Reptiles, Birds and Mammals

Our scaly, feathered and hairy friends!

3 Key Adaptations for Life on Land• 1. Amniotic Egg• 2. Internal Fertilization• 3. Water-tight skin• An amniotic egg is a waterproof egg with a shell.• It is named for a particular membrane called the

amnion.• The amnion protects the embryo from drying out

and surround a fluid filled cavity that cushions it.

Key Adaptations

• The other membranes formed during development of the embryo function in gas exchange, waste removal and supplying nutrients.

• The amniotic egg makes it possible to lay an egg on land without needing to return to the water like an amphibian.

Key Adaptations• In internal fertilization, the male deposits sperm within the

female’s body.• The sperm then swims inside the reproductive tube towards

the egg.• This allows for reproduction to take place outside of water.• Amniotes have a water-tight skin enriched with a

waterproofing protein called keratin.• The keratinized skin prevents dehydration.

Key Adaptations

• Reptile skin has scales which are hard, overlapping structures made of keratin.

• Birds have feathers made of keratin.• Mammals have hair, nails and horns made of

keratin.

Vocabulary

• Ectotherms-main source of body heat is the environment-cold-blooded

• Endotherms-body heat generated internally by cell metabolism, warm-blooded

History of Reptiles• The oldest reptile fossils have been found in rocks dating from

the Carboniferous period about 300 mya.• Reptiles diversified in the Mesozoic era.• At that time, dinosaurs occupied every habitat and ecological

role.• Some were very quick and agile indicating that they might

have been endotherms.

• Some fossils of dinosaurs have been found with feathers.

• Dinosaurs became extinct 65 mya from a massive collision with a comet or asteroid.

Snakes

Lizards

Crocodilians

Alligator

Crocodile

Crocodilians

Gavial

Caiman

Tuaturas

• Rare, old species• Different structures than lizards, vestigial third

eye and slowest metabolism in reptile class• Endangered• Live only on islands near Australia and New

Zealand

Tuatara-living fossil

Reptiles

Turtles and Tortoises

Lizards andsnakes Crocodilians Tuataras

Hard shellMade of scutes

Can be legless orHave limbs

AlligatorsCrocs

caimans

Rareendangered

Longest livedreptiles

Snakes evolvedFrom lizards

Related to dinosaurs

Different physicalCharacteristics

Than lizards

History of Birds

• Molecular and fossil evidence indicated birds and crocodilians are more closely related to dinosaurs than any other reptiles.

• Feathers-modified scales made of keratin used for flight and insulation

Birds• Birds have a system of branching air sacs that

function with their lungs in respiration.• The air sac system helps supply the high levels of

oxygen that support a high rate of metabolism.

• Air sacs also reduce the overall body weight of the bird.

• Bird bones are honeycombed and mostly hollow but are still structurally strong.

Bird’s Adaptations to Decrease Body Weight

• 1. Air sac system• 2. Honeycombed bones• 3. Absence of many internal organs• 4. Absence of teeth

Birds

• Gizzard- muscular organ often containing small stones that grind seeds and other food

• Crop- sac like organ used for temporarily storing food

• 4 chambered heart is efficient by keeping oxygen rich blood completely separate from the oxygen poor blood.

Origin of Birds

• Many paleontologists agree the ancestor of birds was a small, feathered dinosaur.

• A famous bird fossil, Archaeopteryx lived 150 mya.

• It had a mixture of bird and reptilian features.

Archaeopteryx

Flying Styles• Rapid altitude changes-finches, cardinals• Soar and glide on air currents-falcons and albatrosses• Flap or buzz quickly and can hover or go backwards-

hummingbirds• Flightless swimming/diving birds-penguins• Flightless running birds-ostriches, emus

Beak Adaptations

• Made of keratin• Modified to the food source• Toothless and cannot chew

Foot Structure

• Perching-songbirds• Grasping-woodpeckers, nuthatches• Raptors-eagles, hawks• Swimming-ducks, geese

Perching Birds

Swimming Birds

Raptors

Birds

Perching grasping raptors swimming

Cardinalssongbirds woodpeckers Eagles

hawksDuckgeese

Behavioral Adaptations

• Complex courtship behaviors• Complex song communications• Caring for offspring• Nest building

Origin of Mammals• The oldest fossils of mammals date back about 200 mya to

early Mesozoic era.• Fossil evidence indicates mammals evolved from reptiles

called therapsids.• Early mammals coexisted with dinosaurs but were mouse-

sized and ate insects.• These early mammals were nocturnal and endothermic.• Mammals took over all habitats and diversified once the

dinosaurs went extinct.• Mammal-endothermic vertebrate that possesses

mammary glands and hair

All Mammals have:• 1. Mammary glands • 2. Hair• 3. Lungs• 4. Muscular diaphragm that separates lungs and

heart from the rest of the body• 5. 4 chambered heart• 6. Reproduce sexually with internal fertilization (a

few exceptions)• 7. Most give live birth with few exceptions

Mammals

Placentals Monotremes Marsupials

Embryo developsIn a uterus Lay eggs Have a pouch

Placenta providesNutrients to

embryo

Only live in Australia andNeighboring

islands

Young born beforeFully developed

Contains amnion like bird and reptile

eggs

Mixture of reptilianAnd mammaliancharacteristics

Most live in Australia andNeighboring

Islands, exceptopossum

4,200 species Platypus and echidna

KangaroosKoalas

OpossumsEtc..

Monotremes

Marsupials

Marsupial babies

Placental Mammals

Early Hominids

• Oldest evidence for bipedalism or upright walking was Australopithecus about 4 mya.

• Famous fossil called Lucy.