Organisms in the Environment & Feeding Relationships

Question 1

Define biotic factors

Answer 1

The biological (living) factors that influence the number and distribution of organisms in an ecosystem

Question 2

Define abiotic factors

Answer 2

The chemical and physical (non-living) factors that influence the number and distribution of organisms in an ecosystem

Question 3

Define ecosystem

Answer 3

A distinct and self supporting system that relies on interactions with each other and the physical environment around

Question 4

Define decomposers

Answer 4

Organisms that break down dead organic matter (detritus) into soluble substances (e.g. sugars)

Question 5

Define population

Answer 5

All organisms of a particular type of species found in an ecosystem at a certain time

Question 6

Define community

Answer 6

The population of all species together in an ecosystem at a certain time

Question 7

Define biodiversity

Answer 7

The amount of variation shown by species in an ecosystem

Question 8

Biodiversity is the combination of which 2 measurements?

Answer 8

• The number of different species present (species richness)
• The relative abundance of each species (‘evenness’ of numbers)

Question 9

Define biome

Answer 9

Large areas of the Earth which are dominated by a specific type of vegetation (plants and tress collectively)

Question 10

What is the start of all food chains?

Answer 10

The sun

Question 11

Give 4 examples of biotic factors that might affect a species’ abundance and distribution

Answer 11

• Disease
• Presence of certain species
• Organic pollution
• Availability of space for habitat

Question 12

Give 4 abiotic factors that might affect a species’ abundance and distribution

Answer 12

• Light intensity, temperature, water availability
• Hours of daylight
• Soil conditions (nitrate level, pH, water content)
• Inorganic pollution

Question 13

Why is random sampling used? (2)

Answer 13

• To avoid bias
• To compare the abundance of an organism in two sites

Question 14

Why is systematic sampling (belt or line transect) used?

Answer 14

In order to look at the distribution of an organism

Question 15

Describe an experiment to compare the population of two plants in two different habitats (8)

Answer 15

• Select two different areas of study
• Generate 10 sets of coordinates using random numbers (1-10)
• Lay out two 10m tape measures at right angles to form two sides of a square on the first area
• Use the coordinates and lay the quadrat
• Count the number of plants of each species in the quadrat
• Repeat for the other 9 sets of coordinates
• Repeat the process in the second area
• Use the data to estimate the total population size of each species on the two different lawns

Question 16

Define trophic levels

Answer 16

It describes the position of the organism in a food chain

Question 17

What does a food web show?

Answer 17

The interactions between multiple food chains

Question 18

Why is only about 10% of energy transferred from trophic level to the next? (5)

Answer 18

• Lost through respiration
• Some parts are not eaten
• Lost through heat from metabolic processes
• Used for movement and growth
• Not absorbed and egested with faeces

Question 19

Define biomass

Answer 19

The measure of total mass of living material in each trophic level

Question 20

What are pyramids of number? (2)

Answer 20

• Represents the number of organisms in each trophic level of a food chain
• Irrespective of mass

Question 21

What are pyramids of biomass?

Answer 21

• Represents the total mass of organisms of each trophic level
• Irrespective of their numbers

Question 22

What are pyramids of energy?

Answer 22

• Measured in kJ per m2 per year
• Represents the energy a group of organisms in a trophic level adds to their biomass per year