Lecture 8 - natural selection & adaptions Flashcards
What type of individuals leave more offspring?
better adapted individuals survive longer & mate more frequently
- poorly adapted individuals due sooner or fail to mate so leave fewer offspring
What are the 3 ingredients for natural selection?
- variability - individuals vary in most traits
- heritability - variation is passed on via inheritance
- competition & fitness - individuals compete for limited resources
What is variation?
commonly observed that there is variation within a species - not all individuals are alike & there is even variation between parent & offspring
What are 2 types of variation?
- continuous - continuous range of variation in handing intensity
- discrete - e.g. discrete colour morphs
What is heritability?
- individuals inherit their characteristics from their parents
- the basis for this inheritance is genetic
- i.e. variation is not completely random, but has a deterministic genetic basis
What are epigenetics?
describes changes to RNA due to the environment, leading to faster evolution
Why is mendelian inheritance important?
because it doesn’t produce a directional change in gene frequency:
P generation: S = 0.5 s = 0.5
F1 generation: S = 0.5 s = 0.5
F2 generation: S = 0.5 s = 0.5
What is competition?
There is a finite amount of resource available to members of a species & this means that some individuals are successful & others are not
- consequently not all individuals in a population are able to survive to reproduce
- ecological competition is the consequence of limited amounts of resources
What are examples of resources?
include food, water, shelter, space or mates
What is fitness?
a measure of reproductive success of an individual
- if an individual pass on copies of 100% of their genes to the next generation, on average, the fitness = 1.0
How does an organism achieve a fitness = 1.0?
diploid organisms need to produce at least 2 offspring
Why is colour important for mushrooms?
- relationship between thermoregulation and colour
- darker ones absorb more heat, whereas white ones don’t absorb heat so warm up slowly.
- lighter mushrooms in the south, darker in the north
What are 2 different types of selection?
- natural selection
- sexual selection
What is fecundity & fertility?
number of offspring that can be produced in one cycle
How can some behaviours only be explained from the perspective of sexual selection?
e.g. large feathers - attracts attention which makes it more vulnerable to predation, however it attracts a mate
When does selection occur?
when genotypes differ in their ability to pass genes on the next generation
What happens if a genotype is successful?
its genes will increase in frequency
What happens if a genotype is unsuccessful?
its genes will decrease in frequency
What are 3 different types of selection?
- directional selection
- stabilising selection
- disruptive selection
What is directional selection?
- selection generates a long-term change in a trait
- e.g. evolution of feet in horses - digits to hoof
- e.g. the evolution of long necks in giraffe
What is stabilising selection?
- selection against extreme trait values
- e.g. eyespots in butterfly’s provide defence against predators
- selection against eye spots that are too large or small
- the spots mimic an eye so predator doesn’t eat them
What is disruptive selection?
- selection for multiple optimum trait values
- e.g. 2 different groups with 2 peaks & no intermediates - evolved to 2 different optima - e.g. depending on what seeds are available for birds
