Bio 191 Exam 1

evolution

descent with modification ; the process by which species accumulate differences from their ancestors as they adapt to different environment over time ; also defined as change in the genetic composition of a population from generation to generation

fossils

a preserved remnant or impression of an organism that lived in the past

adaptation

inherited characteristics of an organism that enhances its survival and reproduction in a specific environment

natural selection

a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits

artificial selection

process in which humans select and breed individuals that have desired traits

homology

similarity in characteristics resulting from shared ancestry

homologous structures

structures in different species that are similar because of common ancestry ; these similar structures may or may not have similar functions

convergent evolution

the evolution of similar features in independent evolutionary lineages

analogous

having characteristics that are similar because of convergent evolution, not homology

biogeography

the study of geographic distribution of species

phylogeny

the evolutionary history of a species or group of related species

taxon (plural taxa)

a named taxonomic unit at any given level of classification

phylogenetic tree

a branching diagram that represents a hypothesis about the evolutionary history of a group of organisms

branch point

the representation on a phylogenetic tree of the divergence of two or more taxa from a common ancestor

evolutionary lineage

the sequence of ancestral organisms leading to a particular taxon ; represented by a branch (line) in a phylogenetic tree

sister taxa

groups of organisms that share an immediate common ancestor and hence are each other’s closest relatives

rooted

describing a phylogenetic tree that contains a branch point (often, the one farthest to the left) representing the most recent common ancestor of all taxa in a tree

basal taxon

in a specified group of organisms, a taxon whose evolutionary lineage diverged early in the history of the group

shared ancestral character

a character that is shared by members of a particular clade but that originated in an ancestor that is not a member of that clade

shared derived character

an evolutionary novelty that is unique to a particular clade

outgroup

a species or group of species from an evolutionary lineage that is known to have diverged before the lineage that contains the group is being studied ; it is selected so that its members are closely related to the group of species being studied, but not as closely related as any study-group members are to each other

ingroup

a species or group of species whose evolutionary relationships are being examined in a given analysis

maximum parsimony

a principle that stated when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts

clade

a group of species that includes an ancestral species and all of its descendants

monophyletic

pertaining to a group of taxa that consists of a common ancestor and ALL of its descendants ; equivalent to a clade

paraphyletic

pertaining to a group of common taxa that consists of a common ancestor and SOME, but not all, of its descendants

polyphyletic

pertaining to a group of taxa that includes distantly related organisms but does NOT include their most recent common ancestor

molecular clock

a method for estimating the time required for a given amount of evolutionary change, based on the observation that some regions of genomes evolve at constant rates

horizontal gene transfer

the transfer of genes form one genome to another through mechanisms such as transposable elements, plasmid exchange, viral activity, and perhaps fusions of different organism

genetic variation

differences among individuals in the composition of their genes or other DNA sequences

phenotypic plasticity

the ability of an individual genotype that is capable of producing different phenotypes when exposed to different environmental changes

neutral variation

genetic variation that does not provide a selective advantage or disadvantage

adaptive evolution

a process in which traits that enhances survival or reproduction tend to increase in frequency in a population over time

genetic drift

a process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next ; effects are most pronounces in small populations

founder effect

genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene poop composition is not reflective of that of the original population

bottleneck effect

genetic drift that occurs when the size of a population is reduced, as by a natural disaster or human actions ; typically the surviving population is no longer genetically representative of the original population

gene flow

the transfer of alleles from one population to another, resulting in the movement of fertile individuals and their gametes

relative fitness

the contribution of individual makes the gene pool of the next generation, relative to the contribution of other individuals in the populations

directional sleection

natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully that do other individuals

disruptive selection

natural selection in which individuals on both extremes of a phenotypic range survive or reproduce more successfully than do individuals with intermediate phenotypes

balancing selection

natural selection that maintains two or more phenotypic forms in a population

heterozygote advantage

greater reproductive success of heterozygous individuals compared with homozygotes ; tends to preserve variation in a gene pool

gene pool

the aggregate of all copies of every type of allele at all loci in every individual in a population

population

a group of individuals of the same species that live in the same area anf interbreed, producing fertile offspring

