Evolution Study Guide: Phylogenetics, Natural Selection, and Speciation

What is the root of a phylogenetic tree?

The base of a phylogenetic tree.

What are the tips of a phylogenetic tree?

The ends of the branches of a phylogenetic tree.

What is a node in a phylogenetic tree?

A split in a phylogenetic tree that represents the most recent common ancestor of two descendant groups.

What are sister taxa?

Groups that are more closely related to each other than to any other groups.

What is a monophyletic group?

A group of species that share a single common ancestor not shared with any other species.

Why are phylogenetic trees best described as hypotheses?

They can be used to make testable predictions, but cannot guarantee how evolution will occur.

What are the four main requirements for life?

Avoid decay/disorder, require energy, create a closed system, and have a molecule that carries genetic information.

What is LUCA?

The last universal common ancestor, a highly evolved, complex cellular organism with DNA, RNA, and proteins.

What is the key distinction between the three-domain model and the two-domain model?

The three-domain model includes Archaea, Eukarya, and Bacteria, while the two-domain model includes only Archaea and Bacteria.

What are three shared characteristics between human cells and LUCA?

Using DNA for genetic instructions, having a bilayer lipid cell membrane, and relying on ATP for energy.

How does adaptation lead to diversification of life on Earth?

Adaptation causes populations to evolve different traits, leading to reduced interbreeding and the formation of new species.

How did new ideas about geology influence Darwin's ideas?

Geological principles showed that small changes over time can lead to major evolutionary changes.

What is adaptation in the context of evolution?

A trait that enhances the fitness of an organism to its environment.

What is fitness in evolution?

A measure of an individual's ability to survive and reproduce relative to others.

What is natural selection?

The process by which organisms with heritable traits better suited to their environment survive and reproduce.

What are the three main requirements for natural selection?

Variation in a trait, heritability of variation, and influence of variation on reproductive success.

What is the major outcome of natural selection?

Adaptive evolution, where advantageous traits become more common over generations.

How can cancer cells illustrate natural selection?

Cancer cells that survive selective pressures develop resistance and proliferate, demonstrating adaptive evolution.

What is the difference between particulate inheritance and blending inheritance?

Particulate inheritance involves discrete genetic particles, while blending inheritance suggests a mix of traits.

What is genetic variation?

Genetic differences among individuals in a population.

What is an allele?

A gene variant; one of two or more forms of a gene.

What is polymorphism?

Any genetic difference among individuals present in multiple individuals in a population.

What is a homozygote?

An individual with two copies of the same allele.

What is a heterozygote?

An individual with two different alleles for a trait.

What is a genotype?

The genetic constitution of an individual.

What is a phenotype?

An individual's observable characteristics or traits.

Why is mutation the raw material of evolution?

Mutations generate new alleles, and beneficial mutations can improve survival and reproduction.

What are mutations?

Mutations are random changes in the genome that can generate new alleles.

What determines the effects of mutations?

The effects depend on the context of the environment, location within the genome, size of mutation, and type of cell.

When might a mutation have positive effects on fitness?

When it is beneficial and increases an individual's fitness, allowing them to pass on their genetics.

What are neutral mutations?

Mutations that have no effect on an individual's fitness.

What are deleterious mutations?

Mutations that negatively impact an individual's fitness and are not usually passed on.

Why are mutations considered random?

Because organisms cannot gain mutations to benefit themselves; the effects are context-dependent.

Why do only germ cell mutations contribute to evolutionary change?

Germ cells are involved in reproduction, while somatic cells are not passed on to offspring.

How does meiosis contribute to variation in a population?

Meiosis ensures offspring inherit half of their DNA from each parent, increasing genetic diversity.

When is asexual reproduction favored?

In stable, predictable environments because it is fast and energy-efficient.

When is sexual reproduction favored?

In new, stressful environments because it generates genetic variance necessary for evolution.

What is a gene pool?

All alleles present in all individuals in a population or species.

What is a genetic locus?

The location of a gene on a chromosome.

What is allele frequency?

The proportion of a specified genotype among all genotypes for a particular gene in a population.

What is fixation in population genetics?

The process by which one allele replaces all other alleles in a population.

What is genotype frequency?

The proportion of a specified genotype among all genotypes for a particular gene in a population.

What are the 5 conditions for Hardy-Weinberg Equilibrium?

No natural selection, large population, no migration, no mutation, random mating.

What does it mean for a population to be in Hardy-Weinberg equilibrium?

No evolution is occurring; allele and genotype frequencies remain constant.

What happens when you deviate from Hardy-Weinberg Equilibrium?

It indicates that evolution is occurring at a genetic locus.

What is directional selection?

Selection that favors one phenotype over others, shifting allele frequencies in that direction.

What is disruptive selection?

Selection that favors extreme phenotypes and selects against intermediate forms.

What is stabilizing selection?

Selection that favors intermediate phenotypes and selects against extremes.

What is balancing selection?

A form of natural selection that maintains multiple alleles at a locus over time.

What is heterozygote advantage?

When individuals with two different alleles have higher fitness than either homozygote.

What is negative frequency-dependent selection?

When the fitness of an allele increases as it becomes rarer.

Why is maintaining genetic variation advantageous?

It allows populations to adapt to selective pressures like disease and environmental changes.

What is genetic drift?

A mechanism that causes allele frequencies to change due to random sampling effects in small populations.

Why does genetic drift have a greater effect on small populations?

In small populations, each individual represents a large fraction of the gene pool, leading to significant shifts in allele frequencies.

What is gene flow?

The movement of alleles from one population to another due to migration.

How does gene flow affect genetic diversity?

Gene flow increases genetic diversity within a population and decreases it between populations.

What is the difference between genetic drift and gene flow?

Genetic drift is a random change in allele frequencies, while gene flow is the change due to migration and exchange of alleles.

What is microevolution?

A small scale genetic change within a single population.

What is macroevolution?

A large scale genetic change that transcends a single species.

Define the biological species concept.

A group of individuals that can exchange genetic material through interbreeding to produce fertile offspring.

What are pre-zygotic barriers?

Factors that prevent the fertilization of an egg.

What are post-zygotic barriers?

Factors that cause the failure of the fertilized egg to develop into a fertile individual.

What is speciation?

The process by which new species arise.

What is allopatric speciation?

Speciation that occurs when a population is separated by a geographical barrier.

What is sympatric speciation?

Speciation that occurs when a species evolves from a common ancestral population in the same geographical location.

What is adaptive radiation?

Unusually rapid evolutionary diversification in which natural selection accelerates speciation.

What are the conditions for adaptive radiation?

New, uncolonized land, reduced competition, lots of genetic variation, isolation, and strong selective pressures.

What is the effect of mass extinction events on biodiversity?

Short-term reduction in biodiversity, but long-term increases in biodiversity.

What does 'evo-devo' study?

The study of developmental biology to understand evolutionary changes in body structures.

What does it mean that evolution is a 'tinkerer'?

Evolution modifies old genes to create new structures rather than inventing entirely new features.

What role do microevolutionary processes play in macroevolution?

Microevolutionary processes like mutation, genetic drift, and selection contribute to macroevolutionary processes such as speciation.