Diversity in living organisms

By group 1

The bewildering variety of life around us has evolved on earth over millions of years.

We do not have enough time to view each and every fraction of these living organisms alone.

Instead we look at them as a whole and find similarities and dissimilarities among the organisms which allows us to classify them into different types.

Evolution of living organisms

Basis of classification Attempts at classifying living

things into groups have been made since the time immemorial.

Greek thinker Aristotle classified animals according to where they lived i.e. land, water or air.

This was then rejected by the people of that time since it wasn’t an appropriate way to classify animals by the basis of their habitat.

What is meant by characteristics?

• When trying to classify a diverse group of organisms, finding ways in which some of them are similar enough to be thought of together is the easiest.

• Characteristics mean a particular form or function. Eg. Humans have 5 fingers in each hand.

Characteristics for hierarchical classification -

Characteristic No.1 An eukaryotic cell has membrane bound

organelles including a nucleus which allows cellular process to be carried out easily.

Organisms which do not have a clearly demonstrated nucleus need not have their biochemical practices always organized.

This would effect every aspect of the cell design.

Eukaryotic cell

Characteristic No. 2

• Cells that group together to form a single organism use the principle of division of labour.

• In such a cell type, all the cells wouldn’t be identical .

• Groups of cells will carry out specialized functions

• Eg. An amoeba and a worm.

Amoeba and a worm.

Characteristic No. 3

• Some organisms can produce their own food like plants.

• The other cannot produce their own food and depend on the environment they live in for food like bear, lion, zebra.

• The organisms which can produce food are more organised and complex than the one’s who cant produce food on their own.

Plant and lion.

Characteristic No.4

•There are different ways in which some animal’s body organs develop faster or more complexly from the other animals.•There are also some special organs for a particular function in some animals. Eg, A cheetah’s leg’s muscular contraction and relaxation speed.

A Cheetah

Classification and evolution

• All living things are categorized on the basis of their body design and function.

• Once a certain body design comes into existence it will shape the effects of all other subsequent body designs.

• There is an important role of time in the change of characteristics.

Human life stages

• The classification of life forms are closely related to their evolution.

• Evolution means the accumulation of the changes in body design which allow the organism to survive better in its surroundings.

• Charles Darwin described this idea of evolution in his book -The origin of species

An camel’s eye – Charles Darwin – His book The origin of species.

The hierarchy of classification of groups

• Biologists Ernst Haeckel, Robert Whittaker and Carl Woese have tried to classify all living organisms into broad categories called kingdoms.

• The classification Robert Whittaker proposed has five kingdoms namely

a) Monera b) Protistac) Fungid) Plantaee) Animalia

Ernst Haeckel, Robert Whittaker and Carl Woese

Monera• These organisms do not have a defined

nucleus or organelles nor do any of them show multi-cellular designs.

• Some have cell walls and some do not.• Can be seen only through a microscope.• Some synthesize their own food

(autotrophic) and some get it from the environment (heterotrophic)

• Eg. Bacteria, cyanobacteria and mycoplasma.

Cyanobacteria and mycoplasma

Protista

• Includes many unicellular eukaryotic organisms.

• Some use appendages like cilia or flagella for moving around.

• Mode of nutrition can be autotrophic or heterotrophic.

• Eg. Unicellular algae, diatoms and protozoans.

Unicellular Algae, Diatoms and protozoans.