Evolution Flashcards
Gene pool
All the genes of all the members of the population
Genetic drift
A random change in allele frequencies that occurs in a small population
Stabilizing selection
Type of natural selection in which phenotypes at both extremes are selected against
Vestigial structure
Structure that evolution has reduced in size because it is no longer used
Hardy-Weinberg theorem
Founding principle of population genetics proves allele and genotype frequencies d not change in a population that meets the conditions of no mutation, no migration, large population size, random mating, and no natural selection
Homologous structure
Structure that is similar in related organisms because it was inherited from a common ancestor
Disruptive selection
Middle of the phenotypic distribution are selected against, resulting in two overlapping phenotypes, one at each end of the distribution
Directional selection
One of the two extremes phenotypes is selected for resulting in a shift the phenotypic distribution toward that extreme
Analogous structure
Structure that is similar in unrelated organisms because it was evolved to do the same thing
Allele frequency
How often an allele occurs in a gene pool
Bottleneck effect
A population suddenly gets much smaller and the ones that survive are the ones that make up the new gene pool (natural disasters)
Founders effect
A small group separates from the main group and starts a new population which now has a new gene pool
Microevolution
Evolutionary change that occurs over a relatively short period of time
Macroevoltion
Evolutionary change that occurs over geologic time above the levels of species
Explain and give examples of the three types of selections
- Stabilizing: Phenotypes at both extremes of the phenotypic distribution are selected against (Baby weight: Very large and very small are less likely to survive infancy)
- Directional: Two extreme phenotypes are selected for (Beak size of the Galapagos finches)
- Disruptive: When phenotypes in the middle of the range are selected against (sexual dimorphism - males and females have different heights, weights, and body shapes)
What is the difference between micro and macro evolution? Examples of each?
- Micro: Occurs over a short period of time within a population of species (Evolution in the beaks of Darwin’s finches over the years)
- Macro: Occurs over a long period of time above the level of species (Fossil records show this - species will develop certain traits as they adapt to their environment (ex. Apes to humans))
Explain how scientists use vestigial, analogous, and homologous structures to see how animals are related or share a common ancestor
- Vestigal: Evolution has reduced the size of the appendix because they are no longer used (used to be needed to digest food)
- Analogous: Wings of bats and birds function the same, but evolved independently in the two groups of animals (seen in the wing structure)
- Homologous: Inherited bone structures (like the forelimbs) from common ancestors but now function in different ways
- Scientists can look at these and see they are all similar, but also spot the differences between them to determine if the species share a common ancestor or not
What is natural selection and how does it lead to changes in a population and adaptions? How des it affect allele frequencies?
- Natural selection: Process in whcih some living things produce more than others so the characteristics of organisms change over time
- There are more species so there is more competition - species are forced to adapt
- Some with certain dominant characteristics reproduce more than others, and if the bottleneck effect happens with a specific species over time different characteristics will appear more frequently
Explain genetic drift, founders effect, and bottleneck effect, and be able to explain how each occur
- Genetic drift: A random change in allele frequencies that occurs in a small population (reproduction: allele frequencies in the offspring may differ from what was expected)
- Bottleneck: Population suddenly gets much smaller (natural disaster or hurricane)
- Founder: When individuals start a new population (Select number of people emigrate to an unfounded place)
What is the Hardy-Weinberg equation? Solve for p and q
- Shows allele frequencies don’t change in a population if certain conditions are met
- P(2) + 2PQ + Q(2)
What 4 effects did Darwin base his theories on?
- Species produce many offspring
- No one species has overrun the earth
- Individuals must compete to survive
- Only some survive the competition and are able to reproduce
