Population size and ecosystems

Question 1

What is a population?

Answer 1

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

Question 2

What is a community?

Answer 2

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

Question 3

What is an ecosystem?

Answer 3

A balanced biological system where all the living and non-living interact in a particular location

Question 4

What is a habitat?

Answer 4

The place where an organism lives

Question 5

What happens in the lag phase of an animal population graph?

Answer 5

May last a few days to a few years. Slow growth rate. Adaption to new environment

Question 6

What happens in the log/exponential phase of an animal population graph?

Answer 6

Plentiful resources meaning exponential growth. No limiting factors/environmental resistance

Question 7

What happens in the stationary phase of an animal population graph?

Answer 7

Rate of growth slows due to competition. Birth rate = Death rate. Environmental resistance. Intraspecific competition. Carrying capacity reached

Question 8

What happens in the death phase of an animal population graph?

Answer 8

Death rate > Birth rate
e.g. no food available as all plants eaten

Question 9

What happens in the lag phase of a bacterial/yeast population graph?

Answer 9

Bacteria synthesising new enzymes and proteins. Rate of cell division is slow

Question 10

What happens in the log/exponential phase of a bacterial/yeast population graph?

Answer 10

Plenty of space and nutrients. Divide at max rate. Exponential growth

Question 11

What happens in the stationary phase of a bacterial/yeast population graph?

Answer 11

Cell death = cell production
Limiting factors such as nutrients running out start to impact

Question 12

What happens in the death phase of a bacterial/yeast population graph?

Answer 12

Cell death > production
Due to build up of toxic waste (ethanol, acid)

Question 13

What is carrying capacity?

Answer 13

Max pop size that can be sustained over a period of time in a particular habitat or ecosystem

Question 14

What is environmental resistance?

Answer 14

Environmental factors that slow down pop growth

Question 15

What factors contribute to the environmental resistance of a bacterial culture?

Answer 15

Available food, overcrowding, competition, accumulation of toxic waste

Question 16

What biotic factors contribute to the environmental resistance of an animal/plant population?

Answer 16

Predation, parasitism and disease, intra and interspecific competition

Question 17

What abiotic factors contribute to the environmental resistance of an animal/plant population?

Answer 17

Light intensity, water supply, water mineral content, temperature, soil pH, amount of space available

Question 18

What density-dependent (biotic) factors regulate population size?

Answer 18

Predation, disease, competition, parasitism, food availability, accumulation of toxic waste, territory and shelter availability

Question 19

What density-independent (abiotic) factors regulate population size?

Answer 19

Sudden violent changes (flood, fire and freezing), soil pH, light intensity and mineral availability

Question 20

When do density-dependent factors affect a higher proportion of the population?

Answer 20

If pop is denser

Question 21

When do density-independent factors affect the population?

Answer 21

All members equally affected. Does not depend on pop size

Question 22

What is the definition of biomass?

Answer 22

The mass of a biological material in living, or recently living, organisms

Question 23

What is the definition of trophic level?

Answer 23

Feeding level. The number of times that energy has been transferred between the sun and successive organisms along a food chain

Question 24

What is the definition of a saprobiont?

Answer 24

A micro-organism that obtains it’s food from the dead or decaying remains of other organisms

Question 25

What is the definition of photosynthetic energy (PE)?

Answer 25

A measure of how well a plant is able to capture light energy

Question 26

How can photosynthetic efficiency be worked out?

Answer 26

PE = GPP divided by quantity of light energy falling on plant x 100

Question 28

What are the units of photosynthetic efficiency?

Answer 28

%

Question 29

What is the definition of GPP?

Answer 29

The rate of production of chemical energy in organic molecules by photosynthesis in a given area. Quantity of energy incorporated into product

Question 30

What is the average GPP?

Answer 30

0.2%

Question 31

What are the units for GPP?

Answer 31

kJ/m-2/year-1

Question 32

What is the definition of NPP?

Answer 32

Potential food/biomass available to primary consumers

Question 33

What is the equation for working out GPP?

