Lecture 3 - Energy in the Ecosystem

Question 1

What are producers?

Answer 1

Photosynthetic organisms that manufacture organic substrates using light energy, water and carbon dioxide.

Question 2

What are examples of a producer?

Answer 2

Green plants and phytoplankton

Question 3

What are autotrophs?

Answer 3

Organisms that synthesise their own organic molecules from inorganic substrates.

Question 4

What are consumers?

Answer 4

Organisms that obtain their energy by consuming other organisms

Question 5

What are primary consumers?

Answer 5

Animals that directly eat producers

Question 6

What are secondary consumers?

Answer 6

Animals that eat primary consumers

Question 7

What are tertiary consumers

Answer 7

Animals that eat secondary consumers

Question 8

What are decomposers?

Answer 8

1. Feed on the remaints of producers and consumers to obtain energy
2. They break down complex substrates to simple molecules releasing minerals and elements into forms absorbable by plants

Question 9

What are examples of decomposers?

Answer 9

Fungi and bacteria

2. Detritvores such as earth worms can also help

Question 10

What is a food CHAINS?

Answer 10

2. The feeding relationship from producers through to tertiary consumers.
3. Each stage in a food chain is a tropic level where the arrows represent the flow of energy

Question 11

What are tropic levels

Answer 11

1. Producer
2. Primary Consumer
3. Secondary Consumer
4. Teritary Consumer
5. Quanternary consumer

Question 12

What are food WEBS

Answer 12

Series of interlinking food webs showing the flow of energy through a habitat
2. Illustrate that an organism are eaten by more than one type of consumer

Question 13

Why is most of the suns energy not converted into organic matter?

Answer 13

1. 90% of sun energy reflected by dust and clouds into space
2. Not all wavelengths of light are used by photosynthesis and leaf also reflect light
3. Light might not fall on chlorophyll molecules
4. Other limiting factors

Question 14

How do you calculate energy converted

Answer 14

NPP= GPP-R

1. Plant use energy from sunlight to synthesise plant tissue or bio mass (GPP)
2. Respiration (R)
3. Energy left (NPP)

Question 15

What is GPP

Answer 15

Total quantity of light energy that plants in a community convert to organic matter in a given area and time

Question 16

What is NPP

Answer 16

rate at which energy is stored by plants

Question 17

Why is there low % energy transfer for consumers

Answer 17

1. Not all parts of an organism is eaten
2. Some parts are consumed but not digested
3. Some energy lost in excretory materials e.g. urine
4. Energy lost as heat from respiration

Question 18

What is the % of energy lost between the tropic levels

Answer 18

1. Sun 1.3% –>
2. Primary Producers 5-10% –>
3. Primary Consumers 5-20%
4. Secondary Consumers 15-20%

Question 19

Why are food chains limited to 4 or 5 organisms

Answer 19

1. Relative inefficiency of energy transfer
2. Usually have 4 to 5 trophic levels, not enough energy to support large breeding populations and levels higher than this
   3 Biomass of organisms is less at higher levels
3. Total amount of energy stored at each level is less

Question 20

How to calculate efficiency of energy transfer?

Answer 20

energy transfer =
(energy available after transfer/ (divide)
energy available before transfer)
x 100

Question 21

What are ecological pyramids?

Answer 21

1. Provides quantitative data such as numbers of biomass and energy stored at each tropic level

Question 22

Why is there sometimes fewer organisms in the lower tropic energy levels?

Answer 22

1. Size: One oak tree is treated the same as a parasite

2. The number of individuals is so great that they cannot be accurately drawn to scale

Question 23

What is biomass

Answer 23

total mass of plants and or animals

Question 24

What is Fresh biomass

Answer 24

Includes water content- which is variable

Question 25

What is dry biomass

Answer 25

Measured without water but involve the killing of an organism as we dry it out.

Question 26

How is biomas measured?

Answer 26

Grams per square meter (g m ^-2)

or Grams per cubic meter (g m ^-3)

Question 27

What is a problem of Ecological pyramids?

Answer 27

1. Do not take into account seasonal differences

2. E.g. aquatic environments where zooplankton relative to phytoplankton can vary.

Question 28

What are the benefits of Ecological pyramids?

Answer 28

1. Measuring energy stored in organisms give the most accurate representation of energy flow
2. Collecting the data is complex
3. Data are collected in a given area (e.g. 1 square metre) for a set time (1 year)
4. Units are usually kj m-2 year -1