BIO(Diversity)

    Diversity in Living Organisms

        

      There are many plants and animals

around us. We know very little about them.

Most of them belong to a world not visible

to the naked eye, as you have already studied

in the chapter on, ‘Microbial World’. The

types of organisms that we have studied so

far are also in lakhs, existing from mountain

peaks to deserts and plateaus to the deep

oceans, from extreme cold conditions to

extreme hot ones and many more, such

diversity is the symbol of nature.

Studying about diversity as it is, would

be a very chaotic and difficult task.

Moreover describing and naming each

organism individually without knowing the

organisms that might be sharing common

characteristics would be insignificant. Thus

people who have tried to study diverse

organisms in nature have tried to make

groups of them on the basis of differences

and similarities found among them. This

helped to identify largely varied and closely

related groups of organisms.

Thus our knowledge of the entire living

world depends on first making meaningful.

groups to carry out our study in a

systematic manner.

In this lesson we will try to study the

diversity present among several living

organisms, classify and appreciate nature's

miracle

Diversity in plants:

Here as we finish our activity we would have established some common characteristics of land plants- those having two seed leaves are called dicotyledons, while those having single seed leaf are

called monocotyledons.

They share some common

characteristics like venation (dicots have

reticulate/branched, while monocots have

parallel venation).

By doing the above activity we can

understand how grouping is done in biology

by observing the similarities and

differences among diverse groups in the

sample under study. We will do some

similar exercises with animals now.

Diversity in animals:

Observation of external characters of insects Collect housefly, mosquito, ant, dung beetle, butterfly, moth and cockroach from your surroundings. Observe them carefully. Take the help of a magnifying lens to get a closer view. Are all insects of the same size or shape?

What differences did you observe

with regard to legs?

What differences did you observe

with regard to wings?

Is there any relationship between

the number of wings and legs?

Did you find any two insects with same

characters? If yes, display in the class. If

no, note down the differences in your note

book.

Even though all these are insects and

you see that they show several differences.

Can you find at least one character that is

similar to the whole group, what is it?

How do you group insects? Would it

be based on number of body segments or

number of legs they have?

The examples of insects given above

are of different species. Hence they show

a lot of difference and we say they are

diverse. If we were to compare insects of

the same type that is to say two houseflies

we will be perhaps still find some

differences(try it out yourself) and these

would be variations.

Let us see some variations that are

present in human populations

Monera

Observe the given slides carefully and

say

How many cells are found in the

organism?

Do you find any nucleus in the

middle of the cell?

Are there any other cell organelles

found in the cell?

By observing the above characteristics

we conclude that Monerans are:

A. One-celled organisms

B. Cells have no membrane bound nucleus

C. Reproduce by splitting into two.

D. Absorb nutrients from outside their

bodies

E. They move with the help of

locomotory organs like flagella, cilia

or hair like structures present on them.

F. Some monerans cause diseases, but

others are helpful to people.

G. Examples: bacteria

        Nostoc

        Bacteria

Three major groups of organisms come under this group. They are archaebacteria (ancient bacteria present till date, some species found in hot springs come under this), eubacteria (streptococcus, rhizobium, e.coli etc) and cyanobacteria which are also called blue green bacteria as they appear similar to blue green algae externally but internally are more like bacteria(but they are not bacteria).

Protista (protoctista):

Observe the given slides carefully and

say

How many cells are found in the

organism?

Do you find any nucleus in the

middle of the cell?

Are there any other cell organelles

found in the cell?

Are there any locomotory organs

in them?

Characteristics of protists

A. Most are one-celled (unicellular),

but some have many cells.

B. Cells have a membrane around the

nucleus.

C. Some get nutrients and energy by

eating other organisms.

D. Some get energy from the sun, and

nutrients from the water around

them.

E. These live either solitary or in a

colony.

F. Some of the cell organelles are

present inside the cell.

G. Mostly reproduce by splitting into

two (Binary fission).

H. Examples are paramoecium,

amoeba, algae, etc.

              Amoeba

           Paramecium

Fungi:

Observe the specimen and diagrams

given below and answer the following

questions.

What is the colour? Can they

prepare their own food as green

plants?

Make a sketch of the main parts of the

body

Do you find root like structures?

Guess why?

Characteristics of fungi

A. Most are many-celled (multi

cellular) and some are one-celled

organisms.

