Origin of Birds and Class Aves

Question 1

What animal did birds likely evolve from?

Answer 1

theropods (small, fast dinosaurs)

Question 2

what evidence suggests that birds were ancestors of theropods?

Answer 2

evidence of dinosaurs with feathers (usually ones that they couldn’t fly with but just for courtship or gliding?)

Question 3

What species shared a common ancestor with birds (sister taxa of birds)?

Answer 3

Archaeoptryx –> it had feathers, and wings and it could fly
- but …. it had teeth, body tail and claws which modern birds don’t have and they could not pick up flight from off the ground and had to be on a tall surface to pick up flight

Question 4

What is the name of the extant group that birds and crocodiles are a part of?

Answer 4

archosaurs

Question 5

are birds endotherms or ectotherms?

Answer 5

birds are endothermic and they use metabolic energy to maintain body temperature –> they have a really high rate of metabolism

Question 6

What are derived characters of birds that are used as adaptation for flight?

Answer 6

1. Feathers –> these are the most important synapomorphies and they are homologous with scales and they have subdivided into keratinous scales
2. they have reduced number of forelimbs (one main digit and two tiny ones) and no claws
3. Horny beaks that lack teeth
4. gizzard –> part of their stomach thats muscular and it grinds hard food because they don’t have teeth
5. reduced organs (they have one ovary, no urinary bladder –> they poop and pee at the same time)

these adaptations were made to reduce body weight and be able to fly

Question 7

how do birds care for their feathers? what occurs in this process?

Answer 7

they care for their feathers by preening –> moving oil from gland at base of the tail to the rest of the feathers to keep them supple

Question 8

What is the structure of a feather in birds? what does preening do to the looks of the feather?

Answer 8

• the feathers have a hook and barb structure and when birds preen, they “Zip up” the hooks and barbs and make their feathers look tidy and ready for flight
• similar to velcro

Question 9

How do birds reproduce?

Answer 9

they reproduce via internal fertilization (copulation) but they don’t have a intermittent organ

Question 10

What do birds use during copulation if they don’t have intermittent organs

Answer 10

they use the cloaca —> common opening for digestive, urinary and reproductive tract (which is also present in amphibians and reptiles) and male and female birds press cloacas together and transfer sperm

Question 11

Which two birds have intermittent organs?

Answer 11

ostriches and waterfowls

Question 12

what kind of eggs do birds make?

Answer 12

eggs with hard calcareous shells (calcium carbonate)

Question 13

How do birds provide parental care?

Answer 13

they incubate their eggs using their body heat, they usually care for their young after birth (either the mom does or both parents do)

Question 14

What does precocial mean?

Answer 14

means that the young may be able to feed themselves

Question 15

What does altricial mean?

Answer 15

means they are born helpless and featherless (often featherless and blind and rely on mom for care)

Question 16

What usually determines if the babies of a species of birds will be precocial or altricial?

Answer 16

depending on the number of predators in their area… for example ducklings are precocial when born because they follow their mom and are able to eat things right away

Question 17

What habitats and ecology do birds usually live in?

Answer 17

they are mainly terrestrial, freshwater and marine (but all use land for breathing)
- they can be predators, herbivores, scavengers and omnivores … their feet and beak give good clues as to what they eat

Question 18

How has flightlessness evolved in some species of birds for example penguins, and ostriches?

Answer 18

it evolved secondarily many times (they lost it, and then gained it and then lost it) for example, penguins flippers evolved from wings because the birds ancestors could fly
- these species have denser bones than flighted birds

Question 19

What are some economic importance from birds?

Answer 19

their meat is important source of protein

• the birds are also farmed for eggs and feathers (there are welfare concerns about how this is done)
• bird hunting is also a sport
• bird watching is a source of ecotourism in some countries
• some people keep birds as pets