20 Human Influence on Ecosystem
(Core / Extended)

20.1 Food Supply
What you need to know:

1. Describe how humans have increased food production, limited to: (a) agricultural machinery to use larger areas of land and improve efficiency (b) chemical fertilisers to improve yields (c) insecticides to improve quality and yield (d) herbicides to reduce competition with weeds (e) selective breeding to improve production by crop plants and livestock 
2. Describe the advantages and disadvantages of large-scale monocultures of crop plants
3. Describe the advantages and disadvantages of intensive livestock production

Videos: Human Influences on the Environment - Overview

Videos: Food Production

• Monoculture
  
• Herbicides
• Pesticides
  
• Livestock
  

Videos: Food Production - Fertilisers

Videos: Food Production - Crop Plants and Greenhouoses

Videos: Food Production

• Arable farming
• Ploughing and harrowing
  
• Soil fertility
  
• Weeding
  
• Pastoral Farming
  
• ​Shifting cultivation
  

20.2 Habitat Destruction
What you need to know:

1. Describe biodiversity as the number of different species that live in an area 
   
2. Describe the reasons for habitat destruction, including: (a) increased area for housing, crop plant production and livestock production (b) extraction of natural resources (c) freshwater and marine pollution
   
3. State that through altering food webs and food chains, humans can have a negative impact on habitats
   
4. Explain the undesirable effects of deforestation as an example of habitat destruction, to include: reducing biodiversity, extinction, loss of soil, flooding and increase of carbon dioxide in the atmosphere

Videos: Biodiverstiy and Waste- 20.2.1

Videos: Maintaining Biodiverstiy - 20.2.1

Videos: Habitat Destruction - 20.2.2

Videos: Pyramid of Biomass

Videos: Ecological Pyramids

Videos: Pyramid of Biomass & Trophic Levels

20.3 Pollution
What you need to know:

1. Describe the effects of untreated sewage and excess fertiliser on aquatic ecosystems
2. Explain the process of eutrophication of water, limited to: (a) increased availability of nitrate and other ions  (b) increased growth of producers (c) increased decomposition after death of producers (d) increased aerobic respiration by decomposers (e) reduction in dissolved oxygen (f)death of organisms requiring dissolved oxygen in water 
3. Describe the effects of non-biodegradable plastics, in both aquatic and terrestrial ecosystems
   
4. Describe the sources and effects of pollution of the air by methane and carbon dioxide, limited to: the enhanced greenhouse effect and climate change
   

Videos: Land and Water Pollution - Eutrophication and Bioaccumulation

Videos: Eutrophication

Videos: Air Pollution and Climate Change

Videos: Pollution  - Carbon Monoxide

Videos: Problems with Plastics

Videos: 3 Unexpected Effects of Plastic Pollution

20.4 Conservation
What you need to know:

1. Describe a sustainable resource as one which is produced as rapidly as it is removed from the environment so that it does not run out
   
2. State that some resources can be conserved and managed sustainably, limited to forests and fish stocks
   
3. Explain how forests can be conserved using: education, protected areas, quotas and replanting
   
4. Explain how fish stocks can be conserved using: education, closed seasons, protected areas, controlled net types and mesh size, quotas and monitoring
   
5. Explain why organisms become endangered or extinct, including: climate change, habitat destruction, hunting, overharvesting, pollution and introduced species
   
6. Describe how endangered species can be conserved, limited to: (a) monitoring and protecting species and habitats (b) education (c) captive breeding programmes (d) seed banks
   
7. Describe the reasons for conservation programmes, limited to: (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
   
8. Describe the use of artificial insemination (AI) and in vitro fertilisation (IVF) in captive breeding programmes
   
9. Explain the risks to a species if its population size decreases, reducing genetic variation (knowledge of genetic drift is not required)
   

Videos: Sustainable Development

Videos: Biodiversity and Conservation

Videos: Can they survive - Genetic Diversity Explained

Videos: Endangered Species Consevation

EXAMPLE QUESTIONS

Quiz: 50 MCQ questions. Click Here.  Select HIDE ANSWERS and then try the questions.

Question 1

The correct answer is B (as sulfur dioxide levels increase, the number of lichen decreases).
This is because the graph shows that as the levels of sulfur dioxide increase, the number of lichen species decreases.
A is incorrect because there is a correlation between sulfur dioxide levels and the number of lichens.
C is incorrect because some lichens are surviving even at relatively high levels of sulfur dioxide.
D is incorrect because sulfur dioxide levels increase and the levels of lichens do not increase.