B17 - Organising an ecosystem

Question 1

How can feeding relationships be represented, and what do they always start with?

Answer 1

-food chain/web
-always starts with a producer

Question 2

What do the arrows on a food chain/web represent?

Answer 2

the transfer of biomass/energy

Question 3

What are producers?

Answer 3

photosynthetic organisms (plants/algae) that synthesise glucose molecules from PS to produce the biomass for all the life on earth

Question 4

How do algae get energy?

Answer 4

from light that is absorbed by its chloroplasts

Question 5

What are the types of consumers?

Answer 5

-primary (eats producer)

-secondary (eats primary)

-tertiary (eats secondary)
(top is apex predator)

Question 6

What is a predator/prey?

Answer 6

-predators hunt + eat other animals
-prey are eaten by predators

Question 7

Describe the cyclic relationship between the populations of predators and prey:

Answer 7

-food availability increases, prey increases (grows and reproduces successfully)

-more food for predators, predators increase

-prey decreases because they get eaten, less food for predators so they decrease too

-less predation, so the prey population increases again
-repeat

Question 8

What is a problem that a primary consumer might have with their food?

Answer 8

-must use a variety of methods to digest cellulose which is hard to do
-needs to find/eat enough food to get nutrients

Question 9

What is a problem that a higher consumer (secondary/tertiary) might have with getting food?

Answer 9

must hunt the prey because they move around, but it is good because they are high in protein/fat

Question 10

What gets recycled in an ecosystem, and why is it important?

Answer 10

-chemical abiotic factors (water, carbon) gets cycled through other abiotic and biotic factors in an ecosystem

-important as it provides the building blocks for future organisms

Question 11

Why is the water cycle important?

Answer 11

continuously provides fresh water for animals/plants on land before draining into the sea again

Question 12

What are the main processes that occur during the water cycle?

Answer 12

-evaporation/transpiration/respiration
-condensation
-precipitation
-runoff (surface/river)

(E, CPR)

Question 13

What is a carbon sink? Give some examples:

Answer 13

-a “locked up” store of carbon that absorbs more CO₂ than it can release

-carbonate-based rocks (limestone)
-oceans (CO₂ dissolved in it)
-fossil fuels
-atmosphere
-peat bogs

Question 14

Why is the carbon cycle important?

Answer 14

it returns carbon from organisms to the atmosphere as CO₂ which can then be used by plants for PS, which produce the biomass for all life on Earth

Question 15

Describe the full process of the carbon cycle:

Answer 15

-plants take in CO₂ from the atmosphere for PS
-plants eaten by primary consumers that both respire
-plants + consumers die/produce waste
(2 paths after)

-either decomposed, returns CO₂ to atm. (by resp.) and releases mineral ions to soil
-or it is fossilised and forms fossil fuels which are combusted, releasing the carbon back into the atm.

Question 16

What role do microorganisms have in an ecosystem?

Answer 16

they cycle materials through an ecosystem by returning carbon to the atmosphere as CO₂, and mineral ions to the soil

Question 17

What factors affect the rate of decomposition?

Answer 17

-temperature (enzymes)
-moisture (microorganisms grow faster)
-oxygen (for resp.)
-presence of decomposers (more = ^rate)

Question 18

What happens if decay occurs without oxygen, and what can it be used for?

Answer 18

-slower anaerobic decay, which produces methane gas

-process can be done in a biogas generator for fuel

Question 19

How is compost made and what is it used for?

Answer 19

-food/garden waste is decomposed (gardener’s try to ensure optimum conditions for the process)

-natural fertiliser for growing garden plants/crops

Question 20

How can the distribution of species in an ecosystem be affected?

Answer 20

-environmental changes in temperature, water availability, and atmospheric gas composition

-these changes may be seasonal, geographical, or caused by human interaction

An example of how composition of gases affects the ecosystem is with lichen - it doesn’t grow as much in areas which have lots of air pollution

Question 21

RP10 - How would you prepare the apparatus for investigating the effect of temperature on the rate of milk decay?

Answer 21

-add lipase to labeled boiling tube
-add Cresol red to another boiling tube then add milk and label it
-add sodium carbonate to the milk tube (should make it purple)
-put both milk and lipase tubes into water bath and allow temperatures to equilibrate

Question 22

RP10 - Using the previously made test tubes in the water bath, how would you use them to find the effect of temperature on the rate of decay?

Answer 22

-use pipette to transfer 1cm^3 lipase to the milk and start timing
-record time for colour change of purple to yellow
-repeat experiment for at least 5 temperatures
-plot graph of time taken vs temperature

The lipase accelerates the decay of the milk

Remember the practical where you asked for a reference colour to compare to the yellow solution

Question 23

RP10 - Explain the reason for the colour change in the milk decay experiment:

Answer 23

-lipids in milk are broken down into fatty acids by lipase
-the fatty acids decrease the pH
-the Cresol red indicator turns from purple to yellow (more acidic)

The original colour of purple is from the sodium carbonate solution added, which makes the solution more alkaline