Chapter 7
DIVERSITY IN LIVING ORGANISMS
1. Why do we classify organisms?
2. Give three examples of the range of variations that you see in life forms around you.
What is biodiversity? Explain it on the earth.
Biodiversity- Existence of varied species of organisms in the geographical area is called biodiversity.
Biodiversity means the diversity of life forms.
It is a word commonly used to refer to the variety of life forms found in a particular region.
Different forms of life occur on earth.
On one hand we have microscopic bacteria of a few micrometer in size.
While on the other hand we have blue whale and red wood trees of California of approximate sizes of 30 meters and 100 meters respectively.
Some pine trees live for thousands of years while insects like mosquitoes die within a few days.
Life also ranges from colourless or even transparent worms to brightly coloured birds and flowers.
This bewildering variety of life around us has evolved on the earth over millions of years.
However, we do not have more than a tiny fraction of this time to try and understand all these living organisms, so we cannot look at them one by one.
Instead, we look for similarities among the organisms, which will allow us to put them into different classes and then study different classes or groups as a whole.
Define classification. Give its importance.
“A method of forming groups or classes of the organisms on the basis of similarities of the characters is called classification”.
In order to make relevant groups to study the variety of life forms, we need to decide which characteristics decide more fundamental differences among organisms.
This would create the main broad groups of organisms.
Within these groups, smaller subgroups will be decided by less important characteristics.
What is the Basis of Classification?
For the classification of living organisms various criteria were used by scientists time to time.
Greek thinker Aristotle classified animals according to whether they lived on land, in water or in the air. This is a very simple way of looking at life, but misleading too.
For example, animals that live in the sea include corals, whales, octopuses, starfish and sharks.
We can immediately see that these are very different from each other in numerous ways.
In fact, their habitat is the only point they share in common.
This is no good as a way of making groups of organisms to study and think about.
What are perfect criteria or characteristics for classification?
We need to decide which characteristics to be used as the basis for making the broadest divisions.
Then we will have to pick the next set of characteristics for making sub-groups within these divisions.
This process of classification within each group can then continue using new characteristics each time.
Before we go on, we need to think about what is meant by ‘characteristics’.
When we are trying to classify a diverse group of organisms, we need to find ways in which some of them are similar enough to be thought of together.
These ‘ways’, in fact, are details of appearance or behaviour, in other words, form and function.
What we mean by a characteristic is a particular form or a particular function.
That most of us have five fingers on each hand is thus a characteristic.
That we can run, but the banyan tree cannot, is also a characteristic.
Example how classification can be done?
Now, to understand how some characteristics are decided as being more fundamental than others, let us consider how a stone wall is built.
The stones used will have different shapes and sizes.
The stones at the top of the wall would not influence the choice of stones that come below them.
On the other hand, the shapes and sizes of stones in the lowermost layer will decide the shape and size of the next layer and so on.
The stones in the lowermost layer are like the characteristics that decide the broadest divisions among living organisms.
They are independent of any other characteristics in their effects on the form and function of the organism.
The characteristics in the next level would be dependent on the previous one and would decide the variety in the next level.
In this way, we can build up a whole hierarchy of mutually related characteristics to be used for classification.
What are the recent criteria used to classify living organisms according to five kingdom system?
The living organisms are classified into five kingdoms on the basis of three to four important criteria They are
Nuclear organization- whether cell is prokaryotic or eukaryotic.
Cellular organization- whether eukaryotic organism is unicellular or multicellular.
Mode of nutrition- whether eukaryotic organism is autotrophic or heterotrophic.
Ecological status-whether heterotrophic organism is saprophytic, parasitic or holozoic in mode of nutrition.
Describe these criteria in details.
Now-a-days, we look at many inter-related characteristics starting from the nature of the cell in order to classify all living organisms.
Some concrete examples of such characteristics used for a hierarchical classification are….
Nuclear organization:
A cell which has membrane-bound organelles, including a nucleus, which allow cellular processes to be carried out efficiently in isolation from each other is called eukaryotic cell. The organisms made of such cells are called eukarytotic organisms. E.g. plants, animals etc.
The organisms which do not have a clearly demarcated nucleus and other organelles would need to have their biochemical pathways organized in very different ways, such cells are called prokaryotic organism. e.g. bacteria, cyanobacteria, mycoplamas etc.
This would have an effect on every aspect of cell design.
Further, nucleated cells would have the capacity to participate in making a multicellular organism because they can take up specialized functions.
Therefore, this is a basic characteristic of classification.
2. Cellular organization-
Do the cells occur singly or are they grouped together and do they live as an indivisible group? Cells that group together to form a single organism use the principle of division of labour.
In such a body design, all cells would not be identical.
Instead, groups of cells will carry out specialized functions.
This makes a very basic distinction in the body designs of organisms.
As a result, an Amoeba and a worm are very different in their body design.
3. Mode of nutrition:
Do organisms produce their own food through the process of photosynthesis?
Being able to produce one’s own food versus having to get food from outside would make very different body designs necessary.
Of the organisms that perform photosynthesis (plants), what is the level of organization of their body?
Of the animals, how does the individual’s body develop and organize its different parts, and what are the specialized organs found for different functions?
In these few questions that we have asked, a hierarchy is developing.
