Module 1; Lecture 3, Variation & Darwin

Question 1

What do you need to have evolution through natural selection?

Answer 1

there has to be phenotypic variation. Without phenotypic variation, there is no evolution.

Question 2

What is the correct answer ( MIDTERM)

Answer 2

Correct answer is D, because individuals have to reproduce in order to increase their fitness. Its not really about surviving the longest its more a question of production.

Question 3

How is Sexual Selection described by Darwin?

Answer 3

• Many animals have traits that maximize their reproductive success
• Traits may even decrease survival, but while still improving FITNESS because it increases reproduction.

Question 4

Different kinds of sexual selection

Answer 4

1.Intrasexual selection( within a sex)
2. Intersexual selection (between the sexes)

Question 5

What is intrasexual selection? Example?

Answer 5

When individuals intimidate, deter, or defeat same-sex rivals
Often male vs male but not always
eg; Over territory defence or fighting or other direct competition.

Question 6

What is intersexual selection, what is the example given in class?

Answer 6

Individuals make themselves more attractive to the opposite sex. Traits to try and impress the opposite sex.

Mate choice or mate preferences

Example given in class: Fidler crabs ( huge claws to impress female crabs), Primates, Birds.

Question 7

Explain the intersexual selection that happens in the fiddler crab example and what does this result in ?

Answer 7

Because the bigger claw crabs are the ones who mate the most are reproduce the most, the mutation that they carry ( the ones that allows for bigger claws) is the one that is passed down, so with time there are more and more individuals with bigger claws. The result is that this Skew our population towards larger claws as a consequence of female preference. BUT at some point having huge claws isn’t proper for survival so natural selection will serve as a barrier for this. pushing things back, limiting increases in claw size.
SO,
Sexual selection: Female preferences drives increase.

Natural Selection: May limit increases.

Question 8

The Flashy Sex

Answer 8

Whichever sex which has greater Variance (or skew) in reproduction will evolve more elaborate traits.

Question 9

The choosy sex:

Answer 9

Whichever sex has greater investment in reproduction will be more selective about who to mate with.

Question 10

What do we mean by investments?

Answer 10

For example we mean species who have greater maternal and paternal tasks animals given as examples in class; tigers, polar bears, cellar spiders, happens in a lot of fish.

Question 11

True or False, the choosy sex isn’t necessarily the female.

Answer 11

True, example, Seahorses; men do most of the paternal care, ( greater investment in reproduction) so males are picky with who they mate.

Question 12

What happens if no one is especially flashy? Give an example:

Answer 12

For example, like albatross birds, they are both producing equal, there isn’t much variance because all these males pair with one female for sure so nothing really changes because they all mate.

Question 13

What happens if one if especially TOO flashy? Give example:

Answer 13

Peacocks, here some males don’t reproduce and some males reproduce a lot. So more variation in females… Reproductive success for females is equal ( they all mate) but reproductive variance is high for males because some don’t reproduce at all and variance = width of distribution. So distribution is very skewed.

Question 14

Three (3) models to explain this sexual selection ( there isn’t only 3 but these are teachers favourite):

Answer 14

1.Direct benefits
2. Good genes/immunocompetent
3.Pre-existing Sensory bias and sensory exploitation

Question 15

What is phylogeny?

Answer 15

A history of organismal lineages as they change through time

Question 16

Direct benefits? Example

Answer 16

• One sex gains something from another( more food, protection from predators, etc)
• Male cardinals
• Effect doesn’t have to be heritable, doesn’t necessarily mean that the trait is descendent.

Question 17

Good genes/immunocompetent?

Answer 17

• Some males are genetically more resistant to parasites or infection = they would survive longer and have more offspring = they would be less likely to infect females,
• And their offspring would also survive longer, reproduce more. (Fitness)

These are all genetic traits, so the same genes protection certain males making them resistant is a trait the females would want for her kids. Females are choosing males that are of higher quality.

Question 18

Pre-existing Sensory bias and sensory exploitation?Example

Answer 18

• different direction from good genes/immunocompetences
• Female have a bias for sensory stimuli, biases result from the way that their brain is set up.
• Evolved for reasons outside of sexual selection (ex; foraging)
• Brains are “tuned to pay attention to certain things which is why certain species like females can’t go without noticing it ( it can be sounds or colours), etc…
• Frog example

Question 19

what is Parsimony ?

Answer 19

Parsimony is the idea that in order to explain the existence of a trait today, you try to figure out the path that would require the fewer changes to get there… The frog chuck examples is an examples of this…

Question 20

Is music a sexually selected trait? Who thought so?

Answer 20

Darwin thought that music was a consequence of sexual selection, turns out that music has evolved for the purpose of signaling genetic quality to potential mates and thus increasing mating success.

Question 21

Why is it hard to have a consensus on the best songs in the world?

Answer 21

Because no one has the same consensus of songs they like the most, just how we cant always explain why some animals prefer certain sounds over others…