B4.2 Ecological Niche

Factors affecting the niche of species

BIOTIC factors

• include living things

• food availability, predators

ABIOTIC factors

• temperature, soil nutrients, light, and other non-living factors

Niche Construction

the process by which an organism alters its own or other species local environment

• ex: earth worms chemically + physically modify the soil, thus other aquatic animals can live on the land

Types of Ecological Niches

Fundamental niche

• niche of an org. when there are no limiting factors on the environment + resources the organism can use

• theoretical, pre-competitive

• potential of a spp based on adaptations + tolerance limits

Realized niche

• niche that’s occupied by a viable population of a species in the presence of competitor spp

• post-competitive, actual

• actual extent of a spp when in competition with other spp

Competitive exclusion

two diff spp cannot occupy the same niche → if 2 spp share a niche, this leads to INTERSPECIFIC COMPETITION for resources

• inevitably, 1 spp will hv an advantage over the other

• the less well-adapted spp will struggle to survive and reproduce

Resource Partitioning

2 spp can avoid competing for the same resource by choosing different time for feeding or different foraging behavior

Types of Resource Partitioning

• temporal

  • same resources but diff time

• spatial

  • use of diff habitat of resources

• morphological

  • use of body shape + size

Importance of ecological niches

• niches reduce competition for resources

• interspp competition → evolutionary change

• niche includes spot in food chain (if missing → may cause whole chain to die)

• segregation of organisms into niches avoids confusion of activities in the community + more order

• allows for full exploitation of all available resources

Differences b/t obligate anaerobes, facultative anaerobes, obligate aerobes

Obligate Aerobes: require O2

Obligate Anaerobes: killed by O2

Facultative Anaerobes: grow better with O2 but can live without it

Mode of Nutrition in different organisms

an organism’s mode of nutrition depends a lot on its ecological niche + the adaptations to the biotic and abiotic factors

Autotroph

• synthesize organic compounds (sugar, aa, fats) by using other sources of energy

  • photoautotroph

    • produce organic compounds from CO2, water, and light energy thru PS

  • chemoautotroph

    • producce org. compounds from other elements (iron, NH3) thru chemosynthesis

Heterotroph

• obtain org. compounds by consuming other organisms internally or externally

  • saprotrophs

    • secrete enzymes onto dead + decaying matter and digesting externally (decomposer)

  • parasites

    • obtains food from other organism without killing it

  • holozoic

    • complex food particles are taken in and broken down

    • herbivore

    • carnivore

    • omnivore

    • detritivore (an animal that feeds on dead organic material, especially plant detritus)

Mixotroph

• organism that uses a mix of different sources of energy and carbon, instead of having a single trophic mode, on the continuum from complete autotrophy to complete heterotrophy

Photosynthesis as the mode of nutrition in plants, algae, and several groups of photosynthetic prokaryotes

yes

Holozoic (obtaining nourishment as animals do by ingesting complex organic matter) nutrition in animals

animals obtain their nutrients by consuming food

the large food molecules must be broken down into smaller ones before they can be absorbed into the bloodstream + transported to cells in the body where needed

• ingestion: eat

• digestion: breaking down food

• absorption: moving food into cells

• assimilation: making food part of cells

• elimination/egestion: remove unused food

single celled organisms like amoeba can do holozoic nutrition even w/o multi-organ controlled digestive system by endocytosis/engulfment