31.3 Vertebrates (cont’d) Amphibians, Reptiles, and Mammals

Amphibians O About 6,600 species O Live on both land and water ( = amphi) O Include frogs, toads, newts, salamanders O Differences from fishes: O jointed appendages O four limbs O eyelids (keep eyes moist) O voice-producing larynx O lungs (although many adults breathe through their skin) O 3-chambered heart

Reptiles O About 15,000 species O Include many extict species, including dinosaurs O Include snakes, lizards, alligators, turtles and birds

Reptiles (continued) O Adaptations to land life: O Hard scales O Tongue as sense organ O 3 or 4-chambered heart (incomplete septum in ventricles in some species) O Sexual reproduction is direct (sperm directly deposited into female and fertilization takes place internally in the female) O Amniotic egg produced is typically leathery, flexible and shelled O Most are ectothermic (cold-blooded)

Birds (continued) O Birds are actually feathered reptiles O Differences b/t birds and other reptiles: O Endothermic (warm-blooded) O Hard-shelled eggs O Feathers O Septum in ventricle complete (4-chambered heart)

Mammals O Evolved from reptiles O About 4,600 species O Mammalian groups include: 1. Monotremes a) Lay hard-shelled eggs b) Include spiny anteater and duckbill platypus (both found in Australia) c) After hatching, remain in burrow where they are nursed for up to 2 months

Mammals (continued) 2. Marsupials a) Begin development inside female’s body b) Born immature and finish developing in a pounch in mother’s abdomen c) Attach there to nipples of mammary gland and continue development d) Mainly found in Australia e) Underwent adaptive radiation there w/o competition with placental mammals f) Include koalas, kangaroos, Tasmanian devil,

Mammals (continued) 3. Placental mammals a) Vast majority of mammals b) Extraembryonic membrane adapted for internal development within the uterus c) Attachment to placenta through umbilical cord (allows for nutrient, gas and waste exchange b/t mother and fetus’ blood) d) Extremely well-adapted to life on land (hair, large lungs) e) Very developed brain f) Differentiated teeth