Biology Exam - Evolution

Key Definitions:

Adaptation: An inherited trait that increases an organism's chance of survival and reproduction in its environment.

• Allopatric speciation: Speciation that occurs when populations are geographically isolated.

• Analogous structures: Structures that have similar functions but different evolutionary origins.

• Artificial selection: The selective breeding of domesticated plants and animals by humans.

• Bottleneck effect: A sharp reduction in the size of a population due to a chance event, reducing genetic variation.

• Convergent evolution: The independent evolution of similar traits in different lineages due to similar environmental pressures.

• Divergent evolution: The accumulation of differences between groups which can lead to the formation of new species, usually a result of diffusion of the same species to different and isolated environments which blocks the gene flow among the distinct populations allowing for the accumulation of different mutations.  

• Evolution: The change in the heritable characteristics of biological populations over successive generations.

• Extinction: The complete disappearance of a species from Earth.

• Fitness: The ability of an organism to survive and reproduce in its environment.

• Founder effect: The loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.  

• Gene flow: The transfer of genetic variation from one population to another.

• Gene pool: The total collection of genes in a population.

• Genetic drift: Random changes in allele frequencies within a population, especially in small populations.

• Homologous structures: Structures that have a common evolutionary origin but may have different functions.

• Macroevolution: Large-scale evolutionary changes, such as the formation of new species and higher taxonomic groups.

• Microevolution: Small-scale evolutionary changes within a population, such as changes in allele frequencies.

• Molecular evidence: Evidence for evolution based on similarities and differences in DNA, RNA, and proteins.

• Mutation: A change in the DNA sequence.

• Natural selection: The process by which organisms with advantageous traits are more likely to survive and reproduce.

• Reproductive isolation: Mechanisms that prevent interbreeding between different species.

• Selective pressure: Environmental factors that influence survival and reproduction.

• Sexual selection: A form of natural selection in which individuals with certain traits are more likely to obtain mates.

• Speciation: The process by which new species arise.

• Stabilizing, disruptive, directional selection: Types of natural selection: stabilizing favors intermediate phenotypes, disruptive favors extreme phenotypes, directional favors one extreme phenotype.

• Survival of the fittest: A phrase describing natural selection, where the "fittest" are those best adapted to their environment.

• Sympatric speciation: Speciation that occurs within the same geographic area.

• Vestigial structures: Structures that have lost their original function but are retained in an organism.

Key Concepts:

• 1. Evidence of Evolution:

  • Fossil record: Shows changes in organisms over time.

  • Comparative anatomy: Homologous, analogous, and vestigial structures.

  • Embryology: Similarities in early development.

  • Molecular biology: DNA and protein similarities.

  • Biogeography: Geographic distribution of species.

• 2. Vestigial, Homologous, Analogous Structures:

  • Vestigial Structures: Structures with no apparent function (e.g., human appendix).

  • Homologous Structures: Structures with similar underlying anatomy but different functions (e.g., human arm, bat wing). Evidence of common ancestry.

  • Analogous Structures: Structures with similar functions but different underlying anatomy (e.g., bird wing, insect wing). Result of convergent evolution.

• 3. Charles Darwin's Contribution to Evolution:

  • Theory of evolution by natural selection.

  • "On the Origin of Species" (1859).

• 4. Theory of Natural Selection:

  • Overproduction of offspring.

  • Variation within populations.

  • Struggle for existence (competition).

  • Differential survival and reproduction (survival of the fittest).

  • Inheritance of advantageous traits.

• 5. Artificial Selection - Selective Breeding:

  • Humans select desired traits and breed individuals with those traits.

  • Examples: Domesticated animals, crop plants.

• 6. Gene Flow/Genetic Drift:

  • Gene Flow: Movement of genes between populations.

  • Genetic Drift: Random changes in allele frequencies, especially in small populations.

    • Founder Effect: Small group establishes a new population, limited genetic diversity.

    • Bottleneck Effect: Population size drastically reduced, loss of genetic diversity.

• 7. Reproductive Isolation:

  • Mechanisms that prevent interbreeding between species.

  • Prezygotic: Prevent mating or fertilization (e.g., habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation).

  • Postzygotic: Prevent the formation of viable or fertile offspring (e.g., reduced hybrid viability, reduced hybrid fertility, hybrid breakdown).

• 8. Speciation (Allopatric & Sympatric):

  • Speciation: The formation of new species.

  • Allopatric Speciation: Geographic isolation leads to speciation.

  • Sympatric Speciation: Speciation occurs within the same geographic area (e.g., through polyploidy in plants or behavioral isolation).