HL Bio - Ecology (I): B4.2 Ecological Niches

Define niche

The role of a species within its habitat####What happens when two species fill the same niche?

Biotic factors - camouflage to avoid predation####Define obligate aerobes

Organisms which require continuous oxygen supply, so only live in oxic environments

Requires oxygen to metabolise substance to produce ATP through aerobic cellular respiration####Define obligate anaerobes

Organisms that are killed by oxygen, so only lives in anoxic environments

Lack enzymes to break down toxic forms of oxygen####Define facultative anaerobes

Organisms which use oxygen in available, so can live in either oxic or anoxic environments####Define photosynthesis

Facultative: can survive using one method of nutrition, supplemented by the other####Describe Euglena and its mixotrophic nutrition

Euglena is a well known freshwater example of a protist that is both autotrophic and heterotrophic

Euglena cells can take in bacterial cells by endocytosis, and digest them using digestive enzymes in lysosomes

Euglena cells also contain a light sensitive spot that enables them to position themselves so that maximum light reaches chloroplasts####Define saprotrophs

Heterotrophs that ingest the tissues of dead organisms and waste material by secreting enzymes onto their food and digesting it externally

Fungi and bacteria####Define archaea

A diverse group of single celled organisms comprising one of three domains####Describe adaptations of herbivores for feeding on plants and plants for resisting herbivory (stylets, mandibles, toxins)

Insects such as caterpillars and beetles have mandibles which allow them to cut through leaves

Nettles have tiny hairs that contain toxins which irritate the skin####Describe adaptations of Predators for finding, catching and killing prey and of prey animals for resisting predation (chemical, physical, behavioural)

Chemical: predators produce venom which makes prey easier to catch. Spider venom contains toxins - subdue prey

Physical: predators have sense organs that help them detect the presence or prey. Birds have excellent vision - detect prey

Behavioural: ambush predators lie in wait without moving for extended periods. Puff adders can remain motionless for weeks at a time while they wait for prey to come near####How do trees, lianas, strangler epiphytes, shade tolerant shrubs and herbaceous plants adapt to harvest light?

Trees: maximise height, to gain the most sunlight; carries out photosynthesis at a high rate

Lianas: use tree trunks as their main supporting structure to gain height

Epiphytes: grows high up in tree branches; gains nutrients from high in the canopy

Strangler Epiphytes: grows roots downward to the floor to gain nutrients and water from the soil

Shade tolerant shrubs and herbaceous plants: contains different photosynthetic pigments, allowing them to absorb different wavelengths of light####Distinguish between fundamental niche and realised niche

Fundamental - the full range of conditions and resources in which a species could survive and reproduce, based on its adaptations and tolerance limits

Realised - the actual conditions and resouces in which a species exists, due to biotic interactions####What happens when one species is competitively excluded?

Either:

Forced to occupy a new, slightly different niche

or

Made locally extinct####