Natural Selection and Phylogeny

What is a selective pressure?

Any reason for organisms with certain phenotypes to have either a survival benefit or disadvantage

What is mechanical/chemical isolation?

A physical incompatibility between reproductive organs of two organisms

What is behavioral isolation?

Species cannot reproduce together because they perform different mating rituals

What is temporal isolation?

When species that could interbreed do not because the different species breed at different times

What is ecological isolation?

Two species that could interbreed do not because the species live in different areas

What part of a binomial is capitalized?

The genus

How is evolution defined?

Descent with modification or gradual change over time

What things evolve?

Populations NOT individuals

What is the origin of all variation?

Mutations

What is adaptive evolution?

A process in which traits that enhance survival or reproduction tend to increase in frequency over time

What is natural selection a cause of?

Adaptive evolution

What is artificial selection?

Modification in a species by human selection

What were Darwin's 4 observations?

1. There's variation in the characteristics of members of the same species.

2. Organisms produce more offspring than survive

3. Characteristics are inherited from parents

4. Not all of offspring survive

What were Darwin's 2 inferences?

1. Individuals with favorable traits are more likely to survive and reproduce (survival of the fittest)

2. The favorable variations will accumulate in populations over time

Why are high variations in populations evolutionarily advantageous?

Organism can be developed to survive in adverse conditions, be more resistant to diseases, and the creation of diversity

What is the fossil record?

Provides evidence of the extinction of species, the origin of new groups, and changes withing groups over time

What is homology?

Similarity resulting from common ancestry

What are homologous structures?

similar structures that related species have inherited from a common ancestor (similar structure, different function)

A homologous structure provides evidence of what?

A common ancestor

What is a vestigial structure?

Remnants of features that served important functions in the organism's ancestors, but are now useless

What is convergent evolution?

Evolution of similar or analogous structures in distinctly related groups (similar functions, different structures) does NOT provide evidence of a common ancestor

What is an analogous structure?

Structures what are similar in structure but are not inherited from a common ancestor (similar functions, different structures)

What are endemic species?

Species that originated in a specific location, but do not exist anywhere else on Earth (contain similarities to other pre-existing species)

What is phylogeny?

Evolutionary history of a species or group of related species

What is a binomial?

A common term for the two-part, latinized format for naming a species, consisting of the genus and specific epithet.

Does the same genus or species suggest more similarity?

Same species

What is a phylogenetic tree?

Branching diagram that shows evolutionary relationships

What does a branch point represent on a phylogenetic tree?

Divergence of two evolutionary lineages

What is a morphology?

A structural similarity between organisms

What is a cladistic?

Another way to group organisms biologically, based on their evolutionary novelties (like hair)

What is a shared derived character?

An evolutionary novelty unique to a particular clade (can also describe LOSS of a character)

What is a clade?

A group of species that includes an ancestral species and all its descendants.

What is an ingroup?

A group of species being studied

What is an outgroup?

A species or group of species closely related to but not apart of the ingroup

What is a domain?

The broadest classification group

What is microevolution?

Change in allele frequencies in a population over generations.

What produces variation in gene pools?

Mutation and sexual reproduction

What is the Hardy-Weinberg equation used for?

To test whether a population is evolving

What is a population?

A localized group of individuals capable of interbreeding and producing fertile offspring

What is a gene pool?

All the alleles in a population

What is the formula for the frequency of all alleles in a population?

p + q = 1

If a population does not reach the criteria of the Hardy-Weinberg principle, what is determined?

That the population is evolving

What is the Hardy-Weinberg equilibrium?

States that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.

What is the equation for the Hardy-Weinberg equilibrium?

p^2 + 2pq +q^2 = 1 (where p and q represent the frequencies of the homozygous genotypes, and 2pq represents the frequency of the heterozygous genotypes)

What are the five conditions for non-evolving populations?

• No mutations

• Random mating

• No natural selection

• Extremely large population size

• No gene flow

What three major factors alter allele frequencies and bring about the most evolutionary change?

