Ch. 6-Communities and Ecosystem Dynamics

Habitat

A place or environment where an organism lives, defined by specific physical and biological conditions such as climate, water availability, soil type, and food resources

Niche

The role and function of an organism in an ecosystem, including how it uses resources, its behavior, diet, reproduction, interactions, and where/when it is active

Habitat Determining Factors

Climate, availability of water, soil type, and availability of food and shelter that influence where organisms can live

Niche Determining Factors

Diet, activity patterns, location in the ecosystem, interactions with other organisms, reproduction strategies, and resource use

Tolerance

The range of environmental conditions (temperature, pH, salinity, etc.) in which a species can survive and reproduce

Importance of Tolerance

Determines where a species can live and survive; organisms outside their tolerance range will die or fail to reproduce

Resource Sharing

When organisms reduce competition by dividing or sharing available resources instead of directly competing for the same ones

Competition

Interaction where organisms compete for limited resources such as food, space, light, or mates; it can limit population size and influence behavior and evolution

Competitive Exclusion Principle

Two species cannot occupy exactly the same niche in the same habitat for long; one will outcompete and exclude the other

Predator-Prey Relationship

Interaction where one organism (predator) hunts, kills, and eats another organism (prey), influencing population cycles and adaptations

Herbivore–Plant Relationship

Interaction where herbivores consume plants or plant parts for energy, affecting plant populations and driving plant defenses

Keystone Species

A species that has a disproportionately large effect on its ecosystem relative to its abundance; its removal can cause major ecosystem changes

Example of Keystone Species (Sea Otters)

Sea otters control sea urchin populations; without otters, urchins overgraze kelp forests, leading to ecosystem collapse

Symbiosis

A close and long-term relationship between two different species living together

Mutualism

Symbiotic relationship where both organisms benefit (ex: bees get nectar, flowers get pollinated)

Commensalism

Symbiotic relationship where one organism benefits and the other is neither helped nor harmed (ex: barnacles on whales)

Parasitism

Symbiotic relationship where one organism benefits while the other is harmed (ex: ticks feeding on dogs)

Predation

Relationship where one organism kills and eats another organism

Competition (Ecological Relationship)

Interaction where organisms compete for the same limited resources such as food, space, light, or mates

Ecological Succession

The gradual process by which ecosystems change and develop over time after a disturbance or formation of new land

Primary Succession

Ecological succession that occurs in an area with no soil or life (ex: bare rock); pioneer species like lichens begin soil formation

Secondary Succession

Ecological succession that occurs where soil already exists after a disturbance such as fire or flooding

Pioneer Species

First organisms to colonize a barren or disturbed environment; they help form soil and begin succession

Climax Community

A stable, mature ecosystem that has reached equilibrium and remains relatively unchanged until disturbed

Difference Between Primary and Secondary Succession

Primary occurs with no soil and is slower; secondary occurs with soil already present and is faster

Biodiversity

The variety of life in an area, including genetic diversity, species diversity, and ecosystem diversity

Genetic Diversity

Variation in genes within a species population

Species Diversity

The number and variety of different species in an ecosystem

Ecosystem Diversity

The variety of ecosystems in a region or on Earth

Benefits of Biodiversity

Provides stability, resilience, and ecosystem balance; allows other species to fill roles if one species declines

Ecosystem Services

Benefits humans receive from ecosystems, including food, water, oxygen production, pollination, and raw materials like wood and paper