Evolutionary Biology: Key Concepts and Study Guide

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Darwin and Wallace revolutionized biology by proposing the theory of evolution by natural selection, explaining how species change over time.

Darwin and Wallace's Contribution: Both scientists independently developed the concept of natural selection, placing it in the context of earlier evolutionary ideas.
Supporting Evidence: Key evidence includes the fossil record, biogeography (geographic distribution of species), convergent evolution, direct observations, and homologies (similarities due to shared ancestry).
Homology: Structures derived from a common ancestor, such as the limb bones of vertebrates.
Convergent Evolution: Independent evolution of similar traits in unrelated lineages, e.g., wings in bats and birds.

Natural selection is the process by which organisms better adapted to their environment tend to survive and reproduce more successfully.

Definition: Natural selection acts on heritable variation, leading to evolutionary change.
Key Terms: Descent with modification, homology, analogous structures, convergent evolution, fossil, vestigial structure, evolutionary tree, biogeography, artificial selection, adaptation, evolution.
Example: The peppered moth's coloration changed in response to industrial pollution in England.

Evolution occurs at the population level, where genetic variation is essential for natural selection.

Population: The smallest unit of evolution; a group of interbreeding individuals.
Genetic Variation: Differences in DNA among individuals; necessary for natural selection to act.
Hardy-Weinberg Equilibrium: Mathematical model describing allele and genotype frequencies in a non-evolving population.
Equation: (where p and q are allele frequencies)
Application: Used to predict genotype frequencies and test if a population is evolving.

Natural selection, genetic drift, gene flow, and mutation are key mechanisms driving evolution in populations.

Types of Selection: Directional, disruptive, stabilizing, balancing.
Sexual Selection: Selection for traits that improve mating success.
Genetic Drift: Random changes in allele frequencies, especially in small populations.
Bottleneck Effect: Sharp reduction in population size, reducing genetic diversity.
Founder Effect: New population established by a small number of individuals.
Other Terms: Gene pool, microevolution, macroevolution, adaptation, mutation, horizontal gene transfer.
Example: The cheetah population shows low genetic diversity due to a historical bottleneck.

Speciation is the process by which new species arise, often through reproductive isolation and genetic divergence.

Species Concepts: Biological, morphological, ecological; each defines species differently.
Limitations: Some concepts do not apply to all organisms (e.g., asexual species).
Reproductive Isolation: Prevents gene flow between populations, leading to speciation.
Prezygotic Barriers: Prevent mating or fertilization (e.g., habitat, temporal, behavioral isolation).
Postzygotic Barriers: Prevent hybrid offspring from surviving or reproducing.
Allopatric Speciation: Occurs when populations are geographically separated.
Sympatric Speciation: Occurs without geographic separation, often via polyploidy or habitat differentiation.
Adaptive Radiation: Rapid evolution of many species from a common ancestor.
Example: Darwin's finches on the Galápagos Islands evolved into multiple species via adaptive radiation.

The history of life is marked by key evolutionary events, including the origin of cells, multicellularity, and mass extinctions.

Origin of Eukaryotes: Eukaryotic cells evolved from prokaryotic ancestors via endosymbiosis.
Fossil Record: Provides evidence for the timing and sequence of evolutionary events.
Major Events: Appearance of prokaryotes, eukaryotes, multicellular organisms, land plants, animals.
Environmental Change: Climate and habitat changes have influenced evolution and extinction.
Mass Extinctions: Periods when large numbers of species disappeared.
Example: The Cambrian explosion saw rapid diversification of animal life.

Endosymbiosis: Theory that mitochondria and chloroplasts originated as symbiotic bacteria.
Multicellular: Organisms composed of multiple cells.
Prokaryote vs. Eukaryote: Cells without vs. with a nucleus.
Half-life: Time required for half of a radioactive substance to decay; used in dating fossils.

Phylogenetic trees depict evolutionary relationships among species, constructed using morphological and genetic data.

Phylogeny: Evolutionary history of a species or group.
Systematics: Study of biological diversity and relationships.
Taxon: Group of organisms classified together.
Clade: Group consisting of an ancestor and all its descendants.
Monophyletic, Paraphyletic, Polyphyletic: Types of clades based on ancestry.
Shared Derived Character: Trait unique to a clade.
Homology vs. Analogy: Similarity due to shared ancestry vs. convergent evolution.
Principle of Parsimony: The simplest explanation is preferred in tree construction.
Example: DNA sequence comparisons are used to infer evolutionary relationships.

Sister Taxa: Two groups that are each other's closest relatives.
Homoplasy: Similarity not due to common ancestry.
Horizontal Gene Transfer: Movement of genes between organisms other than by descent.