Unit 2.2 - Evolution Flashcards
Define Evolution
Change that happens over generations in the proportion of individuals in a population which differ in one or more inherited traits `
What are the three type of mutations?
Neutral
Positive
Negative
What type of mutations increase the individual’s fitness?
Positive
What are the three causes of evolution?
Genetic Drift, Natural Selection, Sexual Selection
Is Genetic Drift random or non random?
Random
Define Genetic Drift
Random increase/decrease in the frequency of inherited traits over a number of generations
What type of populations does genetic drift have the biggest effect?
Small populations
What is Natural Selection?
Non random process which affects the allele frequency in the population over generations
What is Sexual Selection?
Non random increase in the frequency of alleles that increase reproductive chances
Define Absolute Fitness
Ratio of frequencies of a particular genotype in one generation compared to the previous generation
Define Relative Fitness
Compares the absolute fitness of one genotype with the absolute fitness of the most successful genotype
What five factors influence the rate of evolution?
Selection Pressures Generation Times Environment Temperature Sexual Reproduction Horizontal Gene Transfer
How do selection pressures influence rate of evolution?
Selection increases the heritability of beneficial traits. When there are higher selection pressures, the traits are being more favoured and so the rate of evolution will be more rapid
How does shorter generation times increase rate of evolution?
More generations in a set period of time
More opportunities for selection pressures to operate and change frequency of traits in populations
If it was a warmer environment would the rate of evolution be increased or decreased?
Increased
Why would a warmer environment increase the rate of evolution?
When the environment gets warmer, all the enzymes in an organism work faster. The germ cells which produce gametes by meiosis divide more frequently and so there is more DNA replication meaning a greater chance of mutation
What does Horizontal Gene transfer allow?
Sharing of beneficial DNA sequences between different lineages of bacteria
What is co-evolution?
When a change in the trait of one species acts as a selection pressure on the other species
What is the Red Queen Hypothesis?
States both species must keep ‘running to stay still’ and must keep evolving to keep up with the changes in the other species
Give examples of co-evolution`
Plants and their Pollinators
- Angiosperms have evolved features to transfer the pollen more effectively to the animal and vice versa
- Animal species evolves features to get nectar more effectively
Parasites and their hosts
- Parasites are specific to their host species
- Hosts are better able to resist and tolerate parasitism are favoured
- Parasites are selected to be better able to feed, reproduce and transmit
What is a selection pressure?
An external factor that affects the heritability of traits.
What are the three types of horizontal gene transfer?
Conjunction, transformation, transduction
