BIOL 1307 Exam 1 Review

Gradual speciation

Gradual speciation

Model that shows how species diverge gradually over time in small steps (large populations)

Punctuated Equilibrium

Model for rapid speciation that can occur when an event causes a small portion of a population to be cut off from the rest of the population (tiny populations)

Genetic drift

Effect of chance on a population's gene pool, more frequent in small populations

Ex: By chance, some individuals will have more offspring than others—not due to an advantage conferred by some genetically-encoded trait, but just because one male happened to be in the right place at the right time (when the receptive female walked by).

Founder effect

Event that initiates an allele frequency change in part of the population, which is not typical of the original population

Ex: a mexican travels to SK, marries a south korean, & have children

Convergent evolution

Process by which groups of organisms independently evolve to similar forms

Ex: For example, flight has evolved in both bats and insects, and they both have structures we refer to as wings, which are adaptations to flight. However, bat and insect wings have evolved from very different original structures. We call this phenomenon convergent evolution, where similar traits evolve independently in species that do not share a common ancestry. The two species came to the same function, flying, but did so separately from each other.

Allopatric speciation

Involves geographic separation of populations from a parent species and subsequent evolution

Ex: environmental conditions, such as climate, resources, predators, and competitors for the two populations will differ causing natural selection to favor divergent adaptations in each group. Isolation of populations leading to allopatric speciation can occur in a variety of ways: a river forming a new branch, erosion creating a new valley, a group of organisms traveling to a new location without the ability to return, or seeds floating over the ocean to an island. The nature of the geographic separation necessary to isolate populations depends entirely on the organism's biology and its potential for dispersal.

stabilizing selection

selection that favors an average phenotype, selecting against extreme variation.

Ex: In a mouse population that lives in the woods, for example, natural selection is likely to favor mice that best blend in with the forest floor and are less likely for predators to spot.

Directional selection

When the environment changes, populations will often undergo — — which selects for phenotypes at one end of the spectrum of existing variation.

A classic example of this type of selection is the evolution of the peppered moth in eighteenth- and nineteenth-century England.

Diversifying selection

Selection that favors 2 or more distinct phenotypes. Sometimes two or more distinct phenotypes can each have their advantages for natural selection, while the intermediate phenotypes are, on average, less fit. Scientists call this — —.

Reproductive isolation

Situation that occurs when a species is reproductively independent from other species

Behavior, location, or reproductive barriers may cause this to happen. Ex: Given enough time, the genetic and phenotypic divergence between populations will affect characters that influence reproduction: if individuals of the two populations were brought together, mating would be less likely, but if mating occurred, offspring would be nonviable or infertile. Many types of diverging characters may affect the — — the ability to interbreed, of the two populations.

Prezygotic barrier

Mechanism that blocks reproduction from taking place, preventing fertilization

Postzygotic barrier

Occurs after zygote formation, includes organisms that don't survive the embryonic stage and those that are born sterile

Reinforcement

DEF 1: continued speciation divergence between two related species due to low fitness of hybrids between them

DEF 2: hybrids are less fit than either purebred species. The species continue to diverge until hybridization can no longer occur.

Fusion

Reproductive barriers weaken until the two species become one

Stability

Fit hybrids continue to be produced

Natural selection

Reproduction of individuals with favorable genetic traits that survive environmental change because of those traits, leading to evolutionary change

Good genes hypothesis

Males develop impressive ornaments to show off their efficient metabolism or ability to fight disease, females choose males with the most impressive traits because it signals genetic superiority which will be passed to offspring

Ex: Peacocks

Macroevolution

Broader scale evolutionary changes that scientists see over paleontological time

(processes that gave rise to new species and higher taxonomic groups with widely divergent characters) (speciation)

Microevolution

Changes in a population's genetic structure

(connects population change over time) (small change)

Population genetics

Study of how selective forces change the allele and genotypic frequencies in a population over time

Cline

Gradual geographic variation across an ecological gradient

Ex: alligators & their eggs

Systematics

Field of organizing and classifying organisms based on evolutionary relationships

(researchers/scientists use data)

Phylogeny

Evolutionary history and relationship of an organism or group of organisms

(it’s just a hypothesis)

Analogous characters

Look different but have a similar function, characteristic that is similar between organisms by convergent evolution not due to the same evolutionary path

Ex: wings of dragonfly and wings of bats

Parsimony

is basic to all science & tells us to choose the simplest scientific explanation that fits the evidence. In terms of tree building that means that all other things being equal, the best hypothesis is the one that requires the fewest evolutionary changes. (events occurred in the most simplest yet obvious way)

Horizontal gene transfer

Transfer of genes between unrelated species

Rooted Phylogeny

Shows a single ancestral lineage to which all organisms relate

Unrooted Phylogeny

Shows relationships among species but does not show a common ancestor

Biological species

The ability of two individuals to successfully reproduce viable, fertile offspring

Phylogenetic species concept

How closely related individuals are evolutionarily, possessing certain defining or derived traits.

Hardy-Weinberg

states that a population’s allele and genotype frequencies are inherently stable— unless some kind of evolutionary force is acting upon the population, neither the allele nor the genotypic frequencies would change. Assumes conditions with no mutations, migration, emigration, or selective pressure for or against genotype, plus an infinite population.

p+q=1

p2+ 2pq+q2=1

5 events that lead to evolution: Pinky finger

genetic drift: effect of chance (small population)

5 events that lead to evolution: Ring finger

non-random mating

5 events that lead to evolution: Middle finger

mutations

5 events that lead to evolution: Index finger

movement/Gene flow (flow of alleles in & out of a population due to migration of individuals or gametes)

5 events that lead to evolution: Thumb

adaptations

Darwin proposed that natural selection occurs in an environment by __________.

heritable features that make the organism better suited to survive & reproduce

What is used to build phylogenies?

Scientists use a tool called a phylogenetic tree (diagram) to show the evolutionary pathways and connections among organisms

Order of taxonomic classification

DK (an artist)

PC (computer)

OF (as in “of” )

Genus & species (scientific name)

In other words, DKPCOFGs