chapter 13 - organisms and their environment

Question 1

producers

Answer 1

• organisms that make their own food through photosynthesis
• contains chlorophyll
• convert light energy from the sun into chemical energy in food
• all food chains start with producers

Question 2

consumers

Answer 2

• organisms that are not able to make their own food
• obtain energy by feeding on other organisms

Question 3

decomposers

Answer 3

• organisms that get their energy by breaking down dead organisms, faeces and excretory products
• decomposition process releases inorganic nutrients like carbon and nitrogen for nutrient cycling

Question 4

food chain

Answer 4

a series of organisms beginning with the producers through which energy and nutrients are transferred, illustrating the feeding relationships among organisms

Question 5

trophic level

Answer 5

the feeding position that an organism occupies in a food chain

Question 6

food web

Answer 6

network of interconnected food chains

Question 7

energy loss in food chains

Answer 7

90% of total energy is lost during transfer from one trophic level to another and only 10% of the energy is converted to biomass to be passed onto the next trophic level. therefore ,shorter food gains are more effective in conserving energy in the system than long food chains. energy is lost as heat during respiration and as trapped chemical energy in uneaten body parts or dead bodies/undigested matter egested by consumers

Question 8

carbon cycle

Answer 8

carbon is constantly removed from and released into the atmosphere in the form of carbon dioxide. conc. of carbon dioxide in the environment is not lost but continually recycled. carbon cycle is important as : it ensures a continuous supply of carbon dioxide for photosynthesis, regulates the amount of carbon dioxide, enable energy to flow through the ecosystem. carbon dioxide is removed by —> photosynthesis (plants absorb carbon dioxide from the atmosphere and use it to produce carbon compounds) —> feeding (carbon compounds become part of body) and fossil fuels (carbon compounds are preserved as fossil fuels).

Question 9

release of carbon dioxide into the atmosphere

Answer 9

• respiration : carbon compounds eg. glucose are broken down into carbon dioxide
• combustion : combustion of fossil fuels release carbon dioxide
• decomposition : dead matter is broken down by decomposers into simple substances like carbon dioxide

Question 10

carbon sinks

Answer 10

stores more carbon than it releases for an indefinite period of time, eg. forests/oceans

carbon sink (ocean) : largest carbon sink, carbon dioxide that dissolves in ocean’s water is absorbed by phytoplankton and algae for photosynthesis, a portion of carbon compounds is in the form of fossil fuels buried under the seabed

carbon sink (forest) : atmospheric carbon dioxide absorbed by plants used in photosynthesis, large amount of carbon compounds stored in trees, remains of dead trees for coal

Question 11

why ocean gives out less carbon than it takes in

Answer 11

more carbon dioxide is taken up by plants for photosynthesis than given out during respiration. carbon dioxide is converted to organic substances/food/glucose, which enters into atmosphere when animals eat/consume plants. animals respire to release carbon dioxide and dead organisms sink to the sea bed and become fossil fuels.

Question 12

effects of deforestation

Answer 12

deforestation : clearing of forests to make land for agricultural and urban development, rate of deforestation > rate they can be replaced
- extinction and reduction of biodiversity : many species habitat destroyed -> remaining land not enough to support a whole population -> animals are endangered or extinct -> loss of biodiversity
- global warming : reduced plant life -> less carbon dioxide removed -> trap heat within earth atmosphere -> warmer climate
- soil erosion : forest provide leafy canopy -> protect topsoil from direct impact of rain and retain water by absorption by plant roots -> no forest -> topsoil easily washed away
- desertification : no leafy canopy -> sunlight fall directly on ground -> water evaporate from ground -> desert like condition

Question 13

effects of carbon dioxide pollution

Answer 13

• greenhouse effect : greenhouse gas -> trap heat -> global warming
• effect on aquatic ecosystem : more carbon dioxide dissolved in water -> more acidic -> calcium carbonate shell react -> weakened

Question 14

how do we reduce effects of global warming

Answer 14

• reduce use of fossil fuels, use renewable sources of energy
• reduce consumption of energy and electricity, water, paper and plastic
• forest management : conservation, restoration
• replace petrol powered vehicles with EV

Question 15

how is water pollution caused

Answer 15

-discharge of untreated sewage into water bodies (might contain disease-causing bacteria causing epidemics)
- excessive use of fertilisers
- dumping of non-biodegradable plastic waste
- dumping of inorganic waste in water bodies

Question 16

eutrophication and its effects

Answer 16

eutrophication : process by which water receives excessive nutrients like phosphates and nitrates, causing excessive growth of algae and water plants

excessive nutrients from fertilisers are flushed into water bodies. the pollutants causes aquatic plant growth of algae, duckweed and other plants. algae blooms, forming an algae layer on the surface of the water body, blocks sunlight from reaching other plants. the plants die and oxygen in the water is depleted by the presence of decomposers. oxygen levels decrease to a point where life is no longer possible.

Question 17

bioaccumulation

Answer 17

inorganic compounds that are non-biodegradable, and cannot be excreted, is stored in fatty tissues of organisms that consume

Question 18

biomagnification

Answer 18

when toxins or insecticides are passed along the food chain, with increasing concentrations in the bodies of the organisms along trophic levels

Question 19

explain why a higher proportion of tertiary consumers died.

Answer 19

insecticides are non-biodegradable and cannot be excreted form the organisms when ingested. due to bioaccumulation, insecticides accumulate in the fatty tissues of the organisms and increase in concentration concentration in the organisms of that trophic level. due to bioamplification, the concentration of the insect ideas increase up the trophic level and hence the consumers at the highest trophic level would have accumulated the highest concentration of insecticides.