Evolution Flashcards
Evolution
Evolution is the slow process of a population changing over time
A population evolves and an individual mutates
Mutations can be harmful, helpful, or neutral
Mutations must be passed on for evolution.
Charles Darwin
Made the correct theory of evolution
Studied various animals
Came up with natural selection for finches.
Thought that they had one common ancestor
Ecological Niches
the way that a species acts and reacts in an environment.
Natural Selection
The environment will naturally reward the advantageous changes and eliminate the individuals with the unfavourable changes. Ex. Peppered Moth.
Artificial Selection
The process of humans selecting traits that we find desirable in species to change their population over time to fix our needs. Applies to both animals and plants.
Artificial Selection Steps
- Choose species to be bred in captivity
- Breed large number
- Choose trait
- Identify individuals who exhibit favoured traits
- Breed only them
- Repeat steps 4 and 5
Evidence of Evolution
To cause people to agree with natural selection, researchers were trying to show evidence.
They were looking for similar features which are called homologous features.
Homologous features
Structured in different species that resulted from a common ancestor.
These features do not have the same function
All mammals share similar bone organization in their arms
Analogous features
Features that serve similar functions but evolved from different sources
Features do not share common ancestors, showing that natural selection doesn’t favour one anatomy over the other if they accomplish the same task.
Embryonic development
Provides support for the theory of evolution.
In early stages, vertebrates look very similar.
Vestigial organs
Useless organs left behind.
If an organ doesn’t harm the individual, there is no selective pressure to remove the organ.
Three Types of Natural Selection
Directional Selection: when outlier trait is selected for→ pushes trait to the extreme. Ex. Long-necked giraffe.
Stabilizing Selection: occurs when the average range of traits is favourable. It reduces the number of extreme characteristics.
Disruptive Selection: selects against the average characteristics and favours both extremes.
Sexual Selection
Favouring any trait that specifically enhances the mating success of individuals.
Leads to males and females of species evolving appearances and behaviours different from each other.
Favours mating over any other trait.
Genetic Drift
Smaller population= traits can disappear by chance.
The population of 25 heterozygous individuals, they each have a 50% chance of having homozygous offspring.
If by chance, a majority of the population has homozygous dominant children, the homozygous recessive trait will decrease.
Genetic Bottlenecks
When a natural disaster occurs and a population is drastically reduced.
The smaller population could have a different gene distribution than starting population→ genetic drift.
Founder Effect
Small groups of individuals are separated from the rest of the population and they will evolve independently from the rest of the population.
If two populations get reunited, several generations later, they might not mate together anymore.
Hardy-Weinberg Principle
States if a population is large enough, and if there is no selective pressure, then allele frequencies will remain constant.
Assumptions of Hardy-Weinberg Equilibrium
- No selection
- No mutation
- No migration
- Large population
- Random mating