when they sit down at the

dining table, but they have learned that good

manners means they should wait until

everyone is seated and ready to eat.

Imitation

People often imitate each other. This

can help them learn something new and

useful, such as new skill in lessons, sport

or at work. It can also lead them to show

less useful or harmful behaviour. For

example, young people may start smoking,

drinking alcohol or taking drugs as a result

of copying each other to ‘fit in’. But it is

very dangerous to our health.

Conditioning

Conditioning can be used to change the

behaviour of people. Advertisers are very

skilled at this. They use pictures of their

products which make them look glamorous

or exciting, often by using famous actors

or sports people. By associating the

product with attractive images the

advertisers are trying to set up a

conditioned response to their product.

People will respond positively and buy the

product.

Investigating behaviour

Behaviour can be investigated in the

‘field’ or in the laboratory. It can be

observed and measured, and experiments

can be designed to test how it works.

Human behaviour is affected by many

variables. It can be more difficult to study

the behaviour of other animals.

Investigations in the field

Some scientists spend many hours

watching and studying the behaviour of

animals. They may be interested in how the

animals live alone, group into families or

form large groups such as herds.

Animals can signal to each other. For

example, they may call each other to warn

danger. Some scientists are interested in

such signals. They record and study them

to work out what the signals mean, you

would have observed how ants respond

when they meet one another.

Tagging

You have studied about bird migration

in the chapter biodiversity and its

conservation. Like birds some other

animals also migrate over large distances

to find food or nesting sites. Animals can

be ‘tagged’ by attaching tracking devices to

them. Tagging help scientists follow the

journeys the animals make.

Activity-1:

Let us observe the following behaviours

of different animals. Identify their

imprinting, instinct, conditioning or imitation.

Our pet dog barks only on

strangers. If you train your dog not

to enter your kitchen. Does it ever

enter into the kitchen?

Ants which usually go in a line

reach sweet kept in a tin. How do

they know the way to reach the tin?

Mosquitoes, cockroaches come

out of their places only when it is

dark. How do they know the

difference between light and dark?

Bats and owl move and search for

food only during night . How could

they know what is a day and what is

a night?

When you untie the neck of your

bull at the time of plouging, it

moves towards plough without any

instructions. In the same way, it

moves towards tub at the time of

feeding. How does the bull respond

differently?

Birds collect material which is soft

and strong to build its nest. How

do they know the quality of the

materials?

Puppies, kitten fight with each

other when they see a piece of

cloth. They try to tear it off, why?

In a particular season, some birds

in our surroundings migrate from

long distances. How do they know

their way?

Offsprings (kids) of different animals,

either they live on land or in water, perform

activities by instinct, imprinting, imitation

or conditioning. Animal behaviour is based

on different bio chemical reactions.

Identifying or smelling ability of dogs and

searching and communicating nature of

ants is because of pheromones. (ask your

teacher about pheromones)

Let us know some interesting behaviour

which reflects their intellectual abilities in

animals. It is very interesting to watch them

making nests. It varies from species to

species. Birds build their nests in different

ways. Tailor bird selects three broad leaves

one for bottom, two for top and sides they

also collect threads to make their nest for

stitching these three leaves. Some of the

birds build its nest only with leaflets.

Some experiments towards

animal intelligence

Let people believe or not, cheating /

bluffing, hiding are also characteristic

features of intelligence In other words,we

can say that you know what others think of

you and vice versa. In order to make them

confused, you do something that others can

not guess your plans. Not only humans, but

there are some other animals also that

show the same behaviour.

A bird called scrubjay hides its food.

But unfortunately when it searches back its

own food, it finds that another scrub jay had

stolen them. An experiment proved that a

scrubjay had hidden its food in presence

of another bird. After some time it was

found that the other bird had stolen it by

fixing a plan.

Squirrels too hide their food in a

fascinating way. They always behave in such

a manner that somebody is trying to steal

their food. In order to misguide others they

dig holes in many places and heap leaves,

straw etc., to cover them. Sometimes, most

of the holes does not contain any food. In

this way, they cheat others to make believe

that these holes contain food. Some times

it forgets the place. In nature it helps in

spreading of seeds.

