The document summarizes key cycles in ecosystems, including the carbon, nitrogen, phosphorus, and water cycles. It explains that carbon and other elements are recycled through these cycles, which involve the uptake of elements by plants and animals, their release through respiration and decay, and their return to the environment. It emphasizes the roles of photosynthesis, cellular respiration, and bacteria in facilitating the movement of elements through the cycles. It also notes that human activity like burning fossil fuels has increased the carbon dioxide level in the atmosphere and contributed to global warming.

1. Cycling of
Materials
in Ecosystems

2. Student should know:
 The steps of carbon cycle.
 The importance of carbon dioxide for greenhouse.
 The impact of increasing carbon dioxide level on
global temperature.
 The steps of nitrogen cycle.
 Identify the role of bacteria in the nitrogen cycle.
 The trial of production of nitrogen fixing plants by
genetic engineering.
 The steps of water cycle.
 The role of plants in the water cycle.
 The steps of phosphorus cycle.

3. Introduction
Many inorganic (non-carbon) substances
that make up the soil, water, and air, such
as nitrogen, sulfur, calcium, and
phosphorus are recycled.
Four substances are particularly
important: water, carbon, nitrogen, and
phosphorus.

5. Carbon is an element. It is
part of oceans, air, rocks,
soil and all living organisms.
 Carbon doesn’t stay in one
place. It is always on the
move!

10. Carbon dioxide in the air or dissolved in water
is used by photosynthesizing plants and algae
as a raw material to build organic molecules.
A. Carbon moves from the atmosphere and
water to living organisms.

11. Through food chains, the carbon that is in
plants moves to the animals that eat them.
Animals that eat other animals get the
carbon from their food too.

12. When plants and animals die, their bodies,
wood and leaves decay bringing the carbon
into the ground. Some becomes buried miles
underground and will become fossil fuels in
millions and millions of years.

13. 1. Respiration:
2. Combustion

14.  Nearly all living organisms, including plants
perform cellular respiration. They use
oxygen to oxidize organic molecules during
cellular respiration, and carbon dioxide is a
byproduct of this reaction.
 Each time you exhale, you are releasing
carbon dioxide gas (CO2) into the
atmosphere.

15.  When humans burn fossil fuels (coal, oil,
and natural gas) to power factories, cars
and trucks, most of the carbon quickly
enters the atmosphere as carbon dioxide
gas.
 The carbon contained in wood may stay
there for many years, returning to the
atmosphere only when the wood is burned.

16. Carbon dioxide is a greenhouse gas and traps
heat in the atmosphere. Without it and other
greenhouse gases, Earth would be a frozen
world. But humans have burned so much fuel
that there is about 30% more carbon dioxide in
the air today than there was about 150 years
ago.
What is the effect of this increase in CO2
production on the environment?
Teachers' Domain Global Warming and the Greenhouse Eff5.mov

20.  The atmosphere is about 78% nitrogen gas, N2.
 However, most organisms are unable to use it in
this form.
Why?
 Because the two nitrogen atoms in the nitrogen
gas N2 molecule are connected by a strong
covalent bond that is very difficult to break.

21. 1. Nitrogen fixation
2. Ammonification
3. Nitrification and assimilation
4. Denitrification

Production of ammonia

22. 1. Nitrogen fixation:
It is the process of combining nitrogen with
hydrogen to form ammonia NH3, (a compound that
organisms can use to make amino acids and other
nitrogen containing organic molecules).
Nitrogen fixation is done by nitrogen-fixing
bacteria

23. Nitrogen-fixing bacteria
- They are bacteria that live in the soil and are also found
within swellings, on the roots of some plants
- They have enzymes that can break the covalent bond
in the atmospheric nitrogen gas, then they bind
nitrogen atoms to hydrogen to form ammonia.

24. 2. Ammonification
It is the production of ammonia by decomposer
bacteria during the decay of organic matter.

25. 1. Nitrification
It is the production of nitrate NO3 from ammonia.
This is performed by nitrifying bacteria which
convert ammonia into nitrate.

26. 2. Assimilation
It is the absorption of ammonia or nitrate and
their assimilation into organic compounds
by plants.

27. C. Denitrification:
It is the conversion of nitrate to nitrogen gas.
This is done by Denitrifying bacteria.
Nitrogen gas is produced and the cycle starts
again.

30. Organisms need nitrogen and phosphorus to build
proteins and nucleic acids. Phosphorus is an
essential part of both ATP and DNA.
Phosphorus is usually present in soil and rock as
calcium phosphate, which dissolves in water to
form phosphate ions.
This phosphate is absorbed by the roots of plants
and used to build organic molecules. Animals that
eat the plants reuse the organic phosphorus.

32. 4. The Water
Cycle

37. The NONLIVING portion of the water cycle:
1. Water vapor in the atmosphere condenses
and falls to the Earth’s surface as rain or
snow.
2. Some of this water percolates into the soil
and becomes part of the ground water.
3. Some runoff that is the water that run across
land collects into river stream and eventually
return to the oceans
4. Most of the remaining water is heated by the
sun, it reenters the atmosphere by
evaporation.

38. The living portion of the water cycle:
1. Water is taken up by the roots of plants. After
passing through a plant.
2. the water moves into the atmosphere by
evaporating from the leaves, a process called
transpiration

39. PLANTS IN RAIN FORESTS CREATE THEIR
OWN RAIN
 In thickly vegetated ecosystems, such as
tropical rain forests, more than 90% of the
moisture in the ecosystem passes through
plants
 Then it is transpired from their leaves, i.e.
plants in rain forests create their own rain.

40. Thank
you