Key Area 2-Organisms Flashcards
What is evolution?
The change over time in the proportion of individuals in a population differing in one or more inherited traits
What they’re processes lead to evolution?
- genetic drift
- natural selection
- sexual selection
What is genetic drift?
A random process where a change in the frequency of particular alleles in a population occurs
How does genetic drift occur?
Usually in small populations, influenced by the founder effect
What is sexual selection?
The non-random proves of selection for traits that increase reproductive success in a species
What is natural selection?
The non-random process as those offspring better adapted due to advantageous genes surviving, and as a result these advantageous genes increase in frequency among the population
What process gives rise to new sequences of DNA and results in variation in traits?
Mutations
What are three possible outcomes of mutations?
Harmful, neutral or beneficial
What is absolute fitness?
The ratio of frequencies of a particular genotype from one generation to the next
What is the stable value for absolute fitness?
1
What is relative fitness?
The ratio of surviving offspring of one genotype compared with other genotypes
How are relative values given?
Most successful is given restive value of one then less successful represented as a proportion of the most successful
What is gene frequency?
The best suits individuals survive and pass on genes therefore through inheritance the favourable traits are more frequency in subsequent generations
How does selection pressure affect evolution?
When selection pressure is high the rate of evolution is high
What factors affect the rate of evolution?
- generation times are short
- environments are warmer
- sharing beneficial DNA sequences through horizontal transfer and sexual reproduction
What is co-evolution?
When the evolution of one species affects the evolution of another closely associated species
What circumstances give rise to co-evolution?
It’s usually seen in pairs of species that interact frequently or closely and a change in the traits of one species acts as a selection pressure on the other
What are four examples of co-evolution?
- herbivores and plants
- pollinators and plants
- predators and prey
- parasites and hosts
What is the role of selection pressure in evolution?
Selection pressure increases the rate of of co-evolution when one species changes traits and the other follows due to selection pressure
What is the red queen hypothesis?
Both organisms must keep running in order to stay still
What organisms are involved in the red queen hypothesis?
Parastites and hosts
How do parasites and hosts represent the red queen hypothesis?
Hosts better able to resist and tolerate parasitism have greater fitness and parasites better able to feed, reproduce and find new hosts have greater fitness
