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Passenger pigeon

Once most abundant bird in N. America; more than all other N.A. birds combined. Last flock destroyed in 1896; last one died in 1914 in a Cincinnati Zoo. Humans killed species in just 50 years

Natural Selection

The process by which traits that enhance survival and reproduction are passed on more frequently to future generations than those that do not, thus altering the genetic makeup of populations through time.

Alfred Russell Wallace

English naturalist who proposed, independently of Charles Darwin, the concept of natural selection as a mechanism for evolution and as a way to explain the great variety of living things

Logistical growth curve

A population graph that initial shows exponential growth and then plateaus because the population maxes out the ecosystems carrying capacity.

Charles Darwin

English naturalist. He studied the plants and animals of South America and the Pacific islands(Galapagos), and in his book On the Origin of Species by Means of Natural Selection (1859) set forth his theory of evolution.


The genetic changes in populations of organisms through generations by means of natural selection.

Adaptive trait

Any heritable trait that enables an organism to survive through natural selections and reproduce better under prevailing environmental conditions


Random errors in gene replication that lead to a change in the sequence of nucleotides; the source of all genetic diversity


The formation of new combinations of the different alleles of each gene on a chromosome; the result of crossing over.

Directional selection

Form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve

Stabilizing selection

Form of natural selection in which the entire curves area begins to form in the middle. Favors intermediate types of the species.

Disruptive selection

Form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle

selective breeding

The process of selecting a few organisms with desired traits to serve as parents of the next generation.

Artificial selection

The selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits.


The variety of organisms in a given area, the genetic variation within a population, the variety of species in a community, or the variety of communities in an ecosystem


A group of organisms so similar to one another that they can breed and produce fertile offspring


A group of organisms of the same species in a given area


The process by which a new species evolves from a prior species, the most basic process in macroevolution.

Allopatric Speciation

Speciation due to organisms of a species being separated by geographical barriers so that eventually they become so different that they cannot interbreed.

Sympatric Speciation

Speciation that occurs within one area - some factor other than geographical separation has prevented free interbreeding between members of the species.

Bottleneck effect

Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population.

Genetic drift

The gradual changes in gene frequencies in a population due to random events

Phylogenetic trees

Also called cladograms, a treelike diagram that represents the history of divergence of species or other taxonomic groups of organisms

Burgess Shale

Canadian fossil formation that contains Cambrian soft-bodied organisms as well as organisms with hard parts. Fossils date from approximately 530 million years ago.


Disappearance of a species from all parts of its geographical range

Survivorship curves

They show the likelihood of survival at different ages throughout the lifetime of the organism. Type 1 (high probability of death at old age - humans, elephants). Type 2 ( straight equal probability of death at all age - birds). Type 3( high probability of death at young age -Toads)


A disease that is constantly present to a greater or lesser degree in people of a certain class or in people living in a particular location

Background extinction rate

The average rate at which species go extinct over the long term. Approximately 10 per year.

Mass extinction events

The extinction of a large proportion of the worlds species in a very short time period due to some extreme and rapid change or catastrophic event. There has been five of these in the bast half billion years.


Father/son team that first proposed that a giant asteroid caused the K-T extinction.

K-T Mass extinction

This mass extinction event was the most recent and occurred approximately 65 million years ago. Killed off 70% of all living species including dinosaurs. Proposed meteorite origin was proposed by the Alvarez scientists by comparing iridium levels.

Adaptive radiation

Process by which a single species or small group of species evolves into several different forms that live in different ways; rapid growth in the diversity of a group of organisms. Example of this is birds with different beaks adapted to different beaks.


All the parts of the planet that are inhabited by living things; sum of all earth's ecosystems

Population ecology

The study of populations in relation to the environment, including environmental influences on population density and distribution, age structure, and variations in population size.

Community Ecology

The study of how interactions between species affect community structure and organization.

Ecosystem Ecology

The study of energy flow and the cycling of chemicals among the various biotic and abiotic factors in an ecosystem.


A specific biological community and its physical environment interacting in an exchange of matter and energy.


The place or set of environmental conditions in which a particular organism lives.

Habitat selection

The process by which organisms actively select habitats in which to live


The full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions


Species with a narrow niche and thus having very specific requirements to survive in their ecosystem.


Species with a broad niche who are able to live in a large variety of habitats or use a wide variety of resources.

Population density

The number of organisms per unit area.

Population dispersion

Also known as distribution, the way in which individuals of a population are spread in an area or volume; the three types are clumped, uniform, and random

Uniform distribution

The distribution characteristic of a population with a relatively regular spacing of individuals, commonly as a result of territorial behavior

Clumped distribution

The most common type of population distribution where many members of the population live close together(usually near resources), humans for example. Also called patchy.

Random distribution

Distribution in which the location of members in a population is totally random, location of each individual is determined by chance.

Sex ratio

The proportion of males to females. To maximize population growth needs to be 50/50.

Age structure

The number and proportion of people at each age in a population

Age Pyramids

A way to display information about the number of organisms alive in particular age groups of a population.

Crude birth rate

The number of live births in a given period of time per thousand organisms.

Crude death rate

The number of deaths in a given time span per 1,000 organisms.

Growth rate

An expression of the increase in the size of an organism or population over a given period of time. (Sorry but this time I'm too lazy to add the formula)


The movement of organisms OUT of a population


The movement of organisms INTO a population

Exponential Growth

Growth of a population that multiplies by a constant factor at constant time intervals(geometric increases). Forms J-shaped curve.

Carrying capacity

The largest number of individuals of a population that a given environment can support at a given time.

limiting factors

Any biotic or abiotic factor that restricts the existence, numbers, reproduction, or distribution of organisms

Environmental resistance

All the limiting factors that tend to reduce population growth rates and set the maximum allowable population size or carrying capacity of an ecosystem

density dependent factors

Limiting factors (such as competition, predation, parasitism, and disease) that are affected by the number of individuals in a given area

density independent factors

Limiting factor that affects all populations in similiar ways, regardless of population size.

Biotic potential

The maximum reproductive rate of an organism, given unlimited resources and ideal environmental conditions

Gestation period

The length of time between fertilization and birth

k selected

Organisms that reproduce later in life, produce fewer offspring and devote significant time and energy to the nurturing of their offspring. Populations usually stabilize at carrying capacity.

r selected

Organisms that reproduce early in life and often and have a high capacity for reproductive growth(biotic potential). Populations usually fluctuate greatly.

Golden Toad

Is now extinct, used to live in the Costa Rican cloud forests; could be due to El Nino, fungus or Global climate change, restricted range of its habitat, airborne pollution, lower pH levels


A form of tourism that supports the conservation and sustainable development of ecologically unique areas.

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