Natural Selection and Evolution

Flashcards covering key concepts, historical figures, mechanisms, and types of natural selection, as well as related evolutionary topics, based on the provided lecture notes.

What is the primary outcome of natural selection regarding allele frequencies?

Allele frequencies change from generation to generation according to the allele’s impact on the survival and reproduction of individuals.

What type of mutations have no long-term evolutionary impact?

Deleterious mutations that are eliminated by natural selection.

What can beneficial mutations lead to over time?

Adaptation to the environment.

How did pre-Darwinian biologists typically interpret the fit of organisms to their environment?

As evidence of a divine Creator’s existence.

In what year did Charles Darwin publish 'On the Origin of Species'?

1859.

What was Darwin's first major challenge to biological convention in 'On the Origin of Species'?

He showed that species are not unchanging, but rather have evolved over time.

What was Darwin's second major challenge, and what mechanism did he suggest for adaptation?

He suggested natural selection as the mechanism that brings about adaptation.

According to Darwin, how does natural selection produce extraordinary adaptations without foresight?

Through a simple mechanism without foresight or intentionality.

Who else independently developed the theory of evolution by natural selection around the same time as Darwin?

Alfred Russel Wallace.

What significant event occurred in 1858 involving both Darwin and Wallace?

A joint paper by Wallace and Darwin was published.

What is the first simple and testable observation that forms the basis of natural selection?

Members of a species differ from one another, meaning there is variation among individuals.

What is the second observation supporting natural selection concerning variation?

Some of this variation is heritable, or passed on to the next generation.

What is the third observation regarding individuals in nature and resources?

In nature, individuals often compete for resources.

Who influenced Darwin and Wallace with his writings on the geometric increase of populations?

Thomas Robert Malthus.

What was the title of Thomas Robert Malthus's influential work?

An Essay on the Principle of Population.

Why do natural populations typically remain stable in size despite their potential for rapid growth?

Resources upon which populations depend are limited.

What is the fourth observation proposed by Darwin and Wallace about individuals in competition?

Those that are best adapted would most likely survive and leave more offspring.

What term did Darwin use for the filtering process that favors advantageous alleles and acts against deleterious ones?

Natural selection.

In evolutionary biology, what does 'fitness' describe?

How well an individual survives and reproduces in a particular environment.

More specifically, what is fitness a measure of for an individual’s genotype?

The extent to which the individual’s genotype is represented in the next generation.

Why is fitness considered 'relative' in evolutionary biology?

It only makes sense to talk about fitness of one organism in relation to the fitness of another, or compared to other individuals of the same species.

What factor significantly influences an organism's fitness?

The environment in which an organism lives.

How does the evolutionary meaning of 'fitness' differ from its common usage?

In evolution, it's the ability to survive and reproduce in an environment, not merely being healthy or physically active.

What critical ingredient did Darwin recognize as essential for his theory, inspired by geologists?

Time.

What is the current theory of evolution called, which combines Darwinian evolution and Mendelian genetics?

The Modern Synthesis.

Why did Darwin never incorporate Mendel's genetic studies into his theory?

Darwin never saw Mendel’s work.

Why was the rediscovery of Mendel's work initially controversial among some biologists?

They argued Mendel's discrete traits didn't account for the continuous variation seen in natural populations.

Who provided the insight that multiple genes could contribute to a single trait, resolving the controversy over continuous variation?

Ronald Fisher.

What effect does natural selection have on the frequency of advantageous mutations?

It increases their frequency, potentially leading to fixation.

What effect does natural selection have on the frequency of deleterious mutations?

It decreases their frequency, potentially leading to elimination.

What is natural selection that increases the frequency of an advantageous allele called?

Positive selection.

What is natural selection that reduces the frequency of a deleterious allele called?

Negative selection.

Why is natural selection often inefficient at eliminating deleterious recessive alleles?

It only acts against them when they are present as rare homozygotes, while most copies exist in heterozygotes that do not express the deleterious phenotype.

What form of natural selection acts to maintain two or more alleles in a population at intermediate frequencies?

Balancing selection.

What specific form of balancing selection occurs when the heterozygote's fitness is higher than that of either homozygote?

Heterozygote advantage.

What human genetic condition is a classic example of heterozygote advantage in regions with malaria?

Sickle-cell anemia.

Which two alleles of the hemoglobin gene are involved in sickle-cell anemia and malaria resistance?

A and S.

In regions with malaria, what advantage do AS heterozygotes have over AA and SS homozygotes?

They do not have severe sickling disease and have some protection from malaria.

What type of natural selection maintains the status quo by acting against extreme phenotypes?

Stabilizing selection.

What is a well-known example of stabilizing selection in humans?

Human birth weight.

What type of natural selection leads to a change in a trait over time, favoring one extreme?

Directional selection.

What happened to the beak size of Galápagos finches after the 1977 drought?

Directional selection favored larger bills because bigger seeds became more available.

What common phenomenon, often related to human interventions, is a strong example of directional selection?

The evolution of antibiotic resistance in bacteria or antimalarial drug resistance in parasites.

What type of natural selection operates in favor of extreme phenotypes and against intermediate forms?

Disruptive selection.

What insect provides an example of disruptive selection related to host trees?

Apple maggot flies (Rhagoletis pomonella).

What term describes the environmental conditions (physical and biological) that cause differential survival and reproduction among organisms?

Selective pressure.

Can natural selection anticipate future environmental conditions?

No, it is not a forward-looking process and can only respond to current conditions.

What is the process called when humans selectively breed organisms for desired traits?

Artificial selection.

What is a key difference between artificial and natural selection regarding their 'goals'?

Artificial selection has a goal set by the breeder, while natural selection has no inherent goal or endpoint.

From what animal were all dog breeds domesticated through artificial selection?

Wolves.