4.2 Energy flow

Question 1

For most biological communities, what is their initial source of energy?

Answer 1

Sunlight

Question 2

How can living organisms harvest sunlight energy?

Answer 2

Photosynthesis

Question 3

What 3 groups of autotrophs carry out photosynthesis? What are they often referred to as?

Answer 3

Plants, eukaryotic algae (e.g. seaweed), and cyanobacteria
Often referred to by ecologists as producers

Question 4

Why are heterotrophs indrectly dependent on light energy?

Answer 4

• They use carbon compounds in their food as a source of energy
• In most ecosystems all oe almost all enrgy in the carbon compounds will originally have been harvested by photosynthesis in producers

Question 5

How does the amount of energy supplied to ecosystems in sunlight vary around the world?

Answer 5

Sahara dessert: high sunlight intensity but less producers = less energy becomes available to organisms

Redwood forests of california: less sunlight intensity but more producers = more energy becomes available to organismss

Question 6

What is light energy converted into in carbon compounds by photosynthesis?

Answer 6

Chemical energy

Question 7

How does light energy get converted into chemical energy?

Answer 7

Producers absorb sunlight using chlorophyll and other photosunthetic pigments. This converts the light energy to chemical energy, which is used to make carbohydrates, lipids and all the other carbon compiunds in producers

Question 8

How do producers release energy from their carbon compounds?

Answer 8

By cell respiration and then use it for cell activities

Question 9

What is the energy released as when producers release energy through cell respiration and cell activities?

Answer 9

lost to the environment as waste heat

Question 10

What part of producers are available to heterotrophs?

Answer 10

Carbon compoinds in cells and tissues of producers

Question 11

How does chemical energy in carbon compounds flow through food chains?

Answer 11

By feeding

Question 12

What is a food chain?

Answer 12

A sequence of organisms, each of which feeds on the previous one.
* usually 2-5 organisms in a food chain

Question 13

What organisms are always first in a food chain? second? third?

Answer 13

Producers <- primary consumers <- secondary consumers <- tertiary and so on

Question 14

What does the arrow in a food chain indicate?

Answer 14

the direction of energy flow

Question 15

How is energy released by in living organisms and what does it convert to?

Answer 15

Energy released by respiration is used in living organisms and converted to heat

Question 16

What cell activities in living organisms need energy for?

Answer 16

• Synthesizing large molecules like DNA, RNA and proteins
• Pumping mplecules or ions across membranes by active transport
• Moving things around inside the cell, such as chromosomes or vesicles, or in muscle cells the protein fibres that cause muscle contraction

Question 17

What supplies energy for cell activites? Where is the energy produced?

Answer 17

ATP
* each cell produces its own ATP supply

Question 18

How do all cells produce ATP?

Answer 18

By cell respiration

Question 19

What is the process of cells producing ATP by cell respiration?

Answer 19

• Carbon compounds (carbohydrates and lipids) are oxidized
• These oxidation reactions are exothermic
• The energy released is used in endothermic reactions to make ATP

So cell respiration transfers chemical energy from glucose and other carbon compounds to ATP

Question 20

What does the second law of thermodynamics state?

Answer 20

Energy transformations are never 100% efficient.
* Not all of the erngy from the oxidation of carbon compounds in cell respiration is transferred to ATP.
* The remainder is converted to heat

Question 21

What are 4 energy conversions living organisms can perform?

Answer 21

• Light energy to chemical energy in photosynthesis
• Chemical energy to kinetic energy in muscle contraction
• Chemical energy to electrical energy in nerve cells
• Chemical energy to heat energy in heat-generating adipose tissue

Question 22

According to the laws of thermodynamics in physics, where does heat pass from?

Answer 22

Heat passes from hotter to cooler bodies, so heat produced in living organisms is all eventually lost to the abiotic environment
* The heat remains in the ecosystme for a while, but is ultimately lost

Question 23

What is biomass?

Answer 23

Biomass is the total mass of a group of organisms

Question 24

What is included in biomass?

Answer 24

it consists of the cells and tissues of those organisms, including the carbohydrates and other carbon compounds that they contain

Question 25

Why does biomass have energy?

Answer 25

Because carbon compounds have chemical energy

Question 26

How can ecologist measure how much energy is added per year by groups of organisms?

Answer 26

Ecologist can measure how much energy is added per year by groups of organisms to their biomass

Question 27

What is the trend found by measuring how much energy is added per year by groups of organisms to their biomass?

Answer 27

The energy added to biomass by each successive trophic level is less
* and secondary consumers the amount of energy is always less per year per square meter of ecosystem done in primary consumers

Question 28

What is the reason for this trend?
(the energy attitude biomass by each successive trophic level is less)

Answer 28

The loss of energy between trophic levels

Question 29

What is the reason for this trend?
(the energy attitude biomass by each successive trophic level is less)

Answer 29

The loss of energy between trophic levels

Question 30

What is the only energy available to organisms in the next trophic level?

Answer 30

Chemical energy in carbohydrates and other common carbon compounds that have not been used up in cell respiration
* The rest is lost by heat

Question 30

What is the only energy available to organisms in the next trophic level?

Answer 30

Chemical energy in carbohydrates and other common carbon compounds that have not been used up in cell respiration
* The rest is lost by heat

Question 31

How may organisms in a trophic level not entirely consumed by organisms in the next trophic level?

Answer 31

Undigestable material
* predators may not eat material from the bodies of the prey such as bones or hair

Question 31

How may organisms in a trophic level not entirely consumed by organisms in the next trophic level?

Answer 31

Uneaten material & indigestible materials

Question 32

What happens to the energy in uneaten materials?

Answer 32

Energy and uneaten material passes to saprotrophs or detritivores rather than passing to organisms in the next trophic level

Question 33

What happens to materials that are indigestible?

Answer 33

It is egested in feces. Energy and feces does not pass all along the food chain and instead passes to saprotrophs or detritivores

Question 34

Because of what losses do only a small proportion of the energy in the biomass of organisms in one trophic level become part of the biomass of organisms in the next trophic level?

Answer 34

• Loss from heat
• Loss from uneaten materials
• Loss from indigestible material -> egested as feces

Question 35

How much energy is transferred to the next trophic level?

Answer 35

10%

Question 36

For what reason is the number of trophic levels in a food chain restricted?

Answer 36

The fact that there is less and less energy available to each successive trophic level

Question 37

Why does biomass also diminish along food chains?

Answer 37

Due to loss of carbon dioxide and water from respiration and loss from the food chain of uneaten or undigested parts of organisms.
* the biomass of higher trophic levels is therefore usually smaller than that of lower levels
* there is generally a higher biomass of producers, the lowest trophic level of all, turn off any other trophic level

Question 38

How can the amount of energy converted to new biomass by each trophic level be represented?

Answer 38

Pyramid of energy

Question 39

How can the amount of energy converted to new biomass by each trophic level be represented?

Answer 39

Pyramid of energy

Question 40

What does each horizontal bar represent in a pyramid of energy?

Answer 40

Each trophic level

Question 41

How should a pyramid of energy be represented?

Answer 41

• The bars should be labeled producers at the bottom
• Each bar is a representation of the amount of energy
• Amount of energy should be per unit area per year
• The pyramid should be stepped, not triangular