[UCSB SUMMER ‘26] EEMB 2 - Evolution: Week 1 Set

What is biological evolution?

Genetically based change in a line of descent over time; descent with modification.

What is microevolution?

Change in allele frequencies in a population over generations.

Do individuals evolve?

No, populations evolve; individuals vary in traits and differ in reproductive success.

What are the five stages of the evolutionary process?

1) Variation, 2) Natural selection, 3) Genetic divergence, 4) Reproductive isolation, 5) Speciation.

What is the key idea linking variation to evolution?

Evolution requires heritable variation among individuals so allele frequencies can change across generations.

What is biogeography?

The study of the geographic distribution of organisms.

What biogeographic observations challenged fixed-species views?

Many species are unique to isolated places, while some species separated by great distances resemble one another.

What is comparative morphology?

The study of similarities and differences in body plans among major groups.

What are homologous structures?

Structures with similar underlying anatomical positions or patterns despite differences in size, shape, or function; they suggest common ancestry.

What are vestigial structures?

Reduced or functionless structures inherited from ancestors; they are evidence of evolutionary history.

What geological pattern supported evolutionary thinking?

Distinct rock layers contain distinct fossils; deeper layers tend to contain older, often simpler forms than shallower layers.

What was Anaximander's evolutionary contribution?

He proposed that the first land-dwelling human ancestors originated in water and that the first human arose from another type of animal.

What was Xenophanes' contribution?

He recognized fish and shell fossils as evidence of past life.

What was Aristotle's Scala Naturae?

A hierarchy of life arranged from simple to complex.

What was Lucretius' contribution?

He described the development of the cosmos, Earth, life, and humans through mechanistic processes.

What is a teleological view of nature?

The view that natural features exist because of purposeful design or an intended end.

What was the 'Great Chain of Being'?

A fixed hierarchy from lower to higher forms in which all links were created together and were considered immutable.

What did Buffon propose?

Life was not immutable, the environment could influence modification, and Earth was much older than traditional estimates.

What did Erasmus Darwin propose?

Species can change in response to the environment, competition can influence species formation, and life may share common ancestry.

What did Thomas Malthus contribute to Darwinian thinking?

Populations can grow geometrically and have the capacity to produce more individuals than the environment can support.

What did Charles Darwin contribute?

He developed the theory of natural selection after observations from the HMS Beagle voyage and later published On the Origin of Species.

What did Alfred Russel Wallace contribute?

He independently developed essentially the same natural-selection idea and sent Darwin a summary in 1858.

What is natural selection in its most basic form?

Differential survival and reproduction of heritable variants, causing some genotypes to increase in frequency.

What is adaptation?

An adjustment or trait change that improves fit to environmental conditions; an adaptive trait increases survival and reproduction.

What is an adaptive trait?

A trait variant that provides an advantage in survival and reproduction.

What is a maladaptive trait?

A trait variant that disadvantages survival and reproduction.

What is a neutral trait?

A trait variant with no net advantage or disadvantage in survival and reproduction under the current conditions.

What three broad trait types characterize populations?

Morphological traits (form), physiological traits (function), and ethological traits (behavior).

What is a discrete character?

A trait with two or more distinct forms rather than a continuum.

What is a quantitative character?

A trait that varies continuously across a range of values.

What is a gene?

A hereditary unit of DNA associated with a trait.

What is an allele?

An alternative molecular form of a gene.

What is a gene pool?

All genes/alleles in a population; the population's pool of genetic resources.

What is a genome?

All the genes in a species.

What is a genotype?

The genetic makeup or set of alleles of an organism.

What is a phenotype?

The observable traits of an organism, determined by genotype plus environmental influences on gene expression.

Why is genotype-to-phenotype not always 1:1?

Different genotypes can produce the same phenotype, such as AA and Aa under complete dominance.

What is phenotypic frequency?

The proportion of individuals in a population exhibiting a particular observable trait.

How do you calculate phenotypic frequency?

Number with the phenotype divided by total population size; multiply by 100 for percent.

What is allele frequency?

The proportion of all copies of a gene in a population represented by a particular allele.

What does the proportion of all copies of a gene in a population represent?

The proportion represented by a particular allele.

How many allele copies are present at one autosomal locus in N diploid individuals?

2N allele copies.

How do you calculate the frequency of allele A from genotype counts?

[(2 × number of AA) + number of Aa] / (2N).

What is the frequency of allele A if AA=30, Aa=40, aa=30?

0.50.

What is genetic equilibrium?

A condition in which allele frequencies at a locus remain stable across generations.

What is the Hardy-Weinberg principle used for?

It predicts allele and genotype frequencies in a non-evolving population.

What equation relates the two allele frequencies in a two-allele Hardy-Weinberg system?

p + q = 1.

What is the Hardy-Weinberg genotype-frequency equation?

p² + 2pq + q² = 1.

What does p represent in Hardy-Weinberg?

Frequency of one allele, conventionally A.

What does q represent in Hardy-Weinberg?

Frequency of the other allele, conventionally a.

What does p² represent?

Expected frequency of genotype AA.

What does 2pq represent?

Expected frequency of genotype Aa.

What does q² represent?

Expected frequency of genotype aa.

Why is the heterozygote term 2pq rather than pq?

There are two ways to form Aa.

What are the five conditions for Hardy-Weinberg equilibrium?

No mutation; very large population; isolated from gene flow; no effect on survival/reproduction; random mating.

What are the three major processes driving populations away from Hardy-Weinberg equilibrium?

Natural selection, gene flow, and genetic drift.

What does it suggest if genotype frequencies do not match Hardy-Weinberg predictions?

One or more Hardy-Weinberg assumptions is violated.

What is the expected AA frequency if p=0.7 and q=0.3?

0.49.

What are the expected genotype counts if p=0.7, q=0.3, N=1000?

AA=490, Aa=420, aa=90.

If a recessive phenotype frequency is 0.16 under Hardy-Weinberg, what is q?

0.40.

If q=0.40, what is p?

0.60.

What is the expected heterozygote frequency if p=0.60 and q=0.40?

0.48.

What are the five basic genetic events that produce variation?

Mutation, crossing over, independent assortment, random fertilization, gene flow.

Which process creates new alleles?

Mutation.

What does recombination do?

Creates new combinations of existing alleles.

What is a point mutation?

A mutation affecting one or a small number of nucleotide positions.

What is a chromosomal mutation?

A large-scale change involving chromosome structure or number.

Why are many mutations neutral or harmful?

Their fitness effects depend on context.

What is positive assortative mating?

Non-random mating with similar partners.

What is negative assortative mating?

Non-random mating with dissimilar partners.

How does positive assortative mating affect homozygosity?

It tends to increase homozygosity.

How does negative assortative mating affect heterozygosity?

It tends to increase heterozygosity.

What is inbreeding?

Mating among genetically related individuals.

What does inbreeding do to genetic load expression?

It increases homozygosity.

What is genetic load?

The burden of deleterious alleles.

What is crossbreeding?

Mating between genetically distinct populations.

What is hybridization?

Interbreeding between genetically differentiated groups.

What are the three broad types of variation?

Normal/continuous, polymorphic, and ecogeographic variation.

What is continuous or normal variation?

Variation distributed across a continuum.

What is polymorphic variation?

Two or more distinct forms of a trait.

What is ecogeographic variation?

Trait variation associated with geographic gradients.

Does a dominant allele automatically increase to fixation?

No, dominance describes expression, not fitness.

Does Hardy-Weinberg say real populations never evolve?

No, it describes conditions when specified evolutionary forces are absent.