Unit 3 Lecture 17

Question 1

Explain the study with brown anoles

Answer 1

• Surgically removed the ovaries from some brown anoles
• Control: surgery without ovary removal
• After they underwent surgery, the ones who ha their ovaries removed, grew more (in size) and lived longer

Question 2

What kind of trade-off is the Brown Anoles experiment?

Answer 2

Both Growth rate-reproduction trade-off and reproduction-survival trade off

Question 3

Explain the castrating parasites with snails

Answer 3

Since the trematode parasite prevents reproduction in snails, this also causes the snails to invest more energy into growth and maintenance of survival

Question 4

Explain the similar study of the Daphnia and the castrating parasites

Answer 4

• Daphnia gets infected with castrating parasite
• The individuals who are infected grow bigger than the uninfected individuals
• Reallocation of energy when you cut off reproduction

Question 5

What does optimal Life history strategy mean?

Answer 5

The life history strategy that maximizes lifetime reproductive success (fitness) in a given environment

Question 6

What factor could affect optimal life history?

Answer 6

predation

Question 7

How would optimal life history strategy differ between populations that experience little predation vs. lots of predation?

Answer 7

• More predation –> start reproducing earlier
• More predation –> produce more, smaller offspring

Question 8

Explain the studies with the opossums in Georgia

Answer 8

• In the mainland, 80% mortality due to predation
• On island, no predators for past 5,000 years
• On the mainland, by 28 months of age, 100% of the opossums are dead, but on the island, up to (maybe past) 44 months
• At any age beyond 10 and 15 months, the individuals on the mainland are in worst condition than the opossums on the island i.e. age faster

Question 9

Who invests more in reproduction, the opossums on the mainland or island? What trade-off is this?

Answer 9

Mainland opossums invest more in reproduction in the first year and make more babies due to the high predation
- Maintenance - reproduction tradeoff

Question 10

When there high predation…

Answer 10

1. Invest more in reproduction in 1st year
2. Benefit = more likely to reproduce
3. Cost = faster aging (reduced maintenance)
4. Comes at a cost of shorter life span (even if you don’t get eaten)

Question 11

Explain the Trinidadian guppies study

Answer 11

• Guppies on the tops of streams above waterfalls where there is a little predation, and at the bottom of waterfall there is high predation
• In high predation site, there was a larger number of offspring of smaller sizes
• Quality-Quantity tradeoff

Question 12

What experiment did they perform with the Trinidadian guppies?

Answer 12

• Moved some fish from high predation streams to predator free streams
• Keep some fish in high predation streams (control)
• Come back 11 years later
• Change in the direction that we expected; the guppies that were moved to the predator free streams grew for longer and had an older age and size at sexual maturity

Question 13

What are extrinsic factors?

Answer 13

Environmental factors outside your control; are important in shaping life history strategies

Question 14

Predation rate can affect what?

Answer 14

• Size and number of offspring
• Age and size at maturation (timing of reproduction)
• Life span

Question 15

What is the average age in America that women reach menopause

Answer 15

51

Question 16

What other animals are known to have menopause

Answer 16

whales

Question 17

Only 3 species known to have menopause (i.e. live long after reproductive life span ends)

Answer 17

1. Killer whales
2. Short-finned Pilot whale
3. Humans

Question 18

Explain the difference in chimps evolutionary graph compared to humans

Answer 18

• Once chimps reproductive stage ends, so does their life
• Once humans reproductive stage goes down around age 50, our survivorship just keeps gradually going down

Question 19

Explain post-reproductive female killer whales

Answer 19

• In killer whales, post-reproductive females are leaders
• Females lead more than males, and post-reproductive females lea more than reproductive females
• Post-reproductive females are better at finding salmon
• Post-reproductive females increase survival of her grandkids

Question 20

What’s the fitness benefit of post-reproductive mammals?

Answer 20

• Passes the trait of living past reproduction to their grandkids
• In humans, having a post-reproductive mother around increases fecundity and decreases age at first reproduction
• Grandkids also have higher survival when grandmother is around

Question 21

What life history trade-off does menopause demonstrate?

Answer 21

Reproduction-survival tradeoff
- Women stop investing energy into reproduction, and as a result live longer

Question 22

The cost of menopause (i.e. fewer offspring) may be offset by benefits of:

Answer 22

1. Increased lifespan
2. Ultimately, increase number and survival of grandchildren

Question 23

More offspring means what?
Fewer offspring means what?

Answer 23

More offspring = greater potential reproductive success, but more mouths to feed

Fewer offspring = more food to go around, but may not be maximizing reproductive potential

Question 24

Animals that optimize parental investment should leave more offspring, but the big challenge is what?

Answer 24

Environment is unpredictable –> optimal family size for a given reproductive attempt may be different

• Female kangaroo will have a baby in her pouch, but if the environment gets bad, she will kick the baby out so that she can survive, and restart the proves when the environment is better

Question 25

Explain the Male sand gobies study

Answer 25

• “fanning” provides oxygen to eggs
• Males sometimes eat some of the eggs

Question 26

Explain the experiment on Sand Gobies

Answer 26

• Let gobies mate and produce clutch of eggs (some produce a lot, some produce few)
• Manipulate oxygen content of water
• Remove some eggs from half of the clutches
• She removed some of the eggs from the clutches to lower the density of the clutches
• Beneficial because it increases the survivorship of the surviving clutch
• More offspring survive in high-oxygen environment with a low density clutch

The cost of eating some of your own eggs (fewer offspring) is offset by benefit of increased survival of remaining eggs

Question 27

Male sand gobies eat more eggs when?

Answer 27

• Oxygen content of water is low
• Eggs are too crowded (preventing some from getting O2)