The characteristics of body design used for classification of plants will be very different from those important for classifying animals.
This is because the basic designs are different, based on the need to make their own food (plants), or acquire it (animals).
Therefore, these design features (having a skeleton, for example) are to be used to make sub-groups, rather than making broad groups.
Classification and Evolution
All living things are identified and categorized on the basis of their body design in form and function. Some characteristics are likely to make more wide-ranging changes in body design than others.
There is a role of time in this as well.
So, once a certain body design comes into existence, it will shape the effects of all other subsequent design changes, simply because it already exists.
In other words, characteristics that came into existence earlier are likely to be more basic than characteristics that have come into existence later.
This means that the classification of life forms will be closely related to their evolution.
What is evolution?
“Gradual directional change leading to more advance or complex form is called as 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.
When we connect this idea of evolution to classification, we will find some groups of organisms which have ancient body designs that have not changed very much.
We will also find other groups of organisms that have acquired their particular body designs relatively recently.
Those in the first group are frequently referred to as ‘primitive’ or ‘lower’ organisms, while those in the second group are called ‘advanced’ or ‘higher’ organisms.
In reality, these terms are not quite correct since they do not properly relate to the differences.
All that we can say is that some are ‘older’ organisms, while some are ‘younger’ organisms.
Since there is a possibility that complexity in design will increase over evolutionary time, it may not be wrong to say that older organisms are simpler, while younger organisms are more complex.
The Hierarchy of Classification-Groups
“The arrangement of groups of organisms (taxa) in a definite order is called hierarchy of classification”.
In any classification system Kingdom occupies top level and species lowermost position in hierarchy.
Biologists, such as Ernst Haeckel (1894), Robert Whittaker (1959) and Carl Woese (1977) have tried to classify all living organisms into broad categories, called kingdoms.
The classification Whittaker proposed has five kingdoms: Monera, Protista, Fungi, Plantae and Animalia, and is widely used.
These groups are formed on the basis of their cell structure, mode and source of nutrition and body organisation.
The Carl Woese introduced modified system of classification called “three domain system”. He classified organism into tree domains. He divide monera into Archaebacteria (or Archaea) and Eubacteria (or Bacteria) is also in use. And Eukarya domain contains remaining 4 kingdoms.
Further classification of Kingdom is done by naming the sub-groups at various levels as given in the following scheme:
Kingdom
Phylum (for animals) / Division (for plants)
Class
Order
Family
Genus
Species
Thus, by separating organisms on the basis of a hierarchy of characteristics into smaller and smaller groups, we arrive at the basic unit of classification, which is a ‘species’.
So what organisms can be said to belong to the same species? Broadly, a species includes all organisms that are similar enough to breed and perpetuate.
The important characteristics of the five kingdoms of Whittaker are as follows:
Kingdom MONERA
These organisms do not have a defined nucleus, i.e. they are prokaryotic.
They lack membrane bound cell organelles,
No any of them show multi-cellular body designs.
On the other hand, they show diversity based on many other characteristics.
Some of them have cell walls while some do not.(mycoplasma)
The mode of nutrition of organisms in this group can be either by synthesizing their own food (autotrophic like BGA) or getting it from the environment (heterotrophic).
This group includes bacteria, blue-green algae or cyanobacteria, and mycoplasma.
Kingdom PROTISTA
This group includes many kinds of unicellular eukaryotic organisms.
Some of these organisms use appendages, such as hair-like cilia or whip-like flagella for moving around.
Their mode of nutrition can be autotrophic or heterotrophic.
Examples are unicellular algae, diatoms and protozoans like Amoeba, Paramaecium, Euglena, Clyamydomonas, dianoflagellates etc.
Kingdom FUNGI
These are heterotrophic eukaryotic organisms.
They use decaying organic material as food and are therefore called saprophytes.
They may also grow on other living organisms therefore, called parasitic. Some are pathogenic.
Many of them have the capacity to become multicellular organisms at certain stages in their lives.
They have cell-walls made of a tough complex sugar called chitin.
Examples are yeast and mushrooms, Mucor, Penicillium, Aspergillus, Rhizopus etc.
Lichen:
Symbiotic and permanent association between fungi and algae is called Lichen.
Some fungal species live in permanent mutually dependent relationships with bluegreen algae (or cyanobacteria).
Such relationships are called symbiotic. These symbiobic life forms are called lichens.
We have all seen lichens as the slow-growing large coloured patches on the bark of trees.
E.g. Parmelia,
Kingdom PLANTAE
These are multicellular eukaryotic organism.
They possesses cell walls.
They are autotrophs and use chlorophyll for photosynthesis.
Thus, all plants are included in this group.
Since plants and animals are most visible forms of the diversity of life around us, we will look at the subgroups in this category later.
E.g. algae, ferns, mango, Cycas etc.
Kingdom ANIMALIA
These include all organisms which are multicellular eukaryotic organisms.
They are without cell walls.
They show heterotrophs and holozoic mode of nutrition.
E.g. Earthworm, insects, birds, reptiles, Mammals like apes, human etc.
Kingdom Plantae
The kingdom Plantae is a very large group of photosynthetic eukaryotic multicellular organism.
The first level of classification among plants
depend on whether the plant body has well differentiated into root stem and leaves.
