4. Modes of Nutrition

Question 1

Define ‘species’.

Answer 1

is a group of organisms with similar characteristics, which can potentially interbreed and produce fertile offspring.

Question 2

Define ‘population’.

Answer 2

is a group of organisms of the same species, who live in the same area at the same time.

Question 3

Can members of the same species be reproductively isolated in separate populations?

Answer 3

Yes.

Question 4

Bearing in mind the definition of ‘species’, is the species that is ‘reproductively isolated in separate populations’ still the same species?

Answer 4

• 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.

Question 5

Give an example of members of the same species that are ‘reproductively isolated in separate populations’.

Answer 5

• wood mouse (Apodemus sylvaticus)
• lives in Britain and Iceland
• two populations do not interbreed, but they could, so they are the same species.

Question 6

What are the two main modes of nutrition?

Answer 6

• autotrophic

- heterotrophic

Question 7

Define ‘autotroph’ (but in a really simple way).

Answer 7

organisms that make their own food

Question 8

Define ‘heterotroph’ (but in a really simple way).

Answer 8

organisms that get food from other organisms

Question 9

What do autotrophs do? (the complicated bit).

Answer 9

• 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.

Question 10

What do heterotrophs do? (the complicated bit).

Answer 10

• 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.

Question 11

What are the 3 main modes of heterotrophic nutrition?

Answer 11

• saprotrophs (saprotrophic nutrition)
• consumers (holozoic nutrition)
• detritivores (parasitism)

Question 12

Where and how do saprotrophs obtain their “food”?

Answer 12

obtain organic nutrients from dead organisms by external digestion

Question 13

How do saprotrophs obtain their “food”?

Answer 13

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

Question 14

What are saprotrophs also known as?

Answer 14

decomposers

Question 15

What sort of organisms are saprotrophs?

Answer 15

bacteria or fungi

Question 16

How do consumers feed?

Answer 16

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

Question 17

Give two examples of consumers feeding.

Answer 17

• deer eat leaves of plants which are alive

- vultures eat parts of an animal which has been killed

Question 18

Where and how do detritivores obtain “food”?

Answer 18

obtain organic nutrients from detritus by internal digestion

Question 19

What is ‘detritus’ in the context of detritivores eating it?

Answer 19

dead material from living organisms

- e.g dead leaves or roots, parts of decomposing animals and feces

Question 20

Give an example of a detritivore feeding.

Answer 20

• 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.

Question 21

What are most plants and algae? Are there any exceptions? If yes, how come?

Answer 21

• autotrophs
• yes
• obtain carbon compounds from other organisms, they are therefore heterotrophs

Question 22

Give 2 examples of plants/algae that are heterotrophic.

Answer 22

• 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

Question 23

There are exceptions to the rule ‘all plants/algae are autotrophs’. What are the implications of this?

Answer 23

we cannot assume that a plant or alga is autrotrophic