Biology 151 Chapter 20-22 And 56-58 Vocab

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Inheritance of acquired characteristics

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Also known as Lamarckism; the theory, now discounted, that individuals genetically pass on to their offspring physical and behavorial changes developed during the individuals' own lifetime.

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Population genetics

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The study of the properties of genes in populations.

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Polymorphism

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The presence in a population o fmore than one allele of a gene at a frequency greater than that of newly arising mutations.

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Hardy-Weinberg principle

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Principle that the original proportions of the genotypes in a population will remain constant from generation to generation, as long as the following assumptions are met:
1. No mutation takes place.
2. No genes are transferred to or from other sources (gene flow).
3. Random mating IS occurring.
4. The population size is very large.
5. No selection occurs.

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Hardy-Weinberg equilibrium

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A methematical description of the fact that allele and genotype frequencies remain constant in a random-mating population in the absence of interbreeding, selection, or other evolutionary forces; usually stated: if the frequency of allele "A" is p and the frequency of allele "a" is q, then the genotype frequencies after one generation of random mating will always be (pp) + 2pq + (qq) = 1.

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Allele frequency

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A measure of the occurrence of an allele in a population, expressed as proportion of the entire population, for example, an occurrence of 0.84 (84%).

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Genotype frequency

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A measure of the occurrence of a genotype in a population, expressed as a proportion of the entire population, for example, an occurrence of 0.25 (25%) for a homozygous recessive genotype.

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Assortative mating

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A type of nonrandom mating in which phenotypically similar individuals mate more frequently.

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Disassortative mating

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A type of nonrandom mating in which pheotypically different individuals mate more frequently.

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Genetic drift

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Random fluctuation in allele frequencies over time by chance.

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Founder effect

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The effect by which rare alleles and combinations of alleles may be enhanced in new populations.

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Bottleneck effect

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A loss of genetic variability that occurs when a population is reduced drastically in size.

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Selection

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The process by which some organisms leave more offspring than competing ones, and their genetic traits tend to appear in greater proportions among members of succeeding generations than the traits of those individuals that leave fewer offspring.

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Frequency-dependent selection

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A type of selection that depends on how frequently or infrequently a phenotype occurs in a population.

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Oscillating selection

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The situation in which selection alternately favors one phenotype at one time, and a different phenotype at another time, for example, during drought conditions versus during wet conditions.

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Heterozygote advantage

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The situation in which individuals heterzygous for a trait have a selective advantage over those who are homozygous; an example is sickle cell anemia.

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Disruptive selection

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A form of selection in which selection acts to eliminate rather than to favor the intermediate type.

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Directional selection

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A form of selection in which selection acts to eliminate one extreme from an array of phenotypes.

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Stabilizing selection

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A form of selection in which selection acts to eliminate both extremes from a range of phenotypes.

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Industrial melanism

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Phrase used to describe the evolutionary process in which initially light-colored organisms become dark as a result of natural selection.

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Homologous structures

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Similar structures that have the same evolutionary origin.

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Biogeography

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The study of the geographic distribution of species.

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Convergent evolution

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The independent development of similar structures in organisms that are not directly related; often found in organisms living in similar environments.

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Sympatric speciation

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The differentiation of populations within a common geographic are into species.

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Subspecies

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A geographically defined population or group of populations within a single species that has distinctive characteristics.

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Biological species concept (BSC)

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The concept that defines a species as groups of populations that have the potential to interbreed and that are reproductively isolated from other groups.

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Reproductively isolated

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Populations whose members do not mate with each other or who cannot produce fertile offspring and therefore, are members of a different species are said to be this.

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Reproductive isolating mechanisms

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Any barrier that prevents genetic exchange between species.

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Prezygotic isolating mechanisms

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A type of reproductive isolating mechanism in which the formation of a zygote is prevented.

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Postzygotic isolating mechanisms

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A type of reproductive isolating mechanism in which zygotes are produced but are unable to develop into reproducing adults.

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Geographic isolation

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A type of prezygotic isolating mechanism in which species occur in different areas and are often separated by a physical barrier, such as a river or mountain range. Example: Similar flowers on different continents would never even get the opportunity to mate.