The next level of classification is based on whether the differentiated plant body has special tissues like xylem and phloem for the transport of water and other substances within it.
Further classification looks at the ability to bear seeds
The further classification includes whether the seeds are enclosed within fruits or naked.
Using the above crieteria Kigdom Plantae is classified into 2 subkingdoms such as Cryptogamae and Phanerogamae.
Cryptogame is further divided into three divisions such as thallophyta, byrophyta and Pteridophyta.
The thallophytes, the bryophytes and the pteridophytes have naked embryos that are called spores.
The reproductive organs of plants in all these three groups are very inconspicuous, and they are therefore called ‘cryptogamae’, or ‘those with hidden reproductive organs’.
THALLOPHYTA
Plants that do not have well-differentiated body design fall in this group.
They don’t have root, stem and leaves.
The plants in this group are commonly called algae.
They have naked embryos that are called spores.
These plants are predominantly aquatic.
Examples are Spirogyra, Ulothrix, Cladophora and Chara
BRYOPHYTA
The plant body is commonly differentiated to form stem and leaf-like structures.
But true roots,stem and leaves are absent.
The vascular tissues like xylem and phloem are also absent.
They have naked embryos that are called spores.
These are called the amphibians of the plant kingdom, as they grow on land but need water for survival and also for reproduction.
However, there is no specialized tissue for the conduction of water and other substances from one part of the plant body to another.
Examples are moss (Funaria) and Marchantia.
PTERIDOPHYTA
They are called vascular cryptogams.
In this group, the plant body is differentiated into roots, stem and leaves.
These plants have specialized tissue for the conduction of water and other substances from one part of the plant body to another.
They have naked embryos that are called spores.
Some examples are Marsilea, ferns and horse-tails.
What are phanerogams?
The plants with well differentiated reproductive tissues that ultimately make seeds are called phanerogams.
Seeds are the result of the reproductive process. They consist of the embryo along with stored food, which serves for the initial growth of the embryo during germination.
This group is further classified, based on whether the seeds are naked or enclosed in fruits, giving us two groups: gymnosperms and angiosperms.
GYMNOSPERMS
This term is made from two Greek words: gymno– means naked and sperma– means seed.
The plants of this group bear naked seeds and are usually perennial, evergreen and woody.
They mostly are taller trees, the largest, tallest tree Sequioa belongs to this group.
They produce male and female cones as reproductive organs.
Examples are pines, such as deodar, Cycas, Chritsmas tree,
ANGIOSPERMS
The Angiosperms word is made from two Greek words: angio means covered and sperma– means seed.
These are also called flowering plants.
The seeds develop inside a fruit.
Plant embryos in seeds have structures called plumule, radical and cotyledons.
Cotyledons are called ‘seed leaves’ because in many instances they emerge and become green when the seed germinates.
Thus, cotyledons represent a bit of pre-designed plant in the seed.
The angiosperms are divided into two groups on the basis of the number of cotyledons present in the seed.
Plants with seeds having a single cotyledon are called monocotyledonous or monocots.
Plants with seeds having two cotyledons are called dicots.
Differences between diocotyledonous plants and monocots.
How many petals are found in the flower of these plants?
Can you write down further characteristics of monocots and dicots on the basis of these observations?
Dicots and monocotyledonous plants are distinguished on the basis of fundamental characteresitcs as follows:
Sr. No. Characters Dicot Monocot
1. Root system Tap roots Adventitious roots
2. Stem Branched Usualy unbranched
Leaves dorsiventral Isobilateral
venation reticulate Parallal.
Floral symmetry Pentamerrous Tri-merrous
Petals Five or four three
Cotyledons in seed two one
Structure of cotyledon Thick and fleshy Thin and does not store food
pollination Entemophily or ornithophily Mostly anemophily.
Examples Pea, Gram, Mango, Groundnut, Wheat, jowar, maize, rice, sugarcane etc.
Kingdom Animalia
These are organisms which are eukaryotic, multicellular and heterotrophic.
Their cells do not have cell-walls.
Most animals are mobile.
They are further classified based on the extent and type of the body design differentiation found.
PORIFERA
The word porifera means organisms with holes. These are non-motile animals attached to some solid support.
There are holes or ‘pores’, all over the body.
These lead to a canal system that helps in circulating water throughout the body to bring in food and oxygen.
These animals are covered with a hard outside layer
or skeleton.
The body design involves very minimal differentiation and division into tissues.
They are commonly called sponges, and are mainly found in marine habitats.
Some examples are Euplectelia, Sycon, Spongilla
COELENTERATA
These are animals living in water.
They show more body design differentiation.
There is a cavity in the body.
The body is made of two layers of cells: one makes up cells on the outside of the body, and the other makes the inner lining of the body.
Some of these species live in colonies (corals), while others have a solitary like–span (Hydra). Jellyfish and sea anemones are common examples.
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, which 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 welldeveloped organs can be accommodated.
The body is flattened dorsiventrally, meaning from top to bottom, which is why these animals are called flatworms.
They are either free living or parasitic.
Some examples are free living animals like planarians, or parasitic animals like liverflukes.
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 worms in the intestines (roundworm or pinworms).Some examples are Ascaris, Wuchereria.
ANNELIDA
Annelid animals are also bilaterally symmetrical and triploblastic.
They have a true body cavity.