Answer 33

GPP = NPP + R

Question 34

What is the equation for working out NPP?

Answer 34

NPP = GPP - R

Question 35

What is the average NPP?

Answer 35

50% of the GPP

Question 36

What are the units of NPP?

Answer 36

kJ/m-2

Question 37

What is primary productivity?

Answer 37

Rate at which energy is converted by producers into biomass

Question 38

What is secondary productivity?

Answer 38

Rate at which consumers accumulate energy in the form of biomass

Question 39

Why is energy transfer between plants and herbivores very inefficient?

Answer 39

Cellulose and lignin hard to digest Much more energy left in faeces of herbivore than a carnivor More energy used in digestion

Question 40

What are the different stages in succession called?

Answer 40

Seral stages

Question 41

What are the seral stages?

Answer 41

Pioneer species Grassland community Shrubs Climax community

Question 42

What is a pioneer species?

Answer 42

First plants to grow in a new habitat. Adapted to harsh conditions e.g. bare rock, roof, sand dune Lichens are symbiotic algae. Means they can grip rocks and photosynthesize. Mosses root into the decomposing lichen

Question 43

What is succession?

Answer 43

The change in structure and composition of species in a community over a period of time

Question 44

What is a grassland community?

Answer 44

The decomposing moss and lichen establish soil. Grass can root in via seeds being blown into the habitat

Question 45

What are shrubs in reference to the seral stages?

Answer 45

Heather. Perennial woody plants which block grass from sun as taller e.g. moorlands

Question 46

What is a climax community?

Answer 46

Equilibrium. A final stable community in an ecosystem. Dominated by trees, had a wide variety of plants and animals

Question 47

What are the changes over time that occur during the seral stages!

Answer 47

Deeper soil. Richer in nutrients. Increased number of woody plants. Organisms live at different levels (birds). Increased biodiversity. Pioneer plants normally die in next stage

Question 48

What is secondary succession?

Answer 48

Repopulation of an area that had been previously colonized, often due to the habit being disturbed or damaged

Question 49

Why is secondary succession much quicker than primary succession?

Answer 49

Soil already present. Nutrients and minerals present in soil. Roots and seeds may be left behind

Question 50

What factors affect succession?

Answer 50

Migration -> arrival of seeds, spores and animals are essential Interspecific competition -> allow progression of stages as plants become outcompeted Facilitation -> all depends on previous conditions. Lichen facilitates everything

Question 51

What group of plants have large numbers of root nodules on their roots?

Answer 51

Legumes

Question 52

What is the advantage of legumes having root nodules?

Answer 52

Allow nitrogen fixing. Root nodules contain Rhizobium. Leghaemoglobin attached to O2 and takes it away to allow nitrogenase to anaerobically fix N2 into NH4+. Allow plant growth in poor soil

Question 53

What are the 5 stages of eutrophication?

Answer 53

1. Fertilizers leach into bodies of water 2. Cause algal bloom 3. Plants and algae die and decompose due to lack of light 4. Decomposers use O2 in aerobic respiration 5. Water becomes anoxic and animals die

Question 54

What are anoxic conditions?

Answer 54

When there is little or no oxygen present

Question 55

How can we reduce the impacts of eutrophication?

Answer 55

Restrict fertiliser use Leave a gap next to the water Crop rotation

Question 56

What is meant by the term carbon footprint?

Answer 56

How much carbon our activities leave on the earth

Question 57

What is the link between CO2 conc and the enhanced greenhouse effect?

Answer 57

As CO2 conc increases, the planet warms up, which leads to an enhanced greenhouse effect as more carbon is in the atmospheric store instead of ocean or sediment

Question 58

What are the six different ways carbon can be released and taken in?

Answer 58

Photosynthesis Respiration carbon transfer (from carbon in plants to carbon in animals) Fossilisation Decomposition Respiration Combustion

Question 59

What are the 5 different carbon stores?

Answer 59

Ocean (3.74%) Sediment (96.12%) Fossil fuels (0.1%) Biofuels (0.06%) Atmosphere (0.07%)