Sexual selection

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Describe the processes in natural selection
1) Variation in traits. 2) Traits may affect likelihood of survival 3) Those will beneficial traits- pass their alleles to next generation 4) If trait continues to give advantage- higher % of species have trait- may lead to evolution...
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How would you define natural selection?
The results of any system that has: Heredity (ability to pass traits on to offspring); Reproduction (ability to multiply + increase popln size; Variation- different traits that affect fitness.
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What is an individuals fitness?
How good a genotype is at contributing offspring to the next generation.
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What is an "evolutionary dead end"?
Where an individual does not pass on its genes to the next generation. Evolutionary fitness=0.
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Natural selection is survival of the fittest. True or false.
False- reproduction of the fittest.
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Why do some organisms have conspicuous features that make them more vulnerable to predators?
Sexual selection- Features may also make them more likely to succeed attracting a mate etc... trade-off
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What is the term for males and females of one species looking different?
Sexual dimorphism
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Examples of sexual dimorphism?
Female spiders tend to be much larger than males; Male seals are much larger than female seals; female pheasants have cryptic colouring whereas males= brightly coloured plumage
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Why is it that often even low-quality females will mate once or twice?
Males of most species will try and mates as many times as possible. Their gametes are small and contain few nutrients so are cheap to make.
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Why are females often more choosy about who they mate with?
Female gametes are often larger and contain all the nutrients needed for new lives to grow. Also if gametes are fertilized- further high costs to female. Need to choose carefully- best traits to combine with own to ensure survival of offspring.
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What is another name for intra sexual selection? Explain.
Within sex rivalry: Male-male rivalry. Where males try to monopolize access to females- best chance of their alleles dominating in the next generation. May include male-male combat or infanticide of offspring of previous dominant males.
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Example of intra sexual selection?
Elephant seals- Males weigh up to 4 tons. Fight fiercely - strong selection for huge canine teeth and large size. Stiff demal shield. Ability to fast for 3 months to retain control of harem/stay beachmaster. Up to 100 females.
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Example of inter sexual selection.
Between sex selection. Normally female-choice. E.g. Peacocks- females choose on basis of attractive plumage- indicates good fitness/health?
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Example of male-choice? Explanation?
Mormon crickets- weigh females: Heavy females produce more eggs. Reproduction=costly for males- produce large spermatophore which female eats to gain nutrients during mating- courtship gift. Production costs males up to 27% body mass. (Gwynne,1981
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What is a Lek?
Area where certain male animals gather to perform their courtship rituals.
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What is a Chichlid bower?
An ornament/crater built by a male Chichlid to attract females. Higher=more attractive. Bower is not a nest.
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Why might a female Northern cardinal choose males with redder feathers?
Indicates- more likely to be a better father? Biparental care- more likely for offspring to succeed.
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Why do females continue to choose males with elaborate traits even though these are handicaps to survival?
Good genes hypothesis- Show a male has managed to survive increased parasite load or predation risk/energetic cost etc even with the handicap- genes must be strong
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Describe how evolution of brighter plumage in peacocks may have occured?
Females chose males at random- no way to tell which males had better genes. Genetic variation- some develop longer tails. Some males have poor genes-do not survive with handicap. Other males survive-tail becomes indicator of good genes.
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What happened when Petrie 1984 artificially drew on eyespots on to peacock tails?
Those with more eyespots attracted more mates.
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Which study showed female Cichlids prefer males with taller bowers?
McKaye et al 1990- artificially changed heights.
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Other cards in this set

Card 2

Front

How would you define natural selection?

Back

The results of any system that has: Heredity (ability to pass traits on to offspring); Reproduction (ability to multiply + increase popln size; Variation- different traits that affect fitness.

Card 3

Front

What is an individuals fitness?

Back

Preview of the front of card 3

Card 4

Front

What is an "evolutionary dead end"?

Back

Preview of the front of card 4

Card 5

Front

Natural selection is survival of the fittest. True or false.

Back

Preview of the front of card 5
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