Download La biosphère : les cycles biogéochimiques

Name: ____________________________________________
Group: __________
Support activities – Second Year of Secondary Cycle Two
ACTIVITY 34
Date: __________________
EST
STUDENT BOOK: Chapter 8, pages 254–261
RELATED HANDOUT: Concept review 34
The biosphere: biogeochemical cycles
1. Complete the following sentences, using the words or groups of words in the box below. You
may use some words more than once.
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air
algae
ammonia
ammonium
atmosphere
bacteria
biogeochemical
biogeochemical cycle
biosphere
calcium carbonate
carbonate rock
decomposed
decomposers
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decomposition
DNA
eat
erosion
essential
eutrophication
fossil fuels
fungi
glucose
herbivores
hydrogen
hydrosphere
lithosphere
live
living organisms
loops of recycling
methane
nitrates
nitrogen-rich fertilizer
oxidized
phosphates
photosynthesis
plankton
plant
proteins
respiration
• rock
• sediment
• soap
• solid
• spread manure
• sulphur
• take in
• teeth
• temperature
• volcanic eruptions
a) The ________________________ is the part of the Earth where human, animal or plant life
is possible. It is composed of the lithosphere (the ________________________ outer
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covering of the Earth), the ________________________ (the layer of water) and the
atmosphere (the layer of ________________________). In other words, the
________________________ is the entire system of ________________________ and
their habitats.
b) The chemical elements ________________________ to life are found in the biosphere.
They move in infinite ________________________ called “________________________
cycles.” A ________________________ is a set of processes by which an element can
pass from one environment to another and eventually return to its original environment.
Carbon, ______________________, nitrogen, phosphorus and _______________________
are essential chemical elements because living organisms need to
_______________________ considerable amounts of them to _______________________
and grow.
Observatory / Guide
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Support activities – Second Year of Secondary Cycle Two
ACTIVITY 34
The biosphere: biogeochemical cycles
Name: ____________________________________________
Group: __________
Date: __________________
c) Carbon is very important because it is a basic element in several complex substances, such
as ________________________, lipids and carbohydrates. Carbon atoms are exchanged
between the ________________________, the hydrosphere and the lithosphere.
d) The carbon cycle can be described as follows: It starts with ________________________, a
process by which plants capture carbon dioxide and transform it into
_______________________. To take in the carbon they need, herbivores or carnivores
_______________________ plants or other animals. Through _______________________,
living organisms return the carbon they have ingested to the atmosphere. The rest of the
carbon they have taken in is eliminated as waste and ________________________ by
organisms called decomposers, producing carbon dioxide and _______________________.
Forest fires also release large amounts of carbon dioxide into the atmosphere. Part of the
carbon dioxide dissolved in water becomes ________________________. On the ocean
floor, this substance is changed and gradually forms ________________________. At the
surface, the rock can release part of the carbon it contains by melting on contact with
magma during ________________________. ________________________ also provide an
important supply of carbon dioxide.
e) The amount of carbon dioxide emitted in the ________________________ has increased
rapidly since the beginning of the industrial era. Human activities have upset the natural
balance of the carbon cycle, with the unfortunate consequences we know too well.
f) Nitrogen is essential in the formation of ________________________ and DNA. However,
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living organisms cannot use it in the form of molecular nitrogen (N2), as it exists in the air.
________________________ must first change it into ammonia (NH3),
________________________ (NH4+), nitrites (NO2–) or nitrates (NO3–). Nitrogen exchanges
take place between the atmosphere, the hydrosphere and the _______________________.
g) The nitrogen cycle can be described as follows: Certain bacteria in the ground or water
capture nitrogen from the atmosphere and change it into ________________________ and
ammonium. Bacteria also oxidize ammonium to form nitrites, which in turn can be
________________________ into nitrates. Then, plants can absorb ammonium and nitrates
from the soil and from water. ________________________ eat plants, and carnivores
absorb nitrogen by eating herbivores and other animals. Certain bacteria and
________________________ break down animal and plant waste, resulting in the
transformation of nitrogen into ammonium. Finally, other bacteria convert
________________________ into molecular nitrogen, which returns to the atmosphere.
Observatory / Guide
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Support activities – Second Year of Secondary Cycle Two
ACTIVITY 34
The biosphere: biogeochemical cycles
Name: ____________________________________________
Group: __________
Date: __________________
h) The nitrogen cycle can be disrupted by several natural factors, including
________________________, relative humidity and pH. Human activities have an impact
on this cycle through farming, when ________________________ is applied to the soil to
increase productivity, and through industrial processes, when factories discharge ammonia
in their wastewater. In the long term, this imbalance can interfere with plant growth.
i)
EST Phosphorus is also an essential element, especially as a basic component of
________________________. Many animals need it to form their bones,
________________________ and shells. Phosphorus is exchanged between the
lithosphere, the hydrosphere and living organisms in the form of
________________________ (PO43-).
j)
EST The phosphorus cycle can be described as follows:
________________________ of
rocks by wind or rain wears away a part of the phosphorus in rocks, and it is changed into
phosphates. The phosphates are absorbed by ________________________, herbivores
and carnivores. Some phosphates return to the soil in animal waste (feces and urine), and
others are released through the ________________________ of dead animals and plants
by ________________________. These phosphates make their way into the oceans,
where some promote the growth of ________________________ and others contribute to
sedimentation. Over time, ________________________ containing phosphates forms
________________________, and phosphorus returns to its original state.
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k) EST Human activities also disrupt the phosphate cycle when farmers
________________________ that is rich in phosphates on their land or when people
dispose of wastewater containing phosphate-laden ________________________ residues.
An excess of phosphorus in lakes and rivers accelerates ________________________
growth. This surplus can trigger ________________________ in aquatic environments. The
affected bodies of water suffer an oxygen shortage due to the presence of organisms like
algae that consume the dissolved gas.
2. Name two processes by which carbon dioxide is captured and used to produce other
substances.
Observatory / Guide
11129-B
3
Support activities – Second Year of Secondary Cycle Two
ACTIVITY 34
The biosphere: biogeochemical cycles
Name: ____________________________________________
Group: __________
Date: __________________
3. How have human activities contributed to disrupting the carbon cycle?
4. EST Which biochemical cycle or cycles are involved in each of the following situations?
a) sheep grazing in fields
b) the dead leaves left on the lawn last fall
c) the b)
fireLes
of afeuilles
charcoal
barbecue
mortes
laissées sur le gazon l’automne dernier.
Les cycles du carbone, de l’azote et du phosphore.
d) the steak you ate for supper yesterday
b) Les feuilles mortes laissées sur le gazon l’automne dernier.
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Les cycles du carbone, de l’azote et du phosphore.
Observatory / Guide
11129-B
4
Support activities – Second Year of Secondary Cycle Two
ACTIVITY 34
The biosphere: biogeochemical cycles