Lecture 23 Flashcards
Amniota
amniote clade includes reptiles and mammals, terrestrial adaptations, amniotic egg
amniotic egg - 4 extra-embryonic membranes
- amnion
- yolk sack
- allantois
- chorion
+ most have eggshell impervious to water loss
amnion
protects embryo from mechanical shock
yolk sack
contains food (absent in most mammals)
allantois
waste disposal and gas exchange
chorion
in contact with liquid surrounding embryo and eggshell (when present), gas exchange
3 amniote characteristics allowing for terrestrial life
- copulation and internal fertilization
- waterproof skin (reduces water loss to atmosphere)
- muscles associated with ribcage efficiently ventilate lungs
Hylonomus
earliest fossil amniote, Atlantic Canada
2 major amniote clades
- Reptilia
2. Synapsida
diapsid skull
two holes per side behind eye socket
synapsid skull
one hole per side behind eye socket
anapsid
zero holes behind eye socket (only turtles)
characteristics of non-avian reptiles
- skin covered by thick protective keratinous scales
- leathery eggshell
- ectotherms
- only require 10% calories compared to mammals (no metabolic energy spent on heating)
- cloacas
ectotherms
rely on environmental heat to maintain appropriate temperature, most enzymes only work in a particular range of temperatures, control temperature behaviourally
3 main groups of non-avian reptiles
- testudines
- lepidosauria
- crocodilia
testudines
turtles and tortoises, bony dorsal and ventral shields, skull is a solid box with large openings behind eyes, sole living representatives of Anapsida, can withdraw head inside carapace for protection, males have an intromittent organ
lepidosauria 2 lineages
- tuataras
2. squamata
tuataras
teeth fused to jaw bones, copulate but lack intromittent organ
squamata
snakes and lizards, loosely jointed jaws and skull, paired hemipenes in males, lizards have external ear openings snakes do not, snakes have no obvious external limbs and kill prey by suffocation or venom
crocodilia
alligators, crocodiles, gharials, cannot chew (swallow prey whole or spin to rip off chunks), can walk about on land, males have single intromittent organ, crocodilians show maternal care
economic importance of non-avian reptiles
- turtle flesh, eggs, and shells harvested
- lizards and snakes as pets and zoo exhibits
- some snakes dangerous to humans - antivenins available
parareptiles
extinct anapsid reptiles, may be related to turtles
2 extinct aquatic diapsids
- ichthyosaurs (look like reptilian dolphins)
2. plesiosaurs (look like loch ness monsters)
archosauria
crocodilians, birds, and extinct non-avian dinosaurs and pterosaurs
dinosaurs
largest animals ever to inhabit land, may have been endotherms
endotherm
warm-blooded
class aves
birds
feathers
finely subdivided keratinous scales, most important synapomorphy of birds
origin of birds
fossil evidence supports small fast theropod dinosaurs with feathers
Archaeopteryx
most famous extinct bird, wings with teeth and wing claws
characteristics of birds
- feathers
- keratinous beaks that lack teeth (grind hard food in gizzard)
- no claws
- adaptations for flight (hollow bones and reduced organs)
- endothermic
- care for feathers by preening
- cloaca
- all copulate but most do not intromit (press cloacas together)
- parental care
gizzard
muscular part of stomach, often with added pebbles for grinding food
endothermy in birds
use metabolic energy to maintain constant body
temperature, homeothermic
homeothermic
maintain same temperature
preening
- moves oil from gland at base of tail all over feathers
- keeps feathers supple
- may act as antibiotic
- ‘zips up’ flight and contours feathers to keep in good
shape, tiny hooks and rays link like velcro - removes some parasites (feather lice)
flightlessness in birds
evolved several times (penguins, ostriches), denser bones than flighted birds (diving birds also have denser bones)
precocial
young able to feed themselves
altricial
young born helpless and featherless
economic importance of birds
- meat, eggs, feathers
- hunting sport
- pets
- bird-watching
