Evolutionary Fitness
Biology: IB Diploma Higher Level, topic 3.3.2
Survival
Individuals must survive and reproduce to pass on their genes to their offspring. The likelihood of an individual surviving and passing on their genes is a measure of evolutionary fitness.
Evolution over time
- Evolution is the change in genetic composition of a population over generations, resulting from differential reproduction of individuals with certain alleles.
- Individuals do change over their lifetime, obviously, but this is called development.
- Development involves changes programmed by the set of genes the individual acquired at birth in coordination with the individual’s environment.
Factors affecting evolution
- Many biotic (living) and abiotic (non-living) factors affect evolution.
- These factors fluctuate and impact the rate and direction of evolution.
- Populations simply track their changing environment with adaptations that maximize their reproduction in a particular environment at a particular time.
- Some factors that affect evolution are listed below.
Predation
- Predation can decrease the probability of survival.
- If an individual is exposed to high predation, they are more likely to be eaten by a predator.
- If an individual is better at avoiding predators, they are more likely to survive and reproduce.
- The genes that allow an individual to avoid predation are more likely to be passed onto offspring.
Disease
- Disease can decrease the probability of survival.
- If an individual is better at combatting disease or avoiding infection, they are more likely to survive and reproduce.
- The genes that allow an individual to avoid disease are more likely to be passed onto offspring.
Competition
- Competition can decrease the probability of survival.
- Competition can exist between species (interspecific) or within species (intraspecific).
- If an individual is better at outcompeting other individuals, they are more likely to survive and reproduce.
- The genes that allow an individual to outcompete are more likely to be passed onto offspring.
Test yourself on Evolutionary Fitness
Which of the following statements about survival are true?
What is the most probable outcome if an individual is better at combatting disease than others?
Which of the following is not a factor determining the likelihood of an individual to survive?