TOPIC 13: MATING SYSTEMS

Question 1

Asexual Reproduction

Answer 1

Originally organisms would have reproduced using binary fission

Similar to mitotic cell division

All new individuals would have been clones of the original
Evolution could only have occurred due to mutations of the original cell line (NO GENETIC
DIVERSITY!

Question 2

Major Advantage of sexual reproduction

Answer 2

genetic diversity within a population of a species

Question 3

List some Disadvantages of sexual reproduction

Answer 3

1) Only half of an individuals genes are passed to the next generation

2) Growth rate is half that of asexual reproduction (takes two to make one)

3) Some unfavourable recombinations
All of these factors can serve to reduce fitness

Question 4

Gender Biases in Animals typical pattern

Answer 4

Typical Pattern: Males do the courting and females do the choosing

Male fitness is often dependent on acquiring multiple mates

Female fitness is often dependent on access to abundant resources

Question 5

Anisogamy

Answer 5

Gender biases are a result of unequal investment in gametes (Anisogamy)

Question 6

explain anisogamy

Answer 6

Egg cells are much more energetically costly to produce than sperm cells
Theoretically a single man could fertilize all the eggs of all the women in the world
Males fitness increased by fertilizing multiple eggs
Females fitness increased in continued investment in costly egg
Also results in females having already invested more in gamete production to continue
to invest in parental care

Question 7

Secondary Sex Characteristics

Answer 7

Males evolution driven by sexual selection imposed by limited female partners

Traits to enhance attractiveness
2) Traits to enhance competitive ability with other males

Question 8

Traits to enhance attractiveness

Answer 8

hypothesized that displays advertise good genes and a healthy condition.
Further enforced through runaway selection
- males inherit genes for impressive display
-females inherit preference for display

Question 9

Traits to enhance competitive ability with other males

Answer 9

impose dominance hierarchy
- sneaky male strategy
- mate guarding
- sperm competition
- nuptial gifts

Question 10

Mating System

Answer 10

the number of partners that males and females have
* Can vary among and within species
* Also includes aspects of parental care

Question 11

4 General Categories

Answer 11

• 1) Polygyny*
• 2) Polyandry
• 3) Monogamy
• 4) Promiscuity

Question 12

Polygyny

Answer 12

a single male takes multiple female mates
Most commonly observed of the mating systems

Question 13

Female Defense

Answer 13

Where females cluster together for predator defense or resource
patches

Question 14

Resource Defense

Answer 14

Where resources are clumped and male will control area that is
attractive for females

Question 15

Lek Polygyny

Answer 15

An area where a male will set up an often elaborate mating
display to attract mates (no resources involved)

Question 16

) Scramble Competition

Answer 16

Where timing window for mating may be short, so it is a first
come first served basis

Question 17

Polyandry

Answer 17

Rare in nature.
When something limits the brood size of the female below that of which it is capable it may
take multiple mates
Eg. Spotted sandpiper
Gender role reversal

Question 18

Monogamy

Answer 18

a single pair bond between one male and one female
Somewhat common in some animal groups like fish and birds
When there is a high risk that female may take multiple partners in absence of mate guarding
When male offers up energetically costly support
Eg. Seahorse
Brood pouch means that male seahorse bears the burden of “pregnancy”

Question 19

Promiscuity

Answer 19

females and males both take multiple mates
Likely the result of coevolution of other mating systems between males and females
Both sexes increase their fitness by having multiple mates