20 Human Influences on Ecosystems

Biodiversity

the number of different species that live in an area.

How humans have increased food production

agricultural machinery to use larger areas of land and improve efficiency
chemical fertilisers to improve yields, increases growth of plants
insecticides to improve quality and yield, removes pests herbicides to reduce competition with weeds, kills weeds
selective breeding to improve production by crop plants and livestock

Advantages of monoculture

Increased yield
Higher revenue
Less space required
Easier harvesting

Disadvantages of monoculture

ecosystem/normally: loss of biodiversity, loss of habitats/ habitat destruction,
disruption of food chain
spreading of diseases
extinction of species

Advantages of intensive livestock production

take up less land
more land could be left in its natural state, providing habitats for other species
sometime provide food more cheaply than extensive systems
help to provide more food for people

Disadvantages of intensive livestock production

release of, (named) greenhouse gases / carbon emissions ; named consequence; e.g. climate change / global warming disease spreading to, wild populations / humans;
use of antibiotics and (spread of antibiotic resistance; ecosystem: loss of biodiversity, habitat loss

Humans negative impact on habitats

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

Reasons for habitat destruction

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

Effects of deforestation

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

Effects of untreated sewage and excess fertilisers / animal waste in aquatic ecosystems

Sewage must be treated to kill pathogens and prevent disease, can be treated by chlorination. Loss of biodiversity, habitat destruction, spread of disease, eutrophication.

Eutrophication of water

increased availability of nitrate and other ions
increased growth of producers on surface that block light from underwater producers
increased decomposition after death of producers underwater
increased aerobic respiration by decomposers
reduction in dissolved oxygen
death of organisms that require dissolved oxygen in water

Effect of plastic on aquatic ecosystem

plastic remains for a long time not decomposed ;
Swallowed and cannot be digested, blocks digestive systems; Caught and suffocate
Plastic blocks light for, photosynthesis ;
May release toxins / harmful chemicals;

Effect of plastic on terrestrial ecosystem

Ingested; and cannot be digested, blocks digestive systems;
Plastic is passed down a food chain ;;
Plastic blocks light for, photosynthesis ;
May release toxins / harmful chemicals;

Methane and carbon dioxide

green house gases. Released by natural processes and human activity, they accumulate and trap infrared radiation emitted from the sun towards the earth. This keeps the planet warm enough to support life. If level of these green house gases rise, more infrared radiation is trapped, this increase the average temperature of earth. Resulting in enhanced green house effect, leading to climate change.

Sustainable resource

produced as rapidly as it is removed from the environment so that it does not run out.Some resources can be conserved and managed sustainably, e.g. forests and fish stocks.

Why an organism becomes endangered

climate change
habitat destruction
hunting
overharvesting
pollution
introduced species + competition from introduced species

How endangered species can be conserved

(a) monitoring and protecting species and habitats (b) education (c) captive breeding programmes (d) seed banks

How can we prevent overfishing

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

how forests can be conserved using

quotas and replanting, protected areas, education

Describe the reasons for conservation programmes

(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

Reasons for conserve animals

maintains natural habitat/ prevent, human interference/ development prevention of extinction less, hunting tourism/ economic reason maintain (bio)diversity/ genetic diversity maintain, gene, pool/diversity maintain, food chain/ balanced ecosystems available for scientific study retain for future generations maintain nutrient recycling maintain, resource provision/ food/ drugs prevent soil erosion/ flooding education

Reasons to maintain ecosystems like wetlands

1. to prevent extinction;
2. maintain biodiversity;
3. provide feeding grounds for animals / ref. to disruption of food, chains / web;
4. provide, breeding grounds / places for breeding;
5. provide, habitats / shelter;
6. vulnerable to the effects of, development / drainage /AW;
7. ref to flooding / natural disasters;
8. ref to nitrogen cycle;
9. ref to maintenance of water cycle;
10. ref to carbon cycle; e.g. greenhouse gas / carbon storage / carbon sink
11. waste disposal;
12. provide, resources / food / fuel / drugs / raw materials;
13. idea of areas for, recreation / (eco) tourism / education;
14. ethical reasons / aesthetic reasons / AW;

The risks to a plant species of having very small numbers

high risk of extinction
high risk of genetic disease
less variation
reduced number of alleles less likely to adapt to change in environment
less reproduction

The disadvantage of captive breeding programme involving very small number of animals

inbreeding less genetic variation reduced number of alleles increased risk of genetic disease can not reproduce not enough animals to breed less likely to adapt to change in environment cost

Artificial insemination

1. Collect sperm

2. freeze sperm

3. selecting / washing / screening, of sperm / AW;

4. use fertility drugs containing hormones for superovulation;

5. determine when female is about to ovulate;

6. insert sperm, into female (vagina/ uterus)

In vitro fertilisation (IVF)

1. collect eggs or donor eggs ;

2. collect sperm or donor sperm;

3. fertilisation happens outside the body in a dish in a laboratory

4. embryo development happens in dish

5. screening of embryos

6. inserting embryos into uterus, give mother progesterone after inserting embryos to maintain lining