Module 5- Ecology and ecosystems

Question 1

What is an ecoystem?

Answer 1

An ecosystem includes all the organisms living in a particular area and all the non-living conditions.

Question 2

What is a producer?

Answer 2

The organism that makes its own food

Question 3

Where is energy and carbon dioxide gained from during photosynthesis?

Answer 3

Energy from sunlight
Carbon dioxide from the atmosphere or dissolved in water in aquatic habitats

Question 4

What is a plant’s biomass?

Answer 4

The mass of living material or chemical energy stored in the plant

Question 5

What are primary/secondary/tertiary consumers?

Answer 5

Primary = eat producers
Secondary = eat primary
Tertiary = eat secondary

Question 6

How can biomass be measured in terms of…

Answer 6

The mass of the carbon that an organism contains or the dry mass of its tissue per unit.

Question 7

How is biomass in an organism found when looking for dry mass?

Answer 7

A sample of an organism is dried. This is done by placing it into an oven at a low temperature and checking the weight at regular intervals. When the mass is constant, the mass is completely dry. The mass of carbon is taken by 50% of the dry mass.

Question 8

How to measure biomass using a calorimeter?

Answer 8

A sample of dry biomass is burnt and energy is released which is used to heat a known volume of water. The change in temperature of water is used to calculate the chemical energy of dry biomass.

Question 9

What is GPP?

Answer 9

The total amount of chemical energy converted from light energy by plants

Question 10

What is respiratory losses?

Answer 10

50% of chemical energy is lost to the environment in heat when plants respire. This is known as respiratory losses.

Question 11

After the respiratory losses, the chemical energy is called what?

Answer 11

NPP = Net primary production

Question 12

What is NPP?

Answer 12

The energy available for a plant for growth and reproduction and the energy available to organisms in the next stage of the food chain.

Question 13

Where is NPP stored?

Answer 13

The plants Biomass

Question 14

What is primary productivity?

Answer 14

The total amount of chemical energy in a given area, in a given time

Question 15

How do consumers collect energy?

Answer 15

When a consumer eats a producer or eats an animal that has eaten a producer

Question 16

How much of the total energy available in the previous trophic level is lost ?

Answer 16

90%

Question 17

Explain why some GPP is so low compared with the original light energy available

Answer 17

Some solar energy is lost because
* It is the wrong wavelength for photosynthesis
* Reflects off the leaf
* Passes straight through the leaf/misses chloroplasts
* Just heats the leaf
* Misses the leaf/strikes a non-photosynthetic part of the plant

Question 18

What are the 3 reasons why not all energy is passed on to the next trophic level?

Answer 18

• Some parts of organisms are indigestible such as the bones etc.
• Some is egested through faeces
• Some is lost to the environment through respiration or urine excretion.

Question 19

What is the total energy that is available to the next trophic level called?

Answer 19

Net production of consumers

Question 20

How is net production of consumers calculated?

Answer 20

N = I - ( F + R )

Question 21

How to calculate energy efficiency?

Answer 21

(Net productivity/total energy available) x 100

Question 22

What are decomposers?

Answer 22

Decomposers break down dead or undigested material

Question 23

What are two ways in which a farmer can increase the NPP?

Answer 23

simplifying the food web and reducing respiratory losses

Question 24

What are 2 ways in which the food web can be simplified to increase NPP?

Answer 24

Insecticides which kill insect pests that eat and damage crops. Killing pests means less biomass is lost from crops
Herbicides kill unwanted weeds which reduces direct competition

Question 25

What are biological agents and how do they increase the efficiency of energy transfer of humans?

Answer 25

Parasites which live or lay their eggs inside a pest and kill them.
Pathogenic bacteria and viruses also kill pests

Question 26

How may a farmer reduce respiratory losses in an organism?

Answer 26

Reducing their movement so that they lose less through respiration
Kept indoors and warm so less energy is used to keep warm

Question 27

What is the negative of farmers reducing respiratory losses in organisms?

Answer 27

Ethical concerns

Question 28

What are the measurements used to measure primary and secondary productivity?

Answer 28

Biomass in a given area in a given time
KJ m-2 year-1

Question 29

How can a student suggest how the mass of carbon for a particular organism could be estimated?

Answer 29

• Calculate the mean diameter of the organism
• Use this to determine the mean biomass
• Use this % water content to find the dried mass
• Use the dried density to calculate the mass of the organism
• Estimate the number of organisms in the given area and multiply by the mean carbon content to find the total carbon.

Question 30

How to determine the chemical energy of a sample.

Answer 30

Dry the mass by placing in an oven at a low temp and checking at regular intervals until the mass is constant. Then burn the dry sample and allo the heat energy being released to heat up a known volume of water. The change in temperature of the water is the chemical energy

Question 31

1 mark

Suggest appropriate units for gross producitvity

Answer 31

mass, per area, per year

Question 32

2 marks

After 6 weeks, the scientists removed the plants from the soil and cut the roots from the
shoots. They dried the plant material in an oven at 90 °C for 3 days. They then determined
the mean dry masses of the roots and shoots of each group of pea plants.
Suggest what the scientists should have done during the drying process to be sure that all
of the water had been removed from the plant samples.

Answer 32

1. Weigh samples at intervals during drying
2. To see if weighings became constant by 3 days)

Question 33

2 marks

In natural ecosystems, most of the light falling on producers is not used in photosynthesis. Suggest 2 reasons why

Answer 33

1. Light is reflected
2. Temperature or low CO2 concentration could be a limiting factor
3. Light didnt hit chlorophyll

Question 34

2 marks

The scientist determined the dry mass of the spinach plants. First, he heated each sample at 80 °C for 2 hours. Suggest what the scientist should do to ensure that he has removed all the water from the sample.

Answer 34

1. Weigh and heat
2. Until mass is constant

Question 35

2 marks

Farming cattle for humans to eat is less efficient than farming crops because of energy transfer. Explain why

Answer 35

1. Energy lost between trophic levels
2. Energy lost via respiration/ excretion/ faeces