Week 13 Flashcards
Define Adaptive Evolution
Evolution resulting in adaptation of a population to its environment so that it increases its fitness
To do so we need to:
A)Maximize reproductive success
B)Optimize structure and function
Which evolutionary mechanism(s) is/are associated with adaptive evolution?
Natural Selection
What are the limits to Adaptive Evolution?
- Available genetic variation
- Decreased by genetic drift
- Replenish (filled up again) by mutations
- Small populations with low genetic variation may be unable to adapt to a rapidly changing environment (they will die) - Evolutionary trade-offs
- Any characteristics has advantages and disadvantages
- It may not be possible to make only multiple effective or best characteristics all at the same time
- E.g. Peacocks get eaten more because of there feathers that are very attractive, but they can also have more chance of matting. - “Historical” contraints
- Adaptive evolution occurs by changes to already existing structures - A changing environment
- Environmental is continuously changing, so it makes adaptation ongoing
- Previous adaptation may not be beneficial
- Small populations may be unable to adapt to a rapidly changing environment, due to low genetic variation
- Fitness ‘landscape’ constantly in flux!!! Even when you are trying to adapt, you can loose it all, it can change any moment)
What is the difference between microevolution and macroevolution?
Microevolution is evolutionary change in a small scale (evolution or selection occurring in a single or few genes) in a population over a short period of time. It revolves around populations.
Macroevolution is evolutionary change on a large scale that happened over a longer period of time. It revolves around species. It contains two things: Speciation and Splitting of lineages
Define species & the biological species concept
Name also the reproductive isolation
Species are a population evolving independently from other populations.
Biological species concept is a group of organisms that can produce fertile offsprings. It can only apply to sexually reproducing organisms. Same species can interbreed, but different species can’t interbreed.
Reproductive Isolation:
- BARRIERS prevents interbreeding between populations
- Restricts gene flow make over time that divergence increases
- SPECIATION: populations become distinct species
Describe Prezygotic barriers and Post-zygoyic barriers
Prezygotic barriers: Prevent mating or fertilizing. You have an egg and a sperm but cannot create a zygote.
Type of reproductive barrier:
-Temporal Isolation (Two species breed at different times (seasons, time of the day, years))
-Habitat Isolation (Two species live in different habitats so they cannot mate)
-Behavioral Isolation (There is little or no sexual attraction between species, due to specific behaviors (that other species don’t like))
-Mechanical Isolation (Female and male sex organs are not compatible (they can’t mate))
-Gametic Isolation (Female and make gametes are not compatible (sperm cannot penetrate egg)(they can mate, but it doesn’t fit so no))
Post-zygotic barriers: Offspring not successful. They can create a zygote, but cannot create an offspring.
Type of barriers:
-Reduced hybrid viability (Hybrids cannot survive to reproduce E.g. Goat mates with a sheep)
-Reduced hybrid fertility (Hybrids can mate, but do not produce offspring)
-Hybrid breakdown (Hybrids survive first few generations but eventually dies out)
Modes of Speciation
- Allopatric: Barrier formed in isolation
- Parapatric: New niche entered in new niche
- Sympatric: Polymorphism occurs within the population
What are the effects of removing barriers from gene flow?
There will be either (go see power point 23 to see pictures):
A)Speciation process completed (there is no going backwards)
B)Speciation process stalled
C)Speciation process reversed (we can reverse completely)
Horizontal gene transfer in prokaryotes is common
There is a transfer/sharing of genetic material so it can be considered as genetic transfer.
Describe large-scale patterns of macroevolution
Macroevolution exist in three ways:
- Gradualism: Continuous change at a constant evolutionary pace
- Punctuated equilibrium: Short bursts of change, with long periods of stability
- Adaptive radiation: Rapid evolutionary diversification from ancestral lineage. It is due to a change in the environment (conditions factors and ?)
There is also Extinction!
Describe causes of extinctions
-Overspecialization
-Localized distribution
-Interactions with other species
-Environmental change (global warming)
-Habitat destruction
-Climate change
-Disease
-Human predation
-Lack of genetic diversity
-Lack of food
-Invasive species
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