Question

Australian Marsupials and placental mammals are suitable example of adaptive radiation and convergent evolution. Explain Given reason?



class 12th CBSE Biology sample paper

Answer 1

The process of evolution of different species in a given geographical habitat starting from a point and radiating to other geographical areas (habitats) is called adaptive radiation.

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When more than one adaptive radiation appeared to have performed in an isolated geographical area that is representing different habitats, is known as convergent evolution.

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Placental mammals that are present in Australia also exhibit adaptive radiation in evolving into varieties of such placental mammals each of which appears to be ‘similar’ to a corresponding marsupials.

Answer 2

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▶Marsupials are a subclass of mammal that have managed to evolve without a placenta.

♦ Australian marsupials evolve from a single ancestor & placental mammals exhibit similarities with their corresponding marsupials such as - Placental & Tasmanian wolves.

Vertebrate➫ The chordates that possess a backbone are called vertebrates.

► It is also a Subphylum Vertebrate.

➧ Characteristics are:-
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❱ Body is bilaterally symmetrical.

❱ Body wall is triploblastic.

❱ Complex differentiation of body tissues & organs

❱ Notochord is present in the Embryo.

❱ nerve cord is divided into brain & spinal cord.

❱ Brain is enclosed in a brain box.

❱ Body is divided into head Thorax & abdomen.

❱ Body has two pairs of fins or names.

❱ Gills either present throughout life or by lungs.

➧ Subphylum Vertebrate divided into Five Classes:-
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❶❭ Class Pisces:-
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❱ These are cold blooded.

❱ These are exclusively aquatic invertebrates.

❱ Body is streamlined.

❱ They have one pair of pectoral & pelvic fins.

❱ Respiration by 5 pairs of gills.

❱ Heart is two chambered.

❱ Skin is slimmy & covered with scales.

►Examples:- Electric Rays & DogFish

➧ Types 0f Class Pisces are:-
▬▬▬▬▬▬▬▬▬▬▬▬▬⤵

➀❭ Cartilaginous Fishes:-
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◉ Mouth is ventral.
◉ It is totally marine.
◉ Tail is heterocercal.
◉ Endoskeleton is Cartilaginous.

②❭ Bony Fishes:-
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◉ Mouth is trrminal.
◉ It is freshwater.
◉ Tail is homocercal.
◉ Endoskeleton is Bony.

❷❭ Class Amphibia:-
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❱ They are cold blooded animals.

❱ Body divided into head, trunk & Tail.

❱ Heart is three - Chambers.

❱ Fertilization is external & lay eggs.

❱ Respiration through gills, lungs & skin.

❱ They undergo hibernation & aestivation.

❱ Embryonic membrane is absent.

❱ Skin is a smooth & moist.

►Examples:- Seahorse & Catla

❸❭ Class Reptilia:-
━━━━━━━━━━━━━━━━━━☟

❱ They are cold blooded animals.

❱ Body divided into head, neck, trunk and tail.

❱ Heart is incompletely four chambered.

❱ Fertilization is internal.

❱ Respiration through gills.

❱ It is the first Terrestrial vertebrates.

❱ Embryonic  membrane is present.

❱ Skin is rough & dry.

►Examples:- Frogs & Toads
                                             
❹❭ Class Aves:-
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❱ These are warm blooded.

❱ Feathers are present on the body.

❱ Respiration by lungs with air sacs.

❱ Mammary gland is absent.

❱ They are 0viparous. Beek present.

❱ Bones are flight.

❱ Sweat & oil gland is absent.

❱ External ear is absent.

►Examples:- Crows & Parrots
                                             
❺❭ Class Mammalia:-
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❱ They are also warm blooded.

❱ Body covered with hair.

❱ Respiration by lungs without air sacs.

❱ Mammary gland is present.

❱ Teeth are present.

❱ Sweet and all gland is present.

❱ Solid bones are present.

❱ Heart is four chamber.

❱ External ears are present.

►Examples:- Humans & Rabbits

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