The document summarizes key nutrient cycles (carbon, water, nitrogen) and their importance for organisms. It also discusses human impacts such as agriculture, pollution, and population growth on ecosystems. Specific pollutants are outlined like greenhouse gases, acid rain precursors, and nuclear fallout. Agriculture can involve deforestation, use of fertilizers and pesticides, and pollution from runoff.

1. Relationships of organisms with
one another and with their
environment

3. NUTRIENT CYCLES
• Carbon cycle
• Water cycle
• Nitrogen cycle

4. CARBON CYCLE

6. CARBON CYCLE
REMOVAL OF CO₂ FROM THE ATMOSPHERE
• PHOTOSYNTHESIS: uses light energy to convert CO₂ into
organic compounds in plants.
ADDITION OF CO₂ TO THE ATMOSPHERE
• RESPIRATION: converts carbohydrates to CO₂ with the release
of energy.
• DEATH AND DECAY: provide plant and animal material for
decomposers – bacteria and fungi.
• COMBUSTION: releases CO₂ by the burning of fossil fuels.
FOSSILISATION: The hydrocarbon fuels, such as coal and
petroleum, come from ancient plants which have only partly
decomposed over the million of years since they were buried.

7. WATER CYCLE

9. NITROGEN CYCLE

11. NITROGEN CYCLE
1)PROCESSES WHICH ADD NITRATES TO SOIL
• Nitrifying bacteria: they use ammonia fron excretory
products and decaying organisms as a source of
energy. In this process they produce nitrates.
There is a special group, the nitrogen-fixing
bacteria, which can absorb N₂ as a gas from the air
spaces in the soil, and build it into compounds of
ammonia, which can be easily be changed to
nitrates by other nitrifying bacteria. Some of these
live in the roots nodules of leguminous plants
(peas,beans, clover).

12. 1)PROCESSES WHICH ADD NITRATES TO SOIL
(cont)
• Lightning: lightning discharges makes some of
the nitrogen gas in the air combine with
oxygen, forming nitrogen oxides. They dissolve
in rain, and are washed into the soil, where
they form nitrates.

13. 2)PROCESSES WHICH REMONVE NITRATES
FROM THE SOIL
• Uptake by plants: plant roots absorb nitrates from
the soil and combine them with the carbohydrates to
make proteins.
• Leaching: as rain water passes through the soil it
dissolves the nitrates and carries them away in the
run-off or to deeper layers of the soil.
• Denitrifying bacteria: They obtain energy by
breaking down nitrates to nitrogen gas which then
escapes from the soil into the atmosphere.

14. POPULATION SIZE
• POPULATION: group of organisms of one
species, living in the same area at the same
time.

16. HUMAN POPULATION GROWTH

18. HUMAN INFLUENCES ON THE
ECOSYSTEM
• AGRICULTURE
• POLLUTION
• CONSERVATION

20. POLLUTION
• WATER POLLUTION by sewage and chemical
waste.
• AIR POLLUTION by: - sulfur dioxide.
- greenhouse gases
- nitrogen oxides
• POLLUTION DUE TO PESTICIDES AND
HERBICIDES.
• POLLUTION DUE TO NUCLEAR FALL-OUT

21. POLLUTION OF WATER: the 2 pollutants that
reduce oxygen in water are:
• Fertilisers: nitrates and phosphates are added
to the soil by farmers. Some are washed from
the soil by rain into the nearest pond, lake or
river. This process is called leaching.
• Sewage: contains an excellent source of
organic food from bacteria, and also contains
phosphates from detergents.

23. AIR POLLUTION
• BY SULFUR DIOXIDE and NITROGEN OXIDES:
contributes to acid rain.
• BY GREENHOUSE GASES CONTIBUTING TO GLOBAL
WARMING.
Carbon + O₂ → carbon monoxide (CO)
and carbon dioxide (CO₂)
Sulphur + O₂ → sulphur dioxide (SO₂)
Nitrogen + O₂ → nitrogen monoxide (NO)
and nitrogen dioxide (NO₂)

24. Greenhouse effect:gases contributing
GAS % ESTIMATED MAIN SOURCES
CONTRIBUTION
Carbon dioxide 55 Burning fossil fuels
Methane 15 Decay of organic matter;
waste gases from digestive
processesin cattle and
insects; natural gas leaks
CFCs (chlorofluorocarbons) 24 Refrigerators and air
conditioning systems;
plastic foams
Nitrogen oxides 6 Fertilisers; burning fossil
fuels, especially in vehicles.

30. Pollution due to nuclear fall-out
• IONISING RADIATION MAY CAUSE CANCER
Accidents at nuclear power stations may release substances into
the atmosphere. Exposure to large amounts of radiation from
these substances can cause radiation sickness and burns. They
can also increase mutation rates in DNA in our cells, which
may lead to cancer.
- Alpha particles
- Beta particles
- Gamma rays

31. AGRICULTURE
• DEFORESTATION
• FERTILISERS