Evolution of reproductive behaviour

Question 1

What is Potential Reproductive Rate? Are males or females higher?

Answer 1

The maximum number of offspring an individual can produce over a unit of time.
Males are high, females are low.

Question 2

What is sexual selection and who introduced it?

Answer 2

It is an evolutionary force that acts on individuals chances of mating and passing genes to the next generation. Charles Darwin 1871.

Question 3

What are the 2 forms of sexual selection? Define them.

Answer 3

1. Intrasexual (male-male competition): competition within a sex to fight for the lady (gain fertilisation).
2. Intersexual (mate choice): one sex competes to attract the attention of the other sex (pretty feathers, dancing, mating call etc.)

Question 4

What are the 2 forms of intrasexual selection? Define them.

Answer 4

1. Pre-copulatory: competition between two males to mate with the female
2. post-copulatory (sperm competition)

Question 5

What are the 4 favoured traits for pre-copulatory male-male competition?

Answer 5

1. Ornaments
2. Aggressive displays
3. Armaments (antlers etc weapons)
4. Physically aggressive behaviour

Question 6

How do the less dominant males get to reproduce?

Answer 6

By being sneaky i.e. can appear as females then drop their sperm.

Question 7

What 5 traits are favoured by sperm competition?

Answer 7

1. Mate guarding
2. Sperm-removal behaviour (barbed penis)
3. Increased sperm production (like the lottery)
4. Longgg sperm (take up all the room in female reproductive tract)
5. Toxic seminal fluid production (kills sperm of other males and sedates females)

Question 8

What are the 2 forms of Intersexual Selection?

Answer 8

1. Pre-copulatory mate choice: female chooses who they want to mate with
2. Post-copulatory mate choice: once inseminated with the sperm, females can actually kill off the weaker sperm by increasing their WBC count

Question 9

What are the 2 traits favoured by pre-copulatory choice?

Answer 9

1. Elaborate courtship displays and mating signals (visual, acoustic, phermones)
2. Elaborate ornaments: feathers colours etc.

Question 10

What are the 2 genetic benefit hypotheses?

Answer 10

1. Good genes: females choose a mate with good genes e.g. peacocks with bigger eyes on the tail have better genes
2. Genetic compatibility: females choose males that they are more compatible with genes wise.

Question 11

Explain sex-role reversal

Answer 11

Occurs when males have a lower PRR than females which leads to female-female competition, and male-mate choice.

Question 12

What leads to different mating systems?

Answer 12

Different social and ecological selection pressures

Question 13

What are the three types of mating systems?

Answer 13

1. Monogamy: both sexes have one partner
2. Polygamy: one sex has multiple partners (Polygyny: the male has multiple partners, polyandry: the female has multiple partners)
3. Polygyny-andry: both sexes have multiple partners

Question 14

What benefits do females gain by being choosy in their mate-choice?

Answer 14

• Direct benefits: some males have traits that benefit the female’s survival and that of her offspring
• Indirect benefits: males have traits that can be inherited and influence the attractiveness or genetic quality of offspring