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Ecological isolation

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A type of prezygotic isolating mechanism in which species occur in the same area, but occupy different habitats and rarely encounter each other. Example: The ranges of lions and tigers overlapped until about 150 years ago. No natural hybrids occurred because lions stayed in the open grassland in groups and tigers tended to be solitary and live in the forest.

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Behavioral isolation

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A type of prezygotic isolating mechanism in which species differ in their mating rituals. Example: The Galapagos blue-footed boobies select their mates only after an elaborate courtship display. They display behavior of the other two species of Galapagos boobies is very different, as is the color of their feet.

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Pheromones

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Chemical substance released by one organism that influences the behavior or physiological processes of another organism of the same species. Pheromones serve as sex attractants, as trail markers, and as alarm signals.

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Temporal isolation

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A type of prezygotic isolating mechanism in which species reproduce in different seasons or at different times of the day. Example: Two different species of wild lettuce grow together along roadsides throughout Southeastern United States. Hybrids between these two species are easily made experimentally and are completely fertile, but do not normally occur in nature because one lettuce flowers in early spring and the other flowers in summer.

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Mechanical isolation

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A type of prezygotic isolating mechanism in which structural differences between species prevent mating. Example: In many insect and arthropod groups, the sexual organs, particularly those of the male, are so diverse that they are used as a primary basis for distinguishing species.

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Prevention of gamete fusion

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A type of prezygotic isolating mechanism in which gametes of the one species function poorly with the gametes of another species or within the reproductive tract of another species. Example: In animals that shed gametes directly into water, the eggs and sperm derived from different species may not attract or fuse with one another.

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Allopatric speciation

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The differentiation of geographically isolated populations into distinct species.

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Reinforcement

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A process in which initially incomplete isolating mechanisms are reinforced by natural selection until they are completely effective.

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Hybrid inviability or infertility

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A type of postzygotic isolating mechanism in which hybrid embryos do not develop properly, hybrid adults do not survive in nature, or hybrid adults are sterile or have reduced fertility. Example: The offspring of a horse and a donkey, mules are infertile.

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Polyploidy

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Condition in which one or more entire sets of chromosomes is added to the diploid genome.

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Positive frequency-dependent selection

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By favoring common forms, this type of frequency-dependent selection tends to eliminate variation from a population.The rarer a genotype becomes, the greater the chance it will be selected against.

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Negative frequency-dependent selection

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Rare phenotypes are favored by this type of frequency-dependent selection. Rare genotypes should become increasingly common, and their selective advantage will decrease correspondingly.

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Autoploidy

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A polyploid organism that contains a duplicated genome of the same species; may result from a meiotic error.

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Allopolyploidy

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A polyploid organism that contains the genomes of two or more different species.

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Adaptive radiation

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The evolution of several divergent forms from a primitive and unspecialized ancestor.

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Key innovation

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A newly evolved trait in a species that allows members to use resources or other aspects of the environment that were previously inaccessible.

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Character displacement

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A process in which natural selection favors individuals in a species that uses resources not used by other species. This results in evolutionary change leading to species dissimilar in resource use.

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Gradualism

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The view that species change very slowly in ways that may be imperceptible from one generation to the next but that accumulate and lead to major changes over thousands or millions of years.

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Stasis

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A period of time during which little evolutionary change occurs.

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Metapopulations

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Species that exist as a network of distinct populations that interact with one another by exchanging individuals. Usually occur in areas in which suitable habitat is patchily distributed and is separated by intervening stretches of unsuitable habitat.

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Source-sink metapopulations

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Species may also exhibit a metapopulation structure in areas in which some habitats are suitable for long-term population maintanence, but others are not. In these situations, the populations in the better areas (the sources) continually send out dispersers that bolster the populations in the poorer habitats (the sinks). In the absence of such continual replenishment, sink populations would have a negative growth rate.

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Demography

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The properties of the rate of growth and the age structure of populations.

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Generation time

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The average interval between the birth of an individual and the birth of its offspring.

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Fecundity

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The number of offspring produced in a standard time.

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Mortality

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The number of individuals that die in a standard time.

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Age structure

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The relative number of individual's in each cohort defines this part of a population.

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Life table

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This tabulates the fate of a cohort from birth until death, showing the number of offspring produced and the number of individuals that die each year.

