(U2) Human Impact On Biodiversity

Question 1

What are the advantages of polyculture? (3)

(growing many different crop species)

Answer 1

• more food webs
• species diversity increased by increasing no. of herbivores - more ecological niches
• increased soil fertility due to a particular ion not being over consumed

Question 2

What are the disadvantages of monoculture? (2)

(growing 1 crop species)

Answer 2

• soil depleted of particular nutrients e.g. mineral ions like nitrates - less fertile
• susceptible to pest & disease spread year on year

Question 3

What are the advantages of crop rotation? (2)

Answer 3

• increased soil fertility due to a particular ion not being over consumed - year on year
• prevents pests and pathogens becoming established year on year

Question 4

How should hedgerows be managed? (6)

What is the overall impact of these measures?

Answer 4

1.

• variety of heights and widths for nesting birds
• trim from September to February rather than March to August when nests can be destroyed
• trim on a 2/3 year rotation, allows establishment of berry, insect and bird populations
• avoid trimming all in the same year - promote hedge diversity
• don’t cut native hedgerows - support more food webs due to more habitats
• make them stock proof to avoid damage via grazing

2. Greater biodiversity

Question 5

How do predator strips at field margins promote biodiversity? (2)

Answer 5

• encourages natural predators to populate the area
• allowing recovery of priority species by removing pests

Question 6

What is a pest? (2)

Answer 6

Any organism that:

• reduces crop species
• to a level that causes economic damage

Question 7

What are the disadvantages of pesticides? (4)

Answer 7

1. pests can develop resistant alleles over many generations
2. broad spectrum pesticides:

• allow pest resurgence by killing a natural predator, or
• allow a secondary pest outbreak, where a minor pest population grows without competition

3. Persist in the environment and affect other ecosystems
4. Bioaccumulation: build up along food webs, leading to toxic levels in predators

Question 8

How does a biological control work? (4)

Answer 8

• it is a natural predator to the pest
• survives and thrives
• decreases pest population
• below level that causes economic damage

Question 9

What are the features of integrated pest managment? (6)

Comment on each

Answer 9

• selecting varieties best suited for local growing conditions - avoid ones susceptible to pests
• crop rotation / intercropping - harder for pest to become established
• monitoring pest levels - determine need for control measures
• using photodegradable plastic between crops - regular and wide spacing prevents growth of weeds, limiting use of herbicides
• biological control use - long-term control without problems of chemical control, also doesn’t completely eradicate
• narrow spectrum, biodegradable pesticides as a last resort (if pests cause significant economic damage) - pollinators and natural predators not affected; no bioaccumulation in food chains

Question 10

What are the advantages of artificial fertilisers? (4)

Answer 10

• easy to spread
• known mineral content
• can be applied in a controlled manner
• easy to store

Question 11

What are the disadvantages of artificial fertilisers? (3)

Answer 11

• soluble and leads to leeching & eutrophication
• poor crumb structure in soil
• doesn’t replace trace minerals in soil

Question 12

What are the advantages of organic fertilisers? (5)

Answer 12

• adds humus to soil
• improves soil crumb structure and quality
• lower solubility, less likely to cause leeching & eutrophication
• cheap
• replaces trace minerals in soil

Question 13

What are the disadvantages of organic fertilisers? (4)

Answer 13

• don’t know mineral content
• kills edaphic detritivores - less aeration
• difficult to spread
• difficult to store

Question 14

How does eutrophication occur? (8)

Answer 14

• artificial fertiliser dissolves rain water & leeches or runs off surface of soil into a waterway
• algal bloom - algae rapidly absorb nitrates & use them for amino acids, then proteins
• algae deplete water of minerals and die
• shading results in less light for photosynthesis at water bed for plants - they die; lack of light and nitrates
• aerobic decay by saprophytic bacteria of plants and algae increases BOD (biological oxygen demand)
• population explosion of aerobic bacteria - deplete oxygen levels in river water due to respiration
• aquatic vertebrates die as they can’t aerobically respire
• increased turbidity of water by bacteria increases shading further and less photosynthesis occurs

Question 15

How can eutrophication be prevented?

Answer 15

• use organic fertiliser (slurry) instead - less soluble
• don’t spray when wet or near streams

Question 16

What does ASSI stand for?

where does it cover?

Answer 16

• Area of Special Scientific Interest
• UK

Question 17

What does SAC stand for?

where does it cover?

Answer 17

• Special Areas of Conservation
• EU

Question 18

What does DARD stand for?

what did they do?

Answer 18

• Department of Agriculture and Rural Development
• implemented agri-development schemes (e.g. guidelines for hedgerow conservation & grants)

Question 19

What is the purpose of the NI priority habitat and species lists?

Answer 19

outlined species and habitats that were endangered, in order to create awareness

Question 20

What is the negative of cutting grass when wet (for silage) (2)

Answer 20

• destroys habitats
• leads to a decrease in biodiversity in a field

Question 21

How does climate change affect plants and animals? (4)

Answer 21

• makes environments inhospitable (whether that means destruction of habitat or temperatures being too high etc)
• or makes species more susceptible to disease / predation
• leads to endangerment and/or extinction
• leads to a decrease in biodiversity

Question 22

What is the effect of sewage discharge on waterways? (3)

Answer 22

• aerobic decay by saprobiotic bacteria of decomposable material increases BOD (biological oxygen demand)
• population explosion of saprobiotic bacteria - deplete oxygen levels immediately in river water due to respiration
• sewage is broken down further by bacteria decomposition and dilution by currents
• acts fast - but doesn’t last

Question 23

How does Biological Oxygen Demand change downstream? (5)

(After sewage discharge)

Answer 23

• saprobiotic bacteria decline due to less sewage being available
• dilution by currents downstream also reduces sewage
• reed beds remove sewage and photoynthesise to produce oxygen
• increased photosynthesis due to less turbidity and due to nitrate rich water
• fast flowing river water gains oxygen through mixing

Question 24

What is organic pollution

What are the 3 examples?

Answer 24

1. Pollution of water by organic material
2. Sewage, slurry or silage effluent (not artificial ferilisers)

Question 25

Name indicator species in: - Clean water - septic water

Answer 25

1. Clean: - perch - mayflies - trout 2. Septic: - leeches - bloodworms - lack of fish

Question 26

What is the **timescale difference** between: - eutrophication by artificial fertiliser - organic pollution of waterways e.g. silage effluent, slurry, sewage And **why**? | in the context of BOD

Answer 26

*Eutrophication* occurs over a **longer time period**, but **lasts longer**: - eutrophication *requires algal bloom and death* **before increased BOD** - organic pollution *immediately* introduces *dead organic matter with saprobiotic bacteria*; **BOD immediately rises** as these bacteria respire - however the organic pollution is broken down quickly and there is a lack of dead organic matter to meet nutrient demands of the bacteria

Question 27

How can you **reduce eutrophication**? | after its occurs

Answer 27

**reed beds** to *remove nitrates*