B. Eukaryotes with well defined

prominent head (you usually see

them propping out from the ground

or on barks of trees during rainy

season).

C. Get nutrients and energy by

absorbing/ digesting the surface

they live on through root like

structures which are fine thread

like parts of their body.

D. Most of these reproduce by spores.

E. Examples are yeast, mushrooms,

bread moulds, and lichens.

Plantae:

Several plants grow around you. Do

all of them produce seeds?

Think if grass produces seeds

(hint:compare with rice plants and

think).

Name some plants that produce

seeds.

Which part of the plant produces

seeds? Where is it located?(recall

structure of plant parts studied in

earlier classes)

Do all plants have a definite

structure to produce seeds?

Plants are diverse in nature. The basis

of classifying them is the way they acquire

their food, the type of reproductive

structures they have and the way they

reproduce. They are multicellular,

eukaryotic with cell walls. They are usually

autotrophs and use mainly chlorophyll for

photosynthesis.

The first level of classification among

plants depends on whether the plant body

has well differentiated, distinct parts.

The next level of classification is based

on whether the differentiated plant body has

special tissues (vascular tissues) for the

transport of water and other substances

within it. Further classification looks at the

ability to bear seeds and whether the seeds

are enclosed within fruits.

Let's look at some plants like moss and

ferns more closely.

            Funaria

Activity:

Observation of moss plants through

hand lens.

You can collect mosses from the

greenish velvety growth on bricks during

the rainy season. Scrap a bit of this greenish

growth over a slide and observe with a hand

lens or under a dissection microscope. 

These are not exactly flowers but

structures that contain seed like structures

called spores. Spores contain very little

food while the seed stores a lot of it.

Moreover where seeds are produced from

ovule of flower, spores are produced within

structures called as sporangium in a

different manner.

 Sporophylls of Cycas & Fern

Coelenterata/Cnidarians:

These are aquatic forms showing more body design differentiation when compared with Poriferans. There is gastrovascular cavity in the body. The body is made up of two layers of cells: one forming the outer layers while the other forming the inner layers. Some
live in colonies ,like the corals that are tiny nearly 3 to 56 mm but their colonies where we may find several types of them which
form coral islands huge as say an island (1800 sqkm ), is called coral reefs while others like hydra, jellyfish and sea anemones are common examples.

Hydra

Platyhelminthes:

The body of animals in this group is far

more complexly designed than in the two

other groups we have considered so far. The

body is bilaterally symmetrical, meaning

that the left and the right halves of the body

have the same design. There are three layers

of cells from which differentiated tissues

can be made, that is why such animals are

called triploblastic. This allows outside and

inside body linings as well as some organs

to be made. There is thus some degree of

tissue formation. However, there is no true

internal body cavity or coelom, in which

well developed organs can be

accommodated. The body is flattened

dorsoventrally, from top to bottom, that is

why these animals are called flatworms.

They are either free living or parasitic.

Some examples of free living animals like

planarians or parasitic animals like

liverflukes and tapeworms.

        Tapeworm

     Nematoda

The nematode body is also bilaterally symmetrical and triploblastic. However, the body is cylindrical rather than flattened. There are tissues, but no real organs, although a sort of body cavity or a

pseudocoelom is present. These are very familiar as parasitic worms causing diseases, such as the worms causing elephantiasis (filarial worms) or the wormsin the intestine(roundworm or pinworms).

Annelida (Segmented Worms):

Annelida animals are also bilaterally

symmetrical and triploblastic, but in

addition they have a true body cavity. This

allows true organs to be protected in the

body.

There is, thus, extensive organ differentiation. This differentiation occurs in a segmental fashion, with the segments lined up one after the other from head to tail. These animals are found in a variety

of habitats– fresh water, marine water as well as on land.

Protochordata:

These animals are bilaterally

symmetrical, triploblastic and have a

coelom. In addition, they show a new

feature of body design, namely a

notochord, at least at some stages during

their lives. The notochord is a long rod-like

supporting structure (chord=string) that

runs along the back of the animal separating

the nervous tissue from the gut. It provides

a place for muscles to attach for ease of

movement. Protochordates may not have a

proper notochord present at all stages in

their lives or for the entire length of the

animal.

Protochordates are marine animals.

Ex. Herdmania, Amphioxus.

 Herdmania

Amphioxus