Evolutionary Biology (BIOL 2200 UVA Exam 1)

Monophyletic

In phylogenetic classification, a group that includes the most recent common ancestor of the group and all its descendants. A clade is a __________ group.

Paraphyletic

In phylogenetic classification, a group that includes the most recent common ancestor of the group, but not all its descendants.

Polyphyletic

In phylogenetic classification, a group that does not include the most recent common ancestor of all members of the group.

Evolution

Genetic change in a population of organisms; in general, _______ leads to progressive change from simple to complex.

Artificial Selection

Change in the genetic structure of populations due to selective breeding by humans. Many domestic animal breeds and crop varieties have been produced through artificial selection.

Natural Selection

The differential reproduction of genotypes; caused by factors in the environment; leads to evolutionary change.

Population Genetics

The study of the properties of genes in populations.

Genetic Variation

Refers to the difference in alleles of genes found within individuals of a population.

Allele Frequency

A measure of the occurrence of an allele in a population, expressed as proportion of the entire population, for example, an occurrence of 0.84 (84%).

Genotype

The DNA code/allele an individual has.

Phenotype

The gene that an individual expresses.

Homology/Homologous

Similarity in individuals due to common ancestor.

Convergence

Similarity in individual’s form/function due to similar environments.

Phenotypic Plasticity

A genotype that produces different phenotypes in response to an individual’s environment.

Sources of Genetic Variation

Point mutations, chromosomal mutations, crossing over during meiosis.

Dominant Allele

Determines phenotype.

Recessive Allele

Masked in phenotype.

Population

A group of individuals of the same species that live in the same area and interbreed leaving viable offspring.

Alleles

Different variants of a gene (P/p, A/a).

Gene Pool

All copies of all alleles at every locus in all members of the population.

Evolution

Change in the allele frequencies of a population from generation to generation.

Hardy-Weinberg Principle

If alleles are transmitted by meiosis and random mating frequencies DO NOT change over time.

Assumptions of Hardy-Weinberg Equilibrium

1. No selection

2. No mutation

3. No migration

4. Large population

5. Random mating

Mechanisms of Evolution

1. Mutation

2. Gene flow

3. Non-random mating

4. Genetic drift

5. Selection

Modes of Selection

1. Directional selection

2. Stabilizing selection

3. Disruptive selection

Directional Selection

Phenotypic change in one major direction (gets smaller overall/gets bigger overall).

Stabilizing Selection

Phenotype changes to become intermediate (averages; not small, not big, but in the middle).

Disruptive Selection

The most common phenotype in a population is preyed upon and the most extreme phenotypes survive. As a result the phenotypes change to those of the “end” phenotypes.

Genetic Drift

Change in allele frequency due to chance.

Bottleneck Effect

Sudden shirking in a population; may be caused by human activity (i.e. over hunting or habitat loss).

The Founder Effect

Small number of individuals break off from a population to become a new smaller population. (Have lower genetic diversity).

Modes of Sexual Selection

1. Intrasexual selection

2. Intersexual selection

Intrasexual Selection

Selection within a sex to compete for mates.

Intersexual Selection

Selection by one sex for mates (mate choice).

Balancing Selection

Maintains multiple forms of alleles.

Heterozygote Advantage

Heterozygotes have greater fitness than either homozygote (AA or aa).

Negative Frequency-Dependent Selection

Fitness depends on how common the phenotype is in the population.

Constraints of Evolution

1. Laws of physics, thermodynamics, gravity

2. Sources of genetic variation

3. Adaptation is opportunistic

4. Trade-offs

5. Environmental change

p and q; p²+2pq+q² OR (p+q)²

If a population is in Hardy-Weinberg equilibrium with allele frequencies of __ and __ , then the probability that an individual will have one of the three possible genotypes is _________.

Genotype Frequency

A measure of the occurrence of a ________ in a population, expressed as a proportion of the entire population, for example, an occurrence of 0.25 (25%) for a homozygous recessive ________.

Assortative Mating

A type of nonrandom mating in which phenotypically similar individuals mate more frequently.

Sexual Dimorphism

Morphological differences between the sexes of a species.

