NCERT Class 9 Science Notes & Solutions – Chapter 7 – Diversity in Living Organisms

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Notes Diversity in Living Organisms

In-Text Questions & Answers - NCERT Class 9 Science Chapter 7

Exercises Questions & Answers - Diversity in Living Organisms

Diversity in Living Organisms | NCERT Class  9 Science Chapter 7 | Notes and pdf | In-Text Questions & Answers | Exercises Questions & Answers 

Q1. What are the necessities for classification of organisms?

There are about ten millions of species on the earth. Just imagine such a multitude of life-forms in our planet. The bewildering and surprising fact is that each organism is different from the other to a lesser or greater extent. Look at the similarity between you and your friends. There are differences in height, colour, body shape etc. Compare human beings and monkey, there are lots of similarities. But if you compare human beings to animals like cows, the similarities are to a lesser extent than monkey.

Our planet is full of biodiversity i.e. full of diverse life-forms, from microscopic bacteria of few micrometre in size to hundred metre red wood trees (California, USA) to thirty metre blue whale. Some dies in few days while some lives thousands of years (e.g., pine trees). Some are colourless, transparent (e.g., worms) while some are colourful (e.g., birds, flower etc.).

Our planet has so many organisms that if you spend a tiny fraction of time to know an organism, it is not possible to know all organism one by one. So we need to find similarities among organisms to allow to put them into different classes and understand them as a whole. For classification we need to find the characteristics which help to find the fundamental differences among organisms to form desired category. Thus we form broad groups of organisms. Further it we form smaller sub-groups under broad groups considering less important characteristics.

Q2. What are the primary characteristic on which broad division of organisms is made?

To classify a diverse group of organisms, we firstly find the most important or basic or primary characteristics. The basic characteristic is the type of cells. The cell is either eukaryotic or prokaryotic. Based on primary characteristics, we basically find some of the organisms which are similar enough to be grouped together. These characteristics are actually details of their appearance or behaviour, in other words form and function. These primary characteristics help to form broadest groups. After that we create smaller sub-groups under broad groups considering less important characteristics.

Q3. Which is more basic characteristic to classify organisms – the place where they live or the kind of cells they are made of?

Of course, the kind of cells that forms organisms is more basic characteristics. Great Greek philosopher and thinker Aristottle firstly introduced most simple way of classification of animals based on their habitation i.e. land, water and air. But this classification is misleading too. Because we find that whales, starfish, corals etc. live in water but they are different from each other. Only common thing among them is their place of living. So habitation is not a basic, effective and appropriate characteristic for classifying organisms.

Organisms like animals, plants are made of eukaryotic cell. A eukaryotic cell has demarcated nucleus and membrane bound organelles. All biochemical activities occur efficiently in isolation from each other inside a eukaryotic cell. Also nucleated cells form multicellular organisms and they can perform specialised function (connective tissue, muscular tissue etc.).

On the other hand organisms like Bacteria, Gleocapsa etc. are made of prokaryotic cell. A prokaryotic cell does not have demarcated nucleus and other organelles. So cellular processes inside prokaryotic cell occurs in very different ways. So, from aforesaid discussion, we may clearly conclude that type of cells that forms organism, is more basic or primary characteristic than their place of living.

Q4. What basic characteristics put plants and animals into different categories?

The differences in characteristics of body design of plants and animals put them into different categories. Explicitly we find the differences in their appearances and behaviours i.e. forms and functions. Mode of nutrition is also a basic characteristics which put plants and animals into different categories because plants generally produce their own food through photosynthesis whereas animals need to acquire it. Also plant cell has cell wall whereas animal cell lacks it.

Q5. Which region is the region of mega-diversity?

The region of mega-diversity is the warm and humid tropical region between the tropic of Cancer and the tropic of Capricorn.

Q6. Where half of the living organisms is concentrated?

India, China, Indonesia, Malaysia, Australia, Brazil, Colombia, Ecuador, Peru, Madagascar, Zaire and  Mexico are the habitation of more than half of the diverse life-forms on the earth.

Q7. Which are primitive organisms and advanced organisms?

