B4.2 Ecological niches

Niche

Role that an ecosystem plays in its ecosystem

Abiotic interactions

Interactions between an organism and non-living factors in the environment

These can influence where species live and how they survive.

Biotic interactions

Interactions between an organism and other living organisms

These affect access to food, mates, and shelter.

How do biotic and abiotic factors influence a species' growth, survival, and reproduction?

They affect:

• Food availability

• Reproductive success

• Where the species can live (distribution)

• Stress levels and mortality

Obligate anaerobes

Microorganisms that cannot survive in the presence of oxygen.

• In a culture tube organisms move to bottom

• Can use fermentation

Facultative anaerobes

Organisms that can survive with or without oxygen. They can switch between aerobic and anaerobic respiration.

• In a culture tube organisms are dispersed throughout

Obligate aerobes

Organisms that require oxygen to live and carry out aerobic respiration.

• In a culture tube organisms move to top

Holozoic nutrition

A heterotrophic mode of nutrition where organisms ingest, digest, and absorb food internally.

Mixotrophic nutrition

Organisms that can do both (but not fully):

• Autotrophy (e.g., photosynthesis)

• Heterotrophy (e.g., ingestion)

Obtain energy and nutrients from both organic and inorganic sources.

Saprotrophic nutrition

Organisms that obtain nutrients by secreting digestive enzymes, which break up the material into simpler molecules, followed by absorbing and assimilating the nutrients.

• Typically associated with decomposers

Nutrition in archaea

• Metabolism has the ability to survive in extreme environments: extreme salt levels, pH levels, temps, high sulfur, etc.

• Chemoautotrphs: oxidize inorganic chemicals for their metabolism

• Photoautotrphs: light as their source of energy

• Heterotrophs: gain their energy from organic compounds

Dentition in herbivores

Broad, flat molars, small canines → plant grinding

Dentition in omnivores

Mixed teeth → molars (plants) + canines (meat)

These organisms have a combination of broad, flat molars for grinding plants and sharper canines for slicing meat.

Physical Adaptations of Herbivores

• Flat, broad teeth and strong jaws: Adapted for grinding tough plant material.

• Sharp incisors to bite leaves

• Digestive system: ruminant stomach, longer intestines to break down glucose

• Eyes on the sides of the head: Gives a wider field of view to detect predators while grazing.

• Camouflage

Chemical Adaptations of Herbivores

• Saliva can neutralize plant toxins and help with digestion

• Cellulose digestion enzymes

• Detoxification enzymes

Behavioural Adaptations of Herbivores

• Constant search for food

• Social feeding behaviour for protection

• Selective feeding

• Migration to search for areas with fresh plant growth

Adaptations of Plants to Avoid Herbivory

• Thorns and spines

• Thick bark or waxy cuticles: Make it harder for herbivores to chew or digest.

• Trichomes (hair-like structures): Create physical barriers or irritate herbivores.

• Mimicry: Some plants mimic inedible or dangerous species.

• Toxins

• Bitter taste

• Timing of leaf production

• Symbiosis with protective animals

Physical Adaptations of Predators

• Sharp claws and teeth: To catch, kill, and tear prey.

• Forward-facing eyes: For depth perception and better targeting.

• Camouflage: Helps sneak up on prey unnoticed

• Muscular bodies and speed: Allow fast pursuit or pounce attacks

Chemical Adaptations of Predators

• Venom or toxins: Used to immobilize or kill prey

• Digestive enzymes: Start breaking down prey externally or immediately after ingestion

Behavioural Adaptations of Predators

• Hunting in packs: Increases hunting success

• Ambush strategies: Waiting silently for prey to approach

• Luring tactics: Using deception or mimicry to attract prey

Physical Adaptations of Prey to Resist Predation

• Camouflage: Blending with the environment

• Protective structures: Shells, spines, or hard exoskeletons

• Mimicry of dangerous species: Resembling harmful species to deter predators

• Eyes on the sides of the head: Wider field of vision to detect threats early.

Chemical Adaptations of Prey to Resist Predation

• Poision or toxins

• Warning coloration which signal toxicity

• Foul-smelling sprays or secretions

Behavioural Adaptations of Prey to Resist Predation

• Freezing or fleeing: Rapid escape or motionless behavior to avoid detection.

• Alarm calls: Warning others of predator presence

• Group living

• Faking death

Adaptations of plants for harvesting light

• Large leaves to increase surface area

• Chloroplast-rich palisade cells

• Climbing structures to reach sunlight

• Leaf orientation to optimize light absorption

Fundamental niche

The range of environmental conditions in which a particular species can live.

Realized niche

The environmental condition in which the species actually lives.

Competitive exclusion principle

Two species cannot occupy the exact same niche indefinitely. One will outcompete the other, forcing adaptation, relocation, or extinction.

Niche partitioning

The process by which competing species use the environment differently in a way that helps them to coexist. This may be spatial or temporal.