22. Abiotic & Biotic Factors Influencing Organisms

Flashcards covering key terms and concepts related to the abiotic and biotic factors that influence organisms and population growth.

Niche

The environmental factors that influence the growth, survival, and reproduction of a species.

Fundamental Niche

The physical (abiotic) conditions under which a species might live, in the absence of interactions with other species.

Realized Niche

The altered physical conditions under which a species lives as a result of interactions with other species (biotic factors).

Abiotic Factors

Non-living environmental factors that can influence organisms, such as temperature, water, light, and pH.

Biotic Factors

Living factors that affect organisms, including species interactions such as competition, predation, and mutualism.

Intraspecific Competition

Competition between individuals of the same species that can lead to logistic population growth

• Logistic growth occurs when resources are limited and individuals compete for them, slowing growth rate as population reaches carrying capacity

Interspecific Competition

Competition between individuals of different species that can alter population growth.

Competitive Exclusion Principle

Two species with identical niches cannot coexist indefinitely because one will be a more effective competitor for limited resources.

Resource Partitioning

Differentiation of niches that enables similar species to coexist by using similar resources differently

• Species use similar resources but differ in behavior or ecology

• Ex: use different parts of a habitat, feed at different times, etc

Character Displacement

Evolutionary changes in morphology or behavior that reduce competition between species

• Species evolve anatomical differences that allow them to specialize on different resources

• Ex: natural selection favored traits that reduced competition

Camouflage

A form of adaptation where an organism blends with its environment to avoid detection by predators.

Mimicry

The resemblance of one species (the mimic) to another species (the model) to gain some advantage, such as avoiding predation.

Bottom-up Control

Population control influenced by the availability of resources such as food and affects the abundance of organisms at higher trophic levels.

Top-down Control

Population control influenced by natural enemies, such as predators or herbivores and affects lower trophic levels by regulating the populations of prey or plants

Abiotic factors that affect organisms

• Temperature - low temp can freeze organisms, high can denature proteins

• Water - insufficient water limits plant growth, excess water drowns organisms

• Wind - amplifies wind effect and water loss

• Light - insufficient light limits plant growth, and too much can die

• Salinity - high salinity reduces plant growth in terrestrial, affects osmosis in aquatic

  • High concentration of salt in water makes water flow out of organism

• pH - variations in pH affect decomposition and nutrient availability

  • Directly influences mortality in both aquatic and terrestrial habitats

Species Interaction

Various ways in which a species can interact with other species — the biotic factors that define a species’ realized niche

Competition

An interaction that affects two or more species negatively, as they compete over food or other resources (-,-)

• Results in decreased rates of growth, survival, or reproduction that alter population growth rates and can lead to resource depletion.

Predation

An interaction in which the action of a predator results in the death of its prey (+,-)

Herbivory

An interaction in which herbivores feed on plants (+,-)

Parasitism

A symbiotic association in which one organism feeds off another but does not normally kill it (+,-)

Mutualism

A symbiotic interaction in which both species benefit (+,+)

Commensalism

A symbiotic interaction where one species benefits while the other is neither helped nor harmed (+,0)

Types of protection against predators

Chemical defense, displays of intimidation, and armor/weapons

What prevents herbivores from consuming all plants?

1. Predators keep herbivore populations low

2. Plants develop mechanical and chemical defenses

Conditions for a parasite

• May require more than one host at different stages

• May infect many species, or just one or a few

• May reproduce within host, or release juvenile stages outside of host’s body

• May live within host or on host

Resource based mutualism

A mutually beneficial interaction in which both species receive a benefit of energy and nutrients

Ex: Leaf-cutter ants gather leaves and chew them into a pulp that feeds a fungus while fungi produce food for ants

Defensive Mutualism

A mutually beneficial interaction in which one species receives food or shelter in return for defending another species

Dispersive Mutualism

A mutually beneficial interaction in which one species receives food in return for dispersing the pollen or seeds of its partner

10% Rule (regarding bottom-up regulation)

Approximately 10% of the energy from one trophic level is transferred to the next level in a food chain

• Energy is lost as heat and predators don’t fully consume all parts of prey