We categorise living organisms on the basis of their body design in forms and functions. The characteristics that are associated when a certain organism comes into existence are the basic characteristics. Over the time, these basic characteristics make minor to major changes in body design of organisms. Because these changes allow them to survive better. It is called the evolution of organisms. The changes in basic characteristics occurs in accordance to their changes in body design over the time. Most living organisms of present have gone through wide-ranging of changes for their survival.

The organisms whose body design have not changed very much over the time are the primitive organisms. They are also called lower or older organisms. This group shows basic characteristics. It has the simple cell structure & mechanism with no division of labour.

The organisms whose body design have gone through major changes to acquire particular body design relatively recently are the advanced organisms. They are also called higher or younger organisms. It has millions of cells which are formed into different organs for various functions or mechanisms.

Q8. Why advanced organisms are complex organisms?

The body design of organisms shapes the effects of all subsequent changes over the time for their survival. And these major changes introduce complexity in their body design. That’s why advanced organisms are complex and primitive are simple.

Q9. Who introduced the idea of evolution?

In 1859, Charles Darwin in his book ‘The Origin of Species’ first presented the concept of evolution.

Q10. Discuss hierarchy of classification groups.

Biologists tried to classify all living organisms into broad categories known as kingdoms. The classification proposed by Biologist Robert Whittaker (1969) has five kingdoms. These are Monera, Protista, Fungi, Plantae and Animalia. Deciding factors for this widely used classification are i) cell structure, ii) mode and source of nutrition, and iii) body organisation. Later Biologist Carl Woese divided Monera group into two groups. These are i) Archaebacteria (or Archaea) and ii) Eubacteria (or Bacteria). The classification by Biologist Robert Whittaker is widely in use. Modification done by Biologist Carl Woese is also in use.

Further classification happens by adding different sub-groups at various level in the following way –
Kingdom ⇒ Phylum (for animals) or Division (for plants) ⇒ Class ⇒ Order ⇒ Family ⇒ Genus ⇒ Species

So, after classifying organisms into smaller and smaller groups on the basis of a hierarchy of characteristics, finally we get the smallest and basic unit of this classification. This smallest and basic unit is species. All organisms that are similar enough in breeding and perpetuation belong to same species.

diversity in living organisms
Hierarchy of Classification – Groups

Q11. Discuss five kingdoms of living organisms briefly.

♦ Monera:

  • This organism does not have defined nucleus or organelles.
  • This organism does not show multi-cellular body designs.
  • Some of these organisms have cell wall while others lack cell wall.
  • Mode of nutrition of these organisms is either autotrophic (synthesising their own food) or heterotrophic (getting food from environment).
  • For example ⇒ bacteria, blue-green algae or cyanobacteria and mycoplasma.

♦ Protista:

  • Many kinds of unicellular eukaryotic organisms belong to this group.
  • Mode of nutrition of these organisms is either autotrophic (synthesising their own food) or heterotrophic (getting food from environment).
  • Some of them use appendages (hair-like cilia or whip-like flagella) for moving around.
  • For example ⇒ unicellular algae, diatoms and protozoans.
Protozoa

♦ Fungi:

  • These organisms are eukaryotic.
  • Mode of nutrition of these organisms is heterotrophic.
  • Some of these organisms use decaying organic material as their food. For this reason they are called saprotrophs. Others use living protoplasm of their host organism for food. For this reason they are called parasites.
  • Some of them turn into multicellular organism at certain stages of their lives.
  • Tough complex sugar known as chitin forms the cell wall of these organisms. 
  • Some examples are Yeasts, Molds, Mushrooms.
  • We notice symbiotic relationship in some fungal species where they live in permanent mutually dependent relationship with blue-green algae. We term this type of symbiotic life forms as lichens. Slow growing large coloured patches on the bark of trees are examples of lichens.

♦ Plantae:

  • These organisms are eukaryotic.
  • They are multicellular with cell wall.
  • Mode of nutrition of these organisms is autotrophic. They use chlorophyll for photosynthesis.
  • This group includes all plants.

♦ Animalia:

  • These organisms are eukaryotic.
  • Also these organisms are multicellular without cell wall.
  • Mode of nutrition of these organisms is heterotrophic.
  • This group includes all animals.

