Unit 8 Review - Evolution - Veronica Korb

Variations

Inherited variations come from two kinds of changes in an organism's genome (Mutations and Gene shuffling).

Variations can make some organisms better or less adapted to their environment, giving them an "edge".

Divergent Evolution

Gives rise to many new species when organisms move to a new area.

Common when new habitats are discovered, and niches must be filled.

Evolution

Occurs my means of natural selection

All populations have genetic variations (genes code for different phenotypic characteristics)

Most adapted organisms eat the most food and will reproduce the most passing their adapted genes on to the next generation.

Fossil record (Fossil Evidence)

The history of life recorded by the remains of the past.

Homologous structures (Anatomical Evidence)

Structures that are anatomically similar because they are inherited from a common ancestor.

Chemical Evidence

All organisms use the same biochemical molecules including DNA and RNA

Bottleneck effect

Prevents the majority of genotypes from reproducing due to a catastrophe.

Founder effect

Rare alleles occur in a higher frequency in a new population than they do in the general population.

Gene Flow (Causes of microevolution)

Gene flow is the exchange of genes between two populations.

Also known as gene migration.

Movement of alleles between populations due to migration.

Genes are removed from or introduced to the gene pool.

Genetic Mutations (Causes of microeveolution)

Random changes in genes.

Basis for all evolution because it results in variation.

Mutations cause many genes to have multiple alleles.

Natural Selection (Causes of microevolution)

The process that results in the adaptation of a population to the biotic and abiotic environments.

Better-adapted individuals (due to variations) reproduce more, passing those genes onto the next generation.

See a shift in traits (adaptations) in each successive generation.

Adaptation

The physical and behavioral traits that enable an organism to survive.

Natural selection

The struggle for existence selects the best-adapted individuals to survive in nature.

Artificial selection

Method of selective breeding of organisms to produce offspring with desirable characteristics.

Mutations

Random changes in DNA structure potentially affect gene expression.

Mutations occur constantly.

Can be beneficial, neutral, or harmful.

Gene Shuffling

Extensive shuffling occurs when egg and sperm are produced.

Same genes are being recombined in different ways, producing different results.

Heritability

Variations are inherited from generation to generation.

Those with advantageous variations pass them on to their offspring.

Only variations that are genetically based (not acquired) can be heritable.

Overproduction

In most populations, there will be more organisms than food to feed them.

Reproductive Advantage

Organisms with variations better suited to the environment have "Increased fitness"

More fit = more likely to get needed resources = more likely to reproduce.

Increased reproduction passes those genes onto the next generation.

Species

A group of similar-looking organisms that can breed with one another and produce fertile offspring (offspring that can reproduce).

Speciation

A process where some members of a sexually reproducing population change so much that they cannot mate with members of the original population.

Gives rise to new species.

How to create a species

Must somehow separate groups of a species.

Reproductive Isolating Mechanisms

Any structural, functional, or behavioral characteristic that prevents successful and healthy reproduction.

Groups must not be able to breed with one another.

Prezygotic Mechanisms (Prior to mating)

Habitat isolation

- different places

Temporal isolation

- different reproduction timing

Behavioral isolation

- different mating practices

Mechanical isolation

- different reproduction parts

Postzygotic Mechanisms (during & after mating)

Gamete isolation

- Gametes are prevented from meeting

Zygote Mortality

- Fertilization occurs but zygote dies soon after.

Hybrid Sterility

- Offspring is born but cannot reproduce

Allopatric Speciation

Speciation that occurs as a result of a physical barrier.

Ex: mountain ranges, bodies of water, etc.

Sympatric Speciation

Speciation that occurs without any physical barrier.

More common in plants.

Convergent Evolution

When unrelated species that are geographically far apart evolve similar traits due to the similarity of their environments.

May exhibit analogous structures - similar in function but from different origins.

Coevolution

When two species evolve together and affect one another's evolution.

Gradualism

Evolution proceeds very slowly over millions of years.

Punctuated Equilibrium

Rapid evolutionary change over a few thousand years after a long period of equilibrium.

Biogeography (Biogeographical Evidence)

Study of the distribution of plants and animals throughout the world.

Comparative Embryology (Anatomical Evidence)

Similarities in the early stages of development show that similar genes are at work.

Vestigal Structures (Anatomical Evidence)

Anatomical features that are fully developed in one group of organisms but are reduced or have no functions in similar groups.

Microevolution

Evolution within a population (macro scale or micro scale)

Population

Members of the same species in a given area.

Within a population, all of the alleles make up the gene pool.

Evolution will occur if the relative frequencies of alleles are acted on by an outside force causing them to change.

Genetic Drift

Changes in allele frequency due to chance.

The larger the population, the less genetic drift will affect it.

2 types: Bottleneck effect and founder effect

Nonrandom mating (Causes of microevolution)

Inbreeding: close relatives mate, increasing the likelihood of recessive genes appearing.

Assortive mating: mate with individuals with the same phenotypes.

Sexual selection: males compete for the right to reproduce.

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