Unit 3 Evolution Test

Population

All members of a species in a specific area.

Alleles

Pairs of genes that characterize traits.

Gene Pool

All genes of individuals in a population.

Evolution

Change in gene frequencies over time.

Natural Selection

Favours certain phenotypes, driving evolution.

Allele Frequency

Percentage of a specific allele in a gene pool.

Genetic Equilibrium

Stable allele frequencies across generations.

Microevolution

Small changes in allele frequency over time.

Mutation

Change in DNA that introduces new alleles.

Gene Flow

Transfer of alleles between populations.

Non-random Mating

Mating based on specific traits or preferences.

Genetic Drift

Random changes in allele frequencies in small populations.

Harmful Mutations

Most mutations negatively impact individual survival.

Beneficial Mutations

Occasionally advantageous mutations that enhance survival.

Warafin Resistance

Example of beneficial mutation in Norway rats.

Migration

Movement of individuals affecting gene pool diversity.

Genetic Diversity

Variety of genes within a population's gene pool.

Phenotype

Observable traits influenced by genetic makeup.

Evolutionary Change

Result of mutations, selection, and gene flow.

Lethal Mutations

Mutations that are quickly eliminated from populations.

Allele Introduction

New alleles added through migration or gene flow.

Allopatric speciation

Occurs when population is geographically isolated.

Sympatric speciation

Occurs without geographical isolation.

Genetic drift

Changes in the genetic information may become fixed in a small population due to the effects of genetic drift.

Chromosomal changes

Alter gene flow in plants, leading to sympatric speciation.

Non-random mating

Alter gene flow in animals, leading to sympatric speciation.

Polyploidy

Ability to self-fertilize enables diploid cells to fuse with one another to produce tetraploid species.

Gradualism hypothesis

Evolution occurs at a slow, steady rate with small, adaptive changes gradually accumulated over time in populations.

Punctuated equilibrium hypothesis

Environmental changes lead to rapid changes in the gene pool, with rapid bursts separated by long periods of genetic equilibrium.

Convergent evolution

Occurs when unrelated species occupy similar environments in different parts of the world and evolve similar traits independently.

Divergent evolution

Species that once were similar to an ancestral species become increasingly distinct as they adapt to different environmental conditions.

Adaptive radiation

A type of divergent evolution that begins with a recent common ancestor and results in the formation of several new species.

Habitat loss

Most important cause of species extinction, occurring through complete removal, fragmentation, degradation, or frequent human use.

Extinction

Species vulnerable to extinction if they have small distributions, declining population sizes, lack genetic variability, or are harvested by humans.

Mass extinction

Many groups of organisms are wiped off, usually followed by periods of adaptive radiation.

Adaptive radiation in islands

Islands are a prime example where original populations adapt and change with their environment, leading to speciation.

Inbreeding

Can lead to health problems in small populations with little genetic diversity.

Environmental pressures

Similar pressures of natural selection lead to convergent evolution.

Ecological niche

Each species exhibits different traits to exploit an ecological niche in adaptive radiation.

Genetic variability

Lack of genetic variability makes species vulnerable to extinction.

Species

A group of interbreeding populations that share a gene pool and are isolated reproductively from other species.

Reproductive isolating mechanisms

Prevent different species from exchanging genes.

Pre-zygotic isolating mechanisms

Mechanisms that prevent mating or fertilization between species.

Post-zygotic isolating mechanisms

Mechanisms that occur after fertilization, affecting the viability or reproductive capacity of hybrid offspring.

Habitat isolation

Species in the same area occupy different habitats.

Temporal isolation

Species reproduce at different seasons or different times of day.

Behavioural isolation

In animals, courtship behaviour differs, or they respond to different songs, calls, pheromones, or other signals.

Mechanical isolation

Genitalia are unsuitable for one another.

Gamete isolation

Sperm cannot reach or fertilize the egg.

Hybrid inviability

Fertilization occurs but zygote does not survive.