Q12. Draw flowchart of five kingdoms proposed by Biologist Robert Whittaker.

diversity in living organisms

The five kingdom classification of organism by Biologist Robert Whittaker

Q13. What characteristics decide classification of plantae?

The most important and basic characteristics that decide classification of plants at first level are whether the plant body has well- defined differentiated distinct parts or not. The characteristic that decides next level classification are whether the differentiated plant body has special tissue (for the transportation of water and other substances) or not. Further classification depends on whether plants have the ability to bear seeds or not. In addition, it is also considerable whether the seeds are enclosed within fruits or not.

diversity in living organisms
Classification of Plants

Q14. Discuss various groups of plantae.

Thallophyta ⇒

  • It lacks well-differentiated distinct body parts.
  • Plants in this group are algae.
  • They are predominantly aquatic.
  • For example ⇒ Spirogyra, Ulothrix, Cladophora,Ulva, Chara etc.

Bryophyta ⇒

  • The body of these organisms is differentiated to form stem and leaf-like structures.
  • We also term these organisms as the amphibians in the plant kingdom.
  • They lack specialised vascular tissue for transportation of water and other substances from one part to another part in plant body.
  • Some examples of this group are Funaria, Marchantia etc.

Pteridophyta ⇒

  • The plant body is differentiated into roots, stem and leaves.
  • They have specialised vascular tissue for conduction of water and other substances from one part to another part into plant body.
  • Some examples are marselia, ferns and horse-tails.
  • These are called cryptogams as their reproductive organs are very inconspicuous and hidden.
  • Also they do not produce seeds.

Phanerogams ⇒

  • It has well-differentiated reproductive parts to make seeds.
  • Seeds are produced through sexual reproduction process.
  • Seed consists the embryo along with stored food which helps initial growth of the embryo during germination.
  • Further we divide phanerogams into two groups Gymnosperms & Angiosperms. Gymnosperms have naked seeds whereas Angiosperms have seeds enclosed within fruits.

Gymnosperms ⇒

  • Two Greek words gymno (means naked) & sperma (means seed) form the word gymnosperms.
  • It bears naked seed. Also they are usually perennial, evergreen and woody.
  • For example ⇒ pines, deodar etc.

Angiosperms ⇒

  • Two Greek words – angio (means covered) & sperma (means seeds) form the word angiosperms.
  • Plants in this group are flowering plants.
  • An ovary consists the seeds inside it which finally turns into fruit.
  • Plant embryos in seeds have structures called cotyledons. Cotyledons are actually seed leaves which emerge and become green during germination.
  • Further we divide angiosperms into two groups based on the number of cotyledons present in the seed. These two groups are monocots & dicots.
  • Monocots or monocotyledonous are those which contain single cotyledon in seeds.
  • Dicots are those which contain two cotyledons in seeds.

Q15. Draw flowchart for classification of animalia.

Firstly we classify animals based on cell type, cavity etc. as follows ⇒

After that we classify CHORDATA based on presence of notochord as follows ⇒

Further we divide VERTEBRATA as follows ⇒

Q16. Discuss various groups of animalia.

We learnt in Cell chapter that animal cell does not have cell-wall. Further we learnt that animals are eukaryotic, multicellular and heterotrophic. Most of them are mobile. The differences in the body design in various organisms of animal group prepares the base of further classification. Various groups of animalia are –

Porifera ⇒

  • These organism are non-mobile and attached to some solid support.
  • ‘PORIFERA’-word means organisms with holes. These organism have holes or pores all over their body.
  • These holes or pores develop a canal system in the body to bring in food and oxygen.
  • They are covered with a hard outside layer or skeleton.
  • Their body design involves very minimal differentiation and division into tissues.
  • These organism are mainly found in marine habitats and are commonly called sponges.
  • For example ⇒ Spongilla, Sycon. Euplectella etc.