This allows true organs to be packaged in the body structure.
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 land. Earthworms and leeches are familiar examples.
6. ARTHROPODA
This is probably the largest group of animals.
These animals are bilaterally symmetrical and
segmented. There is an open circulatory system, and so the blood does not flow in well defined blood vessels.
The coelomic cavity is blood-filled.
They have jointed legs (the word ‘arthropod’ means ‘jointed legs’).
Some familiar examples are prawns, butterflies,
houseflies, spiders, scorpions and crabs
MOLLUSCA
In the animals of this group, there is bilateral symmetry.
The coelomic cavity is reduced.
There is little segmentation.
They have an open circulatory system.
They have kidney-like organs for excretion.
There is a foot that is used for moving around.
Examples are snails and mussels.
ECHINODERMATA
In Greek, echinos means hedgehog (spines), and derma means skin.
Thus, these are spiny skinned organisms.
These are exclusively free-living marine animals.
They are triploblastic and have a coelomic cavity. They also have a peculiar water-driven tube system
that they use for moving around.
They have hard calcium carbonate structures that they use as a skeleton.
Examples are starfish and sea urchins.
9. 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 support structure (chord=string) that runs along the back of the animal separating the nervous tissue from the gut.
Notochord 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.
Examples are Balanoglossus, Herdemania, and Amphioxus.
10. VERTEBRATA
These animals have a true vertebral column.
They have internal skeleton, allowing a completely different distribution of muscle attachment points to be used for movement.
Vertebrates are bilaterally symmetrical, triploblastic, coelomic and segmented, with complex differentiation of body tissues and organs.
All chordates possess the following features:
(i) have a notochord
(ii) have a dorsal nerve cord
(iii) are triploblastic
(iv) have paired gill pouches
(v) are coelomate.
Vertebrates are grouped into five classes such as
Pisces
amphibian
reptelia
aves
mammals.
PISCES
These are fish.
They are exclusively water living animals.
Their skin is covered with scales/plates.
They obtain oxygen dissolved in water by using gills.
The body is streamlined, and a muscular tail is used for movement.
They are cold-blooded (Poikilothermic)
They have hearts with only two chambers, unlike the four that humans have.
They lay eggs i. e. they are Oviparous.
We can think of many kinds of fish, some with skeletons made entirely of cartilage, such as sharks.
Some with a skeleton made of both bone and cartilage, such as tuna or rohu.
AMPHIBIA
These animals differ from the fish in the lack of scales, in having mucus glands in the skin, and a three-chambered heart.
Respiration is through either gills or lungs. They lay eggs.
These animals are found both in water and on land. Frogs, toads and salamanders are some examples.
REPTILIA
These animals are cold-blooded.
They have scales and breathe through lungs.
While most of them have a three-chambered heart, crocodiles have four heart chambers.
They lay eggs with tough coverings and do not need to lay their eggs in water, unlike amphibians. Snakes, turtles, lizards and crocodiles fall in this category.
AVES
These are warm-blooded animals i.e. homeothermic.
They have a four-chambered heart.
They lay eggs.
There is an outside covering of feathers, and two forelimbs are modified for flight.
They breathe through lungs.
All birds fall in this category- ostrich, parrot etc.
MAMMALIA
Mammals are warm-blooded animals.
They have four-chambered hearts.
They have mammary glands for the production of milk to nourish their young.
Their skin has hairs as well as sweat and oil glands. Most mammals familiar to us produce live young ones thus are called viviparous.
However, a few of them, like the platypus and the echidna lay eggs. (Exceptions).
Some, like kangaroos give birth to very poorly developed young ones.
Nomenclature
Why is there a need for systematic naming of
living organisms?
Naming the organisms is called nomenclature.
Any one plant may have many local names.
These vernacular name creates confusion when study at international or national level.
This problem was resolved by agreeing upon a ‘scientific’ name for organisms by framing universal rules.
They are same manner that chemical symbols and formulae for various substances are used the world over.
The scientific name for an organism is thus unique and can be used to identify it anywhere in the world.
“The scientific method of naming organisms, which consists two parts, is called binomial nomenclature”.
The system of scientific naming we use today was introduced by Carolus Linnaeus in the eighteenth
century.
Certain conventions are followed while writing the scientific names:
The world over, it has been agreed that both these names will be used in Latin forms.
The name of the genus begins with a capital letter.
The name of the species begins with a small letter.
When printed, the scientific name is given in italics.
When written by hand, the genus name and the species name have to be underlined separately.
The scientific name of mango is
Mangifera indigofera Linn.
(Genus) (Species) (Scientist)
Carolus Linnaeus: Brief life history
Carolus Linnaeus (Karl von Linne) was born in
Sweden and was a doctor by profession.
He was interested in the study of plants.
At the age of 22, he published his first paper on plants.
While serving as a personal physician of a wealthy government official.
He studied the diversity of plants in his employer’s garden.
Later, he published 14 papers and also brought out the famous book Systema Naturae from which all fundamental taxonomical researches have taken off.
His system of classification was a simple scheme for arranging plants so as to be able to identify them again.
Note:
Please refer charts, diagrams, figures, questions of the NCERT Text book, while referring the notes.
Add some key points if you get it from some reference books you are using.
These notes are strictly based on NCERT Syllabus.
