Evolution & Natural Selection Flashcards
What 3 things can cause mutations
Radiation
Viruses
Carcinogens
What affect do mutations have on a gene pool
They increase variation
Give an example of an advantageous mutation
Peppered moth - darker pigment helped camouflage to trees in industrial revolution
Give an example of a disadvantageous mutation
Yellow mice - less camouflaged therefore more vulnerable to predation
What is an example of microevolution
dog breeds
What is an example of macroevolution
speciation - Galapagos finches
what is polymorphism and give an example
the occurrence of different forms among the members of a population of colony
i.e: hair colour, eye colour, fur texture, wing shape
Name 3 pieces of evidence for evolution
Any from:
- Fossil record showing change over time of species
- Transitional forms in the fossil record
- Comparative anatomy (similarities in anatomy)
- Homology
- Vestigial structures
- Biochemistry (molecules and genes)
- Antibiotic resistance – natural selection in action
- Geographic distribution of related species
What is homology ?
The similarity of a structure or function of parts of different origins based on their descent from a common evolutionary ancestor
What are Vestigial structures
Structures that have no apparent function - i.e; appendix in humans
What is a human appendix an example of?
A Vestigial structure
briefly outline Darwin’s theory of natural selection
There is variation between individuals in a species
Individuals compete with each other for resources
Those with better characteristics are more likely to survive and reproduce
The less successful individuals die out
What 4 factors does Darwin’s theory of natural selection observe
- High reproductive potential - organisms produce more offspring than will survive
- population size remains constant (despite multiple offspring being born)
- Resources are limited
- competition is inevitable
What are the 4 key points of Darwin’s theory
Natural selection is NOT random
It only works on heritable traits
Environmental factors are variable (right time, right place for ‘good’ traits)
Individuals with better traits survive
What are the 3 types of natural selection
Directional
Stabilising
Disruptive
What is directional selection
a mode of natural selection in which a single phenotype is favoured, causing the allele frequency to continuously shift in one direction
- occurs when environmental conditions favour one extreme of the phenotype
When does directional selection often occur?
When environment changes / individuals change location
What is stabilising selection?
opposite of directional selection – genetic diversity decreases as the population stabilizes on a particular trait value
- intermediate traits are favoured and extreme phenotypes are eliminated
What does stabilising selection do to a population’s gene pool
Reduces genetic variation because there are less extreme phenotypes
What is disruptive selection
when extreme values for a trait are favoured over intermediate values
- extremes at either end of the spectrum (so the mean is selected against = is reduced)
When may disruptive selection occur?
when environmental conditions take distinct forms that selects for individuals with traits at either end of the phenotypic range
Which type of selection can lead to speciation?
Disruptive
Which is the rarest type of selection?
Disruptive
What is artificial selection
the intentional breeding of plants or animals for particular traits or characteristics.
What is sexual selection
where one sex prefers a specific characteristic in an individual of the other sex
What is inTRAsexual selection
competition within one sex for mating opportunities – i.e: male-male fights
What is inTERsexual selection
likelihood to mate is affected by interactions between members of each sex – i.e: as a result of female choice
What are male ornaments? Give an example
Male characteristics of visual aesthetics to attract a mate
- peacock feathers, bright colours, longer tails, antlers
Which type of sexual selection are male ornaments used for
IntERsexual selection (to attract a female)
Which type of sexual selection will antlers be used for
InTRAsexual selection (to fight off other males)
