Evolution (Unit 4)

What is evolution without selection?

Evolution that occurs due to factors unrelated to natural selection.

What is genetic drift?

A chance selection of alleles during mating that can change allele frequencies in a population, particularly prevalent in small populations.

What is a genetic bottleneck?

An extreme reduction in population size that results in genetic drift and decreased genetic diversity.

How does a genetic bottleneck affect a population?

The new smaller population may lack the same diversity or allele frequency as the original population.

Give an example of a species affected by a genetic bottleneck.

Cheetahs, which have low genetic variability and are vulnerable to disease.

What is the founder effect?

When a small group separates from the original population, leading to genetic drift and decreased genetic diversity.

How can the founder effect impact allele frequencies?

The founding population may have a different proportion of allele variations compared to the original population.

Provide an example of the founder effect.

Darwin's finches on the Galapagos Islands, which migrated from South America.

What is the Hardy-Weinberg Principle?

In large populations where only random chance is at work, allele frequencies are expected to remain constant from generation to generation.

What factors can disrupt Hardy-Weinberg equilibrium?

Natural selection, small population size, mutation, immigration/emigration, and horizontal gene transfer.

What is the consequence of artificial selection?

It can lead to a reduction in genetic diversity.

How does human influence affect evolution?

It can reduce genetic diversity and lead to issues like pesticide and antibiotic resistance.

What is one consequence of reduced genetic diversity?

Inability to adapt to climate change.

What is the role of mutation in evolution?

It introduces new alleles to a population.

What is gene flow?

The introduction or removal of alleles in a population due to immigration or emigration.

What is horizontal gene transfer?

The gaining of new alleles from a different species.

Why is genetic drift more prevalent in small populations?

Because chance events have a larger impact on allele frequencies in smaller gene pools.

What happens to allele frequencies during genetic drift?

They can change randomly, leading to potential loss of genetic diversity.

What is the impact of low reproductive success in a population?

It can lead to a decline in population size and further genetic drift.

What is juvenile mortality rate?

The rate at which young individuals in a population die, which can be affected by genetic diversity.

What is a species?

Members of a population that can interbreed under natural conditions.

What is reproductive isolation?

A condition where different species cannot exchange genetic information.

What are the two main modes of speciation?

Allopatric speciation and sympatric speciation.

What is allopatric speciation?

Formation of a new species due to evolutionary changes following geographic isolation.

What is sympatric speciation?

The evolution of a new species from within a large population in the same geographic area.

What are prezygotic mechanisms?

Mechanisms that prevent fertilization and zygote formation.

What are postzygotic mechanisms?

Mechanisms that prevent a fertilized egg from developing into a viable offspring.

Give an example of behavioral isolation.

Different courtship and mating cues used by species to attract mates.

What is temporal isolation?

Different species breed at different times of the year.

What is ecological isolation?

Species occupy different habitats in the same region.

What is mechanical isolation?

Incompatibility of reproductive structures preventing mating.

What is gametic isolation?

Male gametes cannot recognize or fertilize female gametes.

What is zygotic mortality?

Zygote is unable to develop due to genetic differences.

What is hybrid inviability?

Hybrid offspring develop but die before birth or cannot survive to maturity.

What is hybrid infertility?

Hybrid offspring are healthy but sterile, such as mules from donkeys and horses.

What is adaptive radiation?

Rapid evolution of a single species into many new species filling different ecological niches.

Give an example of adaptive radiation.

Darwin's finches evolving into various species to exploit different food sources.

What is divergent evolution?

Large-scale evolution of a group into many different forms to fill specialized ecological niches.

What is convergent evolution?

Evolution of similar traits in distantly related species due to similar selective pressures.

What is coevolution?

Process where one species evolves in response to the evolution of another species.

What is an example of coevolution?

The relationship between plants and seed-eating mammals.

What is natural selection?

The process by which certain traits become more or less common in a population due to environmental pressures.

What is heterozygote advantage?

A situation where heterozygous individuals have a higher fitness than homozygous individuals.

What are the main types of natural selection?

Directional selection, stabilizing selection, disruptive selection, and sexual selection.

What does directional selection favor?

Individuals with extreme variations of a trait, resulting in a shift away from the average.

Give an example of directional selection.

Hummingbirds with longer bills are favored in an environment with longer flowers.

What is stabilizing selection?

Selection that favors individuals with traits close to the population average, reducing variation.

Provide an example of stabilizing selection.

Hummingbirds with average bill lengths are favored in an environment with medium-sized flowers.

