13 Organisation and their Environment Flashcards
briefly describe the non-cyclical nature of energy flow (6) (SFTELT)
1) In any ecosystem, the ultimate source of energy is the Sun. Light
energy from the sun is absorbed by chlorophyll in producers and
converted into chemical energy during photosynthesis
2) Plants make its own food via photosynthesis and contain carbon
in the form glucose, sucrose, starch.
3) Energy is passed from one trophic level to another when primary
consumer feed on the producers and so on.
4) Organisms at each trophic level pass on about 10% energy to the
next trophic level compared to what they receive.
5) This is because energy is lost at every trophic level as heat in
respiration, uneaten organism parts and through excreted and
egested waste material. This energy lost cannot be recycled.
6) Faeces, excretory products and dead organisms contain trapped
chemical energy. This energy is released through the activity of
decomposers. Decomposers use some of this trapped chemical
energy for their needs, releasing CO2. The rest of the energy is
lost as heat.
establish the relationship of the following in food webs: producer, consumer, herbivore, carnivore,
decomposer, food chain, trophic level
- what is food chain (3)
- what is producer (2)
- what is consumer (4)
- what is food web (1)
Food chain
- A food chain is a sequence of energy transferred in the form of food,
between organisms in an ecosystem.
- Each level of the food chain is known as trophic level
- Interconnected food chains form a food web
Producer:
- organisms that contain chlorophyll thus are able to convert light energy
from the sun to chemical energy thus making their own food via
photosynthesis
- provides food for other organisms in the community thus occupies first
trophic level in food chain
Consumer
- Organisms that are not able to make their own food and obtain energy by
feeding on other organisms
- Primary consumers feed on primary producers directly. They are herbivores.
- Secondary consumers feed on primary consumers. They are carnivores.
- Tertiary consumers feed on secondary consumers. They are carnivores.
Food Web
- Food web consists of two or more food chains linked together.
describe energy losses between trophic levels and infer the advantages of short food chains
A shorter food chain means more energy available to the final consumer because less energy is lost to the surroundings. Therefore, a shorter food chain is more efficient than a longer food chain
explain the importance of the carbon cycle outline the role of forests and oceans as carbon sinks
Removal of carbon dioxide
1. Plants convert atmospheric carbon dioxide into glucose during
photosynthesis. Glucose can be converted to other carbohydrates, proteins
and fats within the plants
Return of carbon dioxide
2. Carbon dioxide is returned to the atmosphere when cellular respiration takes
place in living organisms.
3. When the plants and animals die, decomposers such as bacteria and fungi
break down the organic matter into carbon dioxide, which is released back to
the atmosphere
4. Fossil fuels are formed from the fossilised remains of dead plants and animals.
Carbon compounds from these dead organisms are stored as fossil fuels.
5. When fossil fuels and wood are burnt, carbon dioxide is produced.
Importance of carbon cycle
- Ensures that there is a continuous supply of carbon dioxide for plants to carry
out photosynthesis.
- Allows photosynthesis to convert light energy from the Sun into chemical
energy in food, which non-photosynthetic organisms can feed on to stay alive.
- Enables energy to flow through the ecosystem. Carbon compounds carry the
stored energy from organism to organism in the food chains of an ecosystem.
- Maintains the correct concentration of carbon dioxide in the atmosphere.
explain the importance of the carbon cycle outline the role of forests and oceans as carbon sinks
- removal of carbon dioxide (1)
- return of carbon dioxide (5)
- importance of carbon cycle (4)
Removal of carbon dioxide
1. Plants convert atmospheric carbon dioxide into glucose during
photosynthesis. Glucose can be converted to other carbohydrates, proteins
and fats within the plants
Return of carbon dioxide
2. Carbon dioxide is returned to the atmosphere when cellular respiration takes
place in living organisms.
3. When the plants and animals die, decomposers such as bacteria and fungi
break down the organic matter into carbon dioxide, which is released back to
the atmosphere
4. Fossil fuels are formed from the fossilised remains of dead plants and animals.
Carbon compounds from these dead organisms are stored as fossil fuels.
5. When fossil fuels and wood are burnt, carbon dioxide is produced.
Importance of carbon cycle
- Ensures that there is a continuous supply of carbon dioxide for plants to carry
out photosynthesis.
- Allows photosynthesis to convert light energy from the Sun into chemical
energy in food, which non-photosynthetic organisms can feed on to stay alive.
- Enables energy to flow through the ecosystem. Carbon compounds carry the
stored energy from organism to organism in the food chains of an ecosystem.
- Maintains the correct concentration of carbon dioxide in the atmosphere.
evaluate the effects of water pollution by sewage (6)
- Untreated sewage or excess fertilisers runoff is discharged into
waterbodies - It is rich in phosphates and nitrates causing surface algae,
phytoplankton and water plants multiply rapidly - Overgrowth of these plants prevents sunlight from reaching the
submerged plants, causing the submerged plants to die due lack
of sunlight for photosynthesis - These dead plants cause bacteria decomposers to multiply
rapidly. They break down dead plants, using up oxygen in water. - Fish and other organisms die due to lack of oxygen for respiration.
- Anaerobic bacteria break down organic water, releasing foulsmelling gases such as hydrogen sulphide and ammonia
evaluate the effects of pollution due to insecticides including bioaccumulation up food chains and impact on top carnivores (5), (4)
• Bioaccumulation refers to certain substances that cannot be broken
down (detoxified) and excreted by organisms, thus they accumulate in the fatty tissues of organism. It occurs within an organism.
• However, the concentration may not be high enough to cause the
organism to die
• Bioamplification is the increase in concentration of a substances up a
food chain.
• The organism at the higher trophic level contains higher concentration
of substances. It occurs in a food chain across trophic levels.
