Different Forms In Which Life Occurs

Microscopic Bacteria - Few Micrometres
Blue Whale - 30 Metres
Red Wood Trees Of California - 100 Metres
Some Pine Trees - Lives For 100 Of Years
Insects Like Mosquitoes - Live For Only A Few Days

A characteristic is a particular form of a particular function.

All living things are identified and categorised on the basis of their body design in form and function

Basic characteristics used for a hierarchical classification.

Whether the organism is unicellular or multicellular forms one of the most important basic characteristics of classification.
Whether the organism is eukaryotic or prokaryotic.
Another characteristic is understanding whether the cells occur singly or in groups. If the cells occur in groups, does it have division of labour or not.
Whether the organisms are autotrophic or heterotrophic.
What is the level of organisation of the organisms performing photosynthesis (plants).
Of the animals, how does the individual's body develop and organise its different parts and what are the specialised organs found for different functions ?

CLASSIFICATION AND EVOLUTION

Most life forms that we see today have arisen by an accumulation of changes in body design that allow the organism possessing them to survive better. Charles Darwin first described this idea of evolution in 1859 in his book, The Origin Of Species.

The groups of organisms which have ancient body designs that have not changed very much are referred to as primitive or lower organisms.
The groups of organisms that acquired their particular body designs relatively recently are referred to as advanced or higher organisms.

Biodiversity

Biodiversity means the diversity of life forms.
It is the variety of life forms found in a particular region
Land, water, climate etc. are the factors that affect the diversity of stable communities of different species.
Diverse lifeforms share the environment, and are affected by each other too.
The warm and humid regions of the earth having tropical climate, between the tropic of Cancer and tropic of Capricorn, are rich in plant and animal life. This is called the region of megadiversity.
More than half of the diversity of the planet Earth is concentrated in a few countries, namely, Brazil, Columbia, Ecuador, Peru, India, Mexico, Zaire, Madagascar, Australia, China, Indonesia and Malaysia

THE HIERARCHY OF CLASSIFICATION-GROUPS

Ernst Haeckel (1894), Robert Whittaker (1959) and Carl Woese (1977) classified all living organisms into broad categories called kingdoms.
Whittaker proposed classification that has 5 kingdoms : Monera, Protista, Fungi, Plantae and Animalia
They are formed on the basis of : cell structure, mode and source of nutrition and body organisation.
Woese modified this classification by introducing division of Monera into Archaebacteria (Archae) and Eubacteria (Bacteria)

Further classification is done by naming the subgroups at various levels :

Kingdom
Phylum (Animals) / Division (Plants)
Class
Order
Family
Genus
Species

The basic unit of classification is species. Species includes all organisms that are similar enough to breed and perpetuate.

Monera

These organisms are prokaryotic
They are unicellular
Some organisms have cell wall while others don't
They are autotrophic or heterotrophic.
Examples : bacteria, blue - green algae or cyanobacteria, mycoplasma, anabaena.

Protista

unicellular
eukaryotics
some have appendages, such as hair like cilia or whip-like flagella for moving around
autotrophic / heterotrophic
examples : unicellular algae, diatoms, protozoans ( paramecium, amoeba and euglena )

Fungi

Euaryotic
Heterotrophic and Saprophytes
Multicellular / Unicellular
Have cell walls made up of a tough complex sugar called chitin
Examples : Yeast, mushrooms, aspergillus, agaricus, penicillium
Some fungal species live in permanent dependent relationships blue-green algae
Lichen is the symbiotic association between fungi and blue-green algae

Plantae is further divided into sub-groups on the basis of the following :

whether the plant body has well differentiated, distinct components
whether they have vascular tissues or not
whether they have the ability to bear seeds
if they bear seeds, whether they are enclosed within fruits

	Created by Mariya David about 8 years ago

Biology Note on Diversity In Living Organism, created by Mariya David on 21/10/2016.