If we think of logic, we must remember

Dolphins. Dolphins have great logical

thinking power.

It was proven by Hermon. Hermon

studied four bottle nose Dolphins at Kavalo

Basin mammal labarotory of Hawai islands.

He named them Akkikomoi, Phoenix, Allen

and Hippo.

He could understand by his study that

Dolphins can remember their names and

understand a code language if they are

trained by practice. Even they could reply

to complex code language. For example,

the closed fist shows a tub, raised arms

show a ball and one hand raised tells 'bring

here'. The altogether actions are understood

by the Dolphins. If we show the above

actions in a sequence, the Dolphins would

bring the ball from the tub. If we reverse

the actions they throw the ball into the tub.

They remember their names by short

and long whistles.Variety of whistles are

recognised by them. If a Dolphin of

particular whistle is called, all the dolphins

stare at ,while the particular one comes to

you.

Another wonder behaviour is remarked

with Alex, an African grey parrot. In 1977,

Irene Pepperberg bought a parrot and

trained it. Slowly she made it learn more

than 100 words. Then she arranged the

words in such a way that Alex could frame

its own sentences. After some days, She

showed Alex one yellow bowl and another

yellow dish. 

The dialogues between them

are:

Pepperburg: What is the similarity?

Alex: Colour

Pepperburg: What is the difference?

Alex: Shape

BIO(Sense Organs)

                Sense Organs

               We enjoy the beauty of nature with our

eyes, the melodious music with our ears,

the fragrance of flowers with our nose, the

taste of food with our tongue and feel the

cool breeze with our skin. What do we do

when suddenly bright light falls on our eyes

or a hot utensil is touched by chance? All

these situations show just how our senses

pick up information and react to them.

Our senses aren't just a part of us, they

define us. This is because nothing that we

experience in our life, from the most

important to the most boring, would be

possible without the intricate power of our

senses.

Nothing in the entire universe of

scientific exploration can even come close

to matching the ability of our brain to use

information sensed by our eyes, ears, skin,

tongue, and nose to produce a rich sensory

experience in a matter of milliseconds!

But how much do we know about

our senses?

What do our senses do?

Our senses have several roles to play.

They aid our survival by directing us

towards certain informations of our

environment that are important for us and

influence some activity (called as stimuli).

For example tasty food draw us towards

them and our mouth starts watering. Our

senses also help us to locate mates, seek

shelter, and recognize our friends.

Incidentally, our senses also give us the

opportunity to find pleasure in music, art,

athletics, etc.

There are yet other things that our

senses do. You may have experienced

feeling hurt to see someone in pain.

Usually when we have strong emotional

bonds with someone and when he or she

experiences pain, so do we( not just

emotional ties, we could be influenced by

situations not directly related to us and yet

feel the pain e.g. sympathising and feeling

pain of drought affected people).

How do our senses accomplish all this?

The complete answer is complex, but it

involves one elegantly simple idea that

applies across the sensory system. Our

sensory impressions of the world involve

nerve signals. These play a very important

role in the way we react or respond to

various stimuli or even to same stimuli in

different situations.

For example, flavour preference by our

brain is usually based on our body needs,

like cooked fish. may not smell good to some people.

But if the person is very hungry and has no

other option and particularly if the body has

a need for protein, fish may suddenly smell

good!

Stimuli from the environment around

are received by our body through sense

organs. As we already know, they are the

eyes, ears, nose, tongue and skin. Let's try

to understand the path of receiving a

stimulus and expressing a response

(sensation).

Stimulation to Sensation:

There are certain conditions,

substances etc., in nature that trigger the

process of sensing them by our body. These

are stimulants. Information carried by these

stimulants are picked up by certain organs

called as receptors present in our sense

organs and converted into nerve signals.

