BI210 Exam 2

Adaptive evolution

A process of evolutionary change in which traits that confer survival or reproductive advantages tend to increase in frequency in a population over time

Adaptive radiation

An event in which a group of organisms gives rise to many new species that expand into new habitats or new ecological roles in a relatively short time

Allele

One of two or more forms of a gene that result in the production of different versions of the protein that the gene encodes

Cline

Patterns of change in a characteristic of an organism over a geographic region

Directional selection

Selection that favors individuals with one extreme of a heritable phenotypic trait

Disruptive selection

Selection that favors individuals with a phenotype at either extreme over those with an intermediate phenotype

Evolution

A change over time in the frequencies of different alleles in a population

Evolutionary tree

A branching diagram that represents the evolutionary history of a group of organisms

Fixation

An allele that occurs in a population at a frequency of 100%

Gene flow

Alleles move between populations via movement of individuals or gametes

Genetic drift

A process in which chance events determine which alleles are passed from one generation to the next, thereby causing allele frequencies to fluctuate randomly over time; the effects of genetic drift are most pronounced in small populations

Genotype

The genetic makeup of an individual

Mass extinction

Events in which large proportions of Earth’s species were driven to extinction worldwide in a relatively short time- a few million years or less.

Mutation

A copying error made when cells divide

Natural selection

Individuals with certain heritable traits that survive and reproduce more successfully than other individuals

Phenotype

Observable characteristics that are influenced by the genotype

Recombination

The production of offspring that have combinations of alleles that differ from those in either of their parents

Speciation

The process by which one species splits into two or more species

Stabilizing selection

 Selection that favors individuals with an intermediate phenotype

Trade-off

An organism's allocation of its limited energy or other resources to one structure or function at the expense of another

Allocation

The relative amounts of energy or resources that an organism devotes to different functions

Alternation of generations

A complex life cycle, found in many algae and all plants, in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte

Anisogamy

Production of two types of gametes of different sizes

Competitive plants

Plants that are superior in their ability to acquire light, minerals, water, and space that have a selective advantage

Complex life cycles

A life cycle in which there are at least two distinct stages that differ in their habitat, physiology, or morphology

Direct development

A simple life cycle that goes directly from fertilized egg to juvenile without passing through a free-living larval stage

Dispersal

The movement of organisms or propagules from their birthplace

Fitness

The genetic contribution of an organism's descendants to future generations

Isogamy

The production of equal-sized gametes

Iteroparous

Having the capacity to reproduce multiple times in a lifetime

Life history

The major events relating to an organism's growth, development, reproduction, and survival; these events include the age and size of first reproduction, the amount and timing of reproduction, and longevity

Life history strategy

The overall pattern in the timing and nature of life history events, averaged across all the individuals of a species

K-selection

In the r-K continuum used for classifying life history strategies, the selection pressure for slower rates of increase faced by organisms that live in environments where population densities are high (at or near the carrying capacity, K)

Metamorphosis

 An abrupt transition from a larval to a juvenile life cycle stage that is sometimes accompanied by a change in habitat

Morphs

Discrete phenotypes with few or no intermediate forms

Paedomorphic

Resulting from a delay of a developmental event relative to sexual maturation

Phenotypic plasticity

The ability of a single genotype to produce different phenotypes under different environmental conditions

r-selection

 In the r-K continuum used for classifying life history strategies, the selection pressure for high population growth rates faced by organisms that live in environments where population densities are usually low

Ruderals

Plants that are adapted to habitats with high levels of disturbance and low levels of stress,

short life span, rapid growth rates, heavy investment in seed production are favored

Semelparous

Reproducing only once in a lifetime

Sequential hermaphroditism

A change or changes in the sex of an organism during the course of its life cycle

Stress-tolerant plants

Plants that have slow growth rates, evergreen foliage, slow rates of water and nutrient use, low palatability to herbivores, and an ability to respond temporarily favorable environments

Absolute population size

 The actual number of individuals in a population

Abundance

 The number of individuals of a species that are found in a given area; abundance is often measured by population size or population density

Clone

A genetically identical copy of an individual

Clumped dispersion

A dispersion pattern in which individuals are grouped together

Dispersal limitation

A situation in which a species' limited capacity for dispersal prevents it from reaching areas of suitable habitat

Dispersion

The spatial arrangement of individuals within a population.

