Photosynthesis

Photosynthesis

Middle School

​

Learning Objectives

• Trace the flow of energy and cycling of matter within an ecosystem from the sun.

• Describe how photosynthesis creates molecules that store the sun's energy.

• Explain how cellular respiration releases energy for an organism's life processes.

• Analyze how changes in an ecosystem can impact all of its components.

Key Vocabulary

​

Ecosystem

A community of living organisms interacting with their nonliving environment.

​

Biotic Matter

The living or once-living components of an ecosystem, such as plants and animals.

​

Abiotic Matter

The nonliving components of an ecosystem, such as water, sunlight, and the soil.

​

Producer

An organism that produces its own food, usually through the process of photosynthesis.

​

Consumer

An organism that obtains its energy by feeding on other living organisms like plants.

​

Decomposer

An organism that breaks down dead organic matter, returning nutrients to the soil.

Key Vocabulary

​

Photosynthesis

The process where plants use sunlight, water, and CO₂ to create their own food.

​

Cellular Respiration

The process that releases energy from food molecules in cells for the organism to use.

​

Energy Storage Molecule

A molecule, like sugar or fat, that organisms use to store and later release energy.

​

Carbon Dioxide

A gas, with the formula CO₂, used by plants for photosynthesis and released during respiration.

​

​

Biotic and Abiotic Factors in Ecosystems

Biotic Factors

• ​Biotic factors are all the living or once-living organisms that are found within an ecosystem.

• ​​Some examples include different types of plants, animals, fungi, and even microscopic bacteria.

• ​These living things often depend on one another for essential things like food and survival.

Abiotic Factors

• ​Abiotic factors are the nonliving chemical and physical parts of the environment that affect organisms.

• ​​Key examples include things like sunlight, water, air, soil, temperature, and various minerals.

• ​These factors help determine which specific types of organisms can successfully live in an ecosystem.

Multiple Choice

What is the fundamental difference between biotic and abiotic factors in an ecosystem?

• Biotic factors are living or once-living, while abiotic factors are nonliving.

• Biotic factors are nonliving, while abiotic factors are living or once-living.

• Biotic factors include only plants and animals, while abiotic factors include only water and air.

• Biotic factors determine where organisms can live, while abiotic factors are used for food.

Multiple Choice

What is the primary role of abiotic factors like sunlight, temperature, and soil in an ecosystem?

• They serve as a direct food source for all living organisms.

• They are the living things that depend on one another for survival.

• They help determine which types of organisms can survive in that environment.

• They are microscopic organisms like fungi and bacteria.

Multiple Choice

Why would an ecosystem with many different types of plants and animals fail to thrive without abiotic factors?

• Because living organisms depend on nonliving factors like sunlight and water to live.

• Because nonliving factors like soil and minerals are a primary source of food.

• Because microscopic bacteria are considered a nonliving part of the environment.

• Because plants and animals do not directly depend on one another for survival.

Roles in an Ecosystem

​

Producers

• Producers are organisms that create their own food using sunlight.

• They are also known by the name of autotrophs.

• Producers like plants and algae form the base of every food web.

​

Consumers

• Consumers get their energy by eating other living organisms for food.

• They are also known by the name of heterotrophs.

• They can be herbivores, carnivores, or omnivores depending on their diet.

​

Decomposers

• Decomposers break down dead plant and animal matter for their energy.

• They recycle essential nutrients back into the soil and water.

• Fungi and bacteria are the most common examples of decomposers.

Multiple Choice

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

• To create its own food from sunlight.

• To get energy by eating other living organisms.

• To break down dead plant and animal matter.

• To recycle essential nutrients into the soil.

Multiple Choice

What is the key difference in how consumers and decomposers obtain energy?

• Consumers obtain energy from living organisms, while decomposers obtain it from dead organisms.

• Consumers are autotrophs that make their own food, while decomposers are heterotrophs.

• Consumers recycle nutrients from dead matter, while decomposers eat other organisms.

• Consumers are typically plants or algae, while decomposers are herbivores or carnivores.

Multiple Choice

What would be the most likely long-term effect on an ecosystem if all the decomposers were removed?

• The recycling of nutrients would stop, which would harm the growth of producers.

