Reptiles & Birds

Ch 31 Turboblaaasssssst.

What is a reptile?!

• All reptiles evolved from stem reptiles, the first animals to become adapted to life on land– Complete life cycles entirely on land, no water required– Have dry, scaly skin (protection, prevents water loss)– Reproduce on land – lay eggs!• No aquatic larvae, the developmental stages all take place

within the egg• Reptile young are less vulnerable to swimming predators

Which came first, the chicken or the egg? (the egg did.)

• An amniotic egg provides safety, nourishment, and total life-support system for developing embryo

• Eggs are deposited from a urogenital opening called a cloaca

Stronger skeletons• Legs placed more directly under the body rather

than right-angles give greater body support, makes walking/running easier

• Claws for catching prey & self-protection• Jaw & teeth structures evolved to allow reptiles to

use other resources and niches on land

Better circulation, too• Some had 3-chambered heart, some had 4-

chambered heart (more efficient)• Better able to circulate oxygen• Higher level of energy

use required by land animals

• Internal fertilization, eggs are laid & then embryos develop– Eggs are hidden under rocks, bark, grasses, sometimes buried in

holes for protection/incubation• Reptiles are ectotherms (depend on external heat)– Must move into appropriate temperature zones – Don’t live in very cold climates, mostly desert or tropical

• Very diverse methods of obtaining food– Tortoises/turtles – slow, mostly herbivores, some ominvorous– Lizards – primarily feed on insects, eggs, small animals– Snakes – effective predators (subdue prey with venom,

constriction)• Sense organs help detect danger or potential prey– Heat-sensitive pits (snakes) http://youtu.be/wYxiffT7izY

– Keen sense of smell & sight http://youtu.be/8avVFYTspE8

• Reptile diversity– Chelonia: Turtles & Tortoises

• shells made of keratin, attached to ribs and spine—carapace and plastron

– Crocodilia: Crocodiles, Alligators, Caimans• floating predators, eyes & nostrils above water, powerful jaws and

sharp teeth to drag prey underwater• Lay eggs in nests, guard eggs and young closely, carry offspring

gently in mouths– Squamata: Snakes & Darting Lizards

• Snakes have no limbs or bones to support them (some vestigial pelvic bones in pythons), flexible vertebrae, kill prey with constriction, venom, or grabbing with mouth and swallowing whole

– Rhynchocephalia: Tuataras (2 living species)• Only survivors of primitive reptiles extinct 100 mya

What is a bird?• Class Aves (8600+ species modern birds)• Fossil evidence indicates that birds evolved

from feathered dinosaurs (ex. archaeopteryx)– Clawed toes, protein scales on feet, internal

fertilization, shelled amniotic eggs– Some are flightless, but all are winged &

feathered• Feathers- lightweight, modified protein scales– Provide insulation, enable flight– Usually paired, lost in pairs for balance

• Down feathers are soft, no hooks• Flight feathers are rigid, tiny hooks hold filaments

together

Birds have wings• Bird skeletons have modifications to allow for flight– Breast bone = sternum– Muscle attachment in skeleton enables strong pectoral

contractions for wing movement/lift– Strong, mostly hollow skeletons

• Many fused bones

• Birds must maintain a consistent weight for flight• Wing structure indicates ecological behavior of species

– Does it glide? Flit? Hover? Swim? Is it flightless?

Flying takes a lot of energy• Birds have high oxygen demands– 4-chambered heart (provides efficient circulation)– Hearts beat very quickly, high metabolic rate

• Respiratory system pumps air in one direction– 75% of inhaled air passes directly into air sacs, inhaling & exhaling

passes oxygen through lungs—birds receive oxygen both ways

Bird reproduction• Internal fertilization, lay amniotic eggs with

hard, calcified shell (from cloaca)• Bird nests made out of variety of materials,

depending on species, habitat & behavior• Birds incubate their eggs (keep them warm),

often turning eggs over periodically to ensure development, increase survivorship of young

A baby bird’s first task is to escape the hard shell of the egg (special structure on beak aids in cracking the egg)

This is the baby’s first physically demanding effort, uses muscles for the first time

When baby emerges, often very underdeveloped (indicates how much parental involvement is necessary for rearing the chick)

Feathers being to form (in tube-like sheaths that must be removed), first down to keep baby warm, then the flight feathers appear

Maintaining Homeostasis

• Birds are Endothermic = maintains constant internal temp– Internal heating requires a lot of energy

• This advantage allows birds to inhabit greater variety of habitats (almost every environment on Earth)

• Must eat a large amount of food to sustain internal temps– Birds spend a great portion of the day finding food

• Birds (like reptiles) have efficient kidneys and store metabolic waste as uric acid (to limit water loss)– “poop” is actually digestive waste and uric acid http://

youtu.be/18TDNC-3bJQ

Bird Diversity• Despite their basic uniformity (feathers, wings, beaks,

etc.), birds exhibit a broad variety of adaptations to enable their survival in specific habitats– Modifications in:

• Wings, feathers, beaks, eyes, feet• Egg size, color, shell thickness• Social behavior: feeding, mating & courtship, aggression,

mimicry, timing, calls, flocking, migration• http://youtu.be/L54bxmZy_NE http://youtu.be/7siJmzWbCyw

• Bird songs and vocalizations have been compared to language– http://youtu.be/vH5xQbfUdSM http://youtu.be/OuBW9CB6XB4

• Flocking sometimes involves 1000s of birds, emergent properties of a fluid “superorganism” http://youtu.be/M1Q-EbX6dso

• Hawks, eagles, & falcons

• Owls• Passerines - Perching

birds (very diverse) – Pigeons & doves– Songbirds – Hummingbirds– Near-passerines -

Woodpeckers, toucans, & honey guides

– Parrots, lories & cockatoos

• Flamingos, grebes• Herons, bitterns, &

ibises• Penguins, pelicans,

storks, loons• Swans, geese, & ducks• Flightless birds – ostriches, rheas, emus,

kiwis• Turkeys, pheasants,

quail, partridges, grouse, chickens

Origins of birds• Evidence in the fossil record indicates that a group

of dinosaurs did not become extinct– Earliest known bird is Archaeopteryx• Not the common ancestor of all birds, but representative of

bird existence (snapshot)– Bird fossils in China reveal bird evolution from theropod

dinosaurs• (flightless and ran to capture prey)• Feathered (possibly for insulation, camouflage, courtship)• Theropods have sternum, wishbone, shoulder blades, flexible

wrists, 3 fingers on each hand

• The “Life of Birds” series is excellent & on Netflix btw!