Photosynthesis and Oil Spills

In this unit, students are introduced to the dynamic nature of ecosystem phenomena and how disturbances affect them. In this lesson, students observe the effects of an oil spill on the ability of plants to photosynthesize, which can harm an entire ecosystem. This page is a high-level extract of this lesson.

Science Background for Teachers:

Science background gives teachers more in-depth information on the phenomena students explore. Below is an excerpt from this section on photosynthesis and oil spills.

Ecosystem Disturbance

Invasive species aren’t the only disturbance that can affect an ecosystem. A disturbance is any event that changes conditions in an ecosystem.

There are many kinds of disturbances that affect ecosystems, including fires, floods, volcanic eruptions, and extreme weather such as drought and tornadoes. These events can lead to shifts of resources within an ecosystem. They can also affect the populations of organisms that make up the ecosystem.

How energy flows through an ecosystem determines which organisms will live and which will die. Because of this, a change to the ecosystem that removes an energy source will have a ripple effect throughout the ecosystem. This is similar to how the introduction of an invasive species impacts all levels of the food web. One particularly harmful disturbance is massive oil spills.

These are usually a result of human energy production. Oil spills are often the result of accidents that occur when crude oil is being stored or moved. Most oil spilled on water will float on the surface. As it spreads out across the water, it becomes very thin, forming a sheen that often appears silver or gray.

Depending on the circumstances, oil spills can be very damaging to ecosystems. Oil sheen can prevent plants from carrying out photosynthesis by blocking sunlight from plants that live in the water. Because plants form the basis of most marine ecosystems, those species that eat the plants will not have a food source. Without food for energy, they will die. This change will move up through the levels of the food web as regular food sources begin to die off.

How Matter Cycles in an Ecosystem

Matter cycles through ecosystems. Most of the matter that is on Earth today has been around since the planet first formed. Over the years, all of the molecules that make up all matter, including carbon, hydrogen, oxygen, and nitrogen, have been broken down and transformed as they move through food webs. Matter is transferred and recycled at every level of a food web.

For example, photosynthesis and cellular respiration contribute to the oxygen cycle. The oxygen cycle is a back-and-forth exchange of oxygen and carbon dioxide between plants, animals, and the environment.

Plants take in carbon dioxide from the atmosphere so that they can carry out photosynthesis. They produce oxygen along with glucose as a result of photosynthesis. When animals breathe in, they take in some of those oxygen molecules from the air. When animals breathe out, they release carbon dioxide into the atmosphere.

Carbon molecules are also cycled between plants, animals, and the environment. In the atmosphere, carbon bonds with oxygen to form carbon dioxide. When plants take in carbon dioxide to perform photosynthesis, some of the carbon atoms are used for growth, becoming part of the plant.

Animals that eat plants absorb those carbon atoms. When plants and animals die, decomposers break down the carbon atoms and return them to the environment. The carbon atoms can be taken in by plants to help them grow.

Supports Grade 8

Science Lesson: Exploring Photosynthesis and Oil Spills

Once students model how energy flows through ecosystems, they focus on the source of this energy: the sun. Plants harness that energy through the phenomena of photosynthesis, and therefore play a critical role in all food webs. Students create an experiment to investigate how a disturbance such as an oil spill affects the ability of plants to photosynthesize.

Science Big Ideas

  • The ability of plants to access sunlight is important for the entire food web because plants turn sunlight, along with carbon dioxide and water, into glucose and oxygen.
  • Photosynthesis is connected to the oxygen cycle, which is the back-and-forth exchange of oxygen and carbon dioxide between plants, animals, and the environment.
  • A change to the ecosystem that removes an energy source will have a ripple effect throughout the ecosystem, just as the introduction of an invasive species impacts all levels of the food web.
  • Oil spills can cause serious harm to ecosystems.