DIVERSITY IN LIVING ORGANISMS
1. Why do we classify organisms?
2. Give three examples of the range of variations that you see in life forms around you.
What is biodiversity? Explain it on the earth.
Biodiversity- Existence of varied species of organisms in the geographical area is called biodiversity.
Biodiversity means the diversity of life forms.
It is a word commonly used to refer to the variety of life forms found in a particular region.
Different forms of life occur on earth.
On one hand we have microscopic bacteria of a few micrometer in size.
While on the other hand we have blue whale and red wood trees of California of approximate sizes of 30 meters and 100 meters respectively.
Some pine trees live for thousands of years while insects like mosquitoes die within a few days.
Life also ranges from colourless or even transparent worms to brightly coloured birds and flowers.
This bewildering variety of life around us has evolved on the earth over millions of years.
However, we do not have more than a tiny fraction of this time to try and understand all these living organisms, so we cannot look at them one by one.
Instead, we look for similarities among the organisms, which will allow us to put them into different classes and then study different classes or groups as a whole.
Define classification. Give its importance.
“A method of forming groups or classes of the organisms on the basis of similarities of the characters is called classification”.
In order to make relevant groups to study the variety of life forms, we need to decide which characteristics decide more fundamental differences among organisms.
This would create the main broad groups of organisms.
Within these groups, smaller subgroups will be decided by less important characteristics.
What is the Basis of Classification?
For the classification of living organisms various criteria were used by scientists time to time.
Greek thinker Aristotle classified animals according to whether they lived on land, in water or in the air. This is a very simple way of looking at life, but misleading too.
For example, animals that live in the sea include corals, whales, octopuses, starfish and sharks.
We can immediately see that these are very different from each other in numerous ways.
In fact, their habitat is the only point they share in common.
This is no good as a way of making groups of organisms to study and think about.
What are perfect criteria or characteristics for classification?
We need to decide which characteristics to be used as the basis for making the broadest divisions.
Then we will have to pick the next set of characteristics for making sub-groups within these divisions.
This process of classification within each group can then continue using new characteristics each time.
Before we go on, we need to think about what is meant by ‘characteristics’.
When we are trying to classify a diverse group of organisms, we need to find ways in which some of them are similar enough to be thought of together.
These ‘ways’, in fact, are details of appearance or behaviour, in other words, form and function.
What we mean by a characteristic is a particular form or a particular function.
That most of us have five fingers on each hand is thus a characteristic.
That we can run, but the banyan tree cannot, is also a characteristic.
Example how classification can be done?
Now, to understand how some characteristics are decided as being more fundamental than others, let us consider how a stone wall is built.
The stones used will have different shapes and sizes.
The stones at the top of the wall would not influence the choice of stones that come below them.
On the other hand, the shapes and sizes of stones in the lowermost layer will decide the shape and size of the next layer and so on.
The stones in the lowermost layer are like the characteristics that decide the broadest divisions among living organisms.
They are independent of any other characteristics in their effects on the form and function of the organism.
The characteristics in the next level would be dependent on the previous one and would decide the variety in the next level.
In this way, we can build up a whole hierarchy of mutually related characteristics to be used for classification.
What are the recent criteria used to classify living organisms according to five kingdom system?
The living organisms are classified into five kingdoms on the basis of three to four important criteria They are
Nuclear organization- whether cell is prokaryotic or eukaryotic.
Cellular organization- whether eukaryotic organism is unicellular or multicellular.
Mode of nutrition- whether eukaryotic organism is autotrophic or heterotrophic.
Ecological status-whether heterotrophic organism is saprophytic, parasitic or holozoic in mode of nutrition.
Describe these criteria in details.
Now-a-days, we look at many inter-related characteristics starting from the nature of the cell in order to classify all living organisms.
Some concrete examples of such characteristics used for a hierarchical classification are….
Nuclear organization:
A cell which has membrane-bound organelles, including a nucleus, which allow cellular processes to be carried out efficiently in isolation from each other is called eukaryotic cell. The organisms made of such cells are called eukarytotic organisms. E.g. plants, animals etc.
The organisms which do not have a clearly demarcated nucleus and other organelles would need to have their biochemical pathways organized in very different ways, such cells are called prokaryotic organism. e.g. bacteria, cyanobacteria, mycoplamas etc.
This would have an effect on every aspect of cell design.
Further, nucleated cells would have the capacity to participate in making a multicellular organism because they can take up specialized functions.
Therefore, this is a basic characteristic of classification.
2. Cellular organization-
Do the cells occur singly or are they grouped together and do they live as an indivisible group? Cells that group together to form a single organism use the principle of division of labour.
In such a body design, all cells would not be identical.
Instead, groups of cells will carry out specialized functions.
This makes a very basic distinction in the body designs of organisms.
As a result, an Amoeba and a worm are very different in their body design.
3. Mode of nutrition:
Do organisms produce their own food through the process of photosynthesis?
Being able to produce one’s own food versus having to get food from outside would make very different body designs necessary.
Of the organisms that perform photosynthesis (plants), what is the level of organization of their body?
Of the animals, how does the individual’s body develop and organize its different parts, and what are the specialized organs found for different functions?
In these few questions that we have asked, a hierarchy is developing.