Frequency-Dependent Selection

A type of selection that depends on how frequently or infrequently a phenotype occurs in a population.

Cladistics

1. Using clades to build a phylogenetic tree

2. Grouping taxa based on shared ancestry

3. Smaller clades are nested in larger clades

Zygote

The first single cell formed when a sperm and an egg meet during fertilization.

Prezygotic

Sperm and egg do not meet.

Postzygotic

After sperm and egg meet.

Modes of Prezygotic Reproductive Isolation

1. Ecological isolation

2. Temporal isolation

3. Behavioral isolation

4. Mechanical isolation

5. Gametic isolation

Ecological Isolation

Species mate in different places.

Temporal Isolation

Species mate at different times.

Behavioral Isolation

Unique behaviors attract different species, like different bird calls.

Mechanical Isolation

Morphological differences prevent mating.

Gametic Isolation

Sperm (chemically) cannot fertilize egg.

Modes of Postzygotic Reproductive Isolation

1. Reduced hybrid viability

2. Reduced hybrid fertility

3. Hybrid breakdown

Reduced Hybrid Viability

Hybrids do not live to maturity.

Reduced Hybrid Fertility

Hybrids do not produce viable offspring.

Hybrid Breakdown

Hybrid offspring viability is reduced after several generations.

Hybridization

When reproductive isolation between two species breaks down.

Reinforcement

1. Hybrid is LESS fit

2. Individuals that hybridize have fewer offspring

3. Reproductive isolation increases

Fusion

1. Hybrid is MORE fit

2. Individuals that hybridize have an equal number or more offspring

3. Reproductive isolation decreases

Stability

1. Hybrids more fit in a specific time or place and hybridization is limited

2. Small hybrid zones or variable conditions

3. Hybrid production continues

Speciation

The result of reproductive isolation.

Evolutionary Processes that lead to Reproductive Isolation

1. Natural selection

2. Genetic drift

3. Mutation

Gene flow reduces ______ _______.

Allopatric Speciation

Speciation due to geographic separation of a species or population.

Sympatric Speciation

Speciation within the same area.

Demography

The properties of the rate of growth and the age structure of populations.

Polymorphism

The occurrence of two or more clearly different morphs or forms, also referred to as alternative phenotypes, in the population of a species.

Autopolyploidy

Where an organism possesses more than two sets of chromosomes, all derived from the same species, usually resulting from mitotic or meiotic errors.

Allopolyploidy

Where an organism possesses two or more complete sets of chromosomes derived from different species, resulting for hybridization followed by chromosome doubling.

Local Adaptation

Species exhibit phenotypes that differ due to local conditions (could lead to speciation over time.)

Acclimation

Physiological response to environment changes an individual’s phenotype within a generation.

Autopolyploids

1. Cell division error doubles chromosomes

2. Twice as many copies of ALL alleles

3. Reproductively isolated from surrounding population

Allopolyploids

1. Cell division error doubles chromosomes AFTER sterile hybrid forms

2. Twice as many copies of MANY alleles

3. Reproductively isolation from surrounding population

Punctuated Equilibrium

Population is in stasis, there is rapid change, population is in stasis again.

Gradualism

Population changes very slowly over many many years.

Mechanisms for Species Radiation

1. Changes in the environment

2. Availability of new habitat

3. New innovations in morphology, development, or behavior

4. New species interactions

Coevolution

Reciprocal evolution of two interacting species (high levels of genetic diversity.)

Red Queen Hypothesis

Interacting species pairs must repeatedly adapt to each other to maintain their relationship (an “arms race.”)

Phylogeny

A visual hypothesis of the evolutionary history of a group of species, population, or genes.

Applied Phylogenetics

1. Conservation: Identify species at risk

2. Agriculture: Targeted breeding

3. Food science: Track food identity

4. Medicine: Infectious disease

Taxa

Some kind of organism at any biological level, described species or families.

Ancestral

Trait originated from the ancestor of the taxon.

Derived

Trait is an evolutionary novelty to the clade.

Synapomorphy

Derived trait shared by all clade members.