Unit 2: KA2 - Evolution Flashcards
Define the term: evolution.
Evolution is the change over time in the proportion of individuals in a population differing in one or more inherited traits.
What happens during evolution?
Changes in allele frequency occur through the non-random processes of natural selection and sexual selection and the random process of genetic drift.
How does variation in traits occur?
Mutations
What is the source of new/novel sequences of DNA?
Mutation
What are the three types of mutation?
- Neutral
- Harmful
- Beneficial
Define natural selection.
Natural selection is the non-random increase in frequency of favourable alleles and the decrease of deleterious alleles.
Describe the process of natural selection.
- Populations produce more offspring than the environment can support, resulting in selelction pressures.
- Individuals with variations that are better suited to their environment tend to survive longer, so produce more offspring, passing on their advantageous alleles.
Define sexual selection
The non-random process involving the selection of alleles that increase the individual’s chances of mating and producing offspring.
What is the cause of dimorphism?
Sexual selection.
Define dimorphism.
Dimorphism is the difference in characteristics inherited due to sexual selection of alleles.
What is the reason for sexual selection?
male-male rivalry or female-choice.
Explain the difference between sexual selection and natural selection.
Sexual selection enhances mating success, while natural selection tends to produce well adapted individuals to their environment.
When does genetic drift occur?
When chance events cause unpredictable fluctuations in allele frequencies from one generation to the next.
Why is genetic drift more important in small populations?
As alleles are more likely to be lost from the gene pool.
Name two examples of genetic drift.
- Bottleneck effect
- founder effect
Explain the founder effect.
- Isolation of a few member of a population
- gene pool is not representative of original population.
How is the gene pool altered by genetic drift?
Certain alleles may be under or over-represented and allele frequencies change.
Define the term: selection pressures.
Selection pressures are the environmental factors that influence which individuals in a population pass on their alleles to the next generation.
Give examples of biotic selection pressures.
- Competition
- predation
- parasitism
- Disease
Give examples of Abiotic selection pressures.
- Temperature
- Light intensity
- Humidity
- pH
- Salinity
How do selection pressures’ strength affect evolution rate?
Evolution can be rapid when selection pressures are strong.
State the Hardy-Weinberg principle.
In the absence of evolutionary influences, allele and genotype frequencies will remain constant over the generations.
What can the H-W principle be used for?
It is used to determine whether a change in allele frequency is occurring in a population over time.
What are the five conditions for maintaining the H-W equilibrium.
- No natural selection
- No mutation.
- No gene flow
- Large population size
- Random mating
What do changes in allele frequency suggest?
That evolution is occurring.
State the H-W equation and the meaning of each variable.
p² + 2pq + q² = 1
- p = Frequency of dominant allele
- q = Frequency of recessive allele
- p² = Frequency of homozygous dominant genotype
- q² = Frequency of homozygous recessive genotype
- 2pq = frequency of heterozygous genotype
Define the term: fitness.
Fitness is an indication of an individual’s ability to be successful at surviving and reproducing.
How is fitness measured?
By the tendency of some organisms to produce more surviving offspring than competitors of the same species.
Define the two types of fitness.
- Absolute: Ratio between the frequency of individuals of a particular genotype before and after selection.
- Relative: ratio between the number of surviving offspring of a particular genotype and the number of surviving offspring of the most successful genotype.
Describe co-evolution.
Co-evolution is the process by which 2 or more species evolve in response to selection pressures imposed by each other.
What is the selection pressure in co-evolution?
A change in the traits of one species acts as a selection pressure on the other.
What type of relationship is often seen from co-evolved species?
Symbiosis
What are the possible effects on organisms in symbiosis?
- Positive (+)
- Negative (-)
- Neutral (0)
Name the three types of symbiotic relationships and give their effects on the organisms involved.
- Mutualism: (+/+)
- Commensalism: (+/0)
- Parasitism: (+/-)
State the ‘Red Queen Hypothesis’.
In a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species.
What does the ‘Red Queen Hypothesis’ mean for the species involved?
Species in co-evolutionary relationships must adapt to avoid extinction.
