Human influences on ecosystems

Question 1

how humans have increased food production

Answer 1

1. agricultural machinery to use larger areas of land and improve efficiency
2. chemical fertilizers to improve yields
3. insecticides to improve quality and yield
4. herbicides to reduce competition with weeds
5. selective breeding to improve production by crop plants and livestock

Question 2

advantages of large-scale monocultures of crop plants

Answer 2

• specialized harvesting techniques
• highly selected strains
• mineral water requirement

Question 3

disadvantages of large- scale monocultures of crop plants

Answer 3

• poor wildlife foods
• spread of disease
• loss of genetic variety
• damage to soil

Question 4

advantages of intensive livestock production

Answer 4

• high conversion ration
• minimise movement- less energy
• hygenic conditions
• more food produced (less area)

Question 5

disadvantages of intensive livestock production

Answer 5

• waste can pollute nearby rivers and lakes
• disease can spread easily from animal to animal
• use of antibiotics can lead to resistant strains
• large amounts of methane

Question 6

what is biodiversity

Answer 6

the number of different species that live in an area

Question 7

reasons for habitat destruction

Answer 7

1) increased area for housing, crop plant production and livestock production
2) extraction of natural resources
3) freshwater and marine pollution

Question 8

what causes a negative impact on habitats

Answer 8

through altering food webs and food chains, humans can have a negative impact on habitats

Question 9

undesirable effects of deforestation

Answer 9

• reducing biodiversity
• extinction of species
• loss of soil
• flooding
• increase of CO2 in atmosphere

Question 10

explain the effect on extinction

Answer 10

forest habitats have a huge range of biodiversity. As habitat is destroyed it causes the loss of large numbers of plant and animal species

Question 11

explain the effect on the loss of soil

Answer 11

without trees, nutrients and minerals remain unused so will be washed away. The loss of soil nutrients is permanent and make it difficult for trees to regrow

Question 12

explain the effect of flooding

Answer 12

without trees the topsoil will be loose and unstable so will be washed away by rain

Question 13

explain the effect of increase of CO2

Answer 13

trees carry out photosynthesis during which they take in CO2. The removal of trees means less CO2 removed from the atmosphere ( less oxygen released)

Question 14

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

Answer 14

untreated sewage and excess fertilizer are rich with nitrates and phosphates. This can stimulate the growth of algae which can lead to algal bloom

Question 15

effects of non- biodegradable plastics in marine habitat

Answer 15

• animals often try to eat plastic or become caught in it
• break down of plastic, release toxins
• very small particles eaten and enters the food chain

Question 16

effects of non- biodegradable plastic on land

Answer 16

• burying in landfills
• releases toxins into soil
• land is no good for growing crops or grazing animals

Question 17

process of eutrophication

Answer 17

• 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 18

describe the sources and effects of pollution of the air

Answer 18

CO2 is produced when fossil fuels are burnt, also released when trees are burnt to clear land for human use. CO2 is a greenhouse gas which contributes the enhanced greenhouse effect leading to climate change

Methane is released by cattle farming, rice fields, landfills. Methane is a greenhouse has which contributes the enhanced greenhouse effect leading to climate change

Question 19

what is a sustainable resource

Answer 19

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

Question 20

why a species can become endangered

Answer 20

• climate change
• hunting
• loss of habitat
• pollution
• introduction of non- native species
• overharvesting

Question 21

describe how endangered species can be conserved

Answer 21

• monitoring and protecting species and
  habitats
• education
• captive breeding programmes
• seed banks

Question 22

explain how forests can be conserved

Answer 22

• education = ensure companies are aware of sustainability
• protected areas = ensures not trees are cut down
• quotas = a proportional number of trees are cut down
• replanting = allows there to be a greater population

Question 23

explain how fish stocks can be conserved

Answer 23

• quotas = controlling the number of fish caught each year
• controlled net types/ mesh types = controlling the size of fish caught. ensure there are enough fish of suitable age for breeding
• closed seasons = controlling time of year fish can be caught. Preventing large scale depletion of stocks when fish come together in certain areas to breed
• education = educating fishermen so they are aware of types of fish which are not produced sustainably and can avoid them when buying fish

Question 24

reasons for conservation programmes

Answer 24

(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 25

captive breeding programmes

Answer 25

there’s a use of artificial insemination (AI) and in vitro fertilization (IVF)

Question 26

Explain the risks to a species if its population size decreases

Answer 26

can lead to reductions in genetic diversity, reproductive fitness and a limited ability to adapt to environmental change increasing the risk of extinction