Evolution Test Study Guide

Theory of Evolution

Theory of Evolution

species change (for diff reasons)

• change bc of natural selection (Darwin and Wallace came up with that)

• genetic drift

  • bottleneck effect

  • founder effect

Natural Selection

individuals with higher fitness survive and reproduce

Natural Selection is identified by

• genetic variation in populations

• competition for resources

• differential reproductive success

• fitness level

• results in changes in the population over time

Directional Selection

natural selection favors one of the extreme variations of a trait

Disruptive Selection

natural selection favors individuals at both extremes of the phenotypic range, but not intermediate

Stabilizing Selection

natural selection that favors intermediate variation

Gene Flow

a change in allele frequency by migration into and out of population

Genetic Drift

a change in allele frequency by chance alone (random)

Bottleneck Effect

a change in allele frequency after a major catastrophe that wipes most of the population

Founder Effect

a change in allele frequency as a result of a small subset of the population starting a new colony

Mutations

cause a change in allele and genotypic frequencies

Evidence for Evolution

• fossils

• comparative anatomy

• comparative biochem/molecular bio

• comparative embryology

• biogeography

Fossils

the preserved remains, or traces of remains, of ancient organism

Limitations to Fossil Records

• documents extinct species

• incomplete (doesn't include all organisms + we haven’t found all the fossils on earth)

Relative Age

an object's age in relation to the ages of other objects

Absolute Age

an exact age

Radioactive Isotope

unstable form of an atom that will decay to another type of atom; rate decay is constant for each radioactive isotope; USED TO FIND ABSOLUTE AGE

Half-Life

the amount of time it takes for 50% of the sample to decay

Homologous Structures

• show evidence of common ancestry (divergent evolution)

• structures that appear different but come from a common ancestor

• examples: forelimbs of whales and humans

Analogous Structure

• convergent evolution = selective forces have resulted in similar structures

• NOT evidence of common ancestry

• examples: bat and insect wings

Vestigial Structures

• organs or structures that have no apparent use but were once functional in an ancestral species

• provides evidence for divergent evolution

• examples: human appendix and tailbone

Comparative Anatomy

homologous structures, analogous structures, vestigial structures

Comparative Embryology

closely related species have similar stages in embryonic development

Comparative Molecular Biology/Biochemistry

• common biochemical pathways found in organisms with common ancestors

• comparison of DNA or protein sequences

• more similarities = the closer evolutionary relationships

Biogeography

the geographical distribution of species and fossils can show evolutionary patterns

Speciation or the Biological Species Concept

barriers to reproduction (includes prezygotic + postzygotic)

Habitat Isolation

same geographic area but different habitat (prezygotic)

Behavioral Isolation

different signals, rituals, attraction for mating (prezygotic)

Geographic Isolation

different geographical locations (prezygotic)

Temporal Isolation

different mating times (prezygotic)

Mechanical Isolation

anatomically incompatible breeding (prezygotic)

Gametic Isolation

gametes can't fuse together (prezygotic)

Hybrid Sterility

hybrid offspring can't reproduce (postzygotic)

Reduced Hybrid Viability

hybrid offspring dies before reproductive age (postzygotic)

Who was Charles Darwin? What did he do?

scientist who studied the galapagos islands species; developed theory of evolution by natural selection; came up with the "tree of life"

Who was Alfred Wallace? What did he do?

scientist who studied the malay-archipelago species; found out the same theory darwin figured out; also realized "tree of life" was a thing

Explain the Theory of Evolution by Natural Selection

organisms with higher fitness are more likely to survive and reproduce, passing their traits on to their offspring

How do we determine the relative age of a rock layer or fossil?

the closer the rock is to the surface, the younger it is

What do we use to find the absolute age of a rock layer?

radioactive isotopes

If you have 2.0 g of a radioactive isotope and the half-life is 1,000 years. How much will be left after 2,000 years?

0.5 g

Convergent Evolution

when 2 species develop similar characteristics + doesn't show common ancestry

Divergent Evolution

when 2 species diverge from a common ancestor and develop different characteristics

What are the requirements for a population to be in Hardy-Weinberg Equilibrium?

- no mutations

- no migration

- random mating

- no natural selection

Is a population in Hardy-Weinberg Equilibrium evolving? Explain your answer.

no bc the hardy-weinberg equilibrium is a state in which the allele and genotype frequencies remain constant from generation to generation, so there’s no evolution

In a population of 1000 mice, 250 have the recessive fur color. Calculate the allele and genotype frequencies for this population.

• q^2 = 0.25

• q = 0.5

• p = 0.5

• p^2 = 0.25

• 2pq = 0.5

In the same population of mice, a natural disaster wiped out most of the mice. Only 100 survived and all but 9 have the dominant fur color. Calculate the new allele and genotype frequencies for this population. Is this population in Hardy-Weinberg equilibrium? Explain your answer.

• q^2 = 0.09

• q = 0.3

• p = 0.7

• p^2 = 0.49

• 2pq = 0.42

• no it isn't hardy-weinberg equilibrium because the allele and genotype frequencies changed

What is a Phylogenetic tree? How would you identify which species are more closely related from a phylogenetic tree?

• branching diagram/tree showing the evolutionary relationships among various biological species based on similarities and differences in their physical/genetic characteristics

• two species are more related if they have a more recent common ancestor