Distribution

The geographic area where individuals of a species are present

Disturbance

An abiotic event that kills or damages some individuals and thereby creates opportunities for other individuals to grow and reproduce

Ecological niche

The abiotic and biotic conditions that a species needs to grow, survive, and reproduce

Genet

A genetic individual, resulting from a single fertilization event; in organisms that can reproduce asexually, a genet may consist of multiple, genetically identical parts, each of which has the potential to function as an independent physiological unit

Geographic range

The entire geographic region over which a species is found including areas occupied during all life stages

Line transect

an observer travels by foot, horseback, or vehicle along a transect line

Niche model

A predictive tool that models the ecological niche occupied by a species based on the conditions at locations the species is known to occupy

Population

A group of individuals of the same species that live within a particular area and interact with one another

Population density

The number of individuals per unit of area

Population size

The number of individuals in a population

Ramet

An actually or potentially physiologically independent member of a genet that may compete with other members for resources

Random dispersion

A dispersion pattern that is similar to what would occur if individuals were positioned at locations selected at random

Regular dispersion

A dispersion pattern in which individuals are relatively evenly spaced throughout their habitat

Relative population size

An estimate of population size based on data that are related in an unknown way to the absolute population size, but which can be compared from one time period or place to another

Age structure

The proportions of a population in each age class

Carrying capacity

The maximum population size that can be supported indefinitely by the environment, represented by the term K in the logistic equation

Cohort life table

A life table in which the fate of a group of individuals born during the same time period (a cohort) is followed from birth to death

Density-dependent

Of or referring to a factor that causes birth rates, death rates, or dispersal rates to change as the density of a population changes

Density-independent

Of or referring to a factor whose effects on birth and death rates are independent of population density

Ecological footprint

The total area of productive ecosystems required to support a population

Exponential growth

Change in the size of a population of a species with continuous reproduction by a constant proportion at each instant in time

Exponential growth rate (r)

A constant proportion by which a population of a species with continuous reproduction changes in size at each instant in time; also called the intrinsic rate of increase

Fecundity

The average number of offspring produced by a female while she is of age x (denoted Fx in a life table)

Geometric growth

Change in the size of a population of a species with discrete reproduction by a constant proportion from one discrete time period to the next

Geometric population growth rate (λ)

 A constant proportion by which a population of a species with discrete reproduction changes in size from one discrete time period to the next; also called the finite rate of increase

Life table

A summary of how survival and reproductive rates in a population vary with the age of individuals; in species for which age is not informative or is difficult to measure, life tables may be based on the size or life cycle stage of individuals

Logistic growth

Change in the size of a population that is rapid at first, then decreases as the population approaches the carrying capacity of its environment

Net reproductive rate

The mean number of offspring produced by an individual in a population during its lifetime

Population regulation

A pattern of population growth in which one or more density-dependent factors increase population size when numbers are low and decrease population size when numbers are high

Stable age distribution

When the age structure of a population does not change from one year to the next

Static life table

Survival and reproduction of individuals of different ages during a single time period

Survival rate

The proportion of individuals of age x that survive to be age x + 1 (denoted Sx in a life table)

survivorship

The proportion of individuals that survive from birth (age 0) to age x (denoted lx in a life table)

survivorship curve

A graph based on survivorship data (lx) that plots the numbers of individuals from a hypothetical cohort (typically, of 1,000 individuals) that will survive to reach different ages

Type I survivorship curve

 A survivorship curve in which newborns, juveniles, and young adults all have high survival rates and death rates do not begin to increase greatly until old age

Type II survivorship curve

A survivorship curve in which individuals experience a constant chance of surviving from one age to the next throughout their lives

Type III survivorship curve

A survivorship curve in which individuals die at very high rates when they are young, but those that reach adulthood survive well later in life

Allele effect

A decrease in the population growth rate (r or .) as the population density decreases

Bottom-up control

 Limitation of the abundance of a population by nutrient supply or by the availability of food

Damped oscillations

A pattern of population fluctuations in which the extent to which the population rises and falls in abundance gradually become smaller over time

Delayed density dependence

Delays in the effect of population density on population size that can contribute to population fluctuations

Demographic stochasticity

Chance events associated with whether individuals survive or reproduce

Environmental stochasticity

Erratic or unpredictable changes in the environment

Eutrophication

A change in the nutrient status of an ecosystem from nutrient-poor to nutrient-rich; such changes occur naturally in some lakes due to the accumulation of sediments, but they may also be caused by nutrient inputs that result from human activities

Habitat fragmentation

The breaking up of once continuous habitat into a complex pattern of spatially isolated habitat patches amid a matrix of human-dominated landscape

Inbreeding

Mating between related individuals

Isolation by distance

A metapopulation pattern in which habitat patches located far from occupied patches are less likely to be colonized than are nearby patches

Jump dispersal

A long-distance dispersal event by which a species colonizes a new geographic region

Metapopulation

A set of spatially isolated populations linked to one another by dispersal

Natural catastrophe

An extreme environmental event such as a flood, severe windstorm, or outbreak of disease that can eliminate or drastically reduce the sizes of populations

Outbreak

An extremely rapid increase in the number of individuals in a population

Population cycles

A pattern of population fluctuations in which alternating periods of high and low abundance occur after nearly constant intervals of time