B4.2 Ecological Niches Notes

Vocabulary flashcards covering niche concepts, modes of nutrition (autotroph, heterotroph, holozoic, mixotrophs), archaeal energy strategies, plant–herbivore interactions, predation adaptations, plant adaptations for light, and niche theory including competitive exclusion.

Niche

The role of an organism in an ecosystem, including how it uses resources and interacts with biotic and abiotic factors, affecting survival, reproduction, nutrition, and growth.

Biotic factors

Living components that affect organisms in an ecosystem (other living organisms and their interactions).

Abiotic factors

Non-living components that affect organisms (temperature, moisture, light, soil, etc.).

Obligate anaerobe

An organism that cannot survive in the presence of oxygen; it uses anaerobic respiration or fermentation.

Facultative anaerobe

An organism that can survive with or without oxygen; can switch between aerobic respiration and fermentation.

Obligate aerobe

An organism that requires oxygen for survival and uses aerobic respiration only.

Autotroph

An organism that makes its own food, typically via photosynthesis or other inorganic energy sources.

Heterotroph

An organism that must obtain food from other organisms; all animals are heterotrophs.

Holozoic nutrition

A form of heterotrophic nutrition where ingestion, digestion, and assimilation of organic material occur.

Mixotroph

An organism that can perform both autotrophy (photosynthesis) and heterotrophy (feeding on others).

Obligate mixotroph

A mixotroph that requires both autotrophic and heterotrophic nutrition to survive; neither mode alone suffices.

Facultative mixotroph

A mixotroph that can switch between autotrophic and heterotrophic nutrition depending on conditions.

Saprotroph

An organism that feeds on dead organic matter by external digestion of food, secreting enzymes.

Archaea

One of the three domains of life; energy can be produced via phototrophy, chemolithotrophy, or organotrophy.

Phototroph

An organism that uses light to make ATP; some examples do not release oxygen (anoxygenic photosynthesis).

Chemolithotroph

An organism that derives energy from the oxidation of inorganic chemicals (e.g., ammonia, nitrites, sulfur).

Organotroph

An organism that derives energy from the oxidation of organic carbon compounds (sugars, fatty acids).

Omnivore

An organism that eats both plants and animals; e.g., Homo sapiens is an omnivore.

Herbivore

An organism that primarily eats plants; e.g., Paranthropus robustus.

Incisors

Front teeth adapted for cutting or ripping food.

Molars

Back teeth specialized for grinding food.

Plant defenses (general)

Strategies to deter herbivores, including physical defenses, chemical defenses, and structural features.

Physical defenses

Structural barriers like thorns or spines that deter feeding.

Chemical defenses

Toxins, tannins, alkaloids, and bitter-tasting compounds produced by plants.

Structural features

Waxy cuticles and silica in leaves that reduce herbivory damage.

Grazing adaptations

Teeth and jaw features adapted for grazing and processing plant material.

Detoxifying enzymes

Enzymes that animals use to neutralize or break down plant toxins.

Symbiotic gut bacteria

Microbes in the digestive system that help digest cellulose from plants.

Allelopathy

The release of chemicals by one organism that affects the germination, growth, survival, or reproduction of another.

Juglone

An allelopathic chemical produced by black walnut trees that can inhibit competitors.

Allelopathic substances

Chemicals secreted by plants (e.g., Tectona grandis, rice, sorghum) to suppress weeds.

Predator adaptations

Physical, chemical, and behavioral traits that help predators find, catch, and kill prey.

Camouflage

A visual disguise that helps predators or prey blend into the environment.

Venom

Toxins injected by some predators to immobilize or kill prey.

Alarm calls

Vocal signals used to warn other individuals of a predator.

Nocturnality/Diurnality

Activity patterns: nocturnal (night) or diurnal (day) to avoid predators or optimize foraging.

Lianas

Woody climbers that ascend canopy trees to reach light; use twisting, adhesive pads, or hooks; rapid, flexible growth; large leaves.

Epiphytes

Plants that grow on other plants (usually branches) to access light; broad leaves and flexible growth.

Strangler epiphytes

Epiphytes that germinate on a host tree, send aerial roots downward, and eventually encircle and outcompete the host for light.

Shade-tolerant shrubs and herbs

Plants with broad leaves, branching, and high chlorophyll to maximize light capture in low light.

Fundamental niche

The potential niche an organism could occupy in the absence of competition.

Realized niche

The actual niche occupied by an organism due to competition and other interactions.

Competitive exclusion principle

No two species can occupy the same ecological niche; the better-adapted species excludes the other.

Chthamalus vs Balanus (barnacles)

Chthamalus has a wider fundamental niche but is excluded from lower zones by faster-growing Balanus; Balanus cannot survive higher zones, so Chthamalus persists there.

Grey squirrels vs red squirrels

Grey squirrels are larger, reproduce faster, and are immune to squirrel pox, allowing them to outcompete red squirrels for food and habitat.