Evolutionary Biology Study Notes

Evolutionary Biology Study Notes

• Darwin's Finches: Speciation on islands. Derived from a small flock of finches that invaded an archipelago. Feeding ecology is diverse, with beak morphologies adapted to different food sources. Finches exhibit variability in morphology. Individual birds marked with bands for identification.

• Heritability: The degree offspring resemble parents, measured as a fraction (0-1). Fraction of population variation due to genetic differences. Heritability = (Variation due to genetics) / (Total phenotypic variation). Narrow sense h² = (Additive genetic variance) / (Phenotypic variance). Broad sense h² = (Total genetic variance) / (Phenotypic variance).

• Genetic Variation: Measured by V, variance in phenotype. Components include genetic effects (V_g), environmental effects (V_e), gene x environment interaction (V_gxe), covariance of genes and environments (Cov(G,E)), and error in measuring the phenotype (V_error). V_g is further broken down into additive, dominance, and epistatic effects.

• Speciation: Evolutionary relationships among living things, focusing on bacteria, plants, fungi, and animals. Key players in global elemental cycles. Key difference in cell structures. Species count estimation, ~1.9 million described. Evolutionary independence occurs when mutation, selection, gene flow, and drift operate on populations separately. Reproductive isolation as the essence of speciation.

• Morphospecies: Concept for identifying species. Using physical characteristics, applying it carefully to avoid ambiguity, especially with extinct or asexual species. Fossil species are also categorized using this method, though soft tissue differences blur identification. Cryptic species concept useful for identical physical traits but distinct genetic origins.

• Phylogenetic Species Concept: Species are identified using phylogenetic analysis resulting in monophyletic groups. The smallest monophyletic group is a species, based on a common ancestor. This method is suitable for assessing species' relatedness in different species. Molecular phylogenies can include an assessment of genetic differences.

• Biological Species Concept: Criteria for identifying evolutionary independence based on reproductive isolation, primarily for sexually reproducing organisms. Failure to hybridize regularly or produce fertile offspring reflects reproductive isolation.

• Isolation: Reduction in gene flow creating population divergence. Types including geographic isolation (dispersal or vicariance), chromosomal changes (like polyploidy), and behavioral isolation (assortative mating). Geographic isolation can lead to different mutations and natural selections occurring within isolated groups.

• Divergence Mechanisms: Natural selection, genetic drift, and different reproductive strategies (like assortative mating) can cause phenotypic divergence, ultimately affecting reproductive success depending on the environment and habitat.

• Hybridization and Gene Flow: Interbreeding between species, especially after geographic separation. Prezygotic (no zygote formation) and postzygotic (reduced hybrid fitness) isolation mechanisms contribute to preventing hybridization. Hybridization may influence speciation, hybrid zones, or reinforcement of prezygotic isolation.

• Human Embryonic Development: Multiple stages of human embryogenesis, including significant events like cell division into blastomeres and genome activation. Study of stages like the 2-cell stage, where separation is fatal, and 4-cell stage, to understand the development of the human embryo. The 8-cell stage is characterized by compaction, as blastomeres flatten and tightly connect. Also included are totipotent cells, where each cell has the potential to develop into any cell type.

Explore the key concepts in evolutionary biology, including Darwin's finches and their speciation, heritability metrics, and the components of genetic variation. This quiz will test your understanding of how these principles apply to real-world examples. Perfect for students delving into this fascinating field.