Evolution Flashcards
1
Q
What is evolution?
A
The change over time in the proportion of individuals in a population differing in one or more inherited traits.
2
Q
What is genetic drift?
A
- The random change in the frequency of a particular allele within a small population.
- It occurs when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. (Natural disasters play a big part).
- More important in small populations, as alleles are more likely to be lost from the gene pool.
- A gene pool is altered by genetic drift because certain alleles may be under-represented or over-represented and allele frequencies change.
3
Q
How do new alleles occur within a population?
A
Random mutations, most of which are deleterious or neutral, and, in very rare cases, may be beneficial to the fitness of an individual.
4
Q
What is natural selection?
A
- The non-random increase in the frequency of advantageous alleles and the non-random decrease in the frequency of deleterious alleles.
- This is done by ‘survival of the fittest’. By this term we mean genetically fit; those organisms which have alleles which will increase survival.
- Organisms which are able to adapt are also genetically ‘fit’.
5
Q
Describe the process of natural selection.
A
- Organisms produce more offspring than the environment can support
- Individuals with variations that best fit their environment are more likely to survive and breed
- Favoured traits are inherited so they are more likely so become more frequent in subsequent generations
6
Q
What is sexual selection?
A
- Sexual selection is the non-random process involving the selection of alleles that increase the individual’s chances of mating and producing offspring.
- Sexual selection does not increase chances of survival, just the likelihood that the organism will reproduce and pass on its alleles.
- It may lead to sexual dimorphism.
7
Q
What are population bottlenecks?
A
- Population bottlenecks occur when a population size is reduced for at least one generation.
- A bottleneck occurs when there is a serious decline in the population. Floods, disease, and even hunting can all cause population bottlenecks.
- It reduces genetic diversity.
8
Q
What is the founder effect?
A
- Founder effects occur through the isolation of a few members of a population from a larger population.
- The gene pool of the new population is not representative of that in the original gene pool.
9
Q
How do selection pressures influence evolution?
A
- Where selection pressures are strong, the rate of evolution can be rapid.
- Selections pressures are the environmental factors that influence which individuals in a population pass on their alleles.
- They can be biotic (competition, predation, parasitism) or abiotic (changes in temperature, light, humidity, pH, salinity).
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10
Q
Describe the Hardy Weinberg principle.
A
- States that, in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations.
- The HW principle can be used to determine whether a change in allele frequency is occurring in a population over time.
- Changes suggest evolution is occurring.
11
Q
What is the HW equation?
A
p2 + 2pq + q2 = 1
* p = frequency of dominant allele
* q = frequency of recessive allele
* p2 = frequency of homozygous dominant genotype
* 2pq = frequency of heterozygous genotype
* q2 = frequency of homozygous recessive genotype
12
Q
What is fitness?
A
- Fitness is an indication of an individual’s ability to be successful at surviving and reproducing.
- Fitness is a measure of the tendency of some organisms to produce more surviving offspring than competing members of the same species.
- It refers to the contribution made to the gene pool of the next generation by individual genotypes.
13
Q
What is absolute fitness?
A
- Absolute fitness is the ratio between the number of individuals of a particular genotype after selection, to those before selection.
- Frequency of a particular genotype after selection / Frequency of a particular genotype before selection
- Value = 1: the frequency of that genotype is stable
- Value = >1: increase in the genotype
- Value = <1: decrease in the genotype
14
Q
What is relative fitness?
A
- Relative fitness is the ratio of the number of surviving offspring per individual of a particular genotype to the number of surviving offspring per individual of the most successful genotype.
- Number of surviving offspring per individuals of a particular genotype / Number of surviving offspring per individual of the most successful genotype.
15
Q
What is co-evolution?
A
- Co-evolution is the process by which two or more species evolve in response to selection pressures imposed by each other.
- A change in the traits of one species acts as a selection pressure on the other interactions.
- Co-evolution is frequently seen in pairs of species that have symbiotic interactions.
- The impacts of these relationships can be positive (+), negative (-) or neutral (0) for the individuals involved.
