Causes of Evolution

How is genetic variation created?
Mutation, sexual reproduction, recombination (crossing over), migration and gene flow, divergent selection at metapopulation level
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What are the factors affecting allele frequencies in populations?
Mutation, genetic drift, natural selection, gene flow, non-random mating
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How does evolution happen due to genetic drift?
Random change in allele frequencies over time: isolation populations slowly drift apart (drift rate is higher in small populations)
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How does evolution happen due to selection?
Selection pressure (rate of change in allele frequencies much higher, reduced number of hetgozygotes
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How does evolution happen due to migration & gene flow?
Migration between populations increases genetic diversity (interbreeding within different populations) increases heterozygosity and evolutionary potential, under strong selection pressure, ecological speciation can occur despite some gene flow
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What is sexual selection?
Natural selection acting on characteristics tat affect the acquisition of a mate or the choice of mate
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What is intrasexual selection?
(Within sex), competition among individuals of one sex, e.g. red deer, stag guarding harem and fighting other males
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What is intersexual selection?
(Between sexes), the choice of a sexual partner, e.g. bird of paradise male dancing to impress female bird
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Intrasexual selection with red deer
Stags guard hinds as harems for later mating, as the oestrous period is only 1-2 days per hind Risks of death from injury (30%) or exhaustion are high for stags (cost), whilst survival allows, participation in additional ruts and increase
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Intersexual competition in male long-tailed widow birds
Defend territories with elaborate displays to attract females and ward off rival males (females select the ones with the longest tails which is unusual as it doesn't have evolutionary advantage- increased cost of flight and increased predation risk)
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Intersexual selection in zebra finches
Females prefer brighter beaked males (carotenoid pigments obtained from food are used in both immune system and colouration, brighter beak indicated immune system competence)
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What is intraspecific variation?
Variation within a species
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What can cause intraspecific variation?
Environment, mutations, diet
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What is phenotypic plasticity?
A change in individuals within a generation due to selection pressure
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What are the selection pressures faced by dog whelk?
When on exposed shores- Wave action/ drag, reduced foraging time, Sheltered shores- Desiccation (dry up), predation risk increased
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Describe the phenotypic plasticity that has occurred in dog whelk due to these selection pressures
Ones who are more exposed to sea developed larger aperture (hole in shell) and bigger foot
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Give 2 disadvantages for dog whelks having a bigger foot and aperture
1) Increased risk of desiccation, 2) Increased risk of predation by crabs on sheltered shores
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What is the peppered moth an example of?
Rapid evolution of cryptic colour polymorphism
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How did an environmental change cause evolution by natural selection for the Galapagos medium ground finch?
A drought in 1977 reduced seed abundance, finches grew bigger by 4% with bigger beak and so they were able to break harder seeds (later when Galapagos was wet, they shrunk by 2.5%)
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What 3 things does evolution by natural selection require? (Use Galapagos medium ground finch as an example)
1) Intraspecific variation (Original species had smaller beaks), 2) Heritable variation (Finches with a particular beak size produce offspring with similar beak size), 3) Limited resources (Not enough food for all the finches to survive- competition)
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What is the morphological adaption for the European eel?
Head size- broad headed eat larger prey, narrow headed eat smaller prey
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What type of evolution did rattlesnakes undergo?
Cryptic colour polymorphism- lighter substrates, lighter rattle snakes
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Cryptic colour polymorphism in mice (various species)
Coat colour adapted to match habitat, found a single genetic polymorphism is beach mice, light and dark alleles of the Mc1r gene was responsible (in most populations)
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Cryptic colour polymorphism in guppies
More colourful males in streams lacking predatory fish and visa versa
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Describe the experiment used to investigate cryptic colour polymorphism in guppies
10 ponds set up with mixed-origin guppies, after 6 month, ponds were randomly allocated to high, medium and zero predator treatments, then the number of spots on the males were measured at 0,6,11 and 20 months
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What were the results?
Spot number reduced from ~12 to 9.5 in high predation treatment (increased crypsis), Spot number stabilises at 13 for the other ponds (males with fewer spots suffer lower mortality rates where predators are common)
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Other cards in this set

Card 2

Front

What are the factors affecting allele frequencies in populations?

Back

Mutation, genetic drift, natural selection, gene flow, non-random mating

Card 3

Front

How does evolution happen due to genetic drift?

Back

Preview of the front of card 3

Card 4

Front

How does evolution happen due to selection?

Back

Preview of the front of card 4

Card 5

Front

How does evolution happen due to migration & gene flow?

Back

Preview of the front of card 5
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