Lecture 11 - evolution in real time Flashcards
What is evolution in real time?
- examples of evolution in action
- applications - disease & epidemiology
How did evolution occur in the distant past?
accumulation of lots of small changes at the genetic level that then translates into changes at the phenotypic level
What is evolution?
- evolution is gradual
- proceeds by the accumulation of small changes
- big jumps are thought to be unlikely
- the rate of evolution varies through time
- macro-evolution is slow
- micro-evolution is fast
What is a well known example of rapid micro evolution?
biston betularia - very fast responses to change (deposition of soot on trees turned them black leading to a change in environment) - selective force, occurred over a few years
What causes rapid evolutionary change?
- competition
- exploitation
- climate change
- parasites
What is competition?
- competition occurs when 2 species have similar requirements
- e.g. food/shelter
- 2 species with very similar requirements can’t coexist
- 1 species must either go extinct or evolve different requirements
- it is usually thought that ecological process of extinction is faster than evolution
- hence extinction is thought to be more likely
Describe Darwin’s finches
different features for different pressures - classic example of radiation wide species
- competition is shaping the evolution of species
What occurred in response to competition?
the evolution of bill size
- different bills for different food sources
- increase in competition led to a reduced bill size (alternative food source - smaller seeds)
- rates of change are close to values predicted from heritability of the trait
What is exploitation?
humans do something to natural populations because we want to harvest them for food or another resource
- many species are exploited by humans in some way. Much exploitation is selective - e.g. harvest the biggest. This is exactly like the process of natural selection
How can human impacts lead to rapid evolution?
- hunting of Bighorn sheep
- hunted as ‘trophies’
- large rams are a target
Describe the effects of selective hunting on fitness & population size
- reduction in animal size
- reduction in horn length
- fluctuations in population size
Describe the evolution of body size & maturity in cod
- cod are fished for food
- nets target larger fish
- contain an intermediate life cycle (sexual maturity depends on size)
- cold environments often lead to slower development and as a result can reach sexual maturity a lot later
- fishing removes the larger fish from the population. This imposes a natural selection on reproduction. If an individual takes too long to get to maturity, it doesn’t reproduce and therefore isn’t able to pass on their genes (selective pressure on maturation)
Describe changes in maturation schedules
- maturation in 1987 was at a younger age & smaller than 1980
What is a good environment?
lots of resources, temperature is good, suitable conditions = large tree growth
What is a poor environment?
(e.g. much colder/hotter) = don’t grow as fast, some die, they don’t do as well as they could’ve