The characteristics of body design used for classification of plants will be very different from those important for classifying animals.
This is because the basic designs are different, based on the need to make their own food (plants), or acquire it (animals).
Therefore, these design features (having a skeleton, for example) are to be used to make sub-groups, rather than making broad groups.
Classification and Evolution
All living things are identified and categorized on the basis of their body design in form and function. Some characteristics are likely to make more wide-ranging changes in body design than others.
There is a role of time in this as well.
So, once a certain body design comes into existence, it will shape the effects of all other subsequent design changes, simply because it already exists.
In other words, characteristics that came into existence earlier are likely to be more basic than characteristics that have come into existence later.
This means that the classification of life forms will be closely related to their evolution.
What is evolution?
“Gradual directional change leading to more advance or complex form is called as 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.
When we connect this idea of evolution to classification, we will find some groups of organisms which have ancient body designs that have not changed very much.
We will also find other groups of organisms that have acquired their particular body designs relatively recently.
Those in the first group are frequently referred to as ‘primitive’ or ‘lower’ organisms, while those in the second group are called ‘advanced’ or ‘higher’ organisms.
In reality, these terms are not quite correct since they do not properly relate to the differences.
All that we can say is that some are ‘older’ organisms, while some are ‘younger’ organisms.
Since there is a possibility that complexity in design will increase over evolutionary time, it may not be wrong to say that older organisms are simpler, while younger organisms are more complex.
The Hierarchy of Classification-Groups
“The arrangement of groups of organisms (taxa) in a definite order is called hierarchy of classification”.
In any classification system Kingdom occupies top level and species lowermost position in hierarchy.
Biologists, such as Ernst Haeckel (1894), Robert Whittaker (1959) and Carl Woese (1977) have tried to classify all living organisms into broad categories, called kingdoms.
The classification Whittaker proposed has five kingdoms: Monera, Protista, Fungi, Plantae and Animalia, and is widely used.
These groups are formed on the basis of their cell structure, mode and source of nutrition and body organisation.
The Carl Woese introduced modified system of classification called “three domain system”. He classified organism into tree domains. He divide monera into Archaebacteria (or Archaea) and Eubacteria (or Bacteria) is also in use. And Eukarya domain contains remaining 4 kingdoms.
Further classification of Kingdom is done by naming the sub-groups at various levels as given in the following scheme:
Kingdom
Phylum (for animals) / Division (for plants)
Class
Order
Family
Genus
Species
Thus, by separating organisms on the basis of a hierarchy of characteristics into smaller and smaller groups, we arrive at the basic unit of classification, which is a ‘species’.
So what organisms can be said to belong to the same species? Broadly, a species includes all organisms that are similar enough to breed and perpetuate.
The important characteristics of the five kingdoms of Whittaker are as follows:
Kingdom MONERA
These organisms do not have a defined nucleus, i.e. they are prokaryotic.
They lack membrane bound cell organelles,
No any of them show multi-cellular body designs.
On the other hand, they show diversity based on many other characteristics.
Some of them have cell walls while some do not.(mycoplasma)
The mode of nutrition of organisms in this group can be either by synthesizing their own food (autotrophic like BGA) or getting it from the environment (heterotrophic).
This group includes bacteria, blue-green algae or cyanobacteria, and mycoplasma.
Kingdom PROTISTA
This group includes many kinds of unicellular eukaryotic organisms.
Some of these organisms use appendages, such as hair-like cilia or whip-like flagella for moving around.
Their mode of nutrition can be autotrophic or heterotrophic.
Examples are unicellular algae, diatoms and protozoans like Amoeba, Paramaecium, Euglena, Clyamydomonas, dianoflagellates etc.
Kingdom FUNGI
These are heterotrophic eukaryotic organisms.
They use decaying organic material as food and are therefore called saprophytes.
They may also grow on other living organisms therefore, called parasitic. Some are pathogenic.
Many of them have the capacity to become multicellular organisms at certain stages in their lives.
They have cell-walls made of a tough complex sugar called chitin.
Examples are yeast and mushrooms, Mucor, Penicillium, Aspergillus, Rhizopus etc.
Lichen:
Symbiotic and permanent association between fungi and algae is called Lichen.
Some fungal species live in permanent mutually dependent relationships with bluegreen algae (or cyanobacteria).
Such relationships are called symbiotic. These symbiobic life forms are called lichens.
We have all seen lichens as the slow-growing large coloured patches on the bark of trees.
E.g. Parmelia,
Kingdom PLANTAE
These are multicellular eukaryotic organism.
They possesses cell walls.
They are autotrophs and use chlorophyll for photosynthesis.
Thus, all plants are included in this group.
Since plants and animals are most visible forms of the diversity of life around us, we will look at the subgroups in this category later.
E.g. algae, ferns, mango, Cycas etc.
Kingdom ANIMALIA
These include all organisms which are multicellular eukaryotic organisms.
They are without cell walls.
They show heterotrophs and holozoic mode of nutrition.
E.g. Earthworm, insects, birds, reptiles, Mammals like apes, human etc.
Kingdom Plantae
The kingdom Plantae is a very large group of photosynthetic eukaryotic multicellular organism.
The first level of classification among plants
depend on whether the plant body has well differentiated into root stem and leaves.
