Evolution Exam Review

Speciation

• Speciation: Process by which one species splits, creating new biological diversity.
• Microevolution: Changes in allele frequency within a population over time.
• Macroevolution: Broad evolutionary patterns above the species level, resulting from a series of speciation events.
• Speciation bridges micro- and macroevolution.

Biological Species Concept

• Species: A group of populations capable of interbreeding with viable, fertile offspring.
• Gene flow maintains genetic cohesion.
• New species arise when populations become reproductively incompatible.
• Reproductive isolation is key to new species formation.

Reproductive Isolation

• Reproductive isolation: Barriers preventing interbreeding between species.
• Hybrids: Offspring resulting from successful interbreeding between two species.

Prezygotic Barriers:

• Habitat isolation: Species in different environments.
• Temporal isolation: Different breeding times.
• Behavioral isolation: Differing mating rituals.
• Mechanical isolation: Physical incompatibility.
• Gametic isolation: Incompatible eggs and sperm.

Postzygotic Barriers:

• Reduced hybrid viability: Low survival rates.
• Reduced hybrid fertility: Sterility.
• Hybrid breakdown: Weak or sterile hybrid offspring.

Speciation Modes

• Allopatric speciation: Geographic separation leads to divergence.
• It involves mutation, natural selection, and genetic drift.
• Sympatric speciation: Occurs without geographic separation.
• Mechanisms include polyploidy, habitat differentiation, and sexual selection.

Polyploidy:

• More than two sets of chromosomes (common in plants).
• Autopolyploid: Multiple chromosome sets from one species.
• Allopolyploid: Hybridization of different species.

Habitat Differentiation:

• Use of different resources limiting gene flow.

Sexual Selection:

• Selection based on mate preference, drives reproductive isolation.

Hybrid Zones

• Areas where different species can meet and mate leading to:
• Reinforcement: Strengthening of reproductive barriers.
• Fusion: Weakening of reproductive barriers, merging species.
• Stability: Continued hybridization without full fusion.

Macroevolution

• Pattern of evolution above the species level over vast time scales.

Origin of Life

• Abiotic synthesis of small organic molecules.
• Joining of molecules forming macromolecules.
• Molecules packaged into protocells.
• Self-replication begins.
• Alkaline vents and meteorites introduces molecules.

Fossil Records

It provides a biased view favoring species that existed longer, were abundant/widespread, and had hard parts.

Geological Record

• Divided into eons (Hadean, Archaean, Proterozoic, Phanerozoic) and eras (Paleozoic, Mesozoic, Cenozoic).

Key Events:

• Oxygen revolution: Accumulation of atmospheric oxygen.
• Eukaryotes Originated 1.8 BYA by endosymbiosis
• Evolution of multicellular eukaryotes: Increasing diversity and complexity.
• Ediacaran period: Emergence of complex, soft-bodied organisms.
• Cambrian explosion: Sudden appearance of modern animal phyla.
• Colonization of land: Plants, fungi, and animals adapt to terrestrial environments.

Plate Tectonics

• Movement of plates causes habitat and climate change as well as allopatric speciation.

Mass Extinctions

• Events causing significant species loss.

Permian Extinction:

• Volcanic activity, global warming, ocean acidification.
• Cretaceous Extinction: Asteroid impact, habitat change, climate change.

Adaptive Radiation

• Rapid evolution of diverse species from a common ancestor.
• Often follows extinction events or the evolution of new traits.

Phylogeny

• Evolutionary History of a species or group represented by tree branching diagrams.
• Key concepts in tree building.
• Rooted tree: Includes a common ancestor.
• Branch point: Shows divergence of lineages.
• Sister taxa: Closest relatives.
• Basal taxon: Early diverging lineage.
• Polytomy: Unresolved lineage with multiple branches.

Taxonomy

• It’s a classification and naming of organisms which follows the Linnaean system.
• Hierarchical classification:
• Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
• Binomial nomenclature (Genus species).

Phylogenetic Trees Interpretations

• They show decent not phenotype and branching pattern not timeline. They also don’t indicate that a species evolved from an adjacent taxon.

Phylogenies

They’re inferred from morphological and molecular data using homology versus analogy.

Cladistics:

• Uses shared homologous characteristics to infer phylogeny.
• Identify clades (monophyletic, paraphyletic, polyphyletic).

Characters:

• Shared derived (unique to a clade) vs. shared ancestral characters.