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BIOLOGICAL DIVERSITY -II





Plant Kingdom ( Plantae):

The plant kingdom has been divided into two sub-kingdoms- Cryptogamae and Phanerogamae.

Cryptogamae: Cryptogams includes seedless and flowerless plants. These plants reproduce by producing spores.

It includes three divisions- Thallophyta, Bryophyta and Pteridophyta.

Thallophyta:

  • Most primitive and simple plants. The body is not differentiated into stem, root and leaves, but it is in the form of an undivided thallus.

  • They do not possess a vascular system.

  • The mode of nutrition is either photosynthetic (autotrophic) or heterotrophic.

  • They reproduce both asexually and sexually. Asexual reproduction is generally takes place by spore formation.

  • Sex organs are simple, single celled and there is no embryo formation after fertilization.

Examples- Green algae- Spirogyra, Chara etc.

Bryophyta:

  • They are small, multicellular green pants which inhabit shady damp places.

  • The plant body is commonly differentiated to form stem and leaf-like structures.

  • In them a true vascular system is absent.

  • The sex organs are multicellular. An embryo is formed upon fertilization. Water is required for fertilization so bryophytes are called amphibians of the plant kingdom.

Examples- Moss (Funaria) and Marchantia.

Pteridophyta:

  • They have a well-differentiated body comprising of roots, stem and leaves.

  • They possess vascular system (xylem and phloem).

  • Sex organs are multicellular and jacketed by sterile cells/ fertilized egg develops into embryo.

Examples- Fern (Marsilea) and horse-tails.

Phanerogamae: Phanerogamae includes higher pants bearing flowers and seeds.

On the basis of presence and absence of fruits, the sub-kingdom phanerogamae is divided into two sub-divisions: Gymnosperms and Angiosperms.

Gymnosperms:

  • They are most primitive and simple seed plants.

  • The seed produced by these plants are naked and are not enclosed within fruits.

  • Usually perennial, evergreen and woody plants. they do not have flowers.

Examples- Conifers- Pines, Firs and Cycades- Cycas etc.

Angiosperms:

  • They are highly evolved plants and they produce seed that are enclosed within fruits.

  • These are also called flowering plants.

  • Plant embryos in seeds have structures called cotyledons. Cotyledons are called ‘seed leaves’ because in many cases they emerge and become green when the seed germinates.

  • On the basis of number of cotyledons, angiosperms have further divided into two groups-

  • Monocotyledons ( plants with seed having single cotyledon) examples- wheat and rice

  • Dicotyledons (plants with seed having two cotyledons) examples- pea and potato.

Animal Kingdom (Animalia):

Characters to be considered for animal classification:

1.

Diversity of habitat

Aquatic, terrestrial, aerial, arboreal.

2.

Diversity of habit

Free-living, parasitic, symbionts, saprophytic.

3.

Diversity in level of organization

Cellular level, tissue level, organ level, system level.

4.

Diversity of body symmetry

Asymmetry, radial symmetry, bilateral symmetry.

5

Body cavity or coelom

Acoelomate, pseudocoelomate, coelomate.

6.

Body temperature

Cold-blooded, warm-blooded.

7.

Diversity in body support system

Skeleton, digestive system, respiratory system, excretory system, circulatory system and nervous system.

8.

Diversity in reproduction

Asexual, sexual (oviparous, viviparous).

 

Phylum- Porifera:

  • They are non-motile animals attached to some solid support.

  • Porifera means organisms with 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, water and oxygen.

  • They are mulicellular, diploblastic, radial symmetrical or asymmetrical organisms exhibiting cellular level of organization.

  • These animals are covered with a hard outside layer or skeleton.

  • They are commonly called sponges and are mainly found in marine habitats. Examples- Sycon, Spongilla.

Phylum- Coelenterata (Cnidaria):
  • Coelenterates are primitive, multicellular, aquatic animals. Their cells are organized into tissues.

  • They are diploblastic. Body shows radial symmetry.

  • Body contains a large cavity called coelenterons or gastrovascular cavity.

  • Body bears special cells called nematocysts for defence, offence and to capture food.

  • Some of them live solitary life, e. g., Hydra while some live in colonies, e.g., corals.

      Examples- Jellyfish, Sea anemone etc.

Note: Coelenterates exist in two forms- an asexual polyp form and a sexual medusoid form.

Phylum- Platyhelminthes:

  • They are bilaterally ssymmetrical, dorsiventrally flattened animals, commonly called flatworms.

  • They are triploblastic animals. They are without a body cavity.

  • Body is soft, leaf-life (liver fluke) or ribbon-like (tapeworm).

  • Excretory organs are in the form of flame cells. Digestive cavity (when present) with a single opening, the mouth (anus is absent).

  • Mostly parasitic (e.g. Tapeworm) but some are free-living forms (e.g. Planaria).

