SBI3U: Unit 3 Reviewer (Evolution)

Fact

a thing that is known or proven to be true.

Theory

scientifically acceptable general principle or body of principles offered to explain phenomena.

Biological Evolution

scientific theory that states that living things have diverged from shared ancestors / the idea that the universe has a history and that change over time has taken place

Aristotle

all living things had been created in their present forms and were immutable (unable to change)

George Louis Leclerc

Believed species were changing over time, considered similarities between humans and apes and possibility of common ancestor.

Carl Linnaeus & Erasmus Darwin

life changed over time.

Jean-Baptiste de Lamarck

proposed a possible mechanism for why species were so adapted to their environment. (Use & disuse & Inheritance of acquired characteristics).

Georges Cuvier

Believed that species themselves did not change.

Charles Lyell

Theory of Uniformitarianism

(Geological change is slow & gradual rather than fast & catastrophic.) (Suggested the Earth was extremely old.)

Charles Darwin

theory of evolution by natural selection, famous for his book “The Origins of Species”, foundational in evolutionary biology.

Evolution

process where changes in the heritable traits (genes) of a species occur over time.

Microevolution

changes in gene frequency in a population from one generation to the next.

Macroevolution

the descent of different species from a common ancestor over many generations.

Fossil Evidence

Layered chronologically in rock layers & shows how species have changed over time.

Homologous Structures

Have similar structural elements, but have diff. functions. This shows that they share a common ancestor.

Analogous Structures

structures that perform the same function but do not have a common evolutionary origin.

Vestigial Structures

non functioning structures that are homologous to a fully functioning structure in closely related species.

Biogeography

Geographic distribution of organisms based on living species and fossils. (Similar habitats select for similar traits.)

DNA Evidence

the more closely two species are related, the more DNA sequences they have in common.

Cytochrome C

found in almost every animal, suggesting that this protein was inherited from a common ancestor.

Darwin’s Theory of Natural Selection

change in population over time, as advantageous heritable traits become more common generation after generation.

Natural Selection

process in nature whereby one genotype leaves more offspring than another genotype because of superior life attributes.

Stabilizing Selection

moderate trait selected for in a population. (Example: Finches with medium sized beaks.)

Directional Selection

extreme trait selected for in a population. (Example: Thick beak in finches.)

Disruptive Selection

Both extreme traits selected in for a population. (Example: Thin and thick beaks in finches.)

Conditions for Evolution by Natural Selection

1. Variation in characteristics.

2. Differences in fitness.

3. Heritability of characteristics.

Mutations

permanent random change in the genetic material of an organism. (Can be good, bad or neutral.)

Mutation Causes

1. Errors in DNA copying.

2. Nondisjunction errors.

3. Cells that are exposed to mutagens. (Radiation)

Variation

differences between individuals which may be structural, functional, or physiological.

Adaptation

anything that helps organisms survive environmental challenges & enable them to pass on their genetic information to offspring.

Structural Adaptation

physical features of an organism.

Behavioral Adaptation

things organisms do to survive.

Physiological Adaptation

changes or chemical reactions that occur within an organism.

Evolution by Natural Selection

populations change over time to display the trait (or adaptation) that provides the species the best chance of survival.

Gene Pool

collection of genes (traits) found in a population.

Genetic Drift

change in alleles due to chance events, usually results in the decrease of genetic variation.

Bottleneck Effect

a severe event (e.g. natural disaster) decreases a population, by chance, certain alleles (traits) may then be represented more frequently than others among the survivors.

Founder Effect

founders will carry some, but not all, of the alleles from the original population’s gene pool.

Gene Flow (Migration)

Changes to the gene pool (alleles) of a population due to migration.

Sexual Selection

favors selection of traits deemed desirable by females.

Species

group of individuals that interbreed in nature to produce viable or fertile offspring.

Speciation/Macroevolution

formation of a new species, due to accumulation of numerous microevolutionary mechanisms.

Reproductive Isolation

members of two populations cannot interbreed & produce fertile offspring.

Pre - Zygotic Mechanisms

prevent mating between species OR prevent fertilization of eggs.

Post - Zygotic Mechanisms

if fertilization is successful, prevention of zygotes from developing into fertile individuals.

Habitat (Ecological) Isolation

different environments.

Temporal Isolation

different reproductive cycles.

Behavioral Isolation

different mating signals.

Artificial Selection

Humans dictate what phenotypes are beneficial and intentionally breed these. (Decreases genetic diversity.)

Genetic Engineering

introduces desirable traits into a species that doesn’t have the genetic information for that trait.