Interactions Within Ecosystems

Question 1

what is ecology?

Answer 1

study of interactions of organisms with one another, or between organisms and physical factors of the environment

Question 2

what is an ecosystem?

Answer 2

formed when different communities of organisms interact with one another and their environment

Question 3

what are communities?

Answer 3

all populations of organisms living and interacting with one another in a particular habitat

Question 4

what are populations?

Answer 4

group of organisms of the same kind living together in a habitat

Question 5

what are the 6 factors of the physical environment?

Answer 5

(amount of) light
temperature
(availability of) water
air
mineral salts and salinity
pH

Question 6

how does the amount of light affect the biotic environment? (2 points)

Answer 6

affects rate of photosynthesis and growth in plants (some grow better in moist, shaded areas though)

amount of light available determines the kind of plants, and hence, the kind of animals found in a habitat

Question 7

how does temperature affect the biotic environment? (2 points)

Answer 7

low temperatures slow down rate of photosynthesis and stunt plants’ growth, and slow down blood circulation in animals, making them sluggish

most plants and animals can survive 0°C to 45°C

Question 8

how does the availability of water affect the biotic environment? (3 points)

Answer 8

all organisms need water to survive

amount of water in any place depends on the rainfall it receives

generally, more organisms found where water is available

Question 9

4 points

how does air affect the biotic environment?

Answer 9

plants need carbon dioxide for photosynthesis

most organisms needs oxygen for respiration (land organisms from air, aquatic organisms from water)

polluted water usually contains less dissolved oxygen

many fishes cannot survive in polluted water (but some organisms have adapted to)

Question 10

how do mineral salts and salinity affect the biotic environment? (4 points)

Answer 10

mineral salts important in production of many essential substances (e.g. proteins, vitamins, chlorophyll)

plants obtain mineral salts from soil, animals from food

salinity affects water potential of solutions

some aquatic organisms adapted to live in very salty water, others in streams/fresh water ponds

Question 11

how does pH (acidity/alkalinity) affect the biotic environment? (4 points)

Answer 11

land plants/aquatic organisms pH-sensitive as pH affects rate of enzyme reactions

most organisms cannot survive in extreme-pH environments

freshwater organisms tolerate pH ~7, marine organisms pH ~8

pH of water varies during day as photosynthesis uses up dissolved carbon dioxide in water, making it more alkaline

Question 12

what are 3 relationships in the biotic environment?

Answer 12

parasitism
mutualism
predator-prey relationship

Question 13

what is parasitism?

Answer 13

relationship between 2 organisms in which 1 (parasite) benefits at the expense of the other (host)

parasite normally does some harm to host

Question 14

what is mutualism?

Answer 14

relationship between 2 organisms with both benefitting from each other

Question 15

what is a predator?

Answer 15

animal that lives by killing and eating other animals

Question 16

what is a prey?

Answer 16

animal that is killed and eaten by another animal

Question 17

what are producers?

Answer 17

organisms that make their own food by photosynthesis (not just plants), contain chlorophyll

Question 18

why do producers need chlorophyll?

Answer 18

traps light energy to synthesise with glucose from carbon dioxide and water

Question 19

what are consumers?

Answer 19

organisms unable to make their own food and feed on other organisms

primary consumers: feed on producers
secondary consumers: feed on primary consumers
tertiary consumers: feed on secondary consumers

Question 20

what are decomposers and their use?

Answer 20

organisms (fungi & bacteria) that break down complex nutrients in faeces/dead organisms with the help of enzymes

return carbon dioxide into atmosphere, soluble mineral salts into soil

Question 21

what are scavengers and their use?

Answer 21

organisms (e.g. earthworms) that feed on dead/decaying matter

help decomposers break down dead organisms into simple substances faster

Question 22

what is a food chain?

Answer 22

sequence of organisms, each being a source of food for the next, through which energy is transferred from one organism to the next

each feeding stage: trophic level

arrows go from food to feeder (goes into the mouth of)

Question 23

what is a food web?

Answer 23

made of inter-linked food chains

Question 24

what is an ecosystem’s ultimate source of energy?

