19. Human influences on ecosystem

Question 1

Describe how humans have increased food production

Answer 1

(a) agricultural machinery to use larger areas of land and improve efficiency

(b) chemical fertilisers to improve yields- nutrients

(c) insecticides to improve quality and yield- kill insects

(d) herbicides to reduce competition with weeds- kill weeds

(e) selective breeding to improve production by crop plants and livestock

Question 2

Describe the advantages and disadvantages of large-scale monocultures of crop plants

Answer 2

a single crop in production

loss of biodiversity / AW ;
habitat destruction ;
damage to, food chains / food webs ;
soil erosion ;
by, water / wind ;
infertility of soil ;
competition for resources ;
ref to pollution ;
AVP ;; e.g. desertification / flooding / diseases or pests spreading to
wild-varieties / migration (of species)

makes tending, sowing, harvesting and selling a crop more efficient
using machinery to cultivate a large area of land
uniform crop- same height- harvested at once
all crop treated w same herbicides and pesticides in same way & time
large quantities of yield- uniform in size and quality so easy to sell

Question 3

Advantages and disadvantages of intensive livestock production

Answer 3

1 effect of waste (faeces and urine) on, waterways / crops ;
2 disease spreading to, wild populations / humans ;
3 use of antibiotics and (spread of) antibiotic resistance ;
4 use of pesticides ;
5 loss of biodiversity ;
6 release of, (named) greenhouse gases / carbon emissions ;
7 named consequence ; e.g. climate change / global warming
8 providing food for livestock requires monocultures ;
9 deforestation / habitat loss ;
10 idea that livestock production is an inefficient use of, crop
plants / energy ;
11 use of hormones and effect on wild populations / feminisation of fish

Question 4

Explain the effects of soil erosion on ecosystems

Answer 4

1 silting of rivers ;
2 landslides / mudslides ;
3 soil does not absorb (rain)water / increased risk of flooding ;
4 increased rate of evaporation / land is exposed to drying ;
5 desertification / decreased soil water ;
6 reduction in transpiration ;
7 reduction in cloud formation ;
8 change in rainfall patterns ;
9 plants cannot grow (well) ;
10 idea that loss of anchorage for plants ;
11 idea of reduced (soil) fertility / increased leaching / AW ;
12 loss of, habitat / places where organisms live / described ;
13 disruption to food chain(s) / described ;
14 endangered / extinction / migration of, species ;

Question 5

Describe biodiversity

Answer 5

the number of different species that live in an area

Question 6

Describe the reasons for habitat destruction

Answer 6

(a) increased area for housing, crop plant production and livestock production

(b) extraction of natural resources

(c) freshwater and marine pollution

Question 7

How can humans can have a negative impact on habitats

Answer 7

through altering food webs and food chains

Question 8

Explain the undesirable effects of deforestation as an example of habitat destruction

Answer 8

reducing biodiversity
extinction
loss of soil
flooding
increase of carbon dioxide in the atmosphere

Question 9

Describe the effects of untreated sewage and excess fertiliser on aquatic ecosystems

Answer 9

• increased availability of nitrate and other ions
• increased growth of producers
• increased decomposition after death of producers
• increased aerobic respiration by decomposers
• reduction in dissolved oxygen
• death of organisms requiring dissolved oxygen in water

Question 10

Describe the effects of non-biodegradable plastics, in both aquatic and terrestrial ecosystems

Answer 10

direct effects

(non-biodegradable plastic) does not break down ;
idea that ability to breathe affected ;
idea that ability to move affected ;
idea that ability to gain nutrition affected ;
damage / injury / infection / death ;
toxic / poisonous ;

indirect effects

blocks (sun)light, so algae / plants / producers, cannot photosynthesise ;
(so) less, food / energy, enters, food chains / food webs ;
loss of (named), habitat / feeding / breeding area ;
more likely to be predated ;
idea that (plastic) accumulates up the food chain / bioaccumulation ;

reduce, use of / manufacture, single-use plastic ;
use biodegradable plastics instead of non-biodegradable plastics ;
reduce unnecessary packaging ;
reuse plastic product(s) ;
recycle / described ;
education / awareness campaigns ;
fines , for unregulated disposal of plastic
quotas or limits for production / international treaties

Question 11

Describe the sources and effects of pollution of the air by methane and carbon dioxide

Answer 11

livestock farming, decomposers release

deforestation, fossil fuels, vehicle engine, coal, oil

enhanced greenhouse effect, global warming, climate change sea levels rise.

Question 12

Describe a sustainable resource

Answer 12

one which is produced as rapidly as it is removed from the environment so that it does not run out

Question 13

Explain how forests can be conserved & fish stocks can be conserved

Answer 13

education, protected areas, quotas and replanting

education, closed seasons, protected areas, controlled net types and mesh size, quotas and monitoring

Question 14

Explain why organisms become endangered or extinct

Answer 14

climate change, habitat destruction, hunting, overharvesting, pollution and introduced new species

Question 15

Describe how endangered species can be conserved

Answer 15

(a) monitoring and protecting species and habitats

(b) education

(c) captive breeding programmes

(d) seed banks

Question 16

Describe the reasons for conservation programmes

Answer 16

(a) maintaining or increasing biodiversity

(b) reducing extinction

(c) protecting vulnerable ecosystems

(d) maintaining ecosystem functions, limited to nutrient cycling and resource provision, including food, drugs, fuel and genes

Question 17

Explain the process of artificial insemination (AI) and in vitro fertilisation (IVF)

Question 18

Describe the use of artificial insemination (AI) and in vitro fertilisation (IVF) in captive breeding programmes

Question 19

Explain the risks to a species if its population size decreases

Answer 19

reduced variation ;
reproduction rate is lower / harder to find a mate ; extinction ;