Chapter 8: Evolution Flashcards
Evolution
A genetic change in a population over time
Four Types of Evolution
Mutation, genetic drift, migration, and natural selection
Mutation
An alteration of the of the base pair sequence of an individuals DNA
Genetic Drift
A random change in allele frequencies in a population
Fixation
Results when an alleles frequency in a population reaches 100%
Founder Effect
May have different allele frequencies than the original population. If the new population has different allele frequencies evolution has occurred
Population Bottleneck Effect
When large proportions of a population dies the allele frequencies may not be the same as the original population
Migration
Is the movement of some individuals of a species from one population to another. This movement may cause a change in the allele frequencies of the population
Natural Selection
There must be variation for the trait within a population, the variation must be heritable, individuals with one version of the trait must produce more offspring than those with a different version of the trait
Variation for a Trait
Different versions of a trait are present within a population
Heritability
The different versions of a trait may be passed from parents to offspring
Differential Reproductive Success
Individuals with the version of a trait most suited to reproduction in their environment generally leave more offspring than individuals with other versions of the trait
Sexual Selection
Natural selection arising through preference by one sex for certain characteristics in individuals of the other sex
Hardy-Weinberg Equilibrium
If the allele frequencies are known predictions can be made about the genotypes of the offspring that the population produces
Fitness
A measure of the relative amount of reproduction of an individual with a particular phenotype compared with the reproductive output of individuals of the same species with alternative phenotype
First Element of Fitness
An individuals fitness is measured relative to other genotypes or phenotypes in the population
Second Element of Fitness
Fitness depends on the specific environment in which the organism lives
Third Element of Fitness
Fitness depends on an organism’s reproductive success compared with other organisms in the population
Adaptation
Refers both to the process by which organisms become better matched to their environment and to the specific features that make an organism more fit
Artificial Selection
A special case of natural selection because the differential reproductive success is determined by humans rather than by nature
Directional Selection
Individuals with one extreme of the range of variation in the population have higher fitness. Ex. Milk production
Stabilizing Selection
Individuals with intermediate phenotypes are the most fit. Ex. Healthy baby weights are in the middle of the distribution
Disruptive Selection
Individuals with extreme phenotypes have the highest fitness and those with intermediate phenotypes have the lowest fitness. Ex. Salmon reproduction
Fossil
Hard parts of an organism that can be preserved for many years
Radiometric Dating
Helps in telling an organisms evolutionary history by telling us the age of the rock where the fossil was found
Fossil Record
Physical evidence of organisms that lived in the past
Biogeography
Patterns in the geographic distribution of living organisms
Comparative Anatomy and Embryology
Growth, development, and body structures of major groups of organisms
Molecular Biology
Examination of life at the level of individual molecules
Laboratory and Field Studies
Implementation of the scientific method to observe and study evolutionary mechanisms
Homologous Structures
An organ or bone that appears in different animals suggesting there is a common ancestor between them
Vestigial Structures
Homologous Structures sometimes have little or no function at all but they exist because they had value in the ancestor species