• Natural selection

• Genetic drift

• Gene flow

What is genetic drift?

Describes how allele frequencies fluctuate unpredictably form one generation to the next

What is gene flow?

Movement of alleles between populations

What is the founder effect?

States that when a few individuals become isolated from a larger population, allele frequencies in the small founder population can be different from those in the larger parent population

What is the bottleneck effect?

A sudden reduction in population size due to a change in the environment (the resulting gene pool may no longer be reflective of the original population's gene flow)

What type of populations is genetic drift more apparent in?

Small populations

What is gene flow?

The movement of alleles among populations

How can alleles be transferred?

Through the movement of fertile individuals or gametes

What tool consistently results in adaptive evolution?

Natural selection

How does natural selection bring about adaptive evolution?

By acting on an organism's phenotype

What is relative fitness?

The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

What are the three modes of selection?

Directional selection, Disruptive selection, Stabilizing selection

What is directional selection?

Favors individuals at one end of the phenotypic range

What is disruptive selection?

Favors individuals at both extremes of the phenotypic range

What is stabilizing selection?

Favors intermediate variants and acts against extreme phenotypes

What helps maintain genetic variation?

Diploidy in the form of hidden recessive alleles

What is balancing selection?

Occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population

What is a heterozygote advantage?

Occurs when heterozygotes have a higher fitness than do both homozygotes

What is frequency-dependent selection?

The fitness of a phenotype declines if it becomes too common in the population

What is neutral variation?

Genetic variation that does not confer a selective advantage or disadvantage

What is speciation?

Formation of new species

What is microevolution

Adaptations that evolve within a population, confined to one gene pool

What is macroevolution

Evolutionary change above the species level

What is the biological species concept?

A species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring

What is reproductive isolation?

The existence of biological factors (barriers) that impede two species from producing viable, fertile offspring

What is hybrid?

Offspring of crosses between species

What are prezygotic barriers?

Impede mating between species, prevent the successful completion of mating, or hinder the fertilization if mating is successful

What is the morphological species concept?

Defines a species by structural features

What is the ecological species concept?

Views a species in terms of its ecological niche

What is the phylogenetic species concept?

Defines a species as the smallest group of individuals on a phylogenetic tree

What is allopatric speciation?

Geographic isolation which results in speciation

What is sympatric speciation?

A species evolves into a new species without a physical barrier

What is polyploidy?

A condition in which an organism has extra sets of chromosomes due to errors in cell division

What is an autopolyploid?

An individual with more than two chromosome sets, derived from one species

What is punctuated equilibrium?

The hypothesis that evolutionary development is marked by isolated episodes of rapid speciation between long periods of little or no change

What is the gradual pattern model?

Theory that evolution happens gradually over time

What is macroevolution?

The broad pattern of evolution above the species level

What are stromatolites?

Rocks thought to be fossils made by ancient microbes (the first fossils)

When did multicellular organisms evolve?

1.5 billion years ago

What is continental drift?

The gradual movement of the continents across the earth's surface through geological time

What is adaptive radiation?

The evolution of many diverse species from a common ancestor

What events would adaptive radiation typically follow?

Mass extinctions, the evolution of novel characteristics, the colonization of new regions

What is heterochrony?

An evolutionary change in the rate or timing of developmental events

What are homeotic genes?

A set of master control genes that regulates organs that develop in specific parts of the body

What is a HOX gene?

A gene that tells each cell whether it belongs to the head, middle or tail region of the body (misplaces HOX genes can cause body parts to develop in the wrong spots)

How did macromolecules synthesize?

Abiotically in a neutral environment

What are protocells?

Membrane-bound droplets that maintain a consistent internal chemistry

What are ribozymes?

RNA molecules that can catalyze reactions (sometimes are self replicating)

What transformed Earths atmosphere by producing oxygen?

Cyanobacteria

What is genetic recombination?

The production of offspring with combinations of DNA from two sources

What is conjugation?

A process in which 2 prokaryotes exchange genetic material