hardy-weinburg equilibrium

the state of a population in which frequencies of alleles and genotypes remain constant from generation to generation, provided that only mendelian segregation and recombination of alleles are at work

allopatric speciation

the formation of new species in populations that are geographically isolated from one another

biological species concept

definition of a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but do not produce viable, fertile offspring with members of such other groups

ecological species concept

definition of a species in terms of ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment

hybrids

offspring that results from the mating of individuals from two different species from two true-breeding varieties of the same species

hybrid zone

a geographic region in which members of different species meet and mate, producing at least some offspring of some mixed ancestry

macroevolution

evolutionary change above the species level ; ex. the orgin of a new group of organisms through a series of speciation events and the impact of mass extinction on the diversity of life and its subsequent recover

microevolution

evolutionary change below the species level ; change in allele frequencies in a population over generations

morphological species concept

definition of a species in terms of measurable anatomical criteria

postzygotic barriers

A reproductive barrier that prevents hybrid zygotes produced by two different species from developing into viable, fertile adults

prezygotic barriers

A reproductive barrier that impedes mating between species or hinders fertilization if interspecific mating is attempted

punctuated equilibria

in the fossil record, long period of apparent stasis, in which species undergoes little or no morphological change, interrupted by relatively brief periods of sudden change

reproductive isolation

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

speciation

an evolutionary process in which one species splits into one or two more species

adaptive radiation

period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological toles in their communities

mass extinction

the elimination of a large number of species throughout earth, the result of global environmental changes

pangaea

the supercontinent that formed near the end of the Paleozoic era, when plate movements brought all the landmasses of earth together

plate tectonics

the theory that the continents are part of the heat plates of earth’s crust that float on the hot, underlying portion of the mantle ; movements in the mantle cause the continents to move slowly over time

radiometric dating

common technique used to determine the age of a fossil, based on the decay of radioactive isotopes

heterochrony

evolutionary change in the timing or rate of an organisms development

paedomorphosis

the retention in an adult organism of the juvenile features of its evolutionary ancestors

homeotic genes

any of the master regulatory genes that control placement and spatial organization of body parts in animals, plants, and fungi by controlling the developmental fate of groups of cells

prokaryotes

an organism that has a prokaryotic cell ; an informal term for an organism in either domain bacteria or archaea

protocells

an abiotic precursor of a living cell that had a membrane-like structure that maintained an internal chemistry different from that of its surroundings

pathogens

an organism or virus that causes disease

ribozymes

an RNA molecule that functions as an enzyme, such as an intron that catalyzes its own removal during RNA splicing

nucleoid

a non-membrane-enclose region in a prokaryotic cell where its chromosome is located

plasmids

a bacterial plasmid carrying genes that confer resistances to certain antibiotics

transformation

The process by which a cell in culture acquires the ability to divide indefinitely, similar to the division of cancer cells. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell. When the external DNA is from a member of a different species, transformation results in horizontal gene transfer

transduction

A process in which phages (viruses) carry bacterial DNA from one bacterial cell to another. When these two cells are members of different species, transduction results in horizontal gene transfer. See also signal transduction pathway

conjugation

In prokaryotes, the direct transfer of DNA between two cells that are temporarily joined. When the two cells are members of different species, conjugation results in horizontal gene transfer

protists

an informal term applied to any eukaryote that is not a plant, animal, or fungus ; most protists are unicellular, though some are colonial or multicellular

ensodymboiant theory

the theory that mitochondria and plastids, including chloroplasts, originated as prokaryotic cells engulfed by host cells ‘ the engulfed cells and its host cell then evolved into a single organism

endosymbiosis

a mutually beneficial relationship between two species in which one organism lives inside the cell or cells of another organism

secondary endosymbiosis

a process in eukaryotic evolution in which a heterotrophic eukaryotic cell engulfed a photosynthetic eukaryotic cell, which survived in a symbiotic relationship inside the heterotrophic cell

Describe the concept of descent with modification

species come from ancestral species but change over generations ; populations accumulate genetic differences over time, which can result in new adaptations and new species

Compare artificial selection, natural selection, and adaptations

artificial selection - humans modify which organisms reproduce based on desired traits

natural selection - individuals with inherit3ed traits that help them survive and reproduce tend to leave more offspring

adaptation - an inherited characteristic that increases an organism’s survival or reproduction in a particular environment

Understand Darwins two observations and two inferences

Observation 1: Individuals in a population vary in their traits.

