Populations

Question 1

Define ecology

Answer 1

The study of the relationships between living organisms, including humans, and their physical environment.

Question 2

Define ecosystem

Answer 2

A balanced biological system where all the organisms (community) and the non-living components interact in a particular location. There is energy flow and nutrient cycling within the ecosystem.

Question 3

Define community

Answer 3

Interacting populations of two or more species in the same habitat at the same time.

Question 4

Define habitat

Answer 4

The place where an organism lives.

Question 5

Define population

Answer 5

A group of organisms of a single species, interbreeding and occupying a particular habitat.

Question 6

Define environment

Answer 6

The factors in a habitat which affect an organism - both living (biotic) and non-living (abiotic).

Question 7

Define niche

Answer 7

The role and position of an organism within its environment, including all interaction with the biotic and abiotic factors of its environment.

Question 8

When will population size increase? (equation)

Answer 8

reproduction + immigration are greater than deaths + emigration.

Question 9

List the four stages of a population growth curve

Answer 9

Lag, log/exponential, stationary, death/decline

Question 10

What is carrying capacity?

Answer 10

The maximum number of individuals a habitat/environment can sustain

Question 11

What causes the lag phase in a bacterial fermenter?

Answer 11

Enzymes are being synthesised, genes for the enzymes being switched on

Question 12

What could cause the death phase in a bacterial fermenter?

Answer 12

Accumulation of toxic waste, or resources run out (glucose or O2)

Question 13

Define a density dependent factor

Answer 13

A factor that affects population size and is affected by population size

Question 14

Define a density independent factor

Answer 14

A factor that affects population size and is not affected by population size

Question 15

What is the ultimate source of energy for most ecosystems?

Answer 15

The sun

Question 16

What is the difference between inter and intraspecific competition?

Answer 16

Inter is between different species, intra is within one species

Question 17

Why is photosynthetic efficiency not 100?

Answer 17

Sunlight misses the leaves, is transmitted, is reflected, is the wrong wavelength, is not absorbed by the chloroplasts.

Question 18

Give the assumptions made during capture mark recapture (Lincoln Index)

Answer 18

No migration, birth or death, marked individuals distribute themselves evenly, the marking does not increase likelihood of death from predators and is not toxic

Question 19

Define GPP

Answer 19

Gross Primary Productivity is is the rate of production of chemical energy in organic molecules by photosynthesis in a given area. The unit is kJ m-2 year-1

Question 20

Define NPP

Answer 20

Net Primary Productivity = GPP - energy used by plants in respiration. This is the energy available to primary consumers. The unit is kJ m-2 year-1

Question 21

Why is energy lost between trophic levels?

Answer 21

Some tissues are not eaten or are indigestible (egested), energy is lost in respiration and excretory products

Question 22

Why are carnivores more efficient than herbivores?

Answer 22

Meat contains protein and fat, which are easier to digest than plant material

Question 23

What do the arrows show in a food web?

Answer 23

The direction of energy/biomass transfer

Question 24

How do you calculate the efficiency of energy transfer between trophic levels?

Answer 24

Energy in biomass after transfer/energy available before transfer x 100

Question 25

Define primary succession

Answer 25

Succession in a habitat that has never before been colonised. Bare rock- no soil/seeds/humus present

Question 26

Define secondary succession

Answer 26

The reintroduction of organisms into an area that was previously colonised. Soil, seeds and humus are already present

Question 27

The first plants to grow in a new habitat during succession are called?

Answer 27

Pioneer species

Question 28

What is the role of pioneer species in primary succession?

Answer 28

Colonisation of bare rock

Question 29

What are the stages in succession called?

Answer 29

Seral stages/seres

Question 30

What is the climax community?

Answer 30

The final stable collection of plants and animals that succession produces. Equilibrium has been reached. No further change

Question 31

What is the role of photosynthesis in the carbon cycle?

Answer 31

Removal of CO2 from the atmosphere

Question 32

List the five key processes by which carbon moves through the carbon cycle

Answer 32

Photosynthesis, respiration, combustion, decomposition, fossilisation

Question 33

What is a carbon footprint?

Answer 33

The equivalent amount of CO2 generated by an individual a product or a service in a year.

Question 34

What do plants need nitrogen for?

Answer 34

Synthesising amino acids, nucleic acids and chlorophyll

Question 35

Give three forms of nitrogen that plants can take up

Answer 35

NO3- (nitrate), NO2- (nitrite), NH4+ (ammonium ions). Most plants absorb nitrate

Question 36

Name the process that converts atmospheric nitrogen to ammonium or nitrate

Answer 36

Nitrogen fixation

Question 37

What process can fix atmospheric nitrogen to form nitrate?

Answer 37

Lightning

Question 38

Name the two bacteria that perform nitrogen fixation

Answer 38

Azotobacter (free living) Rhizobium (root nodules of legumes)

Question 39

Name the process that converts ammonium to nitrate

Answer 39

Nitrification

Question 40

Which bacterium converts ammonium to nitrite?

Answer 40

Nitrosomonas

Question 41

Which bacterium converts nitrite to nitrate?

Answer 41

Nitrobacter

Question 42

Name the process that returns nitrate to atmospheric nitrogen

Answer 42

Denitrification

Question 43

Which bacterium performs denitrification and where is it found?

Answer 43

Pseudomonas and waterlogged soil/anaerobic conditions

Question 44

List the steps in eutrophication

Answer 44

Leaching of fertilisers into water, algal bloom, plants/algae die, bacteria decompose them and use up O2, animals die

Question 45

What is the effect of ploughing on soil?

Answer 45

Ploughing aerates the soil, increasing nitrification and decreasing denitrification

Question 46

What does a t test show?

Answer 46

If there is a significant difference between the means of two sets of data

Question 47

What is the null hypothesis of a t test?

Answer 47

There is no significant difference between the means of two sets of data

Question 48

When would you reject the null hypothesis of a t test?

Answer 48

When the t value calculated is above the critical value found in the probability table for the correct degrees of freedom