Evolution of Behavior (L7) T2

Question 1

Fossil Record approach to examining evolutionary pathways

Answer 1

Fossils provide few clues to behavior, but often preserve MORPHOLOGICAL STRUCTURES required for certain behaviors to occur.

Question 2

Comparative approach (cladistics/phylogenetic systematics)

Answer 2

1. If a trait is widespread in a group of related species, it is probably a PRIMITIVE trait present in the ancestor of those species.
2. If a trait is represented in only one or a few species, it is probably a DERIVED trait evolved relatively recently.

Question 3

In which animal groups is true, self-powered flight (not gliding) thought to have evolved independently?

Answer 3

Insects, Pterosaurs, birds, a bats.

Question 4

What was the earliest well documented bird?

Answer 4

Archaeopteryx lithographica, of the Jurassic period.

Question 5

Flight morphology: Sternum

Answer 5

Most modern flying birds have a KEELED sternum to which the major flight muscles are attached. Birds that CANNOT fly LACK a keeled sternum.

Archaeopteryx lacked a keeled sternum, suggesting that it could not fly.

Question 6

Flight morphology: Feathers

Answer 6

Flight feathers on the wing and tail of FLYING birds are ASYMMETRICAL. Feathers unimportant for flight/on non-flying birds are symmetrical.

Archaeopteryx possessed asymmetrical flight feathers, suggesting that it could fly.

Question 7

Arboreal (gliding) hypothesis

Answer 7

1. Avian flight began in trees.
2. Advantages: Gain height, gravity, speed, selection for greater surface area of forelimbs.
3. Disadvantages: Possibility of injury, theropod claws straighter, theropods were terrestrial, and muscles differ for climbing and flying.

Question 8

Cursorial (terrestrial) hypothesis

Answer 8

1. Avian flight began on the ground.
2. Advantages: Ecology of theropods, energy for run + jump + glide < continuous running, could jump + then glide + flap while gliding.
3. Disadvantages: Gravity, shift of selection for speed and agility from hind limbs to fore limbs, low initial speed, power curve for flight, and loss of running speed to jump is 30-40%.

Question 9

Evidence for Arboreal Archaeopteryx

Answer 9

1. Forelimbs: long compared to hindlimbs, as in arboreal gliders.
2. Claws on wings: pointed ventrally, presumably useful for climbing.
3. Claws on feet: relatively short and curved, typical of arboreal species of birds. Terrestrial species of birds have relatively long and straight claws.

Question 10

Contradicting evidence for Archaeopteryx

Answer 10

1. Claws on feet: relatively short and curved, obviously arboreal.
2. Lack of keeled sternum (no strong anchor point for flight muscles): flight muscles were small.

Question 11

Archaeopteryx conclusion

Answer 11

Archaeopteryx was a weak flyer unable to fly up from ground or sustain flapping flight, thus supporting the arboreal hypothesis.

Question 12

What did the first moth-like insect probably feed on?

Answer 12

nectar.

Question 13

How many of more than 200K species of butterflies and moths drink blood from animals?

Answer 13

Only 4 in Southeast Asia

Question 14

What do moths and butterflies drink?

Answer 14

Salty solutions from mud puddles, pools of animal urine, or even directly on dead or alive animals (sweat or eyes).

Some moths use the proboscis to scrape the skin of fruit, thus wounding it and inducing it to “bleed” – proboscis is more rigid than in other species.

Question 15

Cladistics: Brood parasitism in cowbirds

Answer 15

• Cowbirds lay eggs in the nest of other species of birds (hosts).
• Some species are specialists–they lay eggs in the nests of only a few species.
• Some species are generalists–they lay eggs in the nests of MANY species.
• Ancestral cowbird was a specialist…derived species are generalists.