Evolution and Microevolution

Flashcards covering concepts of microevolution, Darwin's natural selection, genetic drift, types of selection, and Hardy-Weinberg Equilibrium from the provided lecture notes.

What is microevolution?

Processes of evolution

What are the four mechanisms of evolution according to Darwin's Natural Selection?

Variation, Heritability, Struggle for Existence, and Differential Reproduction

How did Darwin describe evolution?

"Descent with modification"

According to Lamarck's theory, how is variation acquired?

Variation is acquired through changes made by an individual during its life, which are then passed to offspring.

According to Darwin's theory, how is variation acquired?

Variation is inherited, meaning individuals are born with traits and those that are more successful pass them on.

What is a key characteristic of microevolution regarding genetic change?

Heritable change in the genetics of a population

What kind of changes accumulate in microevolution?

Small changes within a population

At what level do changes take place in microevolution?

Below the species level

What is the typical time period for microevolution?

A short time period within a single species

What kind of phenotypic changes characterize macroevolution?

Large phenotypic changes within a species (across many populations of the same species)

What does macroevolution involve the origin of?

New species

What is the typical time period for macroevolution?

A long time period

What is the definition of a population in biology?

A group of individuals of the same species living in the same geographic region

What is a gene?

A section of DNA that encodes information for certain traits

What is an allele?

A version of a gene

What is a genotype?

The genetic make-up of an individual

What is a phenotype?

The physical, observable traits of an organism, which may be external or internal

What is the definition of evolution?

Change in the genetic composition of a population during successive generations, as a result of natural selection

What is another way to describe microevolution in terms of genetics?

Changes in allele frequencies

What are the five main causes of microevolution (changes in allele frequencies)?

Mutation, Gene flow, Nonrandom mating, Genetic drift, and Natural Selection

What is a mutation?

A change or error in the gene

What is the significance of mutation in genetic variation?

It is the only 'new' source of genetic variation

What is gene flow?

The movement of organisms or their gametes from one established population to another, introducing new alleles and changing allele frequencies

How can alleles be transferred via gene flow?

Through the movement of fertile individuals, gametes, or seeds

How does gene flow affect differences between populations?

It can reduce differences between populations over time

Which is more likely to directly alter allele frequencies: gene flow or mutations?

Gene flow

What is nonrandom mating?

Individuals do not choose mates randomly

What is assortative mating?

Individuals tending to mate with those with the same phenotypes

What is sexual selection?

Males competing for the right to reproduce, and females choosing to mate with males possessing a particular phenotype

What is genetic drift?

Changes in allele frequencies due to random chance events

What is the general effect of genetic drift on population size and genetic variability?

It generally leads to a reduction in population size and a decrease in genetic variability due to the loss of alleles

How does population size affect the impact of genetic drift?

It has little impact on large populations and a large impact on smaller populations

What is the Bottleneck Effect?

An event that kills off many individuals in a population and prevents a majority of genotypes from entering the next generation

What is an example of the Bottleneck Effect related to the Northern Elephant Seal?

The Northern Elephant Seal population was reduced to 20 individuals in 1896, leading to no detectable genetic diversity in the current 30,000 individuals.

What is the Founder Effect?

When a few individuals leave an established population and establish a new population, carrying only a small fraction of alleles, which leads to changes in allele frequencies based on those few individuals.

What is an example of the Founder Effect in human populations?

The Old Order Amish community in Pennsylvania, which has an exceptionally high rate of Ellis-van Creveld syndrome due to being descended from one couple who helped found the community.

How does genetic drift impact endangered species?

Endangered species experience population bottlenecks, leading to decreased genetic diversity, making recovered populations less resistant to disease or less able to cope with environmental changes.

What is an example of the conservation implications of genetic drift using African cheetahs?

African cheetahs, after experiencing an environmental catastrophe 10,000 years ago, have uniform genetic makeup, making them susceptible to disease and having reduced reproductive capacity due to abnormal sperm.

What are the three requirements for natural selection to occur?

Heritable variation, Differential survival, and Differential reproduction

What are the three modes of natural selection?

Directional, Stabilizing, and Disruptive selection

What is directional selection?

When an extreme phenotype is the most fit and favored, causing the distribution curve to shift in that direction.

What is an example of directional selection?

Industrial Melanism in the Peppered Moth or horse evolution.

What is stabilizing selection?

When an intermediate phenotype is favored.

What is an example of stabilizing selection?

Clutch sizes in birds where an intermediate number of eggs leads to high survivability, or birth weight in humans.

What is disruptive selection?

When two or more extreme phenotypes are favored over any intermediate phenotype, which has lower fitness.

How common is disruptive selection compared to other types?

It is less common than directional or stabilizing selection.

What is an example of disruptive selection?

Seed-eating finches on Santa Cruz Island in the Galapagos Islands, where extreme beak sizes are favored.

What is Hardy-Weinberg Equilibrium?

A state where a population achieves genetic equilibrium, and neither gene nor allele frequencies change in succeeding generations.

What is the Hardy-Weinberg principle used for?

To test whether a population is evolving.

How does the Hardy-Weinberg principle describe the gene pool of an idealized, non-evolving population?

The gene pool remains constant over generations.

What are the five conditions required for Hardy-Weinberg Equilibrium?

No mutations, No gene flow, Infinitely large population, No natural selection, and Random mating.

What is the Hardy-Weinberg equation for calculating genotype frequencies?

p² + 2pq + q² = 1

What is the Hardy-Weinberg equation for checking allele frequencies?

p + q = 1

In Hardy-Weinberg equations, what do 'p' and 'q' represent?

'p' represents the allele frequency of one allele (dominant), and 'q' represents the allele frequency of the other allele (recessive).

In the Hardy-Weinberg equation, what does p² represent?

The frequency of individuals homozygous for the first allele.

In the Hardy-Weinberg equation, what does q² represent?

The frequency of individuals homozygous for the second allele.

In the Hardy-Weinberg equation, what does 2pq represent?

The frequency of individuals heterozygous for the alleles.

What does the Hardy-Weinberg principle describe?

A population that is not evolving.

What can be concluded if a population does not meet the criteria of the Hardy-Weinberg principle?

The population is evolving.

Why are the conditions for Hardy-Weinberg Equilibrium rarely met in nature?

Because microevolution is constantly occurring, and factors like mutations, gene flow, genetic drift, natural selection, and nonrandom mating are typically present.