Evolution Flashcards
Evolution
Change in genetic makeup of a population of organisms
5 Types of Evolutionary Factors
Natural Selection, Mutation, Gene Flow, Genetic Drift, Non-Random Mating or Sexual Selection
Natural Selection
Difference in survival and reproduction individuals because of differences in genotypes, acts on individuals but it is the population that evolves
Populations
The units of evolution, localized group of individuals belonging to the same species
Species (spp)
Group of organisms capable of interbreeding and producing fertile offspring in nature
3 Types of Natural Selection
Directional, Stabilizing and Disruptive Selection
Directional Selections
Shifts frequency of a trait in a particular direction
Examples of Directional Selection
Peppered moth, DDT resistance in flies, and antibiotic resistant bacteria
Stabilizing Selection
Selects against extremes in phenotype, maintains well adapted traits, eliminates extremes
Example of Stabilizing Selection
Human birth weight is approx. 7.5 lbs, babies at extremes have lower odds of survival
Disruptive Selection
Increases frequency of extreme types
Example of Disruptive Selection
Members of a spp of African finch have either a large or small beak, adaptive because food consists of either soft or hard seeds
Mutation
Change in genetic info of cell, causes evolution, occurs in a gene ~1/mill gametes
Point Mutation
Change in one or a few nucleotides
Transposition (mutation)
Movement of a gene on a chromosome
Chromosome Duplication or Deletion
Type of mutation
Polyploidy (mutation)
More than a complete set of chromosomes
Inversion (mutation)
Flipped sequence of a section of DNA
Mutagens
Agents that cause mutation
3 Types of Mutagens
Ionizing radiation, UV Light, and Chemical Mutagens
Ionizing Radiation
High energy X and gamma rays knock e-s off atoms, creates free radicals which break DNA
UV Light
Absorbed by Cs and Ts of DNA and polymerizes them
Xeroderma Pigmentosum
Rare disorder where people can’t repair UV damage, full of skin tumors
Chemical Mutagens
Alter DNA nucleotides or are nucleotide mimics that are incorporated into DNA
Mutations in Somatic Cells can cause
Cancer, some cancer-causing viruses (oncovirus) have oncogenes as part of their genome
Gene Flow
Movement of genes from one population to another
Genetic Drift
Genetic makeup of an isolated new group will drift away from its ancestral group, inversely related to size of new group
Two Types of Genetic Drift
Founder Effect and Bottleneck
Founder Effect
Allele frequency in a small group that becomes isolated is different from the ancestral group, as founder group grows it becomes more and more different from the ancestral group
Ellis-van Creveld Syndrome
Causes short limbs and extra fingers, example of founder effect because number of cases in the amish is greater than number of cases in the world
Bottleneck
Population undergoes severe decrease in size, population later recovers and grows but retains limited genetic variation, example is cheetahs
Non-Random Mating or Sexual Selection
Mates chosen on basis of physical or behavioral characteristics, consists of female choice and male competition
Sexual Dimorphism
Caused by female choice and male competition
Fisher’s Runaway Selection Theory
Some traits that don’t enhance fitness are selected for because opposite sex finds them more attractive, becomes more extreme over time
Examples of Fisher’s Runaway Selections Theory
Blue eyes and peacock’s tail
How species form
For speciation to occur, populations must become reproductively isolated by some mechanism
Temporal Isolating Mechanism
Populations breed at different times of day, of year or in different years, example is cicadas and skunks
Ecological Isolation Mechanism
Lifestyles or habitats of populations differ, example is lions and tigers
Behavioral Isolating Mechanism
Mating behavior and courtship rituals become so different that species can’t mate, example is meadowlarks
Mechanical Isolation Mechanism
Anatomical incompatibility between body parts or in pollinators
Gametic
Gametes become incompatible, gamete recognition molecules allow flowers to distinguish right pollen, fish eggs the right sperm
Allopatric Speciation
Occurs when two or more populations diverge because of geographical separation
Sympatric Speciation
Speciation occurs without geographical isolation, usually via polyploidy or disruptive selection
Cline
Graded change in a trait along a geographic axis, examples are Bergmann’s Rule and Allen’s Rule
Bergmann’s Rule
Body size in a species increases as you move north
Allen’s Rule
Extremities are shorter as you go north
