4. Modes of Nutrition Flashcards
Define ‘species’.
is a group of organisms with similar characteristics, which can potentially interbreed and produce fertile offspring.
Define ‘population’.
is a group of organisms of the same species, who live in the same area at the same time.
Can members of the same species be reproductively isolated in separate populations?
Yes.
Bearing in mind the definition of ‘species’, is the species that is ‘reproductively isolated in separate populations’ still the same species?
- Yes.
- Even though the two populations do NOT interbreed (‘reproductively isolated’), they still have the potential to interbreed if they came together. They are therefore the SAME species.
Give an example of members of the same species that are ‘reproductively isolated in separate populations’.
- wood mouse (Apodemus sylvaticus)
- lives in Britain and Iceland
- two populations do not interbreed, but they could, so they are the same species.
What are the two main modes of nutrition?
- autotrophic
- heterotrophic
Define ‘autotroph’ (but in a really simple way).
organisms that make their own food
Define ‘heterotroph’ (but in a really simple way).
organisms that get food from other organisms
What do autotrophs do? (the complicated bit).
- absorb: carbon dioxide, water, and inorganic nutrients such as nitrates
- from: the abiotic (non-living) environment and
- use: them to synthesize all the carbon compounds that they need.
- an external energy source - light is needed to do all that.
What do heterotrophs do? (the complicated bit).
- cannot make all carbon compounds they need
- obtain them from other organisms
- many carbon compounds including proteins or starch must be digested before they can be absorbed and used.
What are the 3 main modes of heterotrophic nutrition?
- saprotrophs (saprotrophic nutrition)
- consumers (holozoic nutrition)
- detritivores (parasitism)
Where and how do saprotrophs obtain their “food”?
obtain organic nutrients from dead organisms by external digestion
How do saprotrophs obtain their “food”?
through external digestion:
- secrete digestive enzyme into material
- e.g. dead leaves, wood, dead animals, feces
- protein, cellulose and other carbon compounds are digested externally then saprotroph absorbs substances it needs
What are saprotrophs also known as?
decomposers
What sort of organisms are saprotrophs?
bacteria or fungi
How do consumers feed?
on living organisms by ingestion:
- take other organisms into digestive system for digestion and absorption
- organism may be swallowed whole or in parts
- alive or recently killed
Give two examples of consumers feeding.
- deer eat leaves of plants which are alive
- vultures eat parts of an animal which has been killed
Where and how do detritivores obtain “food”?
obtain organic nutrients from detritus by internal digestion
What is ‘detritus’ in the context of detritivores eating it?
dead material from living organisms
- e.g dead leaves or roots, parts of decomposing animals and feces
Give an example of a detritivore feeding.
- honey bees (this is not the detritiovore) secrete wax to make comb in their colonies
- larvae (this is the detritivore) of the wax moth, feed on the wax comb
- the moths prefer old comb which contains protein-rich pupal cases of honey bees in it.
What are most plants and algae? Are there any exceptions? If yes, how come?
- autotrophs
- yes
- obtain carbon compounds from other organisms, they are therefore heterotrophs
Give 2 examples of plants/algae that are heterotrophic.
- dodder (Cuscuta europaea): obtains carbon compounds directly from plants - specifically the stems of other plants
- ghost orchid (Epipogium aphyllum): obtains carbon compounds from fungi living on roots of trees
There are exceptions to the rule ‘all plants/algae are autotrophs’. What are the implications of this?
we cannot assume that a plant or alga is autrotrophic
