Know circulatory system changes (Fig23.3)!
Fish are the most diverse group of vertebrates
- ca. 30,000 species.
They are ectothermic, have paired fins, scales and have a lateral line system for sensing movement. -
Cartilaginous fish (Class Chondrichthyes) include sharks, skates and rays. Their skeleton is made of cartilage, not bone, and is therefore more flexible -
Bony fish (Class Osteichthyes) include ray-finned fish, lobe-finned fish, and lungfish. They have an operculum to cover the gills and a swim bladder for buoyancy that likely evolved from primitive lungs.
Amphibians (Class Amphibia)
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ectothermic, primitive terrestrial vertebrates (tetrapods) that still need external water for reproduction. -
Their tadpole larvae have lateral lines, gills and a tail - They metamorphose into adults by losing the tail and gills and growing limbs.
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Many adults need moisture as well (respiration, hydration)
Reptiles (Class Reptilia)
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includes snakes, lizards, turtles, crocodiles and alligators and are the most primitive fully terrestrial ectothermic tetrapods. -
Reptiles do not depend on water because of - keratinized scales that reduce water loss
- amniotic egg, which has self-contained exchange, protection and waste facilities.
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Not a good monophyletic group, but useful as category
Birds (Class Aves)
- essentially reptiles modified for flight.
have streamlined bodies with forelimbs like airfoils, and feathers that insulate and help modify wing shape -
To reduce weight, their bones have a honeycomb structure, their feathers are hollow, and they have lost teeth and several vertebrae. -
Their high metabolism, supported by an efficient circulatory system and lungs, allows for endothermy and flight. - Also have keen sight and complex brains.
Mammals (Class Mammalia)
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Endotherms with hair for insulation and mammary glands that produce milk. -
Monotremes like the platypus lay eggs. -
Marsupials and Eutherians nurture their young inside the mother through the placenta (formed from fusion of embryo amniotic layers with maternal tissue), although this association is more intimate and longer in Eutherians.
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