Coelenterata (Cnidaria) ⇒

  • These organism live in water and show more differentiation in body design.
  • Their body is made of two layer of cells and houses a cavity.
  • Out of two layers of cells, one makes up cells on the outside of the body and the other makes inner lining of the body.
  • Some of these organism live in colonies (e.g. corals) and some of them have a solitary like-span (e.g. hydra).
  • For example ⇒ sea anemones, jellyfish etc.

Platyhelminthes ⇒

  • The body design of these animals is more complex than porifera and coelenterata.
  • The left half and right half of the body of these animals have same design which makes them bilaterally symmetrical.
  • Also we term these organisms as triploblastic because their body has three layers of cells.
  • The three layers of cells help in developing outside and inside body linings.
  • That layers of cells also develop well differentiated tissue as well as some organs.
  • The body of these organisms is flattened from top to bottom. In addition, it lacks true internal body cavity or coelom to house well-developed organ.
  • Also we term them as flatworms because of their flattened body.
  • These animals are either parasite like liver-flukes or free-living like planarians.

Nematoda ⇒

  • The body of these animals is triploblastic and bilaterally symmetrical.
  • Also the body of these animals is cylindrical not flattened and houses a sort of body cavity or pseudo-coelom.
  • These organisms are very familiar parasite worms that cause diseases. Examples are filarial worms that cause elephantiasis, roundworms or pin-worms in the intestines etc.

Annelida ⇒

  • The body of these animals is triploblastic and bilaterally symmetrical.
  • Also the body houses a true body cavity which helps true organs to be packaged in the body structure. Thus extensive body differentiation happens in a segmental fashion, with the segments lined up one after another other from head to tail.
  • Generally we find them in a variety of habitats i.e. land, marine water, fresh water.
  • For example ⇒ earthworms, leeches etc.

Arthropoda ⇒

  • The word ‘arthropod’ means jointed legs and animals under this group have jointed legs.
  • Few examples of this group are butterflies, prawns, houseflies, spiders, scorpions, crabs etc.
  • This group is the largest group of animals.
  • The body of these animals is also bilaterally symmetrical and segmented.
  • It has an open circulatory system and the blood does not flow in well-defined blood vessels. The coelomic cavity of it is blood-filled.

Mollusca ⇒

  • The body of these animals is also bilaterally symmetrical with reduced coelomic cavity and little segmentation.
  • It also has an open circulatory system and uses kidney-like organs for excretion.
  • These animals have foot for moving around.
  • Some examples of this group are snails, mussels etc.

Echinodermata ⇒

  • Two Greek words i.e. echinos (means hedgehog) and derma (means skin) form the word echinodermata. It indicates that they are spiny skinned organism.
  • They are triploblastic with a coelomic cavity. They are exclusively free-living marine animals.
  • The body design of these organisms has calcium carbonate (CaCO3) structures used as skeleton. Also the body design has a peculiar-water driven tube system which is used for their movement.
  • For example, sea urchins, sea-stars etc.

Prochordata ⇒

  • These are marine animals. For example, amphioxus, herdmania, balanoglossus etc.
  • These animals are also triploblastic and bilaterally symmetrical with a coelom.
  • The body design of these animal shows a new feature named as notochord. Notochord is a long rod-like support structure running along the back of the animal separating the nervous tissue from the gut and providing a place for muscles to attach for the ease of movement.
  • This feature is only present at some stages of their life not all stages or during entire life.

Vertebrata ⇒

  • The body designs of these animals are triploblastic and bilaterally symmetrical. Also the body design is coelomic and segmented having complex differentiation of body tissues and organs.
  • These organisms have a true vertebral column and internal skeleton which orchestrates a completely different distribution of muscle attachment for using their movement.
  • All chordates of these animals have a dorsal nerve chord and a notochord. Also they have paired gill pouches. These are also triploblastic and coelomate.
  • Further we classify vertebrates into 06 (six) sub-groups. They are Cyclostomata, Pisces, Amphibia, Reptilia, Aves & Mammalia.

Q17. Discuss all sub-groups of Vertebrata.

Following are the groups of vertebrata –

1. Cyclostomata ⇒

♦ These vertebrates are jawless.
♥ Main features of these are eel-like elongated body, slimy skin, circular mouth, scaleless.
♣ These vertebrates are ectoparasites or borers of other vertebrates.
♠ Some examples are Myxine (Hagfish), Petromyzon (Lamprey) etc.

