Topic 4

Question 1

Define species

Answer 1

• Groups of organisms that can potentially interbreed to produce fertile offspring

Question 2

Define population

Answer 2

Group of organisms of the same species who live in the same area at the same time

Question 3

Define autotroph

Answer 3

• Organisms that make their own carbon compounds from CO2 and other substances

Ex) plants

Question 4

Define heterotroph

Answer 4

• Organisms that obtain their carbon compounds from other organisms

Ex) animals

Question 5

Give an example of an organism that uses both autotrophic and heterotrophic method of nutrition

Answer 5

• Euglena gracilis have chlorplasts and carry out photosynthesis with the presence of light
• Feed on detritus or smaller organisms by endocytosis
• Mixotrophic

Question 6

List 3 types of heterotrophs

Answer 6

1. Consumers
2. Detrivores
3. Saprotrophs

Question 7

Define consumers

Answer 7

• Heterotrophs that feed on living organisms (plants, animals, or both) by ingestion
• Take in undigested materials and digest them to absorb the products

Question 8

Define detrivores

Answer 8

• Heterotrophs that obtain organic nutrients from detritus by internal digestion
• Dead organic materials inclue dead leaves, feathers, ahirs, feces
• Detrivores ingest dead organic matter then digest it internally and absorb the products

Question 9

Define saprotrophs

Answer 9

• Heterotrophs that obtain organic nutrients from dead organic matter by external digestion
• Secrete digestive enzyme into the dead organic matter and digest it externally
• Then absorb the products of digestion

Question 10

Define community

Answer 10

• Formed by populations of different species living together and interacting with each other
• Composed of all organisms living in an area

Question 11

Define ecosystem

Answer 11

• Community of organisms in an area and their non-living environment in a single highly complex interacting system
• Biotic and abiotic factors influence each other

Question 12

Explain how the supply of inorganic nutrients is maintained

Answer 12

• Limited supplies of chemical elements
• Nutrients can be endlessly recycled – organisms absorb the elements, use them, then return them to the environment

Question 13

State the three requirements for sustainability in ecosystems

Answer 13

• Nutrient availability
• Detoxification of waste products
• Energy availability

Question 14

How does energy flow in the ecosystem

Answer 14

• Intial form of energy is sunlight
• Converted into chemical energy through photosynthesis
• Chemical energy in carbon compounds flows through food chains by means of feeding
• Energy is released by repiration and converted to heat

Question 15

What do organisms need energy for

Answer 15

• Synthesizing large molecules like DNA, RNA, and proteins
• Pumping molecules or ions across membranes by active transport
• Moving things around inside the cell or muscle clles in contraction

Question 16

What happens to the heat produced in respiration

Answer 16

• Lost from ecosystem

Question 17

Why do food chains only have a few trophic levels?

Answer 17

• The energy added to biomass by each successive trophic level is less (10%)
• Most of the energy in food that is digested and absorbed is released in respiration and lost as heat
• Organisms are not usually entiredly consumed by the next trophic level
• Not all parts are digested

Question 18

Define biomass

Answer 18

• Total mass of a group of organisms
• Consists of the cells and tissues of those organisms

Question 19

Outline the carbon cycle

Answer 19

• Carbon exists in aquatic habitates as dissolved gas CO2 and hydrogen carbonate ion
• Carbon exists in the atomphere in the form of CO2 gases
• Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds
• Carbon compounds are consumed by the next trophic level and move along the food chain
• CO2 is produced by respiration and diffuses out of organisms into water or the atmosphere

Question 20

Define peat

Answer 20

Forms when organic matter is not fully decomposed because of anaerobic conditions in waterlogged soil

Question 21

Outline the formation of methane

Answer 21

• Bacteria convert organic matter into a mixture of organic acids
• Bacteria produce acetate, CO2, H2
• Archaeans produce metahne from CO2, H2 and acetate
• Methane diffuses into the atmosphere

Question 22

What happens to the methane molecule in the atmosphere

Answer 22

• Oxidized to CO2 and water

Question 23

Outline the formation of coal

Answer 23

• Deposits of peat are buried under other sediments
• Peat is compressed and heated, gradually turning into coal

Question 24

Outline the formation of oil and nautral gas

Answer 24

• Formed in the mud at the bottom of seas and lakes
• Conditions are usually anaerobic, and so decomposition is often incomplete
• The partially decomposed matter is compressed and heated and produce oil and natural gas

Question 25

How does carbon stored in fossilized organic matter enter the carbon cycle again?

Answer 25

• Combusion of biomass and fossilized organic matter produce CO2 and can enter the carbon cycle again

Question 26

Give an example of animal that have hard body parts composed of calcium cabonate

Answer 26

• Mollusc shells contain calcium carbonate
• Hard corals that build reefs produce their exoskeletons by secreting calcium carbonate

Question 27

Outline the formation of limestone

Answer 27

• In neutral or alkaline conditions, calcium carbonate is stable
• When animals with CaCO3 die, it accumulates and forms limestone

Question 28

Construct a labelled diagram of the carbon cycle

Answer 28

Question 29

State three greenhouse gases

Answer 29

• Carbon dioxide
• Water vapour
• Methane
• Nitrous oxides
• Sulphur dioxide

Question 30

Explain the factors that determine the warming impact of a greenhouse gas

Answer 30

• How readily the gas absorbs long-wave radiation (from the earth)
• The concentration of the gas in the atmosphere
• CO2 and Water vapour are the most significant gases while methane and nitrous oxides have less impact

Question 31

Explain the greenhouse effect

Answer 31

• The sun emits short-wave radiation and warms up the earth
• The warmed earth emits longer-wave radiation to the atmosphere
• The longer-wave radiation is reabsorbed by greenhouse gases which retains the heat in the atmosphere
• The heat is trapped in atmosphere and warms up the earth

Question 32

Some people argue that temperature has been fluctuating since the beginning of time; therefore, CO2 concentration does not affect global temperature. Explain why this claim is incorrect

Answer 32

• It ignores the fact that temperature on Earth are influenced by many factors, not just greenhouse gas concnetrations (volcanic activity, ocean currents, etc.)
• Humans are emitting carbon dioide by burning fossil fuels after industrial revolution
• Although the global temperature fluctuates, the general trend is getting warmer

Question 33

Explain the threats to coral reefs from increasing concentrations of dissolved carbon dioxide

Answer 33

• Dissolved carbon dioxide makes the carobnate concnetration lower as a result of chemical reactions
• Difficult for reef-building corals to absorb them to make their skeletons
• Exisitng calcium carbonate tends to dissolve if seawater ceases to be a saturated solution fo carbonate ions