IB Biology Topic B4.2: Ecological Niches Key Definitions

Absorption is the process by which digested nutrients are transported into the body, primarily occurring in the small intestine.

Assimilation is the process by which absorbed nutrients are transported to cells and used for growth, repair, and energy production.

Two species cannot coexist indefinitely in the same ecological niche if resources are limiting.

Digestion is the process of breaking down food into smaller, absorbable molecules.

An ecological niche encompasses more than just the physical location where a species lives (its habitat). It describes how an organism interacts with its environment, including both the biotic (living) and abiotic (non-living) components.

Egestion is the final step in holozoic nutrition, involving the removal of undigested and unabsorbed material as feces.

Extracellular enzymes work outside cells to break down large molecules into smaller, absorbable units.

Facultative anaerobes are versatile organisms that can adapt to both oxic (oxygen-rich) and anoxic (oxygen-free) environments.

Facultative mixotrophs can function as either autotrophs or heterotrophs, depending on environmental conditions.

The fundamental niche represents the full range of environmental conditions and resources a species could theoretically occupy if there were no competition, predation, or other biotic limitations.

A greenhouse gas is a gas that contributes to the greenhouse effect by absorbing infrared radiation

Holozoic nutrition is the process by which animals obtain energy and nutrients by consuming other organisms or organic matter.

Ingestion is the first step in holozoic nutrition, where animals take food into their bodies.

Kleptoplasty is the process by which certain marine mixotrophs "steal" chloroplasts from the algae they consume and use them for photosynthesis.

Mixotrophs are organisms that can obtain energy and carbon through both autotrophic and heterotrophic modes of nutrition.

Obligate aerobes are organisms that depend on oxygen for aerobic respiration, a process that efficiently generates ATP (energy) by breaking down glucose.

Obligate anaerobes find oxygen toxic. These organisms thrive in anoxic (oxygen-free) environments, such as deep ocean sediments, swamps, or the guts of animals.

Obligate mixotrophs require both autotrophic and heterotrophic modes of nutrition to survive.

Pollination is the transfer of pollen from the anther to the stigma, a critical step preceding fertilization.

The true extent of a species’ presence in an ecosystem.

Saprotrophic nutrition is a mode of heterotrophic nutrition where organisms derive energy and nutrients by feeding on dead or decaying organic material.

The range of abiotic conditions a species can withstand.