Observation 2: Organisms produce more offspring than the environment can support.

Inference 1: Individuals with advantageous inherited traits are more likely to survive and reproduce.

Inference 2: Over generations, favorable inherited traits become more common in the population.

Describe the three key features of natural selection

variation - individuals in a population vary in traits

heritability - some differences are inherited by parents

differential reproductive success - individuals with certain inherited traits produce more surviving offspring than others

Explain examples of direct observations of evolutionary change

• bacteria evolving resistance to antibiotics

• insects evolving resistance to pesticides

• changes in coloration of organisms in response to environmental changes

Understand homology and homologous structures and what types of evolutionary relationships they describe

similarity between characteristics because shared ancestry

• homologous structures - structures in different species that are similar because they came from an common ancestor

Understand convergent evolution and analogous structures- be able to compare these to homology and homologous structures

occurs when similar features evolve independently in different evolutionary lineages

Explain what we can learn about evolution from the fossil record and biogeography

• the fossil record provides evidence of organisms that lived in the past and can show how organisms and their characteristics have changed over time

• biogeography is the study of the geographic distribution of species ; patterns in where organisms live can provide evidence of common ancestry, geographic isolation, and evolutionary change

Define phylogeny and explain how phylogenies are used.

phylogeny is the evolutionary history of a species or group of related species ; used to show and analyze evolutionary relationships among organisms

Differentiate between derived and ancestral characters

an ancestral character was present in an ancestor of the group ; a derived character is an evolutionary novelty that appeared most recently in a particular lineage

Identify monophyletic, polyphyletic, and paraphyletic groups

monophyletic - common ancestor and ALL descendants

paraphyletic - common ancestor and SOME descendants

polyphyletic - includes organisms from different lineages but does not include their most recent common ancestor

Understand the concept of maximum parsimony

the principle that the simplest explanation consistent with the evidence should be investigated first ; tree with the fewest evolutionary changes

Describe what molecular clocks are and how they are used

molecular clocks estimate the time required for a certain amount of evolutionary change by using regions of genomes that evolve at relatively constant rates

Explain the importance of horizontal gene transfer

horizontal gene transfer allows genes to move from one organism to another rather than only being inherited from parents ; it can introduce new genetic traits into organisms and is particularly important in prokaryotes

Describe the importance of genetic variation and the ways it arises in populations

Genetic variation provides differences among individuals that evolution can act on. It can arise through mutation, genetic recombination during sexual reproduction, and gene flow.

Understand four sources of genetic variation.

The major sources are mutation, crossing over, independent assortment, and random fertilization. Gene flow can also introduce alleles into a population.

Describe a population and a gene pool.

A population is a group of individuals of the same species living in the same area and interbreeding to produce fertile offspring. A gene pool is the collection of all copies of every allele present in a population.

Differentiate between how natural selection, genetic drift, and gene flow affect allele frequencies in a population.

• Natural selection: Changes allele frequencies because some inherited traits increase survival or reproduction.

• Genetic drift: Randomly changes allele frequencies because of chance events.

• Gene flow: Changes allele frequencies when individuals or gametes move between populations.

Explain specific types of genetic drift: founder and bottleneck effects.

• Founder effect: A few individuals establish a new population, and their allele frequencies may differ from those of the original population.

• Bottleneck effect: A population is drastically reduced in size, and the surviving population may have different allele frequencies from the original population.

Understand the four effects of genetic drift.

Genetic drift can cause allele frequencies to change randomly, reduce genetic variation, cause harmful or beneficial alleles to become more or less common by chance, and cause populations to become genetically different from one another.

Describe relative fitness and three different modes of selection that can lead to it.

Relative fitness is an individual's contribution to the gene pool of the next generation compared with other individuals. Three modes of selection are:

• Directional selection: Favors one extreme phenotype.

• Disruptive selection: Favors both extreme phenotypes over the intermediate phenotype.

• Balancing selection: Maintains two or more phenotypic forms in a population.