Chapter 4.2 Energy Flow

Question 1

Understandings:

Answer 1

1. Most ecosystems rely on a supply of energy from sunlight
2. Light energy is converted to chemical energy in carbon compounds by photosynthesis
3. Chemical energy in carbon compounds flows through food chains by means of feeding
4. Energy released from carbon compounds by respiration is used in living organisms and converted to heat
5. Living organisms cannot convert heat to other forms of energy
6. Heat is lost from ecosystems
7. Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels

Question 2

Distinction between energy flow and cycling of inorganic nutrients

Answer 2

There is a continuous but variable supply of energy in the form of sunlight but that the supply of nutrients in an ecosystem is finite and limited

Question 3

Importance of sunlight to ecosystems

Answer 3

All life on Earth’s surface relies either directly or indirectly on sunlight. Ex: Eggs we eat, Hen lays eggs thanks to energy from grain, plant material eaten by that hen was from a producer, and the producer used sunlight to transform CO2 and H2O into energy-rich carbon compounds

Question 4

Role of Photosynthesis

Answer 4

photosynthetic organisms take simple inorganic carbon dioxide and convert it into energy rich sugar C6H12O6, and with the addition of minerals allows the producers to make complex molecules like cellulose, proteins and lips.

Question 5

Chemical energy

Answer 5

refers to the fact that organic compounds such as carbohydrates proteins and lipids are rich in energy, thanks to chemical bonds that exist between the carbon atoms and other atoms. (chemical energy measures in calories)

Question 6

Food Chain Process

Answer 6

by feeding on producers, consumers can utilize the chemical energy to grow and stay healthy. (cow (consumer) eating grass (producer) and taking chemical energy from it, digesting the organic compounds to help build meat or milk inside. Humans can consume and benefit from chemical energy from cow obtained from grass. this process called a flow of energy through a food chain

Question 7

Food Chain

Answer 7

a sequence showing the feeding relationships and energy flow between species. Biologist use the term trophic level to indicate how many organisms the energy has flowed through

Question 8

1st trophic level (producer)

Answer 8

Occupied by Autotrophs and Producers

Question 9

2nd trophic level (1st consumer)

Answer 9

Occupied by the primary consumers (organism that eat the producers)

Question 10

3rd trophic level (2nd consumer)

Answer 10

occupied by secondary consumers (organisms that eat primary consumers)

Question 11

Cellular respiration (grasshopper example)

Answer 11

Inside a grasshopper chemical energy is used for cellular respiration. Glucose originally produced by the grass is converted by the grasshopper’s cells into CO2 and H2O. –> generates a small amount of heat in each of the grasshopper’s cells, which is then lost in environment. If grasshopper is eaten, then some of the chemical energy in its body (in form of protein) is passed to next organism. If grasshopper dies not eaten, decomposers and detritivores use its available energy. The cells of decomposers carry out cellular respiration and as a result, any heat produced this way will be lost to environment.

Question 12

Heat not recyclable

Answer 12

• When energies lost, it has not disappeared, however it has been converted into a form that the organism can no longer use as a source of energy
• heat is passed from one trophic level to the next and when it leaves the ecosystem it is not reusable
• only chemical energy can be used by the next trophic level and only a small amount of the energy that an organism absorbs is converted.
• only 10-20% of the energy available is used from the previous step in a food chain –> as much as 90% is lost at each level

Question 13

Main Reasons why not all of the energy present in an organism can be used by another organism in the next trophic level

Answer 13

• not all of an organism is swallowed as a food source
• not all foods swallowed can be absorbed and used in the body
• some organisms die without having been eaten by an organism from the next trophic level
• considerable heat loss as a result of cellular respiration at all trophic levels

Question 14

Pyramid of Energy

Answer 14

used to show how much and how fast energy flows from one trophic level to the next in a community

• units are kilojoules per square meter per year (kJm-2yr-1)
• time is part of unit –> take into account the rate of energy production

Question 15

Energy Levels in Trophic Levels

Answer 15

• number of levels is limited by how much energy enters the ecosystem –> because so much energy lost at each trophic level, if it starts with low energy it will quickly be lost
• number of organisms in the chain and quantity of light available at the beginning will determine how long the chain is

Question 16

Biomass of Trophic Level

Answer 16

an estimate of the mass of all organisms within that level, expressed in units of mass but also takes into account area or volume. Ex: fields of wheat produce more in some areas than others due to sunlight reaching it, influencing the biomass. Cooler climates have a lower biomass and cannot support as many organisms. Some molecules along the food chain are lost (CO2, H2O, Urea), not all biomass gets passed on either.