Question

Which statement about the mammalian circulatory system is correct ?
(1) The thickness of walls of veins is greater than that of arteries.
(2) The order of decreasing velocity of blood flow is : veins > capillaries > arteries.
(3) The total surface area of the capillaries is considerably greater than that of all the arteries and veins combined.
(4) In order to return blood to the heart, the blood pressure in veins is higher than it is in the arteries.

Answer 1

3 option is correct
1 : arteries are thicker
2: velocity of blood is high in ateries as they are under pressure
4: blood pressure is higher in arteries

Answer 2

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▶The total surface area of the capillaries is considerably greater than that of all the arteries and veins combined.

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:-
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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:-
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❱ 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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