Unit 2 - section 2 Flashcards
What is evolution?
The change overtime in the proportion of individuals in a population differing in one or more inherited trait
What are the 3 processes that can lead to evolution?
Are they random or non-random processes?
Genetic drift - random
Natural selection - non-random
Sexual selection- non-random
Describe genetic drift
Change in the frequency of particular alleles in a population
Usually happens in small populations and is influenced by the founder effect
How does natural selection affect evolution?
Natural selection means offspring are better adapted due to advantageous genes and will survive and pass on these genes. Causing an increase in the frequency of advantageous genes in population
How does sexual selection effect evolution?
Female will choose their mate based on a desirable trait. Having these traits increases reproductive success
What are mutations and what can their outcome be?
Mutations are the original source of new DNA sequences in populations and can create novel alleles
Mutations are mostly harmful or neutral but are occasionally beneficial to the fitness of the organism
What is absolute fitness?
The ratio of frequencies of a particular genotype from one generation to the next. Is the ratio of individuals with particular genotype after selection compared to before selection
What is relative fitness?
The ratio of surviving offspring of one genotype compared with other genotypes.
What do absolute and relative fitness values tell us about gene frequency of subsequent generations?
Values greater than one show gene frequency increases
How does selection pressure affect the rate of evolution?
Rate of evolution will be high when selection pressures are high
What are 3 factors that are responsible for increasing rates of evolution?
Short generation times
Warmer environments
The sharing of 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 related species
What are the circumstances that give rise to co-evolution?
When pairs of species interact frequently or closely a change in a trait of one species assists selection pressure on the other causing co-evolution
4 examples of co-evolution
Herbivores and plants - rue plants produce chemicals to reduce grazing by herbivores but species caterpillar evolved to tolerate these chemicals
Pollinators and plants - shape some flowers suit hummingbirds visions and beak shape means hummingbird gets fed and plant gets pollinated
Predators and prey - newt evolved neurotoxins on skin for protection but garter snake evolved resistance to toxin
Parasites and hosts - malaria, mosquito (vector) and human (host) show coincidence
Describe the co-evolutionary arms race and why it is often referred to as the Red Queen
The arms race is between a parasite and its host
It’s referred to as the red queen hypothesis because both organisms must keep running in order to stay still
