Reproductive Stratagies

Question 0

What is the purpose of reproduction?

Answer 0

Reproduction is a survival strategy. It’s purpose is to maintain the population at a stable level by replacing dead individuals. However what reproduction actually replaces is genes.

Question 1

What is the purpose of death?

Answer 1

Reassures are finite and the death of individuals prevents these resources from being over exploited by very large numbers. I.e death is a population survival strategy.

Question 2

What is the species genome?

Answer 2

This is the global species gene pool.

Question 3

What are the two basic methods of reproduction?

Answer 3

Asexual reproduction

Sexual reproduction.

Question 4

What is Asexual reproduction?

Answer 4

This is reproduction by mitosis or cloning.

Question 5

What are the advantages of Asexual reproduction?

Answer 5

There is a higher (double) reproductive rate because every individual can reproduce.

Question 6

What are the disadvantages of asexual reproduction?

Answer 6

All the offspring produced are genetically identical clones. This means that adaption to change is impossible and the species quickly goes extinct.

Question 7

How does sexual reproduction help avoid species extinction?

Answer 7

This helps species resist new selective pressures by generating vast amounts of genetic variation. Natural selection then works on this by selecting the best adapted features (genes). Therefore as the environment changes, the species genotype also changes.

Question 8

In what three ways does sexual reproduction generate genetic variation?

Answer 8

1. ) Meiosis generates genetically variable cells.
2. ) separate sexes - reproduction involves sharing genes from two genetically different individuals
3. ) fertilisation is random.

Question 9

Why are egg cells so large and non-motile?

Answer 9

If both cells were small the zygote would be too and would have a lower chance of survival. Therefore one of the gametes has to be as big as possible. However this cell is now so large that it’s impossible to move it without expending vast amounts of energy. The solution is to make the other gamete (sperm) tiny so it can move and find the static egg.

Question 10

What are the consequences of having two very different sized gametes?

Answer 10

It divides the population into two sexes.

It sets up conflict between males and females with regards to the best reproductive stratagy.

Question 11

How does sexual reproduction create conflict between makes and females in regards of the best reproductive stratagy?

Answer 11

A cell is mostly cytoplasm which contains protein and lots of stored energy as glucose. This originates from food animals eat. Food is precious and must not be wasted, however females have to part with much more of their limited supply because their egg cells are so big - they are investing a much greater % of their food supply than males. This sets up a conflict between makes and females.

Question 12

Why do the survival chances for each gamete matter more in females?

Answer 12

Because Females make a very small number of vary large gametes. i.e there is a bigger investment.

Question 13

How can females maximise the chance of gamete (and hence offspring) survival and what behaviour does this result in to?

Answer 13

By selecting the best possible sperm which in turn means selecting the best possible mating partner. This results in male courtship displays and females choosing the male with which they want to mate. Also Harem systems are explained by this.

Question 14

What is a harem?

Answer 14

This is when on big, strong male mates with and protects a large number of females.

Question 15

What is the best reproductive strategy for males and why?

Answer 15

Because the investment made by males in the next generation is absolutely tiny (no food reserve in sperm) males can afford to waste as much sperm as they like in an attempt to get their genes into the next generation. As a result males seek to mate with as many females as possible.

Question 16

Why is it not always possible for males to mate with as many females as possible?

Answer 16

Often they cannot do this because the females are watching them all the time. this results in some males adopting a sacrifice strategy.

Question 17

What is a sacrifice strategy?

Answer 17

This is where the males sacrifice their ideal interests (mating with all females) in some way that is obvious to females. This could be something as simple as a bond pair i.e mating for life or something as extreme as letting the female eat the male after mating.

Question 18

Why do female mammals invest more in the next generation than other type of animal and what does this result in?

Answer 18

Because they give birth to young at a very late stage of development. this results in the massive contrast in reproductive strategy between males and females - resulting in the most extreme types of courtship displays.