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Humans and the envirionment


endangered species

conserving endangered species

conserving forests/fish stocks

sustainable development

trickling filters and activated sludge

sewage treatment




other types of waste




nuclear fall-out



  • Accidents at nuclear power stations release radioactive substances into the atmosphere
  • Radioactive substances can cause sickness and burns becouse of ionising radiations that damages the DNA molecules in living cells
  • Ionising radiations are: alpha, beta and gamma
  • Aquatic organisms live in aquatic habitats and respire aerobically so need oxygen
  • Fertilisers and untreated sewage cause pollution in fresh water
  • Fertilisers contain nitrates, soluble in water, and phosphates
  • When nitrates are leached, may run into streams and rivers causing the rapid growth of algae and green plants until they cover the surface


  • Light will not reach the plants on the bottom so they will die with the plants in the surface
  • This will be a source of food for bacteria (decomposeres)
  • They will breed rapidly using oxygen
  • There will be little oxygen for other living organisms who will move or die
  • This process is called eutrophication and can happen whenever food for plants or bacteria si added to water


  • Nitrate fertilisers permit to have higher yields to make more profit
  • Cause a lot of pollution for the envirionment
  • To prevent this, inorganic fertilisers have to be used:
  1. in the right amount so plants can absorb them
  2. when will not rain
  3. when plants are growing so not on empty fields
  4. distant from streams and rivers



  • Organic fertilisers such as manure don't contain many nitrates and release nutrients gradually
  • Crops with organic fertilisers are greater than crops with inorganic ones so they are more expensive and someone can't afford it
  • If are not used correctly they can still cause pollution
  • Are substances that kills organisms which damage crops
  • Insects ---> killed by insecticides
  • Fungi ---> killed by fungicides
  • Weeds ---> killed by herbicides
  • Insects and fungi can feed on a monocolture so have inexhaustible food supply
  • Are harmful substances for the envirionment and an example is DDT
  • The use of DDt was stopped and banned in some parts of the worls






  • Hormones containing oestrogen can be taken by women as a method of birth control
  • Some of these hormones will be excreated in woman's urine and will go in sewage
  • Fish and molluscs can be affected by these contraceptives becouse prevent the testosterone working effectively
  • In the last 20 years the sperm count is fallen but no-one knows the real causes


  • Are man-made materials used for many things
  • Are made from fossil fuels
  • Are: cheap, lightweight and can have every shape and colour but are non-biodegradable
  • Can be very dangerous for animals in aquatic habitats


  • Discharge of chemical waste into rivers is a type of pollution
  • Can contain heavy metals that are very toxic for living organisms
  • If enters in aquatic habitats will kill every living organism


The process of looking after the natural environment

  • It attempts to maintain or increase biodiversity
  • Loss of habitats--->greatest threats to biodiversity
  • Habitats under threat: tropical rainforests & wetland
  • We build roads and houses destroying what used to live on that land
  • We farm animals in large numbers
  • Many governments and world-wide organisations are attempting to make sure that especially important habitatas aren't damaged


non-sustainable resources

Resoruces that once used, they have gone foreverMade by compressing partially decayed bodies of plants and bacteria that lived in the Carboniferous period

sustainable resources

A resource that can be removed from the environment without it running oute.g. fish in the sea wood for fuel


People will always need resources we take from our environmentIf careful we can take and use these resources without causing harm to other organsims

  • made of cellulose fibres from plants
  • waste paper is mixed with water+ chemicals to form a pulp, which is passed through filters and treated to leave clean cellulose fibres
  • we get metals from ores found underground
  • mining metal ores uses lots of energy + non-renewable resources
  • metals can be recycled
  • made from fossil fuels
  • we can resuse plastic objects or recycle them





  • made by heating at very high temperatures sand + other chemicals
  • used glass can be crushed, melted at high temperatures and then used to make new objects


sewage= waste liquid coming from houses, bathrooms, roads and citiesraw sewage= untreated sewagesewage treatment enables water to be recycled

Sewage treatment

Process: 1)Raw sewage passes through screens which trap large objects 2)Screened liquid is left in settlement tanks 3)Insoluble particles drift to the bottom and from sediment

  • the liquid from the settlement tanks run into an aeration tank
  • these contain aerobic microorganisms that make the sewage harmless
  • oxygen is provided by bubbling air through the tank
  • sludge is acted on by anaerobic bacteria

Activated sludge

  • the liquid from the settlement tanks is trickled over a trickling filter bed
  • passes onto the sruface of the stones through holes ina a rotating pipe
  • aerobic microorganisms live on the surface of the stones, they feed on nutrients in the sewage
  • clean water drains out of the bottom of the bed

Trickling filters

sustainable development = providing for the needs of an increasing human population without the environment


Sustainable development

Humans have probably always used fish as a source of hagt-protein food.

  • if we do not reduce cathes, the populations will get so small that there will not be enough adult fish left to breed and sustain the popiulation
  • one system of controlling the numbers of fish caught is to impose quotas
  • another way is to breed large number of themin fish hatcheries

Conserving fish stock

It is possible to use forests sustainable.

  • Governments can refuse to grant licences to companies who want to cut down valuable forests
  • no clear-felling but selective felling
  • trees can be cut down to about 1 metre or less = coppiced
  • where large number of trees are cut down, new ones should be planted to replace them
  • education is important to people

Conserving forest

Introduced species



Habitat destruction

new species that are introduced by humans into an ecosystem can threaten the existence of native species

addition of extra carbon dioxide and methane to the atmosphere is causing climate change, this is one of several factors about the extinction of the golden toad

Humans have always hunted animals for food, but sometimes this hunting is so severe that it can destroy an entire species

human activities can destroy habitats. Species with no habitat cannot survive. When huge number of species seem to have become extinct = called mass extinction





Endangered species

Many tactics can be used to conserve endangered species:

  • monitoring and protecting the species in its natural habitat
  • using captive breeding programmes
  • educating local people about the importance of conservation, and what they can do to halp
Animals are not only organisms that are in danger of exinction. Many plant speacies are also under threat, we can use some techniques:
  • bulding up seed banks

Conserving endangered species




by Antoniello Melissa, Podda Sara and Tramonti Sofia