SBI3U Evolution Unit Study Guide - Important Terms to Know

Variation

Physiological, structural or behavioural differences between individuals within a population

Discontinuous Variation

Traits that have distinct categories with no in between values.

Continuous Variation

Traits that have no distinct classes or categories. Characteristics can be measured between a range of two extremes.

Adaptation

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

Physiological Adaptation

Biochemical response

Structural Adaptation

Anatomical feature

Behavioural Adaptation

An activity or habitat.

Selective Pressure

External agents which affect an organism’s ability to survive in a given environment.

Vestigiality

Retention of structures that have lost some or all of their ancestral function.

Homologous Structures

Evolved from common ancestor, similar anatomy, different function.

Analogous Structures

Evolved independently, similar function, different anatomy.

Natural Selection

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

Fitness

The ability of an organism to pass its genes on to its offspring, and the next generation

Sexual Selection

Natural selection arising through preference by one sex for certain characteristics in individuals of the other

Gene Pool

The combination of all the genes (including alleles) present in a reproducing population or species

Selective Pressure

External agents which affect an organism’s ability to survive in a given environment

Stabilizing Selection

The intermediate variation conveys greater fitness than the extremes

Directional Selection

Variations towards one end of the spectrum convey greater fitness

Disruptive Selection

Variations at both extremes convey greater fitness

Transcription

The process where a cell copies a section of DNA into mRNA. It happens in the nucleus and creates a message that can be used to build a protein.

Translation

The process where the ribosome reads the mRNA sequence and assembles amino acids in the correct order to build a protein.

Genetic Drift

The change in allele frequencies within a population over generations due to random chance

Founder Effect

A form of extreme genetic drift wherein genetic variation is lost when a new population is established by a small group

Genetic Bottleneck

A form of extreme genetic drift in which a single event drastically reduces genetic variation within a population

Gene Flow

The transfer of genetic variation from one population to another

Speciation

The formation of one or more distinct species from a preexisting population

Allopatric Speciation

Speciation that occurs when a population becomes geographically isolated, leading to independent evolution and the formation of new species.

Sympatric Speciation

Speciation within the same habitat due to behavioural or temporal changes

Abrupt Speciation

The rapid formation of a new species caused by a sudden genetic change, often through major mutations or chromosome number changes.

Autopolyploidy

Occurs when an organism’s chromosome sets come from one single species (duplication of its own genome).

Allopolyploidy

Occurs when chromosome sets come from two different species

External Causes of Mutations

Radiation, chemicals, viruses

Germ Cell Mutation

A mutation that is passed on to offspring

Somatic Cell Mutation

A mutation that is not passed on to offspring

Internal causes of mutation

Errors during DNA replication (s-phase)

Examples of DNA Altering Chemicals

Carcinogens like asbestos

Examples of DNA Altering Viruses

HPV

Artificial Selection

The process by which humans selectively breed organisms with desirable traits to produce offspring with those traits

Example of artificial selection

Dog breeding for specific traits or cultivating crops with larger fruits