• Producers would have more dead material to use for energy.

• Consumers would have to start creating their own food from sunlight.

• The number of herbivores and carnivores would immediately increase.

​

​

Interpreting Food Webs

Energy Flow

• Energy flows in one direction through a food web, starting from the sun.

• Producers capture the sun's energy, which is then transferred when consumers eat them.

• The energy transfer continues when one consumer is eaten by another consumer.

Matter Cycling

• Unlike energy, the atoms that make up all organisms are continuously recycled.

• Decomposers are vital as they break down dead organisms and waste products.

• They return essential atoms to the soil and air for producers to use again.

Multiple Choice

What is the primary difference in how energy and matter move through a food web?

• Energy flows in one direction, while matter is recycled.

• Matter flows in one direction, while energy is recycled.

• Both energy and matter are recycled continuously.

• Both energy and matter flow in a single direction.

Multiple Choice

What is the main function of decomposers in a food web?

• They capture the sun's energy for the entire food web.

• They break down dead organisms and return atoms to the soil for producers.

• They transfer energy from producers to other consumers.

• They create new matter for organisms to use.

Multiple Choice

If all decomposers were removed from a food web, what would be the most likely long-term consequence?

• The flow of energy through the food web would stop immediately.

• The producers would eventually run out of the atoms needed for growth.

• Consumers would learn to absorb energy directly from the sun.

• The amount of energy from the sun would start to decrease.

​

​

Photosynthesis: Capturing Energy From the Sun

• Producers like plants capture the sun's energy through a process called photosynthesis.

• They use sunlight to convert carbon dioxide (CO₂) and water (H₂O).

• This creates energy-rich food molecules called sugars that the plant can use.

• A byproduct is oxygen, which is released and is vital for life.

Multiple Choice

What is the main purpose of photosynthesis?

• To convert sunlight into usable energy for the plant.

• To release water from the leaves into the air.

• To absorb nutrients from the soil through the roots.

• To help the plant reproduce by creating flowers.

Multiple Choice

Which statement correctly describes the transformation of materials during photosynthesis?

• Carbon dioxide and water are used to create glucose and oxygen.

• Oxygen and glucose are used to create water and carbon dioxide.

• Sunlight and soil are used to create water and air.

• Water and oxygen are used to create sunlight and sugar.

Multiple Choice

If a healthy plant in sunlight was moved into an environment with no carbon dioxide, what would be the most likely outcome?

• The plant would not be able to produce the glucose it needs for energy.

• The plant would start releasing carbon dioxide instead of oxygen.

• The plant would absorb more water from the soil to make up for the lack of air.

• The plant would produce twice as much oxygen with the extra sunlight.

The Plant Cell's Role in Photosynthesis

• The cell wall is a rigid outer layer that provides structural support.

• The cell membrane controls what substances enter and leave the cell.

• Chloroplasts are where photosynthesis occurs, using energy absorbed from the sun.

Multiple Choice

What is the primary function of chloroplasts in a plant cell?

• To perform photosynthesis using energy from the sun.

• To provide a rigid structure for the cell.

• To control what substances enter and leave the cell.

• To store water and nutrients for the cell.

Multiple Choice

Which statement best describes the relationship between the cell wall and the cell membrane?

• The cell wall provides structural support, while the cell membrane controls what passes through.

• The cell wall controls what passes through, while the cell membrane provides structural support.

• Both the cell wall and the cell membrane are primarily involved in making food.

• The cell wall absorbs energy from the sun, while the cell membrane stores it.

Multiple Choice

If a plant cell's membrane stopped functioning correctly, what would be the most likely immediate impact on photosynthesis?

• Photosynthesis would stop because the movement of necessary materials into the cell is disrupted.

• The cell would lose its rigid shape, which would stop photosynthesis.

• Photosynthesis would continue normally because the chloroplasts are still present.

• The cell would absorb too much sunlight, causing the process to fail.

​

​

What Is Cellular Respiration?

• All living things release energy from food through a process called cellular respiration.

• It breaks down molecules like sugar with oxygen, which releases the stored energy.

• The waste products of this process are carbon dioxide (CO₂) and water.

