2.2 ORGANISMS Flashcards
What is evolution?
A change over time in the proportion of individuals in a population differing in one or more inherited traits
Evolution occurs through which processes?
Random and non-random processes
Give an example of a random evolutionary process.
Genetic drift
What is genetic drift?
The random change in the frequency of a particular allele within a population
In which type of population is genetic drift more important?
Small populations
Why is genetic drift important to small populations?
Alleles are more likely to be lost from the gene pool
Give two examples of a non-random evolutionary process.
Natural selection, sexual selection
Why are natural and sexual selection described as non-random processes?
Certain alleles become more frequent in the population because they confer a selective advantage
What is mutation?
The original source of new DNA sequences
What is the result of mutation?
Variation in traits arises as novel alleles are formed
Mutations can be?
Neutral, harmful or beneficial to the evolutionary fitness of an individual
What are the two types of fitness?
Absolute fitness, relative fitness
What is absolute fitness?
Ratio of frequencies of a particular genotype from one generation to the next
What is relative fitness?
Ratio of surviving offspring of one genotype compared with other genotypes
What happens when organisms produce more offspring than the environment can support?
Individuals with variations more suited to the environment are more likely to survive and breed
What happens to selected alleles?
They become more frequent in subsequent generations through inheritance
What is the result of high selection pressures?
Rate of evolution becomes rapid
Name four ways to increase the rate of evolution.
High selection pressures, shorter generation times, warmer environments, sharing of beneficial DNA
How is DNA shared?
Through sexual reproduction and horizontal gene transfer
What is horizontal gene transfer?
Transfer of DNA sequences using plasmids
What is co-evolution?
When a change in traits of one species acts as a natural selection pressure on the other species and vice versa
When does co-evolution occur?
When pairs of species interact frequently or closely
Give four examples of co-evolutionary relationships.
Herbivores and plants, pollinators and plants, predators and prey, parasites and hosts
What is the term given to ongoing co-evolution?
Red Queen Hypothesis
What does the Red Queen Hypothesis state?
Both organisms must “keep running in order to stay still”
What does the Red Queen Hypothesis explain?
Sexual reproduction evolved as a way to produce variation more readily than relying on mutation alone
Co-evolution can be described as?
An ‘arms race’
How can parasites increase their fitness?
Better their ability to feed, reproduce and find new hosts
How can hosts increase their fitness?
Better their ability to resist and tolerate parasitism