  • Mostly hermaphrodite, i.e., both male and female reproductive organs occur in the same individual.

      Examples- Liver fluke, Planaria, Beef tapeworm.

Phylum- Nematoda:

  • Aquatic (freshwater or marine), terrestrial or parasitic forms, commonly called roundworm.

  • Bilaterally symmetrical, triploblastic, unsegmented and pseudocoelomate (false coelom) animals.

  • Body elongated, cylindrical, slender and tapering at the two ends.

  • Straight alimentary canal with mouth and anus.

  • Reproduce sexually, sexes are separate, fertilization internal.

      Examples- Rounworms (Ascaris), Filarialworm.

Note: Parasitic nematodes are pathogenic, meaning they produce disease in the hosts. For example, elephantiasis.

Phylum- Annelida:

  • Body triploblastic, bilaterally symmetrical, soft, elongated, vermiform and cylindrical.

  • Body metamerically segmented, i.e.m divisible into more or less similar segments.

  • True coelom present, which is divided into segments by internal septum.

  • Locomotory organs are setaeor parapodia.

  • Excretory organs arw nephridia. Circulatory system is of closed type.

  • Reproduction is by sexual means. Sexes may be united ( hermaphrodite) or separate.

  • Mostly aquatic, marine or freshwater, some are terrestrial, burrowing in tubes, some free-living forms.

      Examples- Earthworm, Indian cattle leech.

Phylum Arthropoda:

  • Triploblastic, bilaterally symmetrical, coelomate, metamerically segmented bpdy.

  • There is an open circulatory system, so the blood does not flow in well-defined blood vessels. The coelomic cavity is blood-filled.

  • They have joined legs.

  • Excretory organs are malpighian tubules, coxal oe green glands.

  • Sexes are usually separate, sexual dimorphism well marked in several forms.

  • Terrestrial or aquatic, free living or parasitic.

  • Arthropoda probably forms the largest phylum of animal kingdom.

      Examples- Prawn, Spider, Cockroach.

Phylum- Mollusca:

  • Marine, freshwater and terrestrial forms.

  • Body is soft, bilaterally symmetrical, triploblastic and unsegmented.

  • Body cavity is haemocoel. Open type of circulatory system.

  • Excretion by a pair of metanephridia or kidney.

  • Sexes are usually separate.

  • There is a foot that is used for moving around.

     

    Examples are snails and mussels.




Phylum- Echinodermata:

  • All members of this phylum are marine, free-living, having a spiny body surface.

  • The body is triploblastic, coelomate, unsegmented and radially symmetrical.

  • Body wall is covered by spiny hard calcareous (calcium carbonate) plates (ossicles) forming a rigid or flexible endoskeleton.

  • Body cavity is modified into a unique water vascular system which moves respiratory and locomotory organs, the tube feet or podia.

  • Excretory organs absent.

  • Reproduction sexual, asexual or by regeration. Sexes are separate.

      Examples- Starfish, Sea urchins etc.

Phylum- Chordata:

Chordates are characterized by-

  • Bilaterally symmetrical, triploblastic, coelomate animals inhabiting all types of habitat.

  • A dorsal hollow tubular nerve cord is present.

  • Presence of notochord lying ventral to nerve cord. In higher forms, notochord transformed into vertebral column.

  • Presence of paired gill slits in the throat called pharyngeal clefts.

Phylum chordate is divided into two groups:

  1. Protochordata (Acrania)

  2. Vertebrata (Craniata)

Protochordata:

  • Notochord is present only on the tail of free-living tadpole-like larva, sessile adult has no notochord.

  • The notochord is a rod-like suppot structure that runs along the back of the animal separating the nervous tissue from the gut. It provides a place for muscles to attach for ease of movement.

  • Protochordates may not have a proper notochord present at all stages in their lives or for entire length of the animal.

  • Exclusively marine, solitary and colonical.

      Examples- Herdmania, Salpa etc.

Vertebrata:

  • Vertebral column is present.

  • Brain is present inside the brain-box called cranium.

  • Vertebrates are triploblastic, bilaterally symmetrical, coelomic and segmented with complex differentiation of body tissues and organs.

 

 Vertebrates are grouped into five classes:

Class I- Pisces:

These are fishes and aquatic animals.

Streamlined body. Locomotory organs are fins.

Cold-blooded animals.

Heart is two-chambered with single circulation.

Gills are present which help in obtaining oxygen dissolved in water.

Skeletons of some fish are made up of only cartilade (Sharks). Others have skeleton made of both cartilage and bone (Tuna or Rohu).

Sexes are separate. They lay eggs.

Examples- Tuna, Sharks etc.

Calss II- Amphibia:

Cold-blooded, ambhibious form ( i.e., found both on land and in water)

 

 


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