These are carried to the brain and processed

to create a sensation. For example, when

reflected light (stimulus) from the surface

of a green leaf and its surroundings reaches

receptors in our eyes, it is converted into

nerve signals. These signals reach the brain

and are interpreted as green coloured shape

against a background. We see this as the

leaf.

 Brain is the centre for all the sensory

activities. It receives information through

sensory nerves that bring nerve signals

from the sense organs and after

interpretation sends off signals through

another type of nerves called as motor

nerves to parts that respond

Activity-1:

Write a few lines about flower in your

note book.

Write about the stimuli and responses

and the sensory and motor functions with

respect to the sense organs involved.

Do you think our sense organs work

together? Why, why not? Give reasons.

All stimuli may not lead to responses.

Only a particular level of stimulus will give

rise to a response. Moreover changes in

stimulus also go unnoticed if they are not

of a particular level.

Activity-2:

Dissolve a pinch of sugar in a glass of

water. Drink a little of this. Does it taste

sugary? Why?

You could try this for different

concentrations of sugar by, adding a quarter

tea spoon full of sugar every time to find

out how much sugar needed to taste

maximum sweetness. This means sugar in

solution has stabilized your sensation.

You may have often noticed while

drinking tea or coffee that if you eat a very

sweet substance in between, your tea or

coffee appears to be less sweet as compared to the sips taken before eating the sweet (Thus, salty snacks go with tea or coffee!). This usually happens because a higher level of the same stimulus masks that of the lower level. 

Our Sense Organs

 As we all know, we have five main

sense organs, the eyes, ears, skin, nose

and tongue. These sense organs have

sensory receptors. Each type of

receptor is highly sensitive to specific

stimulus types.

1. Eye

Vision helps us detect desired targets,

threats, and changes in our physical

environment and to adapt accordingly. So,

how does the visual system accomplish

this? We shall do a few activities and read

the following section to find out about this

Activity-3:

1. Observe the external structure of

your friend's eye, draw the diagram

and label it (you can take the help

of diagram given in this section).

2. Observe the eye ball of your

friend in normal light. Then focus

a beam of torchlight on your

friend's eye.

What is his or her reaction? Why

is it so?

           Human Eye Cross-sectional view

Now ask your friend to keep the eye

closed for around two minutes. Now let

her/him open the eye. Observe the size of

the small black portion in the centre. Ask

your friend to keep her/his eye open

forcibly as you focus the beam of torch

light this time. Observe what happens to the

small dark portion.

What happened to the small dark

portion called the pupil? Guess why

Structure of the Eye

Our eye contains eye lids, eye lashes,

eyebrows and lacrimal glands. A thin layer,

called conjunctiva covers the front portion

of the eye. The eye ball is located in the

eye socket. Only 1/6 portion of the eye ball

is visible to us.

Eye has three main layers. They are

sclerotic layer or sclera, choroid layer and

retina. The outer most thick, tough, fibrous,

non-elastic and white coloured layer is

sclera. The sclera bulges and forms cornea.

The end of sclera connects to the optic

nerve. The second layer is choroid layer.

This layer is black in colour and contains a

lot of blood vessels. It encloses the eye

except the part pupil. The part formed by

the choroid layer around the pupil is iris.

Radial and circular muscles are present in

the iris. Biconvex Lens is present

immediately behind the pupil which is

attached to the ciliary muscles and

suspensory ligaments.

The lens divides the inner eye ball as

aqueous chamber and Vitreous chamber.

Aqueous chamber is filled with water like

fluid whereas vitreous chamber is filled

with jelly like fluid.

Retina contains the cells, called rods

and cones. The area of no vision, called

blind spot and the area of the best vision,

called yellow spot are present in the retina.

The yellow spot is also called Macula or

Fovea.

Functioning of the Eye:

The Visual Sensation

You might think of the eye as a sort of

“video camera” that the brain uses to make

motion pictures of the world. Like a

camera, the eye gathers light through a

convex lens, focuses it, and forms an image

in the retina at the back of the eye. The lens,

turns the image left to right and upside down

(you may have studied in the chapter on light

that we get an inverted /upside down image

through a convex lens). This visual reversal

may have influenced the very structure of

the brain, which tends to maintain this

reversal in its sensory processing regions.

