Chapter 3: Ecosystems, Biomes, Populations

Biomass

The organic material in living organisms

Species

A group of individuals capable of interbreeding and having fertile offspring

Population

All individuals of the same species living in a given area

Community

All groups of populations in a given area

Ecosystem

The living (biotic) community and non-living (abiotic) factors in a given area

Open system

A type of system which exchanges mass or energy with other systems

Closed systems

A type of system which there is no exchange of mass or energy with other systems

Producers

Autotrophs; organisms capable of photosynthesis

Consumers

Heterotrophs; organisms that are not capable of photosynthesis

Tropic level

In an ecological community all the organisms that are the same number of food chain steps from the primary source of energy

Niche

The role of an organism or species, or the environmental conditions under which an individual or species can persist

Herbivore

An organism that feeds only on autotrophs or plants

Carnivore

An organism that feeds only on heterotrophs/ animals

Omnivore

Plants and animals

Detritivore

An organism that feeds on dead and decaying organisms and waste

Chemosynthesis

The synthesis of organic compounds by energy derived from chemical reactions, such as those involving sulfurs compounds

Ecosystem services

The processes by which life-supporting resources are produced; aka public service functions

Keystone species

A species that has a large effect on its community or ecosystem so that its removal of or addition to the community leads to major changes in the abundance of other species; ex: sea otter

Indicator species

A species that defines a trait or characteristic of the environment, such as the presence of pollutants; ex. Frogs

Specialist species (k-selected strategist)

A type of species characterized by relatively slow growth, a small number of offspring, and a long lifespan

Generalist species (r-selected species)

A type of species characterized by relatively fast growth, a large number of offspring, and a short lifespan

Biome

a type of ecosystem characterized by a dominant type of vegetation

Tundra

Cold and treeless biome with low growing vegetation

Taiga (boreal forest)

Coniferous forest with cold winters and short growing seasons

Conifer

A cone-bearing tree

Evergreen

A tree that does not lose all of its leaves at once

Deciduous forest

A forest comprised of trees that lose all of their leaves at once (autumn)

Habitat

Where an individual, population, or species exists

Succession

The process of establishment and development of an ecosystem

Intermediate disturbance hypothesis

Ecosystems experiencing moderate levels of disturbance are more diverse than those with high or low disturbance

Net [primary] production

The production that remains after utilization; calculated as the gross production minus the energy used in respiration

Gross [primary] production

The production before respiration losses are subtracted

Carrying capacity

The maximum abundance of a population or species that can be maintained by a habit or ecosystem without degrading the ability of that habitat or ecosystem to maintain that abundance in the future

Exponential growth

Rate of increase is a constant percentage of current size; symbolized by a j-shaped curve

Logistic growth

Rapid growth followed by slow-down, until population reaches a constant size; symbolized by an S-Shaped curve

Fertility

Number of births

Morality

Number of deaths

Migration

Movement of individual, population, or species from one habitat to another

Fragmentation

Separation

Biodiversity

Genetic diversity, species diversity and/or ecosystem/habitat diversity

Bottleneck event

a reduction in a populations size reduces its genetic variation

Founder effect

A change in the gene pool descending from a small number of colonizing individuals

Allopathic speciation

Caused by geographic isolation (physical separation from others of the same species)

Sympatric speciation

The evolution of one species into another, without geographic isolation

Competitive exclusion principle

Two populations of different species with exactly the same requirements cannot persist indefinitely in the same habitat

Resource partitioning

Two species divide a resource based on differences in their behavior or morphology

Sex ratio

The ratio of males to females in a population

Density-dependent factors

Influence an individuals probability of survival and reproduction in a manner that depends on the size of the population; ex. Predation, food shortage

Density independent factors

Have the same effect on an individuals probability of survival and reproduction at any population size: ex. Flood, fire

Type 1 survivorship

high survival throughout most of the life span; individuals die most often at old age (k-selected species)

Type 2 survivorship

Relatively constant decline in survivorship throughout most of the life span; ex. Squirrels

Type 3 survivorship

Few individuals reach adulthood; ex. Mosquitos

Gene pool

The available alleles for a particular genetic trait

Background extinction rate

The average rate at which species go extinct; about one species in a million every year

Estuary

Wetlands; places where freshwater and saltwater mingle; nurseries for aquatic species