b4.2 ecological niches

ecological niche

role of a species in an ecosystem

obligate aerobe

require continuous o2 supply so only live in oxic env

obligate anaerobe

inhibited/killed by oxygen so only live in anoxic env

facultative anaerobe

• use oxygen if its avail so live in either oxic or anoxic env. (they switch from aerobic to anaerobic ONLY if there's no oxygen)

Photosynthesis is the mode of nutrition in which types of organisms?

• plants

• eukaryotic algae including seaweeds that grow on rocky shores and unicellular algae such as Chlorella​

• several groups of bacteria including cyanobacteria (blue–green bacteria) and purple bacteria.

• (in 2 of the 3 domains - eukaryotes and bacteria, not archaea)

all animals mode of nutrition

heterotrophic - cannot produce its own food, obtain c compounds from other organisms

holozoic nutrition

whole pieces of food are ingested before being fully digested internally, absorbed and assimilated

mixotrophic

• mixotrophic nutrition is not exclusively autotrophic or heterotrophic

• Example is euglena, a freshwater protist that is both autotrophic and heterotrophic.

• It has chloroplasts and carries out photosynthesis when there is sufficient light (auto), but it can also feed on detritus or smaller organisms by endocytosis (hetero).

obligate vs facultative mixotrophs

• obligate mixotrophs cannot grow unless they utilize both autotrophic and heterotrophic modes of nutrition. (food that they consume supplies them with carbon compound that they cannot synthesise themselves)

• Facultative mixotrophs like euglena can continue to grow using either autotrophic or heterotrophic nutrition, they do not need both at all times

saprotrophic nutrition

• Fungi and bacteria (decomposers)

• secrete digestive enzymes into the dead organic matter (break down carbon compounds) and digest it externally, then absorb the products of digestion.

diversity of nutrition in archea

• phototrophic (absorption of light energy by pigments other than chlorophyll)

• chemotrophic (oxidation of inorganic chemicals, for example Fe2+ ions to Fe3+​)

• heterotrophic (oxidation of carbon compounds obtained from other organisms)​

• they dont photosynthesise!!

Adaptations of herbivores for feeding on plants

• jaw like mouthparts for biting off, chewing and ingesting pieces of leaf

• tubular mouthparts for piercing leaves/stems to reach phloem sieve tubes and feed on sap

Adaptation of plants for resisting herbivory

• tough sharp pointed spines so herbivores risk injury when eating it

• stings to cause pain

• synthesise secondary metabolites that are toxic to herbivores, stored in seeds (attractive to herbivores bcs high conc of protein/starch/oil)

• Note: plant herbivore specificity → herbivores have responded to toxic compounds in plants by developing metabolic adaptations for detoxifying them, only a few species of herbivore adapted to feed on a particular plant

types of adaptations in predators and prey

• chemical (slowest to change)

• physical (longer to develop bcs there must be genetic change)

• behavioral (change relatively quickly)

Adaptations of plant form for harvesting light - forest ecosysems

• Trees have a dominant leading shoot that grows rapidly to great height to reach the forest canopy where they are unshaded by other trees.​

• Lianas climb through other trees, using them for support. This means lianas do not need to produce as much xylem tissue (wood) as free-standing trees. ​

• Epiphytes grow on the trunks and branches of trees, so they receive higher light intensity than if they grew on the forest floor, but there is minimal soil for their roots.​

• Strangler epiphytes climb up the trunks of trees encircling them and outgrowing their branches, to shade out the leaves of the tree. Eventually the tree dies leaving only the epiphyte. (parasite)​

• Shade-tolerant shrubs and herbs absorb light reaching the forest floor

fundamental vs realised niches

• fundamental niche is the potential of a species based on adaptations and tolerance limits (no competitors)

• realised niche is the actual extent of a species niche when in competition with other species

What are the possible outcomes of competition between two species?

• When there are overlapping fundamental niches, and one species outcompetes the other in all parts of the fundamental niche, the outcompeted species does not have a realised niche and will be competitively excluded from the whole ecosystem

• Or, both may be restricted to a part of their fundamental niche

holozoic vs saprotropic

autotrophic vs heterotropic vs mixotroph

facultative vs obligate