Thus, most information from the sense

organs crosses over to the opposite side

of the brain. Likewise, “maps” of the body

in the brain’s sensory areas are typically

reversed and inverted. But while a digital

camera simply forms an electronic image,

the eye forms an image that gets extensive

further processing in the brain.

 The unique characteristic of the eye

that makes it different from other sense

organs, lies in its ability to take the

information from light waves, then

transform the characteristics of light into

neural signals that the brain can process.

This happens in the retina,

the lightsensitive layer of cells at the back of the

eye that acts much like the light-sensitive

chip in a digital camera. As with a camera,

things can go wrong. For example, the

lenses of those who are “nearsighted” focus

images short of (in front of) the retina; in

those who are “farsighted,”the focal point

extends behind the retina. Either way,

images are not sharp without corrective

lenses.

              Cones and rods

Making the fine distinctions necessary

for colour vision is the job of the nearly

seven million cones containing the pigment

iodopsin that come into play in brighter

light. Each cone is specialized to detect the

light waves we sense either as blue, red, or

absorb light energy and respond by creating

nerve impulses.

But why are there two sorts of

photoreceptors? Our eyes function

sometimes in near darkness and sometimes

in bright light. These two types of

processors involving distinct receptor cell

types named for their shapes have evolved

for this purpose.

Nearly 125 million tiny rods containing

the pigment rhodopsin “are present in our

eyes, they detect low intensities of light at

night, though they cannot make the fine

distinctions that give rise to our sensations

of colour.

Eye protection:

Each eye is protected by eyelids, eye

lashes, eye brows and lacrimal or tear

glands. A thin membrane covers the front

part of the eye. This membrane is called

conjunctiva. The conjunctiva is made up of

transparent epithelium. It is also a

protective cover to the eye. Whenever

unwanted substances come in contact with

this layer, the lacrimal glands are stimulated

to wash the substance out of the eye. The

fluids that are filled in the eyeball (vitreous

and aqueous chambers) protect the lens and

other parts of the eye from mechanical

shocks. Cornea is the clean window in the

sclera in front of the Iris. It protects the

eye from direct exposure to light.

Eye: Some structures that bring

about adjustments

The Iris is a muscular structure which

adjusts the size of the pupil which is nothing

but a gap between the iris in front of the

lens. Adjustments are made depending on

light intensity.

Cilliary muscles and suspensor

ligaments are capable of adjusting the focal

length of the eye lens.

Activity-5:

1. Observe the Iris and its surroundings of your friend’s eye.

    Can you find the pupil?

2. Observe the colours and patterns in the iris of your friend' s eyes.

     Is there any difference from one another? Select a minimum of           ten members and note the result. Use a hand lens for close                  observation. Record your observations in your notebook.

Activity-6:

1. Enter into a dark room from a very

    bright place. What happens?

2. Sit in a dark room for some time. Then

    go into a bright lit room. What happens

    discuss your experiences in the class

    room?

   Do you know that the impression of an

   image stays in the retina for about 1/16 of

   a second. If the still images of an object

   are flashed at the rate faster than 16 per

   second, the eye receives it as moving. That

   is how we see movies.

Diseases and defects of the eye:

The main diseases and defects of the eye are - Night blindness, Xeropthalmia, myopia (near sightedness), Hypermetropia

(far sightedness), glaucoma, cataract and colour blindness. Some persons may have eye defects by birth due to various reasons.

Ask your teacher about these eye defects and write one or two sentences for each in your notebook.

Ear:

Apart from hearing ear helps in maintaining the equilibrium of our body. Do you know

by which bone your ears made of? Observe the following picture to know the inner parts of

ear?

1. Outer ear (Pinna)

2. Auditory canal

3. Ear drum

4,5,6. Semicircular canals

7. Cochlea

8 . Vestibular nerve

9. Cochlear nerve

10. Eustachian tube

11. Ear Ossicles (Utriculus)

External ear:

It is the visible part of the ear on either

side of our head. It is a flap like structure,

called the Pinna. It leads to the ear canal.

