Evolution for Ecology

Evolution in Ecology

Key Concepts in Evolution

  • Importance of Evolution for Ecologists

    • Understanding evolution is critical in predicting how populations might change over time.

    • Evolution leads to resistance in populations, such as the development of resistance to pesticides and antibiotics.

    • Knowledge of evolutionary principles aids in tracking behaviors and survival traits within populations.

    • Species are dynamic rather than fixed; interactions with the environment and other organisms can drive changes in genetic composition.

    • “Understanding the past —> helps predict the future”

Definition of Evolution

  • Definition: "Evolution is a change in the genetic composition of a population from one generation to the next.”

    • According to SimUText, this definition emphasizes both microevolution (changes in allele frequency) and macroevolution (large-scale phenotypic changes at the species level).

Genetic Terminology

  • Genetic Components:

    • Chromosome: A thread-like structure where DNA is packaged.

    • Gene: A sequence of nucleotides forming part of a chromosome.

    • Allele: Variant of a gene (e.g., A or B).

    • DNA (Deoxyribonucleic acid): The molecule carrying genetic information, composed of nucleotides (A, T, G, C).

    • Diploid: Organisms having two sets of chromosomes, or typically two copies of each gene.

    • Haploid: Organisms with one set of chromosomes.

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

  • Uppercase vs. Lowercase Alleles:

    • Example in plants:

    • Allele “R”: Codes for red blossoms (dominant).

    • Allele “r”: Codes for white blossoms (recessive).

    • Capital letters indicate dominant alleles, while lowercase indicates recessive alleles.

  • Types of Dominance:

    • Completely dominant: Dominant phenotype expressed with only one copy of the allele (heterozygous).

    • Recessive: Phenotype expressed only with two copies of the allele.

    • Incomplete dominance: Heterozygotes have intermediate phenotypes, such as pink flowers from red and white parents.

    • Codominance: Heterozygotes express both phenotypes, as seen with red and white patches.

Blood Types as an Example of Variation

  • ABO Blood Type System:

    • Variation in blood types (A, B, AB, O) correlates with disease susceptibility.

    • Group O individuals are more susceptible to bubonic plague, while Group A is susceptible to smallpox.

    • Geographic variations exist in allele frequencies for these blood types.

Genotype vs. Phenotype

  • Definitions:

    • Phenotype: Observable traits resulting from genetic constitution.

    • Genotype: The specific alleles inherited for a trait.

  • Examples of Blood Type Genotypes:

    • Type A can have genotypes AA or AO.

    • Type O must have genotype OO.

    • Type B can have genotypes BB or BO.

Evolutionary Processes

Mechanisms of Evolution

  • Natural Selection: Non-random process favoring the survival of individuals with advantageous traits.

  • Mutation: Random changes in DNA that can introduce new alleles into a population.

  • Genetic Drift: Random fluctuations in allele frequencies due to chance events, notably influencing small populations.

    • Bottleneck Effect: A dramatic reduction in population size leading to a loss of genetic variation.

    • Founder Effect: New populations established by a small number of individuals leading to reduced genetic diversity.

  • Gene Flow (Migration): The movement of alleles between populations affecting allele frequencies.

Examples of Evolutionary Processes

  • Mutation Effects:

    • A mutation in coloration genes can result in shifts in populations, such as the emergence of brown beetles from green.

  • Natural Selection:

    • Predators affecting survival rates, such as starlings preferentially preying on green beetles compared to brown ones.

Requirements for Natural Selection

  1. Variation: Individuals exhibit differences in traits.

  2. Heritability: Traits must be inheritable through genes from parents to offspring.

  3. Differential Reproductive Success: More offspring must be produced than the environment can support, allowing only the best-adapted to survive.

  4. Overproduction/ Competition: More offspring must be produced than the environment can support (only the best adapted survive)

Genetic Variation Sources

  • Mutation provides the raw material for evolution by introducing new genetic variations.

  • The relationship between genotype and phenotype is often complex and can involve multiple genes influencing one trait.

Differences Between Ecological and Evolutionary Thinking

  • Ecologists: Focus on interactions between abiotic and biotic factors.

  • Evolutionary Biologists: Examine how and why certain traits evolved in response to environmental pressures.

Interactive Assessments (iClicker Questions)

  • Understanding Mutations and Selection: Assessments on how specific traits may evolve and their implications on populations.

  • Comparative questions to differentiate between ecological and evolutionary perspectives in biology.