Hybrid sterility

Hybrid survives but is sterile and cannot reproduce.

Hybrid breakdown

First generation hybrid is fertile but the second generation hybrid has reduced fitness.

Garter snake (thamnophis sirtalis)

A species that prefers open areas.

Garter snake (thamnophis ordinoides)

A species that is commonly found near water.

Western Meadowlark

A species that does not interbreed with Eastern Meadowlark due to differences in their songs.

Eastern Meadowlark

A species that does not interbreed with Western Meadowlark due to differences in their songs.

Mules

A hybrid of a horse and a donkey that is sterile and cannot reproduce.

Cotton plants

Different species that produce fertile hybrids, but their offspring die as seeds.

Mutation

A change in the DNA sequence of an organism.

Gene Flow

The transfer of alleles or genes from one population to another.

Non-random Mating

Occurs when individuals select mates based on their phenotypes.

Inbreeding

Mating between relatives to a greater extent than by chance.

Genetic Drift

Changes in the allele frequencies of a gene pool due to chance events.

Founder Effect

Occurs when a few individuals found a colony, representing only a fraction of the total genetic diversity.

Bottleneck Effect

Occurs when a population becomes almost extinct, preventing the majority of genotypes from participating in the next generation.

Natural Selection

The process where organisms better adapted to their environment tend to survive and produce more offspring.

Stabilizing Selection

Favours individuals near the middle of the range, resulting in a narrower phenotype range.

Directional Selection

Favours phenotype at one end of the range, resulting in a shifted range of phenotypes.

Disruptive Selection

Favours both extremes of the range, which can result in a split gene pool and possibly the formation of new species.

Sexual Selection

Selection by mating partners, not by the environment, which may lead to exaggerated phenotypic features.

Sexual Dimorphism

Difference in appearance between males and females.

Heterozygotes

Individuals with two different alleles for a specific gene.

Homozygotes

Individuals with two identical alleles for a specific gene.

Polygenic Traits

Traits that are controlled by multiple genes.

Phenotype

The observable physical or biochemical characteristics of an organism.

Genotype

The genetic constitution of an individual organism.

Alleles

Different forms of a gene that can exist at a specific locus.

Gene Pool

The total collection of genes in a population at any one time.

Adaptation

A trait that helps an organism survive and reproduce in its environment.

Population

A population consists of all members of a species that live in an area at a certain time.

Genes

Each member has genes that characterize traits of the population and genes exist as pairs of alleles.

Gene Pool

All genes of the population's individuals make up the population's gene pool.

Evolution

Evolution occurs as a population's genes and their frequencies change over time.

Natural Selection

Natural selection favours some phenotypes over others, causing populations and species to evolve over time.

Individuals

Individuals do not evolve.

Allele Frequency

Percentage of any specific allele in a gene pool.

Genetic Equilibrium

Allele frequency remains the same over generations; not evolving in any way related to that gene.

Microevolution

Small changes that occur over time that may lead to a change in allele frequency.

Mutation

A mutation is a change that occurs in the DNA of an individual.

Gene Flow

Gene flow is the transfer of alleles from one population to another.

Non-random Mating

A factor that affects allele frequency.

Genetic Drift

A factor that affects allele frequency.

Natural Selection (as a factor)

A factor that affects allele frequency.

Harmful Mutations

Most mutations are harmful or even lethal to an individual and are quickly eliminated from the population's gene pool.

Useful Variations

Occasionally a mutation results in a useful variation, which can become part of the population's gene pool.

Warafin Resistant Rats

E.g. Warafin (rat poison) resistant rats in Norway caused increase in rat population.

Migration

One or more individuals migrating into or out of a population may be responsible for marked change in allele frequencies.

Genetic Diversity

Individuals moving into a population may also add new alleles to the established gene pool of a population.

Grey Wolf Example

E.g. If the grey wolf finds another mate in the new population, it will introduce new genes into that gene pool.

Fossils

Remains or traces of organisms from the past, often preserved in sedimentary rock.