c.2- communities and ecosystems

Question 1

most species occupy —— trophic levels in —— —— ——-

Answer 1

different; multiple food chains

Question 2

what does a food web do?

Answer 2

it shows all the possible food chains in a community

Question 3

from what may we be able to predict the type of stable ecosystem that will energy in an area?

Answer 3

from the climate

Question 4

describe how temperature may affect the distribution of organisms

Answer 4

• influences rates of cell respiration, photosynthesis, decomposition, transpiration
• impact on productivity

Question 5

describe how precipitation may affect the distribution of organisms

Answer 5

• influences rates of photosynthesis (the photolysis of water is essential for non-cyclic photophosphorylation) and decomposition
• impacts productivity

Question 6

what depends on respiration rate?

Answer 6

the percentage of ingested energy converted to biomass

Question 7

give the equation for net production value

Answer 7

net production= gross production - respiration

Question 8

define gross production

Answer 8

the total amount of organic matter produced per unit area per unit time by a trophic level in an ecosystem

Question 9

define net production

Answer 9

the amount of gross production remaining after subtraction of the amount used for respiration by the trophic level.

Question 10

describe how gross production, total biomass, and total community respiration vary including a graph

Answer 10

Early stages of primary production:
- high availability of sunlight=> high gross production
- little biomass=> low total amount of respiration.

As succession proceeds:
- biomass increases=> increasing respiration

Later:
- all spaces for stems become filled=> gross production declines
- equilibrium reached:

total community production: total community respiration = 1

Question 11

what is the effect of disturbance to an ecosystem?

Answer 11

it influences the structure and rate of change within ecosystems

Question 12

define secondary succession

Answer 12

the progression of communities where a pre-existing climax community has been disturbed but the soil is already developed

Question 13

what is secondary succession initiated by?

Answer 13

by a change in conditions

Question 14

describe the effects of disturbance on an ecosystem

Answer 14

• close to time of disturbance, rate of system respiration, productivity, and species diversity increase rapidly and there is an accumulation of biomass
• as succession proceeds, the pace of change slows.

Question 15

describe primary succession

Answer 15

Occurs when communities develop on entirely new land without any established soil (ie at river deltas, glaciers, sand dunes or on exposed rock)
- organisms which first colonise the region are called pioneer species and typically consist of lichen or moss
- as the lichen and moss die, they decompose, which creates the first organic soil capable of sustaining plant growth
- as plant species colonise the area, the litter produced by their growth and their decomposing remains will cause soil depth, mineral content, and water retention to increase
- this will allow for the growth of larger plants, which will reduce erosion through the binding action of their roots
- larger plants will eventually outcompete smaller shade intolerant plants

Question 16

give 5 examples of aspects of an ecosystem that you could investigate

Answer 16

• species diversity
• nutrient cycling
• water movement
• erosion
• leaf area index

Question 17

closed system

Answer 17

energy but not matter is exchanged with the surroundings

Question 18

isolated system

Answer 18

theoretical; exchange neither matter nor energy with their surroundings

Question 19

open system

Answer 19

exchange matter and energy with their surroundings

Question 20

define feed conversion ratios

Answer 20

the quantity of dietary input in grams required to produce a certain quantity of body mass in livestock or fish.

Question 21

give an example of how humans interfere with nutrient cycling

Answer 21

agriculture
- phosphate is mined, converted to fertiliser and used.
- nitrogen is produced from gaseous N2 in the Haber process has increased inputs into the n cycle
- these are added to the soil so that agriculture can occur.

Question 22

construct and explain a gersmehl diagram for taiga

Answer 22

check

Question 23

construct and explain a gersmehl diagram for desert

Answer 23

check

Question 24

construct and explain a gersmehl diagram for tropical rainforest

Answer 24

check

Question 25

what is a gerhsmehl diagram?

Answer 25

a model of nutrient storage and flow for terrestrial systems

Question 26

tropical rainforest

Answer 26

• most nutrients stored as biomass; litter is rapidly decomposed and vast roots quickly draw nutrients from soil
• there is a fast rate of transfer between stores; hot and wet weather conditions promote precipitation, runoff, weathering, and leaching

Question 27

taiga

Answer 27

• most nutrients stored as litter; low temperatures slow decomposition which delays nutrient transfer to soil and biomass
• there is little nutrient gain from precipitation or weathering due to low levels of rainfall (cold temperatures produce snow)
• there is little nutrient loss via leaching (due to low rainfall) but surface runoff may be high at certain times (if the snow melts)

Question 28

desert

Answer 28

• most nutrients stored in the soil (few plants exist to store nutrients as biomass or produce litter)
• there is little nutrient gain from precipitation and little nutrient loss via runoff due to very low levels of rainfall
• the amount of weathering and leaching is negligible