The next level of classification is based on whether the differentiated plant body has special tissues like xylem and phloem for the transport of water and other substances within it.
Further classification looks at the ability to bear seeds
The further classification includes whether the seeds are enclosed within fruits or naked.
Using the above crieteria Kigdom Plantae is classified into 2 subkingdoms such as Cryptogamae and Phanerogamae.
Cryptogame is further divided into three divisions such as thallophyta, byrophyta and Pteridophyta.
The thallophytes, the bryophytes and the pteridophytes have naked embryos that are called spores.
The reproductive organs of plants in all these three groups are very inconspicuous, and they are therefore called ‘cryptogamae’, or ‘those with hidden reproductive organs’.
THALLOPHYTA
Plants that do not have well-differentiated body design fall in this group.
They don’t have root, stem and leaves.
The plants in this group are commonly called algae.
They have naked embryos that are called spores.
These plants are predominantly aquatic.
Examples are Spirogyra, Ulothrix, Cladophora and Chara
BRYOPHYTA
The plant body is commonly differentiated to form stem and leaf-like structures.
But true roots,stem and leaves are absent.
The vascular tissues like xylem and phloem are also absent.
They have naked embryos that are called spores.
These are called the amphibians of the plant kingdom, as they grow on land but need water for survival and also for reproduction.
However, there is no specialized tissue for the conduction of water and other substances from one part of the plant body to another.
Examples are moss (Funaria) and Marchantia.
PTERIDOPHYTA
They are called vascular cryptogams.
In this group, the plant body is differentiated into roots, stem and leaves.
These plants have specialized tissue for the conduction of water and other substances from one part of the plant body to another.
They have naked embryos that are called spores.
Some examples are Marsilea, ferns and horse-tails.
What are phanerogams?
The plants with well differentiated reproductive tissues that ultimately make seeds are called phanerogams.
Seeds are the result of the reproductive process. They consist of the embryo along with stored food, which serves for the initial growth of the embryo during germination.
This group is further classified, based on whether the seeds are naked or enclosed in fruits, giving us two groups: gymnosperms and angiosperms.
GYMNOSPERMS
This term is made from two Greek words: gymno– means naked and sperma– means seed.
The plants of this group bear naked seeds and are usually perennial, evergreen and woody.
They mostly are taller trees, the largest, tallest tree Sequioa belongs to this group.
They produce male and female cones as reproductive organs.
Examples are pines, such as deodar, Cycas, Chritsmas tree,
ANGIOSPERMS
The Angiosperms word is made from two Greek words: angio means covered and sperma– means seed.
These are also called flowering plants.
The seeds develop inside a fruit.
Plant embryos in seeds have structures called plumule, radical and cotyledons.
Cotyledons are called ‘seed leaves’ because in many instances they emerge and become green when the seed germinates.
Thus, cotyledons represent a bit of pre-designed plant in the seed.
The angiosperms are divided into two groups on the basis of the number of cotyledons present in the seed.
Plants with seeds having a single cotyledon are called monocotyledonous or monocots.
Plants with seeds having two cotyledons are called dicots.
Differences between diocotyledonous plants and monocots.
How many petals are found in the flower of these plants?
Can you write down further characteristics of monocots and dicots on the basis of these observations?
Dicots and monocotyledonous plants are distinguished on the basis of fundamental characteresitcs as follows:
Sr. No. Characters Dicot Monocot
1. Root system Tap roots Adventitious roots
2. Stem Branched Usualy unbranched
Leaves dorsiventral Isobilateral
venation reticulate Parallal.
Floral symmetry Pentamerrous Tri-merrous
Petals Five or four three
Cotyledons in seed two one
Structure of cotyledon Thick and fleshy Thin and does not store food
pollination Entemophily or ornithophily Mostly anemophily.
Examples Pea, Gram, Mango, Groundnut, Wheat, jowar, maize, rice, sugarcane etc.
Kingdom Animalia
These are organisms which are eukaryotic, multicellular and heterotrophic.
Their cells do not have cell-walls.
Most animals are mobile.
They are further classified based on the extent and type of the body design differentiation found.
PORIFERA
The word porifera means organisms with holes. These are non-motile animals attached to some solid support.
There are holes or ‘pores’, all over the body.
These lead to a canal system that helps in circulating water throughout the body to bring in food and oxygen.
These animals are covered with a hard outside layer
or skeleton.
The body design involves very minimal differentiation and division into tissues.
They are commonly called sponges, and are mainly found in marine habitats.
Some examples are Euplectelia, Sycon, Spongilla
COELENTERATA
These are animals living in water.
They show more body design differentiation.
There is a cavity in the body.
The body is made of two layers of cells: one makes up cells on the outside of the body, and the other makes the inner lining of the body.
Some of these species live in colonies (corals), while others have a solitary like–span (Hydra). Jellyfish and sea anemones are common examples.
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, which 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 welldeveloped organs can be accommodated.
The body is flattened dorsiventrally, meaning from top to bottom, which is why these animals are called flatworms.
They are either free living or parasitic.
Some examples are free living animals like planarians, or parasitic animals like liverflukes.
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 worms in the intestines (roundworm or pinworms).Some examples are Ascaris, Wuchereria.
ANNELIDA
Annelid animals are also bilaterally symmetrical and triploblastic.
They have a true body cavity.
