Energy And Ecosystems <3

Question 1

What is an ecosystem?

Answer 1

All the organisms living in a particular area and all the non-living/abiotic conditions. A living system where both abiotic and biotic factors interact.

Question 2

What are producers?

Answer 2

Organisms that make their own food such as plants and algae through photosynthesis.

Question 3

What do plants do during photosynthesis (think glucose, energy, CO2)?

Answer 3

• Plants use energy from (sunlight) and CO2 (from the atmosphere or dissolved in water)
• To make glucose and other sugars (e.g. maltose, sucrose, etc)

Question 4

What are sugars produced in photosynthesis used for?

Answer 4

• some of the sugars produced are used for respiration in order to release energy for growth
• the rest of the glucose is used to make other biological molecules, like cellulose - these molecules make up the plants biomass

Question 5

What can we call biomass?

Answer 5

The chemical energy stored

Question 6

How does the transfer of energy through an ecosystem work?

Answer 6

Energy is transferred when an organism eats another organism

Question 7

What is the general structure of a food chain?

Answer 7

Producer (grass)
Primary consumer (grasshopper)
Secondary consumer (bird)
Tertiary consumer (fox)

Question 8

What does a food chain show?

Answer 8

How energy is transferred from one living organism to another

Question 9

What two terms can biomass be measured with?

Answer 9

• Mass of carbon an organism contains
• Dry mass of its tissue per unit area

Question 10

What is dry mass?

Answer 10

The mass of an organism with the water removed

Question 11

How do we measure dry mass?

Answer 11

• A sample of the organism is dried (often in an oven set to a low temperature).
• The sample is then weighed at regular intervals (e.g. every day)
• Once the mass becomes constant, you know all the water has been removed

Question 12

What can be done to the result of dry mass to investigate populations if necessary?

Answer 12

It can be scaled up to give the dry mass (biomass) of the whole population or the area being investigated.

Question 13

What is a typical unit of dry mass?

Answer 13

kg m-2

Question 14

What is the mass of carbon in relation to dry mass?

Answer 14

It is generally taken to be 50% of the dry mass.

Question 15

How can you estimate the amount of chemical energy stored in biomass?

Answer 15

• By burning the biomass in a calorimeter
• The amount of heat given off tells you how much energy is in it
  OR
• A sample of dry biomass is burnt and the energy released is used to heat a known volume of water.
• The change of temperature of the water is used to calculate the chemical energy of the dry biomass

Question 16

What is the unit of energy?

Answer 16

Joules (J)

Question 17

Why do we use dry mass and not wet mass?

Answer 17

The water content of living tissue varies.

Question 18

Name the two energy stores in the ecosystems topic

Answer 18

NPP and GPP

Question 19

What is gross primary production/GPP?

Answer 19

The total amount of chemical energy converted from light energy by plants in a given area

Question 20

How is gross primary production lost to the environment?

Answer 20

• Approx. 50% of GPP is lost to the environment
• It is lost as heat as plants respire
• This is called respiratory loss (R)

Question 21

How do we calculate NPP?

Answer 21

GPP - R = NPP

Question 22

What is the net primary production/NPP?

Answer 22

• The remaining chemical energy after respiratory loss
• The energy available to the plant for growth and reproduction
• The energy available to organisms at the next stage/trophic level of the food chain (e.g. herbivores and decomposers)

Question 23

Where is NPP stored?

Answer 23

In the plant’s biomass

Question 24

What rate is NPP often expressed as?

Answer 24

• The total amount of chemical energy (or biomass) in a given area in a given time
• Typical units of this may be kJ ha-1 year-1 or kJ m-2 yr-1
• When NPP is expressed as a rate, it is called primary productivity

Question 25

Where do consumers store there chemical energy?

Answer 25

In their biomass

Question 26

How do consumers get energy?

Answer 26

By ingesting plant material or animals that have eaten plant material

Question 27

How much energy is lost between tropic levels?

Answer 27

- Not all chemical energy stored in the consumers’ food is transferred to the next tropic level - Around 90% of the total available energy is lost in various ways

Question 28

Why is not all the energy from the consumer’ food transferred?

Answer 28

- Not all the food is eaten (e.g. plant roots, bones), so the energy it contains is not taken in - Some parts of the ingested plant are indigestible so are egested as faeces. Therefore the chemical energy store in these parts is therefore lost to the environment - Some energy is also lost to the environment through respiration or excretion of urine

Question 29

What does the consumer do with the energy left after energy transfer?

Answer 29

- All of it is store in the consumers’ biomass - It is now available to the next tropic level - This energy is the consumers’ net production

Question 30

What is the formula to calculate net production?

Answer 30

N = I - (F + R) N - net production I - chemical energy in ingested food F - chemical energy lost in faeces and urine R - energy lost through respiration

Question 31

How do you calculate how efficient energy transfer from one trophic level to another is?

Answer 31

Net productivity of the new level / Net productivity of the prior level x 100