2. Pisces ⇒

♦ These are fish and exclusively aquatic animals. Skin of these is covered with scales or plates.
♥ They use gills to obtain oxygen dissolved in water.
♣ The body design of these is streamlined and they use muscular tail for movement.
♠ They lay eggs and they are cold blooded.
♦ Their hearts have only two chambers.
♥ Formation of their skeleton may be entirely made of cartilage (e.g. sharks) or made of both bone and cartilage.

3. Amphibia ⇒

♦ These animals live both in water and land. Some examples are frogs, toads, salamanders etc.
♥ They intake oxygen through either gills or lungs and they also lay eggs.
♣ Their hearts are of three chambered. They differ from the fish in the lack of scales and in having mucus glands in the skin.

4. Reptilia ⇒

♦ They are cold-blooded and their heart are three-chambered though crocodiles have four-chambered heart.
♥ Their respiration happens through lungs and they lay eggs with tough coverings.
♣ Few examples of this animal are snakes, turtles, lizards, crocodiles etc.

5. Aves ⇒

♦ These are birds. They have an outside covering of feathers. Their two forelimbs are modified for flight.
♥ They are warm-blooded. Their heart are four-chambered. They also lay eggs.
♣ Their respiration also happens through lungs.

6. Mammalia ⇒

♦ These are warm-blooded. Also they have four-chambered heart.
♥ Most mammals produce live young ones. Also mammals have mammary glands for production of milk to nourish their young ones.
♣ Some mammals like the platypus and the echidna lay eggs. Mammals like kangaroos give birth to very poorly developed young ones.
♠ Mammals have hairy skin as well as sweat and oil glands.

In-Text Questions & Answers | NCERT Class 9 Science Chapter 7 | Diversity in Living Organisms
In-Text Questions & Answers | NCERT Class 9 Science Chapter 7 | Diversity in Living Organisms | Page No. 82 

1. Why do we classify organisms?
We classify organisms to study the variety of life forms in Earth. We classify organisms on the basis of similar characteristics & habitat. This classification makes it more convenient to study the characteristic features of organisms.

2. Give three examples of the range of variations that you see in life-forms around you.
Three examples are as follows –
a ⇒ Organisms vary greatly in size. For example, microscopic bacteria of few micrometre to hundred metre red wood trees to thirty metre blue whale.
b ⇒  Life span of organisms also varies greatly. Some dies in few days while some lives thousands of years (e.g., pine trees).
c ⇒  Colour of animals & plants also varies greatly. Some are colourless & transparent (e.g., worms) while some are colourful (e.g., birds, flower etc.).

In-Text Questions & Answers | NCERT Class 9 Science Chapter 7 | Diversity in Living Organisms | Page No. 82

1. Which do you think is a more basic characteristic for classifying organism ⇒ the place where they live or the kind of cells they are made of? Why?

Obviously it is the kind of cell. Because a habitat can host lost of species with different characteristics living in harmony. On the other hand, the organisms with similar cell arrangement posses similar characteristics. Organisms are classified on the basis of cell types i.e. whether it is eukaryotic or prokaryotic. The type of cell expresses lots of things about organisms like whether it has the ability to form multicellular organism or not, etc. # Note – Read Q3 in detail for concept.

2. What is the primary characteristics on which the broad division of organisms is made?

The basic characteristic is the nature of cells i.e. whether the cell is eukaryotic or prokaryotic. This characteristic classifies organisms into eukaryotic & prokaryotic which makes the way for the broad division of organisms within them.

3. On what bases are plants & animals put into different categories?

Write down the answer of Q4.

In-Text Questions & Answers | NCERT Class 9 Science Chapter 7 | Diversity in Living Organisms | Page No. 83 

1. Which organisms are called primitive & how are they different from so-called advanced organisms?

Write down the answer of Q7 in detail.

2. Will advanced organisms be the same as complex organisms? Why?

Advancement organisms are those whose body design have gone through major changes to acquire particular body design relatively recently. This advancement leads to multiple cell arrangements that functions in a unique way. So the advanced organisms will be the same as complex organisms.