The pinna is crumpled and made up of

cartilage.

Have you ever observed wax like

substance in your ear? Do you know

where does it comes from.?

Pinna has ceruminous (wax producing)

and sebaceous glands (oil producing).

These help to keep the ear cannal lubricated

prevent the dust and other particles from

entering into the ear canal. The ear canal

is also called Auditory Meatus. A thin layer,

called tympanum or ear drum is present at

the end of the auditory meatus. It is present

in between the external and middle ear. It

is in the shape of a cone. Its narrow area

connects to the first bone malleus of the

middle ear.

Middle ear:

Middle ear plays an important role in

amplifying the vibrations received on the

tympanum membrane. The chain of three

bones, Malleus, Incus and Stapes helps to

do the same. Oval window is a membrane,

covered ending of the middle ear which

opens into the inner ear through round

window.

Internal ear or Inner ear:

Internal ear consist of bony labyrinth

enclosing the membranous labyrinth. The

membranous labyrinth consists of

Vestibule, three semicircular canals and

cochlea. The anterior part of the vestibule

is Sacculus and the posterior part is

Utriculus. Nerve fibers from them form

vestibular nerve.

The semicircular canals are connected

to the vestibule and filled with endolymph.

Vestibule and semilunar circles together

form vestibular apparatus. It maintains the

equilibrium of the body, pertaining to the

posture and balance of the body.

Functions of the ear:

To collect and transform vibrations produced by sound to nerve

impulses to be carried to the brain for processing. To maintain balance or

equilibrium:

Ask your teacher in what way ears

maintain balance.

Nose:

Structure of nose

Our external nose has two nostrils.

They lead to the nasal cavity. Nasal septum

divides the nasal cavity into two halves. The

nasal cavity is lined with mucous membrane

and small hairs. Olfactory receptors are

present in the mucous membrane.

Smell and our Nose:

Smell serves a protective function by

sensing the odour of possibly dangerous

food or, for some animals, the scent of a

predator. We humans seem to use the sense

of smell primarily in connection with taste

to locate and identify foods, avoid spoiled

foods etc. Human beings use the sense of

smell in much limited manner as compared

to other animals.

The Smell or Olfactory sensation

Smell of certain flowers like Artabotrys

(Sampenga) and certain fruits like Jack fruit

(Panasa) are liked by some people but not

by others. How do you come to know

something smells good or bad?

Biologically, the sense of smell, or

olfaction, begins with chemical events in

the nose. There, odour (in the form of

airborne chemical molecules) interact with

receptor proteins associated with

specialized nerve cells. These cells,

incidentally, are the body’s only nerve cells

that come in direct contact with the outside

environment. Receptors present at the base

of the skin lining, the inner walls of the

nose, are highly sensitive to odour

chemicals. These odour chemicals can be

complex and varied. For example, freshly

brewed coffee owes its scent to as many

as 600 volatile compounds (substances that

reach gaseous state quickly as they have low

boiling points.)

Tongue

Structure of the tongue

Our tongue is made up of voluntary

muscles. It contains about 10 thousand

taste buds. The taste buds are located in the

walls of the papillae.

Taste and our tongue

Like smell, taste is also a sense based

on identifying chemicals in food and the

texture of it. But the similarity doesn’t

end there: The senses of taste and smell

have a close and cooperative working

relationship. So many of the subtle

distinctions you may think of as flavours

really come from odours. (Much of the

“taste” of an onion is odour, not flavour.

And when you have a cold, you’ll notice that

food seems tasteless because your nasal

passages are blocked.)

Skin:

The sense of touch had received

supreme importance in the sphere of

senses from ancient time. The organ

involved is our skin

Skin and touch:

Skin is the outer most covering of our body. It regulates the body temperature and eliminates certain waste material through

sweat. It is the sense organ of touch. The sense of touch is done by the cutaneous receptors. It is the largest organ of all. It provides the first level of protection to the body.