Energy in Food Chains

In this model, which group of consumers is likely to obtain the most energy from the producers?

• producers

• primary consumers

• secondary consumers

• tertiary consumers

• decomposers

Answer explanation

Primary consumers, such as herbivores, directly consume producers (plants) and obtain the most energy from them. They are the first level of consumers in the food chain, making them the group that gains the most energy from producers.

In this model, how much energy will the tertiary consumers receive directly from the producers?

• 100%

• 10%

• 0%

• 0.1%

Answer explanation

Tertiary consumers do not receive energy directly from producers; they obtain energy by consuming secondary consumers, which receive their energy from primary consumers. Therefore, the energy they receive directly from producers is 0%.

Of all the energy present in the producer level, how much energy will the tertiary consumers eventually receive?

• 100%

• 10%

• 0%

• 0.1%

Answer explanation

In an energy pyramid, only about 10% of energy is transferred from one trophic level to the next. Therefore, tertiary consumers receive approximately 0.1% of the energy from producers, making 0.1% the correct answer.

In an ecosystem, if a producer has 1000 J of energy, what typically happens to this energy as it moves through the food chain?

• All of the energy is transferred to primary consumers.

• Approximately 10% of the energy is transferred to primary consumers, while the rest is lost as heat.

• About 90% of the energy is transferred to primary consumers, with 10% lost as heat.

• All of the energy is lost as heat to the environment.

Answer explanation

In an ecosystem, only about 10% of the energy from producers is transferred to primary consumers, while the majority is lost as heat due to metabolic processes, making the correct choice the second option.

Examine the food web model. Select all organisms that are secondary consumers through at least one food chain.

• grasshopper

• fox

• bird

• snake

Answer explanation

In the food web, secondary consumers are organisms that eat primary consumers. The fox and bird are both secondary consumers as they prey on organisms like grasshoppers and other smaller animals, while the grasshopper is a primary consumer.

Examine the food web model. Select all organisms that are tertiary consumers through at least one food chain.

• owl

• fox

• hawk

• snake

Answer explanation

In the food web, owls and snakes are tertiary consumers because they prey on the secondary consumers, birds and frogs.

Hawks and foxes can also be tertiary consumers, but they are not included in the correct answers here.

Which statements are true about trophic levels in an ecosystem?

• Half of the energy in each level is passed on to the next level.

• Energy is transferred from organisms in one level to those in the level above.

• Energy is transferred down each level of the energy pyramid.

• Only a small amount of energy is passed on to the next level.

• Most of the energy in each level is used up by organisms for life processes.

Answer explanation

Energy is transferred from one trophic level to the next, but only a small amount is passed on (about 10%). Most energy is used by organisms for life processes.

TRUE or FALSE: Most of the energy in each trophic level is destroyed.

• TRUE

• FALSE

Answer explanation

Energy cannot be created or destroyed. It can only change form. Most of the energy becomes a less useful form of energy, but is not destroyed.

TRUE or FALSE: Eventually, all the energy is recycled back to the producers.

• TRUE

• FALSE

Answer explanation

Energy is not recycled in ecosystems.

Producers must receive a constant input of energy.

The energy eventually becomes a form unusable by organisms and is transferred elsewhere.

Which type of energy transformation occurs in photosynthesis?

• Chemical to thermal

• Radiant to chemical

• Thermal to radiant

• Chemical to radiant

Answer explanation

In photosynthesis, plants convert radiant energy from sunlight into chemical energy stored in the chemical bonds of the glucose molecule.