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14 Cards in this Set
- Front
- Back
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What defines being male vs. female
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Males have smaller gametes than females (determination factor).
There has been selection in some species for larger gametes in males but if they end up being bigger than female gametes the males would be termed females instead |
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What is the significance of producing smaller gametes?
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If there is production of smaller gametes (as in most males) there is a faster rate of production therefore males have a higher potential rate of reproduction. This means that the more females a male can get to the higher its reproductive success.
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What is the significance of the Drosophila Experiment?
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Fruit flies were raised in separate vials. One vial contained fewer males with an abundance of females. The second vial contained multiple males with very few females. The experiment demonstrated that the mean number of offspring produced by males increased with the number of mates available. In the vial with fewer females, less offspring were produced. Thus males increase their reproductive success by mating with more females.
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What limits male reproduction and what a male's strategy to increase it's chance of reproduction?
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The male is limited by his access to females. His strategy is to compete with other males.
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What limits female reproduction and what is a female's strategy to increase her chance of reproduction?
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The female is limited by her access to resources. Her strategy is to choose a high quality mating situation. This includes finding a good male with good genes and finding a place with lots of nutrition for her offspring.
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What are the mechanisms of sex determination?
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- differential production or motility of X and Y sperm
- differential implantation or abortion - environmental sex determination - differential neglect |
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Stable Sex Ratio?
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1:1
Invest equally in males and females |
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Local Mate Competition
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This is an example of biased sex allocation.
You produce 2 sons and 2 daughters. The 2 daughters leave and 2 males stick around to wait for a female to show up, if there was one female then the 2 males would compete with each other for that female, might as well have just produced one son e.g. acarophenax mite – parent females carry around their offspring inside their body until they mature (extreme case of keeping all kin in one place), they mate inside the female mite, and if there is a 50/50 sex ratio produced, only one of the males would be required to reproduce with both females |
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Local Resource Competition
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This is an example of biased sex allocation.
e.g. bush baby Males leave and daughter stay with mothers, females compete for resources so they produce fewer daughters because less competition |
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Local Resource Enhancement
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This is an example of biased sex allocation.
Want all the offspring to hang around. a. e.g. red cockaded woodpeckers – sons stay and help defend nest, feed young so produce more sons to help with offspring – when kin stay -> biased sex ration |
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Give three examples of biased sex allocation based on interactions between relatives.
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1) Local mate competition
2) Local resource competition 3) Local resource enhancement |
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Conditional Sex Allocation
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This is an example of biased sex allocation.
The better the environment ( abundance of mates, food, safety) the better off the offspring will be. It is better to produce females in low quality environments. It is better to produce males in high quality environments because males have a greater payoff in good conditions. |
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Give two example of how sex allocation depends on the condition of the individual.
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1) Attractiveness:
If you mate with an attractive mate who will likely to be able to get more mates (like a colorful male), you are better off producing sons because they are going to be attractive sons too. e.g. great tits – larger males are more successful at attracting females thus more males are produced by females based on this 2) Maternal Condition e.g wild horses -stallions go around in groups of females to mate with -generally, the larger the mare (the mother), the greater the bias in the sex ratio -larger mares tend to produce more males because they are in better condition |
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Sex Changes in Fish
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Some species, when they are small, they start out as females, and then they reach a certain size and they switch sex and start producing sperm and therefore become male
In other species, females get the big pay-off, they start off as small males and then they reach a certain size where they are big enough to store a lot of eggs and become females |
