The roles of genes and environment in evolution (part 1)
- Created by: une-meduse
- Created on: 22-05-13 20:36
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- THE ROLE OF GENES AND ENVIRONMENT IN SELECTION
- Stabilising or evolutionary forces of natural selection
- All organisms reproduce
- Therefore all have potential to increase population size
- Many reach carrying capacity and remain stable
- Not all young reach adulthood
- If they did the population would continue to grow
- Not all young reach adulthood
- Many reach carrying capacity and remain stable
- Therefore all have potential to increase population size
- Environmental factors limit growth of a population
- Not enough space
- Availability of food
- Light intensity/ availability
- Availability of minerals or water
- Predation
- Infection by pathogens
- All of these factors offer ENVIRON - MENTAL RESISTANCE
- Some are abiotic (non living components)
- Some are biotic (other living organisms)
- Over time population size fluctuates around the mean
- If a strong environmental resistance, population size reduces
- This in turn reduces competition, and population size will grow
- As it increases there is more intraspecific (within the population) competition such as for food, shelter or mates
- Eventually population size falls again
- As it increases there is more intraspecific (within the population) competition such as for food, shelter or mates
- This in turn reduces competition, and population size will grow
- If a strong environmental resistance, population size reduces
- All organisms reproduce
- Which individuals survive
- Variation within a population will mean that some members will be better adapted and will be able to out compete other members
- The organism that can run the fastest, camoflage itself the best, have sharper teeth and claws will have an advantage in the struggle for existence
- It has a greater change of surviving to adulthood, producing offspring and passing on its advantageous alleles
- The organism that can run the fastest, camoflage itself the best, have sharper teeth and claws will have an advantage in the struggle for existence
- Variation within a population will mean that some members will be better adapted and will be able to out compete other members
- Selection pressures are environmental factors that confer greater changes of survival to reproductive age on some members of the population
- Mice with better camoflaging ability, such as a darker coat, will be more likely to escape predation and live to reproduce. The predation is the selective pressure
- Stabilising selection, when natural selection selects the individuals that will survive and reproduce, to keep things the way they are
- Mice with better camoflaging ability, such as a darker coat, will be more likely to escape predation and live to reproduce. The predation is the selective pressure
- If a new phenotype arises in the same environmental conditions, it is unlikely to confer an advantage and will therefore not be selected
- If the environment does change, then this is a new selection pressure, eg new weather, new predator, then animals with an advantageous phenotype will have a selective advantage
- Frequency of these alleles would increase
- Directional selection is shown here, which is an evolutionary force of natural selection
- Frequency of these alleles would increase
- If the environment does change, then this is a new selection pressure, eg new weather, new predator, then animals with an advantageous phenotype will have a selective advantage
- Stabilising or evolutionary forces of natural selection
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