T19 Feeding Relationships

Question 1

define trophic levels

Answer 1

e feeding levels in a food chain

Question 2

describe what happens at each tropic level

Answer 2

Producers - Organisms that make their own food by photosynthesis, e.g. plants and
algae
Primary consumers - Herbivores that only eat plants (producers)
Secondary consumers - Carnivores that eat primary consumers
Tertiary consumers - Carnivores that eat secondary consumers. They have no predators and so
are called the apex predators
Decomposers - Bacteria and fungi that break down dead animal’s body and waste for
energy, using enzymes

Question 3

arrows go from the ____ to the ________ showing the transfer of ______

Answer 3

prey
predator
energy

Question 4

what do pyramids of numbers show

Answer 4

Shows the population of each organism at each trophic level of
food chain

Question 5

how do pyramids of numbers work

Answer 5

● Producers are at the bottom and bars usually get smaller the
further up you go
● However, if the producer is a large plant, e.g. a tree, the size of the bar is very small as one tree can feed many insects (primary consumers)

Question 6

what does pyramid of biomass show?

Answer 6

s show the relative biomass/ dry mass at each trophic level

Question 7

what is biomass

Answer 7

all water removed from organism, to measure against starting mass

Question 8

how does the pyramid of biomass work

Answer 8

● There is less biomass as you move up the trophic levels.
● Not all the food consumed by an animal is converted into biomass – this means the biomass of the organism in the level above another will always be higher, as not all the organism can be consumed and converted into biomass.

ALWAYS SHAPE OF PYRAMID - less energy at each trophic level

Question 9

why can it be difficult to get valid data for a pyramid of biomass:

Answer 9

measuring dry biomass means that all the water has to be removed from the organisms

an organism may belong to more than one trophic level, so it cannot easily be represented by one bar

Question 10

what does a pyramid of energy transfer show?

Answer 10

approximately 10% of the biomass of each trophic level is transferred to the next
SO ALWAYS PYRAMID SHAPED

Question 11

why is only approximately 10% of the biomass of each trophic level transferred to the next:

Answer 11

Not all biomass can be eaten.
○ Carnivores cannot generally eat bone, hooves, claws and teeth.
● Not all of the biomass eaten is converted into biomass of the animal eating it.
○ Lots of glucose is used in respiration, which produces the waste product carbon dioxide
○ Urea is a waste substance which is released in urine
○ Biomass consumed can be lost as faeces - herbivores do not have all the enzymes to
digest all the material they eat, so it is egested instead

Question 12

Efficiency of biomass transfers =

Answer 12

(Biomass transferred to the next level / Biomass available at the previous level) x 100

Question 13

why is it common to have only 4 trophic levels?

Answer 13

Because less biomass is transferred each time it is common to have a limited number of trophic levels
and to find less animals in the higher trophic levels.

Question 14

equation for photonsynthesis

Answer 14

glucose + oxygen –> carbon dioxide + water + some ATP

Question 15

equation for photosynthesis

Answer 15

carbon dioxdie + water –> glucose + oxygen

Question 16

describe the stages of the carbon cycle:

Answer 16

Respiration
● Plants and animals aerobically respire, which
releases CO2 into the air
● Decomposers also respire while the break
down compounds
Photosynthesis
● Plants remove CO2 from the air through
photosynthesis to make glucose for respiration
Decomposition
● Dead plants and animals are broken down by
decomposers
● The carbon is then returned into the
atmosphere by repiration of plants and animals
Combustion
● When plants and fossil fuels (remains of dead animals) are burnt, the carbon dioxide are
released into the atmosphere

Question 17

Describe the stages of the nitrogen cycle:

Answer 17

Assimilation
Plants absorb nitrogen from the soil in the form of nitrates (unlike the carbon cycle where they absorb carbon in the form of CO2 from the air)
Feeding
Animals obtain nitrogen containing compounds such as protein from the plants and animals they feed on (just like the carbon cycle)
Decomposition
When plants and animals decay the nitrogen containing compounds are digested by
bacteria and fungi. They are converted to ammonia and released into the soil (unlike the C cycle where CO2 is released into the air by the process of respiration)

Nitrifying bacteria
Plants can’t take up ammonia directly. The ammonia is converted (oxidised) to nitrites then nitrates by nitrifying bacteria.
The cycle can then start again.
Denitrifying bacteria
Denitrifying bacteria convert N compounds in the soil to nitrogen gas reducing the amount of nitrate in the soil. This occurs in low oxygen environments such as Water logged Soil.
Nitrogen fixation
Nitrogen fixing bacteria convert nitrogen gas from the atmosphere to ammonia
Some nitrogen fixing bacteria are free living in the soil and release ammonia into the
(peas)
soil, others live in root nodules of I & gum inous plants e.g. clover and the bacteria have a mutualistic relationship donating amino acids to the plant in return for
glucose

Lightning - so much energy, reacts nitrogen and oxygen to form nitrates in soil
Leguminous plants - nitrogen fixing bacteria in root nodules

Question 18

What is a food chain

Answer 18

Shows feeding relationships between organisms, organised by trophies levels

Question 19

What are food webs

Answer 19

Collection of different food chains to show how organisms in habitat interact with each other, and how population numbers can affect the whole ecosystem