In-Text Questions & Answers | NCERT Class 9 Science Chapter 7 | Diversity in Living Organisms | Page No.  85 

1. What is the criterion for classification of organisms as belonging to kingdom of Monera or Protista?

The main criterion for classification of organisms belonging to Monera or Protista is the presence or absence of a well-defined nucleus or membrane bound organelles. Monera group includes the ones which has no nuclear membrane. On the other side, Protista group includes the ones which has well-defined nuclei membrane. 

2. In which kingdom will you place an organism which is single-celled, eukaryotic & photosynthetic?

An organism which is single-celled, eukaryotic & photosynthetic belongs to the Kingdom Protista. For example, Euglena. It is unicellular, eukaryotic & photosynthetic.

3. In the hierarchy of classification, which grouping will have the smallest number of organisms with maximum common characteristics & which will have the largest number of organisms?

Species stands at the bottom level in the hierarchy of classification. So it will have the smallest number of organisms with maximum common characteristics. On the other hand, kingdom stands at the top level in the hierarchy of classification. So it will have the largest number of organisms. Read Q10 in detail to learn more.

In-Text Questions & Answers | NCERT Class 9 Science Chapter 7 | Diversity in Living Organisms | Page No.  88 

1. Which division among plants has the simplest organisms?

Thallophyta or algae is the lowest group & simplest organisms among plants. It lacks well differentiated body design.

2. How are pteridophytes differ from the phanerogams?

The reproductive organs makes the difference between pteridophytes & phanerogams. Pteridophytes have a naked embryo & unclear reproductive organ. So they are called cryptogams or those with a hidden reproductive organ. On the other hand, phanerogams have a covered embryo & well-defined reproductive organ.

3. How do gymnosperms & angiosperms differ from each other?

 The seed structure makes the difference between gymnosperms & angiosperms. In case of gymnosperms, seeds are naked. On the other hand, seeds are enclosed inside fruits in angiosperms. Also gymnosperms are non-flowering plants while angiosperms are flowering plants.

In-Text Questions & Answers | NCERT Class 9 Science Chapter 7 | Diversity in Living Organisms | Page No.  94 

1. How do poriferan animals differ from coelenterate animals?

Porifera Coelenterate
Coelom is absent.
Coelom is present.
Division of labour is absent.
Division of labour is present
It has cellular level organisation.
It has tissue level organisation.
2. How do annelid animals differ from anthropods?
Answer:

Annelida

Arthropods
Skeleton is absent.
Exoskeleton is present.
Body is segmented into rings. Due to this, it is commonly called segmented animals.
Body of arthropods is segmented into head, abdomen & thorax. Due to this, it is commonly called animals with joint legs.
Annelid animals have true coelom or body cavity.
It has body cavity filled with blood i.e. called haemocoel.
3. What are the differences between amphibians & reptiles?
Answer:

Amphibians

Reptillia
Amphibians respire through skin, lung & gills.
Reptiles respire through lungs.
It has soft & moist skin.
It has hardened skin.
Amphibians can live both in water & land.
They can live in water but they need to come to surface to breathe.
4. What are the differences between animals belonging to the Aves group & those in the mammalia group?
Answer:

Aves Groups

Mammalia Groups
Body is covered with feathers.
Skin is covered with hair.
It has bones with air cavities.
Bones are hard & solid. Also it is filled with bone-marrow.
It has no presence of mammary glands.
Mammary glands are present. It produces milk to nourish the young ones.
They lay eggs.
Most mammals produces young ones. Though there are some exceptions. For example, Platypus & Echinda lay eggs. Also Kangaroos give birth to very poorly developed young ones.
Their two fore limbs are modified to fly.
Their fore limbs are modified to climb or for some purpose in few cases.
Exercises Questions & Answers| NCERT Class 9 Science Chapter 7 | Diversity in Living Organisms | Page No. 97
1. What are the advantages of classifying organisms?