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Mortality rate

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The proportion of individuals that started a certain interval alive but died by the end of it.

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Survivorship

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The percentage of an original population that survives to a given age.

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Semelparity

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A life history adaptation in which an organism focuses all their reproductive resources on a single large event and then die.

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Iteroparity

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A life history adaptation in which an organism produces offspring several times over many seasons.

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Biotic potential

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The rate at which a population of a given species increases when no limits are placed on its rate of growth.

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Carrying capacity

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The maximum number of individuals that the environment can support.

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Sigmoidal growth curve

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The plot of N (number of individuals present at any one time) versus t (time) that is charcteristic of many biological populations. This curve has a double curve like the letter "S".

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Density-dependent effects

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As a population size increases, either reproductive rates decline or mortality rates increase, or both. This occurs when reproduction and survival are affected by population size.

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Density-independent effects

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Growth rates in populations sometimes do not correspond to the logistic growth equation. Such patterns often result because growth is under the control of these.

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K-selected population

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A population that is adapted to thrive when the population is near its carrying capacity.

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r-selected population

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A population in which selection favors individuals with the highest reproductive rates.

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Population pyramid

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A bar graph displaying the numbers of people in each age category.

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Community

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The species that occur at any particular locality.

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Species richness

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The number of species present in a community.

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Productivity

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The amount of energy produced in a community.

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Holistic concept

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This views communities as an integrated unit. The community is viewed as a superorganism whose constiuent species coevolved to the extent that they function as part of a greater whole.

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Ecotones

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Places where the environment changes abruptly.

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Niche

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May be described in terms of space utilization, food consumption, temperature range, appropriate conditions for mating, requirements for moisture, and other factors.The total of all the ways an organism uses the resources of its environment.

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Interspecific competition

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This occurs when two species attempt to use the same resource and there is not enough of the resource to satisfy both.

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Interference competition

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Physical interactions over access to resources are referred to as this.

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Exploitative competition

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Consuming the same resources is called this.

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Fundamental niche

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The entire niche that a species is capable of using, based on its physiological tolerance limits and resource needs, is called this.

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Competitive exclusion

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This principle states that if two species are competing for a limited resource such as food or water, the species that used the resource more efficiently will eventually eliminate the other locally.

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Realized niche

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The actual set of environmental conditions, including the presence or absence of other species, in which the species can establish a stable population is this.

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Resource partitioning

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This occurs when species competing for a similar resource subdivide the niche to avoid direct competition with one another.

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Predation

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The consuming of one organism by another.

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Coevolution

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The process by which adaptations are selected in lockstep fashion in two or more interacting species.

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Batesian mimicry

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A form of defense against predators in which mimics were avoided by the predators which had been fooled into thinking the mimic was the distasteful species it looked like.

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Mullerian mimicry

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This occurs when several unrelated but protected species come to resemble one another. If animals that resemble one another are all poisonous or dangerous, they gain an advantage because a predator will learn more quickly to avoid them.

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Commensalism

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Type of relationship in which one species benefits and the other neither benefits nor is harmed.

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Mutualism

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Type of relationship in which both participating species benefit.

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Parasitism

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Type of relationship in which one species benefits but the other is harmed.

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Parasitoids

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Insects that lay eggs in or on living hosts.

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Endoparasites

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Parasites that live within the body of their hosts and occur within many different phyla of animals and protists.

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Keystone species

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Species whose effects on the composition of communities are greater than one might expect based on their abundance are termed this.

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Succession

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The tendency of a community to change from simple to complex, even when the climate of an area remains stable year after year.

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Secondary succession

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This occurs in areas where an existing community has been disturbed but organisms still remain. Such as if a wooded area is cleared and left alone, and plants slowly reclaim the area.

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Primary succession

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This occurs on bare, lifeless substrate where organisms gradually move into an area and change its nature.

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Aquifers

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Permeable, underground layers of rock, sand, and gravel that are often saturated with water.

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Nitrification

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A process in which, after NH3 has been synthesized, other prokaryotic microbes oxidize part of it to form NO3.

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Nitrogen fixation

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The synthesis of nitrogen-containing compounds from N2.

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Denitrification

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The process in which additional prokaryotic microbes are able to convert the nitrogen in NO3 into N2.