Lecture 20 - evolution, adaptation, and natural selection Flashcards
what is the definition of evolution?
the change over time in allele frequencies, the genetic makeup, in a population of organisms and is the foundation of modern biology, genetics, and ecology.
what did Charles darwin observe?
> descent with modification and identified natural selection as the mechanism
what is one of the major mechanisms behind evolutionary change?
Natural selection
Why was the Darwin/Wallace theory revolutionary?
> overturned the idea that species are ‘immutable’
it emphasised the importance of variations among organisms within the same species and variations among populations
it allowed scientists to make testable predictions to evaluate through observation and experimentation, a key feature of any scientific idea.
what are the four points needed for selection to occur?
> variation within populations
heritability of at least some of this variation
Excess offspring per generation
non-random survival and reproduction
what are some other comments on selection?
> selection is more efficient in large populations
natural selection acts on phenotypes
selection moves a population towards optimal solutions, but that optimality depends on context (place and time)
evolutionary change due to selection can be rapid
most natural populations have extensive genetic variation that can be selected to produce a diversity of phenotypes
What is Ns?
N = population size s = selection coefficient (-1,1)
what are the different types of selection
> directional selection
disruptive selection
stabilising selection
what does the response time of the selection depend on?
> strength of selection
population size
generation time
What are the key concept from this lecture?
> populations evolve; individuals do not > genetics underlines the mechanisms of evolution > natural selection requires - variability - heritability - excess offspring - non-random survival/reproduction
