Energy and Changes to Populations

Energy and Changes to Populations

Middle School

​

Learning Objectives

• Define energy storage molecules and their importance to living things.

• Explain how available resources affect birth and death rates in a population.

• Analyze how a change in one population affects others in a food web.

• Describe the roles of producers, consumers, and decomposers in an ecosystem.

Key Vocabulary

​

Population

A group of the same type of organism living in the same specific area.

​

Ecosystem

All the living and nonliving things that are interacting within a particular shared environment.

​

Resource Population

A group of organisms that is consumed by another population to obtain necessary energy.

​

Consumer Population

A group of organisms that eats another population of organisms to get their energy.

​

Energy Storage Molecule

A molecule that organisms can use to release the energy needed for their survival.

​

Producer

An organism, such as a plant, that produces its own energy storage molecules.

Key Vocabulary

​

Consumer

An organism that must eat other organisms to get its energy.

​

Decomposer

An organism that breaks down dead organisms, recycling nutrients back into the ecosystem.

​

Competition

The struggle between organisms for the same limited resources like food or water.

​

Reproduction

The biological process by which new individual organisms are produced from their parents.

Energy for Life: Energy Storage Molecules

​

Carbohydrates

• Carbohydrates are the body’s main and quickest source of energy.

• Your body breaks them down easily to fuel all your activities.

• They are found in foods like bread, pasta, and various fruits.

​

Lipids

• Lipids are fats and oils that store large amounts of energy.

• This energy is saved for the body to use at a later time.

• Find them in foods like avocados, butter, nuts, and cooking oils.

​

Proteins

• Proteins are mainly used for building and repairing your body’s tissues.

• They can be a source of energy if the body needs it.

• Good sources of protein include meat, beans, and also some eggs.

Multiple Choice

Which type of molecule is the body's main and quickest source of energy?

• Carbohydrates

• Lipids

• Proteins

• Tissues

Multiple Choice

How does the body's use of carbohydrates for energy differ from its use of lipids?

• Carbohydrates provide quick energy, while lipids store energy for later.

• Lipids provide quick energy, while proteins are used to build tissues.

• Carbohydrates are for building tissues, while lipids are for quick energy.

• Proteins store energy for later, while carbohydrates repair the body.

Multiple Choice

An athlete is preparing for a long-distance race tomorrow and needs to store energy for the event. Which meal would be the most effective choice and why?

• A meal with avocados and nuts, because lipids are excellent for long-term energy storage.

• A meal with bread and pasta, because carbohydrates are the only source of energy.

• A meal with meat and beans, because proteins are the body's preferred source of energy.

• A meal with fruit, because it provides the largest amount of energy for later use.

How Matter and Energy Move in Ecosystems

• Producers, like plants, create their own food using the sun's energy.

• Consumers get energy by eating other organisms.

• Decomposers recycle matter from dead organisms back into the soil.

Multiple Choice

What is the primary role of a producer in an ecosystem?

• By using energy from the sun to make food.

• By eating other organisms for energy.

• By absorbing nutrients from the soil.

• By breaking down dead organisms.

Multiple Choice

What is the main difference in how producers and consumers obtain energy?

• Consumers obtain energy by eating other organisms, while producers make their own food.

• Producers obtain energy by eating consumers, while consumers make their own food.

• Both producers and consumers get energy by breaking down dead organisms.

• Producers get energy from the soil, while consumers get energy from the sun.

Multiple Choice

What would most likely happen in an ecosystem if all the decomposers were removed?

• Matter from dead organisms would not be recycled back into the soil.

• Producers would have more nutrients available to them.

• Consumers would have more food to eat.

• The sun's energy would not be available to producers.

​

​

Population Changes: Births and Deaths

• A population’s size changes based on the number of births and deaths.

• The rates of births and deaths are linked to available resources.

• More resources provide more energy to a consumer population, increasing its birth rate.

• A larger consumer population can cause more deaths in the resource population.

Multiple Choice

What are the two primary factors that determine how a population's size changes?

• The number of births and deaths in the population

• The number of predators in the area

• The climate of the habitat

• The size of the individual organisms

Multiple Choice

What is the relationship between the availability of resources and the birth rate of a consumer population?

• The birth rate of the consumer population is likely to increase.

• The consumer population will stop reproducing.

• The death rate of the consumer population will increase.

• The consumer population will migrate to a new area.

Multiple Choice

If a lack of predators allows a consumer population to grow very large, what is the most likely outcome for its main food source?

• The resource population will likely decrease because more consumers are eating it.

• The resource population will increase to support the consumers.

• The resource population will not be affected by the number of consumers.

• The resource population will also have a higher birth rate.

​

​

Competition and Ecosystem Changes

Competition

• When organisms need the same limited resources, like food or water, they are in competition.

• The ability to get these resources can limit the growth and reproduction of each organism.

• For example, two species of birds may compete for the same type of seeds for food.

Ecosystem Disruptions

• Ecosystems can be disrupted by changes to their physical or biological components, affecting populations.

• A physical change, such as a fire or drought, can destroy habitats and important food sources.

• A biological change, like a new predator, can cause a rapid decline in a population.

Multiple Choice

What is competition between organisms in an ecosystem?

• When they help each other find food and shelter.

• When they require the same limited resources, such as food and water.

• When they are part of the same family but live in different habitats.

• When one organism hunts another organism for food.

Multiple Choice

How can a physical change, such as a fire or drought, disrupt an ecosystem?

• By introducing a new predator that hunts native species.

• By causing the population of all organisms to increase rapidly.

• By destroying habitats and reducing the availability of food sources.

• By increasing the number of resources available to all organisms.

Multiple Choice

A new, more aggressive squirrel species is introduced to a forest where the main food source for native squirrels is acorns. What is the most likely long-term effect on the native squirrel population?

• The native squirrel population will not be affected by the new species.

• The native squirrel population will likely decline due to increased competition for acorns.

• The native squirrels will immediately switch to a different food source.

• The new squirrel species will be eliminated by the native squirrels.

​

Common Misconceptions

Misconception	Correction
Food chains are simple, straight lines.	Ecosystems have complex food webs, not simple lines.
Organisms create their own energy.	Energy is transferred and transformed, not created.
Ecosystem populations are always stable.	Populations are dynamic and fluctuate naturally over time.
A change to one population will not affect others.	A change in one population can affect all others.

​

Summary

• Organisms use energy storage molecules for growth and reproduction.

• Producers make food, consumers eat others, and decomposers recycle matter.

• The availability of resources impacts the birth rate of its consumer population.

• An increase in consumers leads to more deaths in a resource population.

• Competition and disruptions can cause large changes in population sizes.

• Matter cycles within an ecosystem, while energy flows in one direction.

Poll

On a scale of 1-4, how confident are you about explaining how resource availability affects population size?

• 1 (Not confident)

• 2 (A little confident)

• 3 (Mostly confident)

• 4 (Very confident)