Ecosystems and Material Cycles

Question 1

Individual definition

Answer 1

A single organism

Question 2

Population definition

Answer 2

All organisms of one species in habitat

Question 3

Community definition

Answer 3

All organisms of different species in a habitat

Question 4

Ecosystem

Answer 4

Community of organisms along with all abiotic conditions

Question 5

Interdependence definition

Answer 5

Organisms depend on each other (e.g. for food) as to survive and reproduce
Changes in a population of one species can impact other species in same community

Question 6

Mutualism definition

Answer 6

Relationship between two organisms that benefits both

Question 7

Examples of abiotic factors

Answer 7

Temperature
Amount of water
Light intensity
Levels of pollutants

Question 8

Examples of biotic factors

Answer 8

Competition

Predation

Question 9

Impacts of environmental changes

Answer 9

Population size may change

Distribution of population may change

Question 10

Quadrant definition

Answer 10

Square from enclosing a known area

Question 11

How to use quadrat to study distribution of small organisms

Answer 11

Place quadrat on ground at random point
Count all wanted organisms in quadrat
Repeat steps 1 and 2
Work out mean number of organisms within first sample area
Repeat 1 to 4 for second sample area
Compare the two means

Question 12

How to estimate population size from small sample area

Answer 12

Scale up (extrapolate) mean to total area of habitat

Question 13

How to use belt transfers to study distribution along a gradient

Answer 13

Mark out a line in wanted area to study
Collect data along line using quadrats placed adjacently or at regular intervals
Collect data by counting all organisms of wanted species or by estimating percentage cover
Can collect other data e.g. mean height
Repeat steps 1 to 3 and find mean number of organisms
Plot graphs to study distribution and changing abiotic factor

Question 14

Why most food chains don’t get past 5 trophic levels

Answer 14

Much energy is lost at each trophic level so there is not enough left to support more organisms last 5 trophic levels
Usually fewer organisms at each higher trophic level

Question 15

How energy is left in the food chain

Answer 15

Respiration
Heat
Inefficiency (e.g. undigested material)
Waste (e.g. not all of organism is eaten)

Question 16

What pyramids of biomass show

Answer 16

How much each level of food chain would weigh if all put together
Also see how much energy is at each stage (biomass = energy)

Question 17

Biodiversity definition

Answer 17

Variety of living organisms in an ecosystem

Question 18

Eutrophication steps

Answer 18

Fertilisers enter water, adding excess nitrates in water
Excess nitrate cause algae to grow fast and block sunlight
Underwater plants can’t photosynthesise and die
Microorganisms feed on decomposing plants and increase in number
Organisms that need oxygen (e.g. fish) due to too many microorganisms using up oxygen too

Question 19

How fish farms reduce biodiversity

Answer 19

Food added to nets creates huge waste, which can leak in to open water and cause eutrophication
Fish farms can be breeding ground for parasites, which can escape and kill wild animals
Predators can be lured into nets, get trapped and die
Farmed fish can escape and could cause problems for wild populations of indigenous species

Question 20

How introduction of non-indigenous species can reduce biodiversity

Answer 20

They compete for resources better than indigenous species
Causes natural species to decrease in number or die out
Can also bring new diseases to habitat