2.2 Communities and ecosystems

Question 1

What is the definition of “ecology”?

Answer 1

“The study of relationships between living organisms and between organisms and their environment”

Question 2

What are the two feeding methods?

Answer 2

Autotrophy: Organisms which produce their own food from organic molecules
Heterotrophy: Organisms which derive energy from other living organisms

Question 3

Autotrophic organisms make their own food, therefore they are p_______

Answer 3

Producers

Question 4

Heterotrophic organisms derive energy from other living organisms therefore they are c_______

Answer 4

Consumers

Question 5

What are two types of Autotrophy?

Answer 5

1. Photoautotrophy (photosynthesis, green plants)
2. Chemoautotrophy (chemosynthesis, deep see bacteria)

Question 6

What are two types of decomposers?

Answer 6

• Detritivores
• Saprotrophs

Question 7

What are detritivores?

Answer 7

Eat dead organisms and wastes (earthworms, woodlice)

Question 8

What are saprotrophs?

Answer 8

Lives in or on non-living organic matter, secreting digestive enzymes into it and absorbing digestive products (bacteria, fungi)

Question 9

What is a food chain?

Answer 9

A food chain is a diagram which shows the flow of energy from one organism to another as they consume each another.

Question 10

What is another name for “trophic level”?

Answer 10

Energy level

Question 11

What are some advantages and disadvantages of a food chain?

Answer 11

ADVANTAGES:
- Simple line of animals showing what eats what
- Easy to understand
DISADVANTAGES:
- Shows only one trophic level for each organism
- Only has one arrow to and from each organism (oversimplified)

Question 12

What are some advantages and disadvantages of a food web?

Answer 12

ADVANTAGES:
- Different species are a part of it
- Numerous food organisms make it stable
DISADVANTAGES:
- Complex mass of lines (difficult to understand)
- Can be confusing at times

Question 13

What do food webs show?

Answer 13

All the feeding relationships within a habitat.

Question 14

What are the 3 types of pyramids?

Answer 14

1. Pyramid of numbers
2. Pyramid of biomass
3. Pyramid of productivity/ energy

Question 15

Why are pyramids USUALLY narrower as one ascends?

Answer 15

Because by the 2nd law of thermodynamics, energy can not be transferred with 100% efficiency, therefore energy decreases along food chains

Question 16

What does a pyramid of numbers show?

Answer 16

Diagram shows the numbers of organisms at each trophic level of a food web.
Typically there are decreasing numbers as you go through the trophic levels (but there are exceptions).
–> Represents the *NUMBERS* of individual plants and animals in the food web, this does NOT take the organism size into account.

Question 17

How could you sample/ determine a pyramid of numbers?

Answer 17

• Sample using a 1m2 quadrat
• Count plants
• Collect animals, identify them and sort into trophic levels
• Count number of primary and secondary consumers
• Repeat measurements and calculate the mean

Question 18

What does a pyramid of biomass show?

Answer 18

Illustrates the total biomass of the organisms at each successive trophic level
Biomass = mass of living material per unit area

Question 19

How could you sample/ determine a pyramid of biomass?

Answer 19

• Take quantitative samples – known area or volume
• Cut plants and remove, collect leaf litter
• Collect different groups of animals separately
• Dry samples to remove water weight
• Measure the whole habitat size
• Take dry mass for sample then extrapolate for habitat size

Question 20

What are some disadvantages of pyramids of biomass?

Answer 20

• Based on an assumption that all individuals at that trophic level are the same
• Only uses samples (impossible to measure exactly)
• Time of year affects results
• Some organisms must be killed to measure dry mass (very unethical)

Question 21

What does a pyramid of productivity show?

Answer 21

Shows rate at which stock is generated at each level.
In contrast to the pyramid of numbers and biomass, the pyramid of productivity will ALWAYS be a pyramid shape
–> Due to the 2nd law of thermodynamics, energy can not be transferred 100% efficiently, so energy decreases as you go further up the trophic levels

Question 22

Which pyramid will always be pyramid shaped?

Answer 22

Pyramid of productivity (due to 2nd law of thermodynamics)

Question 23

What are some disadvantages of a pyramid of productivity?

Answer 23

• To measure energy you have to burn the sample (unethical)
• Difficult to collect all the data

Question 24

What is bioaccumulation?

Answer 24

The build-up of persistent or non-biodegradable pollutants within an organism or trophic level because they cannot be broke down.
They accumulate in biological tissue-stored in fat tissue. Organisms at any trophic level may be capable of bioaccumulation.

Question 25

What is biomagnification?

Answer 25

The increase in concentration of a persistent/ non-biodegradable pollutant along a food chain.
Builds up from one trophic level to next. Primarily affects top carnivores-where harmful effects are seen.

Question 26

What is biological control?

Answer 26

Biological control is when a natural predator of the insects affecting the crops is released into the habitat. This will cause a decrease in the population of those insects leading to less crops being destroyed. This is the preferred method of pest control as it does not leave any chemicals behind, instead it’s a natural mechanism to keep the insect population under control.

Question 27

What is the word equation of respiration?

Answer 27

Glucose + oxygen —(OXIDATION)—> carbon dioxide + water + energy

Question 28

What is the word equation for photosynthesis?

Answer 28

water + carbon dioxide —(sunlight + light)—-> oxygen + glucose

Question 29

Explain what happens during photosynthesis?

Answer 29

Plants take in carbon dioxide (from the air) and water (from the soil) and build these up into a sugar called glucose . The sugar can then be converted into other useful substances such as fats and proteins which plants need to live and grow. Oxygen is released as a waste product.

The energy for the reaction comes from the sunlight (light energy) falling on the plant that is absorbed by a green pigment called chlorophyll found in the chloroplasts .

Question 30

What are some of the factors affecting the rate of photosynthesis?

Answer 30

Light intensity

Leaf surface area

Soil moisture

Temperature

Concentration of carbon dioxide

Moisture in soil