What is disruptive selection?

Selection that favors individuals at both extremes of a trait variation.

Give an example of disruptive selection.

Hummingbirds with either very long or very short bills are favored when average-sized flowers decrease.

What is sexual selection?

A form of selection that favors traits enhancing reproductive success, even if they are disadvantageous for survival.

What are some outcomes of sexual selection?

Sexual dimorphism and the development of mating and courtship rituals.

What factors can affect a population through natural selection?

Both biotic factors (like disease) and abiotic factors (like climate and resource availability).

What is the result of stabilizing selection?

A shift towards the average trait in a population while reducing extremes.

How does directional selection affect trait distribution?

It causes a shift in the population's trait distribution towards one extreme.

What does disruptive selection indicate about the environment?

It suggests an environment that supports multiple phenotypes rather than a single average phenotype.

What is a key characteristic of sexual dimorphism?

Distinct differences in size or appearance between the sexes of the same species.

How can natural selection lead to genetic variability?

Natural selection acts on genetic variations that arise through mutations and recombination.

What is the role of selective pressures in natural selection?

Selective pressures determine which traits are favored or disfavored in a population.

What happens to traits that deviate from the average in stabilizing selection?

They are selected against, leading to a reduction in variation.

What is the effect of sexual selection on male traits?

It can lead to the development of extravagant traits that may not contribute to survival.

How does the environment influence natural selection?

The environment can favor certain traits over others, impacting survival and reproduction.

Who is known for developing the system of binomial nomenclature?

Carl Linnaeus

What did Carl Linnaeus theorize about species?

He theorized that new species could arise through different mechanisms.

What anatomical puzzle did Georges-Louis Leclerc, Comte de Buffon, encounter?

He was puzzled by anatomical features that seemed to serve no purpose in the organism.

What was Buffon's belief about species?

He believed that species had been created in a more perfect form but had changed over time.

Who was the first scientist to propose a mechanism for the evolution of species?

Jean-Baptiste Lamarck

What is Lamarck's first principle of evolution?

Use and disuse: used structures become larger and stronger, while unused structures become smaller and weaker.

What is Lamarck's second principle of evolution?

The inheritance of acquired characteristics: organisms can pass on gained characteristics.

What flaw exists in Lamarck's theory?

Not all characteristics can be changed through use and disuse, and acquired characteristics are generally not heritable.

What did Georges Cuvier study?

Fossils and their distribution in rock layers.

What is Cuvier's theory of catastrophism?

Global catastrophes could lead to widespread extinction of species, which are then replaced by new species.

What principle did Charles Lyell introduce?

Uniformitarianism: geological processes in the past are the same as those occurring in the present.

What was Thomas Malthus's contribution to evolutionary theory?

He proposed that populations produce more offspring than their environments can support, leading to competition for resources.

What major work did Charles Darwin publish?

On the Origin of Species

What is the theory of natural selection?

Nature favors the reproductive success of some individuals over others based on their adaptations to the environment.

What does 'survival of the fittest' mean in the context of Darwin's theory?

It refers to individuals that are better suited to local conditions surviving to produce more offspring.

What is biogeography?

The scientific study of the geographic distribution of organisms based on living species and fossils.

What observations did Darwin make about species on the Galapagos Islands?

He noted an unusual assortment of species, many not found elsewhere, resembling species on the nearest continental land mass.

What are homologous features?

Structures with a common evolutionary origin that may serve different functions in modern species.

Give an example of homologous features.

Humans, moles, horses, porpoises, and bats have similar limb structures despite different functions.

What are analogous features?

Structures that perform the same function but are not similar in origin or anatomical structure.

Provide an example of analogous features.

The wings of flying insects and the wings of birds serve the same function but differ in structure.

What are vestigial features?

Rudimentary structures that are homologous to fully functioning structures in closely related species.

Give an example of vestigial features.

Cave fish have eye sockets but either tiny vestigial eyes or no eyes.

What did Darwin conclude about competition within populations?

Populations are limited in size by their environment, leading to competition for survival among members of the same species.

What is the significance of Darwin's observations in the Galapagos Islands?

They helped him formulate his theory of evolution based on natural selection.

What did Darwin mean by 'fitness' in the context of natural selection?

Fitness refers to an organism's ability to survive and reproduce in its environment.

What is the relationship between evolution and environmental adaptation?

All species evolve over time in response to their environment, becoming better adapted.

How does Darwin's theory explain the variation within populations?

Individuals of a population vary extensively, and much of this variation is heritable.