BIO 1130 Lecture Notes - Lecture 37: Oviparity, Adaptive Radiation, Autapomorphy
Phanerozoic - Cenozoic era
● Continents shift into final locations
● Therapsids have survived
● Survivor: reptile with feathers - unique: feathers were used to thermoregulate
● Endothermy: by birds and mammals - generate heat to maintain body temp (homeothermy -
keeping body at precise and constant temp)
● Amniote animals: includes reptiles, birds & mammals - have eggs with amnion (water-filled sac)
surrounding the developing embryo
● Birds: same as therapsids - feeding when cool
○ Feathers: not only found in birds (were common in dinosaurs)
○ Used feathers for catch prey (insects) - by swiping through air
○ Ground-up theory of birds: while birds were trying to catch prey, realized that swiping up
and down could lift them & help escape from predator (origins of flight)
○ Tree-down theory: bird climbs tree, jumps down from branch and glides with feathers as it
eats insects
○ Feather becomes complex - keratinized structure (beta keratin because reptile)
■ Small elements that are locked together → makes lightweight structure w/ holes
that are small enough that can push against air
■ Barb: branches of a feather, possess barbules; maintain feathers’ structures
(even during vigorous activity)
■ Barbule: hook-like processes on barbs of feathers - interlock filaments of feather
together; maintain feathers’ structures (even during vigorous activity)
○ Lighter organism → altered bones to become light → tail gone, jaw gone (replaced by
beak of keratin), vertebrate gone, and # of bones in wing reduced
■ Wing: only skinny piece of bone (even though it looks big) → feathers do all the
work
■ Power to lift wing becomes centralized → all organ systems centralized (center of
gravity) → lifting force is above center of gravity
■ Muscle lifts wing → 1 pulls up, another 1 pulls down
■ Sternal keel: modified sternum (breastbone) in birds; the attachment
(anchor) of the flight muscles
■ Bones are filled with air (not solid) = lighter (pneumatized bone)
○ Engage in parental care: does make appearance with reptiles → but birds lay eggs,
incubate & take care of offspring
■ Few offspring every year, but guaranteed success of offspring → good, effective
reproductive strategy
● Mammals - great apes: includes chimpanzees, gorillas & orangutans; group that humans have
the most chromosomal similarities to
● Synapsid: mammals and mammal-like reptiles (ex. humans)
○ Synapsid skull - 1 opening for jaw muscle
○ Keratin - alpha keratin only (in skin) (automorphy of mammals) → makes hair, toenails
○ Skin: glandular → loaded with glands = makes materials on surface of skin
■ Later modified to make nourishment for feeding young with → mammary gland
& lactation
■ Follicle cell: makes hair
■ Sebaceous gland: makes oils and waxes (need to keep hair supple and smooth)
→ need to be able to lift hair up (and with hairs going down) = makes insulative
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Survivor: reptile with feathers - unique: feathers were used to thermoregulate. Endothermy: by birds and mammals - generate heat to maintain body temp (homeothermy - keeping body at precise and constant temp) Amniote animals: includes reptiles, birds & mammals - have eggs with amnion (water-filled sac) surrounding the developing embryo. Birds: same as therapsids - feeding when cool. Feathers: not only found in birds (were common in dinosaurs) Used feathers for catch prey (insects) - by swiping through air. Ground-up theory of birds: while birds were trying to catch prey, realized that swiping up and down could lift them & help escape from predator (origins of flight) Tree-down theory: bird climbs tree, jumps down from branch and glides with feathers as it eats insects. Feather becomes complex - keratinized structure (beta keratin because reptile) Small elements that are locked together makes lightweight structure w/ holes that are small enough that can push against air.