Revolutionary Theory and Evolutionary Concepts

These flashcards cover key concepts related to evolutionary theory and major contributors to the field, including definitions and distinctions of terms relevant to the understanding of evolution.

Evolution

Change in allelic frequencies over time; descent with modification.

Natural Selection

Mechanism of adaptive evolution proposed by Darwin that explains how certain traits become more common in a population.

Gradualism

The idea that changes on Earth occur by small steps over long periods of time, as proposed by Hutton.

Catastrophism

Theory that catastrophic events (such as volcanoes and floods) are responsible for mass extinctions and the formation of landforms, as outlined by Cuvier.

Uniformitarianism

The idea that geologic processes occurring today have shaped the Earth's features over long periods, as presented by Lyell.

Linnaeus's Taxonomy

System of classification for organisms proposed by Carolus Linnaeus that organizes species into hierarchical categories.

Subspecies

A taxonomic designation for populations within a species that are differentiated by geographic or ecological factors.

Homologous Structures

Similar structures derived from a common ancestor but adapted to different functions in different species.

Analogous Structures

Structures in different species that serve similar functions but do not share a common ancestor.

Vestigial Structures

Anatomical features that were once functional in an ancestor but are now reduced or non-functional in the descendant.

Phylogeny

The evolutionary history and relationship among species based on genetic, morphological, and fossil evidence.

Clades

Groups of organisms that consist of a common ancestor and all its descendants.

Artificial Selection

A process in which humans select specific traits in organisms for breeding.

Adaptive Radiation

The rapid evolution of diversely adapted species from a common ancestor when introduced to new environmental opportunities.

Malthusian Catastrophe

A theory proposed by Thomas Malthus that population growth will outpace resource availability, leading to famine and conflict.

Lamarck's Theory of Evolution

Theory suggesting that traits acquired during an organism's lifetime can be passed down to its offspring.

Darwin's Theory of Evolution

Theory that natural selection drives evolution, where individuals with favorable traits reproduce more successfully.

Descent with Modification

Darwin's concept that all organisms share a common ancestor and that species change over time, leading to both the unity and diversity of life.

Natural Selection

The mechanism of adaptive evolution proposed by Darwin, explaining how certain traits become more common in a population.

Hardy-Weinberg Equilibrium

Principle stating that allele frequencies in a population will remain constant in the absence of evolutionary influences. Conditions for equilibrium: no mutations, random mating, no natural selection, large population, and no gene flow.

Gene Pool

The total collection of alleles in a population.

Genetic Drift

Random changes in allele frequencies in a population, especially significant in small populations, including effects such as the founder effect and bottleneck effect.

Mechanisms of Evolution

Factors contributing to evolutionary change, including natural selection, genetic drift, gene flow, mutation, and sexual selection.

Reproductive Isolation

Mechanisms that prevent species from interbreeding; can be prezygotic (before fertilization) or postzygotic (after fertilization).

Speciation

The process through which new species arise, which can occur through allopatric (geographic separation) or sympatric (same area) means.

Types of Natural Selection

Stabilizing selection (favoring average traits), directional selection (favoring one extreme), and disruptive selection (favoring both extremes).

Evolution Patterns

Cladogenesis (branching evolution) and anagenesis (linear evolution) represent different ways in which evolution can proceed.

Darwin’s Theory

Core Idea: Evolution = descent with modification (species change over time).

Natural Selection

Differential survival and reproduction based on traits; acts on individuals but evolution happens in populations.

Fitness

The ability to pass genes to the next generation.

Types of Selection

1. Directional → favors one extreme

2. Stabilizing → favors average

3. Disruptive → favors both extremes.

Microevolution

Change in allele frequencies over time.

Gene Pool

The complete set of alleles in a population.

Allele Frequency

How common an allele is in a population.

Hardy-Weinberg Equilibrium

Conditions for no evolution: no mutations, random mating, no natural selection, large population, and no gene flow. Formulas: p + q = 1, p² + 2pq + q² = 1.

Mechanisms of Evolution

1. Natural Selection

2. Genetic Drift (random change)

   • Bottleneck effect (population crash)

   • Founder effect (small group starts new population)

3. Gene Flow (movement of alleles between populations)

4. Mutation (source of new alleles)

5. Sexual Recombination (mixes alleles increases variation).

Genetic Variation

Types: Discrete (specific categories) and Quantitative (range). Only heritable variation matters.

Evidence for Evolution

Includes fossils, biogeography, comparative anatomy (homologous, analogous, vestigial structures), and molecular biology.

Speciation

Formation of a new species; Biological Species Concept: can interbreed and produce fertile offspring.

Reproductive Isolation

Prezygotic (before fertilization): habitat, temporal, behavioral, mechanical, gametic; Postzygotic (after): hybrid inviability, hybrid sterility, hybrid breakdown.

Types of Speciation

Allopatric (geographic separation) and Sympatric (same area), often due to polyploidy in plants or sexual selection.

Adaptive Radiation

One species evolves into many; often occurs when new environments open (e.g., Darwin’s finches).

Macroevolution vs Microevolution

Microevolution = small changes (alleles); Macroevolution = big changes (new species).

Origin of Life

Sequence of events: Earth forms, oceans form, organic molecules, polymers, protobionts, prokaryotes, photosynthesis → oxygen, eukaryotes (endosymbiosis).

What is the Hardy-Weinberg principle?

The Hardy-Weinberg principle states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of evolutionary influences.

When does Hardy-Weinberg equilibrium occur?

Hardy-Weinberg equilibrium occurs when the following conditions are met: no mutations, random mating, no natural selection, large population size, and no gene flow.

How do you calculate q² from q?

q² is calculated by squaring the value of q (the frequency of the recessive allele).

If q = 0.2, what is p?

If q = 0.2, then p = 1 - q = 0.8.

What does 2pq represent in Hardy-Weinberg?

2pq represents the frequency of heterozygous individuals in a population.

If a trait has a recessive phenotype frequency of 16%, what is q²?

If a trait has a recessive phenotype frequency of 16%, then q² = 0.16.

If the frequency of homozygous dominant individuals is 36%, what does this imply about p?

If the frequency of homozygous dominant individuals (p²) is 36%, then p = √0.36 = 0.6.

What is the formula for calculating the frequency of a dominant phenotype?

The frequency of the dominant phenotype can be calculated using the formula p² + 2pq.

What is the significance of gene flow in populations?

Gene flow increases genetic diversity by introducing new alleles into a population, which can impact allele frequencies.

In what scenario would you expect to see higher rates of genetic drift?

Higher rates of genetic drift would be expected in small populations due to random fluctuations in allele frequencies.