Evolution Studying Adaptation

Front 1

what is a trait that increases the fitness of its possessor called?

Back 1

adaptation

Front 2

In order to demonstrate that a trait is an adaptation what two things do we need determine?

Back 2

1. what the trade is for
2. and then show that individuals possessing the trait contribute more to future generations lacking it

Front 3

The traditional adaptive hypothesis for the origin of the giraffe's neck (to forage trees above the reach of their competitors) provides an example that no explanation for the adaptive value of a trait should be accepted simple because it is ________.

Back 3

plausible

Front 4

traditionally the hypothesis used to explain the adaptive value is know as the FORAGING-COMPETITION HYPOTHESIS, if the hypothesis is correct, then during the dry season, when food is scarce, giraffes should spend most of their time foraging above the reach of their competitors

why is this not the case?

Back 4

giraffes spend much of their dry season foraging time browsing on low bushes and not tall trees

Front 5

Simmons and Scheepers offered an alternative scenario for the evolution of the giraffe's neck

what did they suggest about of the evolution of the giraffe's neck?

Back 5

they suggested that the giraffe's neck evolved as a weapon, used by males in combat over opportunities to mate

Front 6

Consistent with the simmons and scheepers hypothesis, __ giraffe's have necks that are 30 to 40 centimeters ___ and 1.7 _____than the necks of ____ of the same age

Back 6

male
longer
heavier
females

Front 7

studies of interactions between males giraffe's in which one bull displaced another from a social group showed that class __ bulls were dominant over classes __ and __ and ___ were dominate over __.

class C: young males
class B: adult males with thin necks, small horns
class C adult males with thick necks, massive horns

Back 7

class a bull were dominated over classes B and C and

B's were dominate over C's

Front 8

Courting and mating Interactions between males and females showed that females preferred to mate with class __ and __ males than with __ males.

Based on these data suggested that among the ancestors of today's giraffe's, Why did the long necked males have higher reproductive success?


why do females have long necks too?

Back 8

A and B that with C males

because they intimidated their rivals and attracted more mates

NOT because they got more to eat

because males pass genes for long necks to their daughters as well as to their sons

Front 9

The Giraffe example demonstrates that we cannot uncritically accept a hypothesis about the adaptive significance of a trait simple because it is PLAUSIBLE, we must submit all the hypothesis to rigorous tests.

Evolutionary biologists use 3 methods to test hypothesis about the adaptive significance of traits, what are they?

Back 9

1. experiments
2. observational studies
3. comparative method

Front 10

what do experiments allow us to do?

Back 10

isolate and test the effect that a SINGLE, WELL DEFINED FACTOR has on the phenomenon in question

Front 11

what were the two hypothesis suggested to explain the behavior of the tephritid fly?

(when this fly is disturbed it holds its wing perpendicular to its body and waves them up and down)

Back 11

1. because the jumping spiders are fast and have a nasty bite, a fly mimicking a jumping spider might be avoided by a wide variety of predators

2 because jumping spiders are Zonosemata's main predators, it has been suggested that the fly uses its wings to make markings and wing waving display to intimidate the jumping spiders themselves

Front 12

3 hypothesis were tested to test the hypothesis that account for the adaptive valve of the trait

1. the flies do not mimic jumping spiders
2. the flies mimic jumping spiders to deter ______
3. the flies mimic territorial threat of jumping spiders to deter ______

researchers found that they could cut the wings of a ______fly and glue them back on. they also found that they could cut the wings of a _____ fly and replace them with the wings of a _____, which are clear and unmarked.

Back 12

other non spider predators

to deter predation by the jumping spiders themselves



Zonosemata
Zonosemata
housefly

Front 13

the five experimental groups of flies were:
A. Zonosemata untreated
B. Zonosemata with own wings cut and reglued
C. Zonosemata with housefly wings
D. Housefly with Zonosemata wings
E. Housefly untreated

the researchers starved 20 jumping spiders for two days, then they presented one of each of the five experimental fly types to each spider in random order.

what did the results show?

what happened when researches tested these treatments to other predators?

these results were consistent with which hypothesis?

Back 13

results:
jumping spiders tended to retreat from flies of experimental groups A and B, these are the flies with marked wings. in contrast they attacked flies that lacked wing markings (C D and E)

all the test flies were captured and eaten

these results were consistent with the third hypothesis: tephritid flies mimic their own jumping-spider predators to avoid being eaten by them

Front 14

the five experimental groups of flies were:
A. Zonosemata untreated
B. Zonosemata with own wings cut and reglued
C. Zonosemata with housefly wings
D. Housefly with Zonosemata wings
E. Housefly untreated

the researchers starved 20 jumping spiders for two days, then they presented one of each of the five experimental fly types to each spider in random order.

what did the results show?

what happened when researches tested these treatments to other predators?

these results were consistent with which hypothesis?

Back 14

results:
jumping spiders tended to retreat from flies of experimental groups A and B, these are the flies with marked wings. in contrast they attacked flies that lacked wing markings (C D and E)

all the test flies were captured and eaten

these results were consistent with the third hypothesis: tephritid flies mimic their own jumping-spider predators to avoid being eaten by them

Front 15

In terms of experimental design, what are the four important points that are critical for every study?
(Zonosemata study)

Back 15

1. defining and testing effective control groups
2. all the treatment must be handled exactly alike
3. Randomizing is an important technique for equalizing other, miscellaneous effects among control and experimental groups
4. repeating the test on many individuals

Front 16

Defining and testing effective control groups is critical. In the Zonosemata study, groups A and B served as controls. what did these control groups demonstrate?

Back 16

wing surgery (wings have been cut and glued) itself had no effect on the behavior of the flies of spiders.

Front 17

Zonosemata experiment

Repeating the test on many individuals is essential, they help two things what are they?

Back 17

1. reduce the amount of distortion caused by unusual individuals or circumstances. (four of the flies were killed before they had a chance to display)
2. understand how precise the estimates are by measuring the amount of variation

Front 18

when experiments are impractical, careful __________can sometimes yield sufficient information to evaluate a hypothesis.

what is a good example of observational studies

Back 18

observations

adaptive value of long necks in giraffes