Key Concepts in Ecology and Population Dynamics

Population

Members of same species living in the same area

Community

A group of populations living in the same area

Ecosystem

Area where organisms in a community interact with their physical environment

Biosphere

Consists of all regions of earth containing living things

Habitat

Type of place where organism usually lives, including other organisms as well as physical, chemical environment

Competitive exclusion principle

When two species compete for the same resources (or occupy the same niche), one is likely to be more successful and the other will be eliminated

Predator

Organism that kills and eats another

Ecological/trophic efficiency

Describes energy proportion represented at one trophic level that is transferred to the next

Trophic level

Energy, biomass, and quantity of organisms is highest at the 1º producer level and lowest at the 3º/4º consumer level

Type I Survivorship Curve

Most survive to middle age and die quicker after that

Type II Survivorship Curve

Length of survivorship is random

Type III Survivorship Curve

Most die young, and few survive to reproductive age and beyond

Energy transfer efficiency

On average, an efficiency of about 10% is transferred to the next trophic level

Energy loss

The remaining 90% is lost to metabolism, heat, & detrivores

Parasite

Organism that spends most of its life living on host and consuming nutrients from it

Herbivore

Organism that eats plants; herbivores have adapted to eating plants only by developing long intestinal tracts to fully absorb nutrients

Niche

Set of conditions & resources an organism needs and interactions it has with other species

Fundamental niche

Niche that an organism occupies when there are no competing species present

1º Producers

Autotrophs that convert sun energy into chemical energy [E.g., plants, cyanobacteria (organisms that can perform photosynthesis)]

1º Consumers

Herbivores that eat primary producers

2º Consumers

Primary carnivores that eat primary consumers

3º Consumers

Secondary carnivores that eat secondary consumers

Detritivores

Consumers that obtain energy by consuming detritus (dead matter consisting of leaves, animal remains, and waste products)

Realized niche

Smaller subset of the niche that species occupy when competition is present

Competition

Interaction between organisms that occurs when resources are limited, and multiple organisms requiring the same limited resources

Symbiosis

Interactions between two species

Mutualism (+/+)

Both organisms benefit [E.g., Nitrogen fixing bacteria & legumes, E.g., Bees pollinating flowers]

Commensalism (+/o)

One benefits, other is unaffected [E.g., Remora & shark, E.g., Whale & barnacle]

Parasitism (+/-)

Benefits at the expense of the host [E.g., Virus & host cell - all viruses are parasites, E.g., Ticks feeding off cats]

Nitrogen Cycle

Describes how nitrogen moves from the environment to living organisms and from living organisms back into the environment.

Fixation

Nitrogen must go through 'fixation' to be converted from its environmental form to a form usable by organisms.

Denitrification

Nitrogen must go through denitrification to be converted from the form used by organisms to the form that exists in the environment.

Biological magnification

As one organism eats another, toxins become more concentrated at higher trophic levels.

Eutrophication

Process where water becomes enriched with excess nutrients and biomass.

Succession

Change in composition of ecological community over time.

1º succession

Occurs on substrates that never previously supported living things (E.g., lichen growing on a rock previously devoid of life).

2º succession

Occurs where communities were entirely/partially destroyed by damaging event (E.g., forest regrowing after wildfire).

Pioneer species

First to colonize a newly exposed habitat; they are usually opportunistic, can tolerate harsh conditions, grow fast, and produce progeny rapidly.

Tropical grasslands

Characterized by high temperature, uneven seasonal rainfall, and scattered trees.

Tropical rain forest

Most diverse biome with high humidity and heavy rainfall.

Savannas

Grasslands with scattered trees and a seasonal occurrence of drought and fire.

Temperate grasslands

Regions with low precipitation, temperature fluctuations, and large mammals grazing.

North American prairie

A type of temperate grassland characterized by large mammals grazing.

Deserts

Regions with very little rainfall, extreme temperatures, and minimal vegetation.

Chaparral

A biome along California coastline with wet winters and dry summers.

Taigas

Cold forests with long cold winters and moderate precipitation.

Tundras

Cold regions with permafrost and minimal vegetation.

Temperate deciduous forests

Forests where large deciduous trees shed leaves during winter.

Vertical stratification

The layering of different plant species in a habitat, often seen in forests.

Detritivorous bacteria

Bacteria that decompose organic matter and can deplete oxygen in aquatic environments.

Realized niche:

Smaller subset of the niche that species occupy when competition is present