Vertebrates 2

Tetrapod adaptations

Four limbs and feet with digits, a neck, fusion of pelvic girdle to backbone, absence gills in non-aquatic species, ears for detecting airborne sounds

Tetrapod origins

Evolved within the aquatic realm

Lissamphibia

amphibians

Caudata (Urodela) - salamanders

Many lack lungs, respiration takes place across the skin, network of capillaries takes blood close to surface for gas exchange

Salientia (anura) - frogs

Frogs lack tails and have powerful hind legs

Gymnophiona (Apoda) - caecillians

Most are terrestrial, burrow through leaf litter and soil. They are legless and nearly blind. They have heavily ossified skulls for burrowing. The have chemosensory tentacles, can taste their way through an environment.

External fertilisation

eggs require some moisture in the environment. In some species, male or females care for their eggs on their back, in their mouth

Amniotes

a group of tetrapods whose living members are reptiles, birds and mammals

Sauropsida

group that unites all traditional reptile taxa with birds

Origin and evolution

Parareptiles were the first main group to arise, as they dwindled diapsids diversified

Diapsids

lepidosaurs and archosaurs

Lepidosaurs

Lizards and snakes. Another group is squamates

Archosaurs

Crocodilians and dinosaurs. Birds are dinosaurs and called neornithes

Turtles

Phylogenetic position remains uncertain. Box like shell is composed of bone and keratin

Mammalia

All mammals have: mammary glands, hair and high metabolic rate

3 living lineages

monotremes, metatherians and eutherians

Monotremata

Monotremes are a small group of egg-laying mammals consisting of echidnas and the platypus

Marsupials

Opossums, kangaroos and koalas

Metatheria

Embryo develops in the uterus and completes development outside uterus

Eutheria

More complex chorioallantoic placenta

Afrotheria

Members have been placed in many distantly related groups

Xenarthra

Giantism is a common theme, large body sizes were achieved independently by at least 5 lineages

Laurasiatheria

Inhabit every type of terrestrial habitat as well as aquatic and areal habitats

Euarchontoglires

Rodentia is the most diverse mammalian group, 20,000 fold difference in body mass within group