Answer 24

the sun

Question 25

how do producers get energy?

Answer 25

they synthesise their own organic food molecules through photosynthesis, using light energy from the sun

Question 26

how do consumers get energy?

Answer 26

when consumers feed on producers/other consumers, energy is transferred

Question 27

how is energy lost along the food chain?

Answer 27

~90% of energy may be lost as heat released during respiration, passed out as undigested materials (only transferred to decomposers) and excretory waste products (e.g. urea) by consumers

total amount of energy decreases along food chain

Question 28

why is the energy flow in ecosystems non-cyclical?

Answer 28

~90% of energy lost as heat

energy lost cannot be recycled

Question 29

what are ecological pyramids?

Answer 29

diagrams showing relationship between producers and consumers at different trophic levels within an ecosystem

Question 30

how are ecological pyramids drawn? (2 important points)

Answer 30

drawn using horizontal bars

producers at bottom, tertiary consumers at top

Question 31

what is the use of a pyramid of numbers?

Answer 31

allows us to compare number of organisms in each trophic level at a particular time

Question 32

how are pyramids of numbers drawn? (2 points)

Answer 32

length of bars represent number of organisms

each bar to be labelled with names of organisms (in bars) or trophic levels (right of bars)

Question 33

what is the use of a pyramid of energy?

Answer 33

shows total energy at each trophic level (amount of energy decreases from one trophic level to the next)

Question 34

how are pyramids of energy drawn?

Answer 34

drawn upright (longest bar at bottom, shortest at top) as the amount of energy decreases from one trophic level to the next

Question 35

what are the differences between aerobic respiration and photosythesis? (conditions needed, energy conversions, equation)

Answer 35

aerobic respiration:
1) requires foods molecules (glucose), oxygen
2) chemical energy stored in food released and converted into other forms in animals, respiration occurs in all living cells
3) glucose + oxygen –> carbon dioxide + water + energy

photosynthesis:
1) requires light energy, chlorophyll, carbon dioxide, water
2) light energy converted into chemical energy and stored as complex nutrients (e.g. glucose)
3) carbon dioxide + water –(light + chlorophyll)–> glucose + oxygen

Question 36

what does the cycle of nutrients involve? (types of processes and environments)

Answer 36

brought about by physical, chemical, and biological processes

involves both abiotic (physical) and biotic environments

(carbon is one of the many nutrients cycled in the environment)

Question 37

how is carbon dioxide removed from the atmosphere? (2 points, plant and animal)

Answer 37

photosynthesis, carbon becomes part of glucose in plants

when consumers feed on these plants, glucose become part of their bodies

Question 38

how is carbon dioxide returned into the atmosphere? (3 ways)

Answer 38

released during:
1) respiration of organisms
2) combustion of wood and fossil fuels
3) decomposition

Question 39

why is the carbon cycle important? (2 points)

Answer 39

ensures continuous supply of carbon dioxide for photosynthesis

understanding carbon cycle helps us study effects of man’s activity on environment, and then taking steps to maintain equilibrium in atmosphere

Question 40

what is conservation?

Answer 40

protecting and preserving of the environment

Question 41

why reduce global warming and prevent disruption of natural cycles?

Answer 41

air pollution harmful to health and contributes to global warming

Question 42

why and how to protect different kinds of plants and animals (including marine life)? (3 points)

Answer 42

water pollution threatens land/aquatic organisms that depend on water to survive

marine ecosystems protected by law in some countries as fishes make up important part of food supply

prevents over-fishing by banning drift nets, regulating fishing ships/periods, raise endangered species of fish in hatcheries

Question 43

why preserve tropical rainforests?

Answer 43

overuse of land and deforestation leads to barren, unproductive land

tropical rainforest have sources of food and raw materials for medicinal drugs

Question 44

what is sustainable living?

Answer 44

lifestyle that aims to meet present needs without damaging environment and depleting resources that future generations may need

Question 45

how to live sustainably? (4 ways)

Answer 45

wind turbines

terrace farming (slows down water run-off, prevents erosion)

ban trade in animal parts

protect endangered animal species