Study Guide for Exam 1 – BIOL42 (Genetics and Evolution)

A comprehensive set of practice flashcards covering core concepts from the BIOL42 study guide, including evolution, Hardy-Weinberg, genetic drift, speciation, species concepts, and sexual selection.

What is the Hardy–Weinberg equation used for in population genetics?

It is a mathematical model of non-evolution used to predict allele and genotype frequencies in a hypothetical non-evolving population.

How should scientific names of species be formatted?

They should be italicised; the genus name is capitalised and the species epithet is not (binomial nomenclature: Genus species).

What is genetic drift and in what context does it matter most?

Genetic drift is random changes in allele frequencies; it matters most in small populations and during bottlenecks or founder events.

Define bottlenecks and founder effects.

A bottleneck is a drastic reduction in population size reducing genetic diversity; a founder effect occurs when a new population is started by a small number of individuals, also reducing genetic diversity.

Distinguish a gene, a genotype, an allele, and a phenotype.

A gene is a DNA segment with instructions for a product; a genotype is the combination of alleles an organism has; an allele is a variant of a gene; a phenotype is the observable trait resulting from gene expression.

How is evolution defined in the notes?

Evolution is a change in allele frequency over generations, occurring in populations and species.

What kinds of effects can mutations have on fitness?

Mutations can be deleterious, neutral, or beneficial; they can also have no effect on fitness.

How can we assess whether a trait is heritable?

By examining data on trait variation and resemblance among relatives, and using methods like parent-offspring comparisons and other genetic analyses to partition genetic vs. environmental effects.

List the assumptions of Hardy–Weinberg equilibrium.

No selection, no mutations, no migration, a very large population (no genetic drift), and random mating.

Differentiate random vs. non-random evolution with examples.

Random evolution includes genetic drift and mutation; non-random evolution includes natural selection and sexual selection, which favor certain traits.

What is non-random mating and how is it related to natural selection?

Non-random mating occurs when mates are chosen based on certain traits; natural selection is a form of non-random evolution that changes trait frequencies due to differential reproductive success.

What is phenotypic plasticity?

Environmental effects cause variability in phenotype without changes in genotype; e.g., color changes in lizards based on habitat.

Explain Mendelian dominant and recessive alleles.

A dominant allele is expressed in the phenotype with one copy; a recessive allele is expressed only when two copies are present.

Provide definitions for the major species concepts listed (morphological, biological, phylogenetic, unified lineage).

Morphological: based on visible traits; Biological: reproductively isolated populations; Phylogenetic: smallest monophyletic groups; Unified lineage (De Queiroz): separately evolving metapopulation lineages.

What is a monophyletic group?

A group consisting of an ancestor and all its descendants (a true clade).

What is a paraphyletic group?

An ancestral group plus some, but not all, of its descendants.

What is a polyphyletic group?

A grouping of taxa that does not include their most recent common ancestor (artificial grouping).

What is a ring species?

A series of connected populations that can interbreed with neighboring populations but not with populations at the ends of the chain.

Define exaptation and give an example.

A trait that evolved for one function but was later co-opted for a different function (e.g., feathers initially for insulation/display later used for flight).

Differentiate allopatric and sympatric speciation.

Allopatric: speciation due to geographic isolation; sympatric: speciation without geographic isolation, often via ecological niches or polyploidization.

What are the two forms of allopatric speciation by geographic isolation?

Dispersal (colonization of a new area) and vicariance (geographic barriers split a population).

What is polyploidization and its role in speciation?

An event creating organisms with extra chromosome sets; can instantly produce a reproductively isolated species, often in plants.

Differentiate pre-mating vs post-mating reproductive barriers and prezygotic vs postzygotic barriers.

Pre-mating barriers prevent mating (e.g., spatial/temporal/behavioral isolation); post-mating barriers occur after mating (e.g., mechanical issues). Prezygotic barriers prevent fertilization (e.g., gamete incompatibility); postzygotic barriers occur after fertilization (hybrid inviability or sterility, chromosomal differences).

What is a simple way to recognize prezygotic barriers in plants vs animals?

In plants, barriers often involve pollinator preferences or timing; in animals, spatial, temporal, and behavioral isolation are common.

What is the concept of a phylogeny and how do you identify sister groups and monophyletic groups in a tree?

A phylogeny is a hypothesis of evolutionary relationships; sister groups are the closest relatives; monophyletic groups include an ancestor and all its descendants.

What is a postzygotic barrier?

Barriers that operate after fertilization, such as hybrid inviability or hybrid sterility.

What is the difference between natural and artificial groups in classification?

Natural groups reflect evolutionary relationships and ancestry; artificial groups are created for convenience and may not reflect ancestry.

What is the difference between a gene and an allele?

A gene is a DNA segment with instructions; an allele is a variant form of that gene.

Define a genotype and give examples.

Genotype is the combination of alleles an individual has, e.g., BB, Bb, or bb.

Define a phenotype.

The observable traits of an organism resulting from gene expression and interaction with the environment.

Name the three main kinds of natural selection and how to recognize each on a graph.

Stabilizing (favors intermediate phenotypes; peak in the middle), Directional (shifts toward one extreme), Disruptive (favors extremes, mid-range is selected against).

What is teleological thinking, and why is it avoided in science?

Teleology ascribes purpose or design to natural processes; science seeks cause-and-effect explanations rather than purpose-driven explanations.

What are the three hypotheses often cited for why sexual selection evolves?

Good genes hypothesis (females gain genetic benefits for offspring), resource gain hypothesis (females gain resources), sexy-son hypothesis (offspring inherit attractive traits).

Explain the concept of sexual dimorphism.

Differences in form between males and females of a species, such as size, coloration, or ornamentation.

Differentiate intra- vs interspecific sexual selection and give examples.

Intraspecific competition refers to competition among members of the same sex within a species (e.g., male-male combat); interspecific selection involves mate choice by females (intersexual selection).