• Thus, the tertiary consumers are most susceptible to problems arising
from such pollutants as the concentration of toxic substances may
reach a fatal level
DDT is a synthetic pesticide used to control mosquitoes. They are extremely
toxic, especially at high concentrations
(a) DDT is non-biodegradable and is transported by water to far-reaching
areas.
(b) DDT is absorbed by the small prawns and accumulates in the fatty tissues
of the consumers
(c) The concentration of DDT increases along the food chain. At the higher
trophic levels, consumers consume a larger biomass than it possesses
due to energy loss at every level
(d) Concentration of DDT increases and reaches the maximum at the top consumer (bears) and the high level of DDT may be toxic enough to killthem
outline the roles of microorganisms in sewage treatment as an example of environmental biotechnology (6)
1.In sewage treatment plants, sewage is added to the settling
tanks for screening, where large solids are removed.
2.The sewage liquid is then sent to the primary settlement tank,
where smaller solid suspensions to settle to the bottom of the
tank as primary sludge and removed.
3.The liquid then flows into an aeration tank, where pure oxygen
is bubbled in and aerobic bacteria are added. The bacteria
decompose the organic waste into harmless substances
4.The treated water is channeled into the final settlement tank. A
portion of the sludge is returned to the aeration tank for reuse.
5.The sewage water leaving final settlement tank is disinfected to
reduce the number of microorganisms in the water before it is
discharged back into the environment.
6.The excess sludge is sent to an anaerobic digester where there
is no oxygen. Anaerobic bacteria decompose the organic matter
in sludge, producing biogas, mainly methane. Methane is used
as a fuel to generate electricity. The remaining solid material is
removed from the tank. It may be used as fertiliser or burnt in an
incinerator
discuss reasons for conservation of species with reference to the maintenance of biodiversity and how
this is done, e.g. management of fisheries and management of timber production
- importance of conservation (5)
- conservation of ocean (10)
-conservation of forest (9)
- Maintenance of biodiversity
• Maintaining a large gene pool is important as many wild plants and animals possess
favourable genes.
• By cross-breeding the different varieties of wild plants and animals, we can improve
agricultural produce such as improving yield and quality of organisms - Scientific research
• Many tropical plants are of great importance as they are sources of medicinal drugs. - Conservation preserves the existence of rich variety of species for us and future
generations to appreciate and enjoy - Economical value
• Tropical rainforests provide raw materials such as timber, cotton and rubber for
industries
• Ecotourism is a source of income for several countries such as Costa Rica,
Madagascar, and Kenya.
• Marine life, tropical rainforests provide food sources such as seafood and maize - Stable and balances ecosystem
• This prevents disruption of natural cycles such as carbon cycles
• Prevents global warming
Uncontrolled fishing practices (ocean)
1. Drift nets are nets that are left to drift freely in the seas. These nets trap almost everything in
their path.
2. Shrimp or prawn trawlers drag large fishing nets along the bottom of the sea, trapping marine
life indiscriminately.
3. Scallop dredges scrape the seabed, destroying coral reefs and organisms that live on the
seabed.
Impact
• Marine life are caught indiscriminately, young fish that are caught will not have a chance to grow
and reproduce while marine organisms that are unintentionally caught often do not survive.
• Populations of organisms will decrease and eventually some species may become endangered
and even extinct
Management of fisheries
1. Banning the use of drift nets, trawlers and dredgers which indiscriminately trap all forms of
marine life.
2. Using nets with a certain mesh size so that young or immature fish are not caught
3. Regulating the entry of ships into fishing grounds
4. Limiting the period of fishing
5. Breeding of endangered fish in captivity then released into the wild to prevent fish population
from depleting
Forest
Negative impact of deforestation
1. Global warming: The ‘slash and burn’ practice used to clear forests for agriculture releases a
large amount of carbon dioxide which contributes to global warming.
2. Soil erosion: When trees are removed, the soil is directly exposed to the force of the rain. There
are also no roots to bind the soil. The topsoil is eroded during heavy rains. Soil erosion can lead
to flooding. The eroded soil may be deposited in rivers and streams, blocking the flow of water.
The water levels in rivers rise rapidly, causing floods.
3. Desertification: When forests are cleared, sunlight falls directly onto the soil. Water evaporates
rapidly from the soil, causing it to harden. The land becomes barren and plants cannot grow in
the soil.
4. Climate change: Rainwater that is retained and absorbed by the roots of trees is lost as water
vapour during transpiration. The water vapour eventually condenses and falls as rain. When
trees are cleared, there are fewer clouds, less transpiration and less rainfall. The area becomes
dry and warm, and annual rainfall decreases.
5. Loss of habitat for many organisms: Forests are habitat for many organism, loss of habitat can
lead to species to become endangered or even extinct. This leads to loss of biodiversity
Management of timber production
- Regulating the rate of logging
- Selective logging where young trees are not cut down
- Designating land as forest reserves
- reforestation, which is the act of restocking forests which have been depleted. New seedlings
are planted to replace trees that have been felled
outline the role of forests and oceans as carbon sinks
- ocean (4)
- forest (2)
An area that that absorbs more carbon than it releases as carbon dioxide
Oceans
• Atmospheric carbon dioxide is absorbed by the ocean as carbon
dioxide dissolves in the ocean’s water
• Dissolved CO2 is used by phytoplankton and algae in photosynthesis.
• Iron compounds increases the photosynthetic activity of
phytoplankton.
• The organisms in the oceans store carbon compound. When they die,
they may sink and be buried deep in the seabed and may form fossil
fuels.
Forests
• The plants in forests absorb atmospheric carbon dioxide for
photosynthesis
• A large amount of carbon compound is stored in trees. When trees
die, they are buried deep in the ground and form coal, a kind of fossil
fuels.