• Respiration and photosynthesis are linked in a cycle by their inputs and outputs.

Multiple Choice

What is the main purpose of cellular respiration?

• To release energy from food for living things to use.

• To create water and carbon dioxide for plants.

• To use sunlight to create sugar and oxygen.

• To form a continuous cycle with the water cycle.

Multiple Choice

Which statement describes the process of cellular respiration?

• It uses oxygen to break down sugar, releasing energy.

• It uses carbon dioxide to create sugar and water.

• It uses energy to combine oxygen and water into sugar.

• It uses sugar to produce oxygen for breathing.

Multiple Choice

Since photosynthesis and respiration are linked in a cycle, what would be the most likely impact on cellular respiration if a planet's plant life suddenly died out?

• The oxygen needed for cellular respiration would decrease.

• The amount of carbon dioxide in the atmosphere would decrease.

• Living things would no longer produce water as a waste product.

• More energy would be available for living things.

The Carbon Cycle

• Plants take carbon dioxide from the air to make food.

• Organisms release carbon dioxide when they breathe.

• Decomposers release carbon when they break down dead things.

Multiple Choice

Which statement best describes the carbon cycle?

• It describes how carbon moves between the air, plants, and other organisms.

• It is the process that plants use to create their own food.

• It is the method organisms use to breathe in oxygen.

• It explains how dead organisms are turned into fossils.

Multiple Choice

What is the relationship between how plants get carbon and how other organisms release it?

• Plants take in carbon dioxide from the air, while organisms release it back into the air.

• Both plants and organisms take in carbon dioxide directly from the air.

• Decomposers provide carbon directly to plants for food.

• Organisms release carbon by eating plants that contain it.

Multiple Choice

What would most likely happen if decomposers were removed from the carbon cycle?

• Carbon from dead things would not be released back into the cycle.

• Plants would have no carbon dioxide left in the air to use for food.

• Organisms would no longer be able to release carbon dioxide by breathing.

• The amount of carbon in the air would immediately and rapidly increase.

​

​

The Greenhouse Effect

• The greenhouse effect is a natural process that warms the Earth's surface.

• Gases like carbon dioxide (CO₂) trap heat from the sun in the atmosphere.

• Human activities, like burning fossil fuels, release more greenhouse gases into the air.

• This can raise global temperatures and disrupt ecosystems by altering weather patterns.

​

Multiple Choice

What is the greenhouse effect?

• A natural process that warms the Earth's surface

• A process that significantly cools the Earth's oceans

• A shield created by humans to block solar radiation

• A cycle that creates clouds in the atmosphere

Multiple Choice

How do greenhouse gases like carbon dioxide contribute to warming the planet?

• By trapping heat from the sun within the atmosphere

• By reflecting all of the sun's energy back into space

• By converting sunlight directly into clean energy

• By causing the Earth's surface to become less reflective

Multiple Choice

If human activities like burning fossil fuels continue to increase, what is the most likely long-term consequence?

• Global temperatures could rise, leading to changes in weather patterns.

• The amount of greenhouse gases in the atmosphere will decrease.

• The Earth will be better protected from the sun's radiation.

• Ecosystems will remain stable and unaffected by air quality.

​

Common Misconceptions

Misconception	Correction
Plants only perform photosynthesis, not cellular respiration.	Plants use both photosynthesis to make food and respiration to get energy.
Energy is created in an ecosystem.	Energy is not created; it flows and changes form, starting from the sun.
Some animals in a food web are more important.	Every part of a food web is important for a balanced ecosystem.
Decomposers are gross and unimportant.	Decomposers are essential recyclers that return nutrients to the ecosystem.

​

Summary

• Energy flows in one direction, while matter is cycled through an ecosystem.

• Photosynthesis uses sunlight, water, and CO₂ to create food and release oxygen.

• Cellular respiration uses oxygen to break down food, releasing energy and CO₂.

• Disruptions to any part of an ecosystem can affect the entire system.

Poll

On a scale of 1-4, how confident are you about explaining the relationship between photosynthesis and cellular respiration?

• 1 (Not Confident)

• 2 (A Little Confident)

• 3 (Mostly Confident)

• 4 (Very Confident)