The advantages of classifying organisms are ⇒
♦ We can easily understand a wide variety of animals or plants very easily in a short period of time.
♥ It also helps to know the characteristics of whole group by studying only few animals.
♣ It also simplifies the study of scientific experiments done on the organisms.
♠ We can recognize the basic plan of a hierarchical structure amongst various species.
♦ It also helps to understand the inter-relationship amongst different group of organisms.
♥ We get to know the evolution in detail.

2. How would you choose between two characteristics to be used for developing a hierarchy in classification?

At first, we consider the basic characteristics among all other characteristics to develop a hierarchy of classification. We check whether the given characteristic is present in small or larger number of organisms. After selection of the basic characteristic, broad division is prepared as the next level of characteristic is dependent on these. Thus it goes on to form a hierarchy of classification.

3. Explain the basis for grouping organisms into five kingdoms.

Following points are considered for grouping organisms into five kingdoms.
♦ Nature of the cells ⇒ either prokaryotic or eukaryotic.
♥ Number of cells ⇒ either unicellular or multicellular.
♣ Presence or absence of cell wall ⇒ whether cell has cell wall or not.
♠ Mode of nutrition ⇒ whether organisms prepare their own food or depend on other for their food.

4. What are major divisions in the Plantae? What is the basis for these divisions?

There are five major division in plants. They are Thallophyta, Bryophyta, Pteridophyta,  Gymnosperms & Angiosperms. This division are based by considering following factors one by one – 

Differentiated plant body or Tissue differentiation ⇒ Thallophyta among aforesaid five groups lacks well-differentiated plant body while others have well-differentiated plant body.

Vascular tissue ⇒ Plants without vascular tissues are included in Bryophyta. Plants of other three groups have vascular tissue in their body.

Reproduction by seeds ⇒ Pteridophyta plants do not produce seeds while gymnosperms & angiosperms plants are reproduced by seeds.

Flowers & fruits ⇒ Gymnosperms are non-flowering plants. It has naked seeds. Angiosperms are flowering plants. It has seeds enclosed in fruits.

5. How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?

We consider following points for divisions in plants.
a) Differentiated or undifferentiated plant body.
b) Presence or absence of vascular tissues.
c) Presence or absence of seed.
d) Naked seeds or seeds enclosed within fruits.

We consider various factors like morphology, cytology, cell layers etc. for classification of animals. For example – 
a) Presence of notochord.  
b) Cellular or tissue level body organisation.
c) Body symmetry.
d) Types of body coelom or cavity, presence or absence of segmentation etc.

6. Explain how animals in Vertebrata are classified into further subgroups.

Vertebrata are advanced chordates with a well-developed cranium or skull in which brain is enclosed. Also it has a segmented spinal or vertebral column. Further we classify vertebrates into 06 (six) sub-groups on the basis of simple to complex forms of structures & their functions. They are Cyclostomata, Pisces, Amphibia, Reptilia, Aves & Mammalia.

Cyclostomata ⇒ They have eel-like elongated body, slimy skin & circular mouth. They are also scaleless & jawless.
Pisces ⇒ These are fish and exclusively aquatic animals. Skin of these is covered with scales or plates. They use gills to obtain oxygen dissolved in water. The body design of these is streamlined and they use muscular tail for movement. They lay eggs. Also they are cold blooded. Their hearts have only two chambers.
Amphibia ⇒ These animals live both in water and land. They intake oxygen through either gills or lungs and they also lay eggs. They differ from the fish in the lack of scales and in having mucus glands in the skin.
Reptilia ⇒ They are cold-blooded and their heart are three-chambered though crocodiles have four-chambered heart. Their respiration happens through lungs and they lay eggs with tough coverings.
Aves ⇒ These are birds. They have an outside covering of feathers. Their two forelimbs are modified for flight. They are warm-blooded & their heart are four-chambered. They also lay eggs. Their respiration also happens through lungs.
Mammalia ⇒ These are warm-blooded. They have four-chambered heart. Most mammals produce live young ones. Also mammals have mammary glands for production of milk to nourish their young ones. Mammals have hairy skin as well as sweat and oil glands.

diversity in living organisms

Diversity in Living Organisms – To Be Continued – Diversity in Living Organisms