This allows true organs to be packaged in the body structure.
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 land. Earthworms and leeches are familiar examples.
6. ARTHROPODA
This is probably the largest group of animals.
These animals are bilaterally symmetrical and
segmented. There is an open circulatory system, and so the blood does not flow in well defined blood vessels.
The coelomic cavity is blood-filled.
They have jointed legs (the word ‘arthropod’ means ‘jointed legs’).
Some familiar examples are prawns, butterflies,
houseflies, spiders, scorpions and crabs
MOLLUSCA
In the animals of this group, there is bilateral symmetry.
The coelomic cavity is reduced.
There is little segmentation.
They have an open circulatory system.
They have kidney-like organs for excretion.
There is a foot that is used for moving around.
Examples are snails and mussels.
ECHINODERMATA
In Greek, echinos means hedgehog (spines), and derma means skin.
Thus, these are spiny skinned organisms.
These are exclusively free-living marine animals.
They are triploblastic and have a coelomic cavity. They also have a peculiar water-driven tube system
that they use for moving around.
They have hard calcium carbonate structures that they use as a skeleton.
Examples are starfish and sea urchins.
9. 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 support structure (chord=string) that runs along the back of the animal separating the nervous tissue from the gut.
Notochord 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.
Examples are Balanoglossus, Herdemania, and Amphioxus.
10. VERTEBRATA
These animals have a true vertebral column.
They have internal skeleton, allowing a completely different distribution of muscle attachment points to be used for movement.
Vertebrates are bilaterally symmetrical, triploblastic, coelomic and segmented, with complex differentiation of body tissues and organs.
All chordates possess the following features:
(i) have a notochord
(ii) have a dorsal nerve cord
(iii) are triploblastic
(iv) have paired gill pouches
(v) are coelomate.
Vertebrates are grouped into five classes such as
Pisces
amphibian
reptelia
aves
mammals.
PISCES
These are fish.
They are exclusively water living animals.
Their skin is covered with scales/plates.
They obtain oxygen dissolved in water by using gills.
The body is streamlined, and a muscular tail is used for movement.
They are cold-blooded (Poikilothermic)
They have hearts with only two chambers, unlike the four that humans have.
They lay eggs i. e. they are Oviparous.
We can think of many kinds of fish, some with skeletons made entirely of cartilage, such as sharks.
Some with a skeleton made of both bone and cartilage, such as tuna or rohu.
AMPHIBIA
These animals differ from the fish in the lack of scales, in having mucus glands in the skin, and a three-chambered heart.
Respiration is through either gills or lungs. They lay eggs.
These animals are found both in water and on land. Frogs, toads and salamanders are some examples.
REPTILIA
These animals are cold-blooded.
They have scales and breathe through lungs.
While most of them have a three-chambered heart, crocodiles have four heart chambers.
They lay eggs with tough coverings and do not need to lay their eggs in water, unlike amphibians. Snakes, turtles, lizards and crocodiles fall in this category.
AVES
These are warm-blooded animals i.e. homeothermic.
They have a four-chambered heart.
They lay eggs.
There is an outside covering of feathers, and two forelimbs are modified for flight.
They breathe through lungs.
All birds fall in this category- ostrich, parrot etc.
MAMMALIA
Mammals are warm-blooded animals.
They have four-chambered hearts.
They have mammary glands for the production of milk to nourish their young.
Their skin has hairs as well as sweat and oil glands. Most mammals familiar to us produce live young ones thus are called viviparous.
However, a few of them, like the platypus and the echidna lay eggs. (Exceptions).
Some, like kangaroos give birth to very poorly developed young ones.
Nomenclature
Why is there a need for systematic naming of
living organisms?
Naming the organisms is called nomenclature.
Any one plant may have many local names.
These vernacular name creates confusion when study at international or national level.
This problem was resolved by agreeing upon a ‘scientific’ name for organisms by framing universal rules.
They are same manner that chemical symbols and formulae for various substances are used the world over.
The scientific name for an organism is thus unique and can be used to identify it anywhere in the world.
“The scientific method of naming organisms, which consists two parts, is called binomial nomenclature”.
The system of scientific naming we use today was introduced by Carolus Linnaeus in the eighteenth
century.
Certain conventions are followed while writing the scientific names:
The world over, it has been agreed that both these names will be used in Latin forms.
The name of the genus begins with a capital letter.
The name of the species begins with a small letter.
When printed, the scientific name is given in italics.
When written by hand, the genus name and the species name have to be underlined separately.
The scientific name of mango is
Mangifera indigofera Linn.
(Genus) (Species) (Scientist)
Carolus Linnaeus: Brief life history
Carolus Linnaeus (Karl von Linne) was born in
Sweden and was a doctor by profession.
He was interested in the study of plants.
At the age of 22, he published his first paper on plants.
While serving as a personal physician of a wealthy government official.
He studied the diversity of plants in his employer’s garden.
Later, he published 14 papers and also brought out the famous book Systema Naturae from which all fundamental taxonomical researches have taken off.
His system of classification was a simple scheme for arranging plants so as to be able to identify them again.
Note:
Please refer charts, diagrams, figures, questions of the NCERT Text book, while referring the notes.
Add some key points if you get it from some reference books you are using.
These notes are strictly based on NCERT Syllabus.