Sample Unit CTA-2
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Science Essential Questions

  • Why are plants important in food webs?
  • Why are there always more producers than consumers in a food web?
  • How do plants use carbon dioxide? How do animals use carbon dioxide?
  • How do plants use oxygen? How do animals use oxygen?
  • How else does carbon cycle between living things?
  • How can oil get into the environment?
  • How does an oil spill affect the environment?

Common Science Misconceptions

Misconception: Ecosystems are static.

Fact: Ecosystems are dynamic and constantly changing.  

Science Vocabulary

Competition : an interaction between organisms that occurs whenever two or more organisms require the same limited resource

Disturbance : an event that changes conditions in an ecosystem

Ecosystem : a community of different species that depend on interacting with each other and their physical environment for survival

Invasive species : non-native species that disrupt the flow of energy through an ecosystem

Oxygen cycle : a back-and-forth exchange of carbon dioxide and oxygen between plants, animals, and the environment

Lexile(R) Certified Non-Fiction Science Reading (Excerpt)

Photosynthesis & Oil Spills

Gulf of Mexico Oil Spill

One of the largest marine oil spills happened in 2010 in the Gulf of Mexico. An oil rig called the Deepwater Horizon exploded and sank. This caused oil to gush into the ocean for 87 days. Eleven people died. Estimates put the amount of oil spilled at 4.9 million barrels, equal to 210 million gallons.

The spill was devastating to the gulf’s diverse ecosystems. These ecosystems include coastal wetlands, underwater canyons, ocean water, and fresh water from rivers in the United States and Mexico. Killer whales, shrimp, oysters, migrating waterfowl, and deepwater coral all live in the Gulf of Mexico. More than 6,000 birds, 600 sea turtles, and 100 mammals were killed as a result of the oil spill.

Long-Term Effects of Deepwater Horizon

Scientists are still trying to figure out the long-term effects of the oil spill. The complex interactions between all of the living things in the Gulf of Mexico and their environment make it difficult for scientists to fully understand the long- term effects of the spill on the ecosystem.

 

Ecosystem Disturbances

Any event that changes conditions in an ecosystem is called a disturbance. There are many kinds of disturbances that affect ecosystems. Fires, floods, volcanic eruptions, and extreme weather such as drought and tornadoes are all disturbances. These events can lead to shifts of resources within an ecosystem. They can also affect the populations of organisms that make up the ecosystem.

How energy flows through an ecosystem determines which organisms will live and which will die. Because of this, a change to the ecosystem that removes an energy source will have a ripple effect throughout the ecosystem. This is similar to how the introduction of an invasive species impacts all levels of the food web.

Photosynthesis & Oil Spills
 
Photosynthesis & Oil Spills

The Importance of Photosynthesis

When a plant captures light energy from the sun and carries out photosynthesis, it uses 90 percent of the energy to perform all of its life functions. This leaves 10 percent of the energy to get passed along to consumers. Because primary consumers only get 10 percent of the energy, they must eat more plants to get enough energy to perform all of their life functions. When a secondary consumer eats a primary consumer, only 10 percent of this energy gets passed along. The decreasing amount of available energy as you move up a food web explains why there are fewer organisms at the top of a food chain than at the bottom.

Energy gets passed along in the form of chemical bonds holding together the molecules of glucose. Each cell in every living thing takes the glucose and performs cellular respiration in its mitochondria. Remember that cellular respiration is the process in which cells extract energy from food. Oxygen is used to break down the glucose so its energy can be stored in molecules of ATP. ATP is the molecule that powers life. In addition to ATP, cellular respiration also produces heat and carbon dioxide as by-products.

This transfer of energy from one organism to another explains why energy moves in one direction through an ecosystem. It also explains why life requires a constant supply of energy from the sun.

 

Hands-on Science Activity

In this lesson, students develop an experiment to examine how an oil spill alters the cycling of matter and the flow of energy through an ecosystem phenomena by disrupting the ability of aquatic plants to photosynthesize. This gives students the opportunity to experiment and evaluate the importance of producers to all food web phenomena because of their ability to capture the sun’s energy.

Science Assessments

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Science Standards

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Standards citation: NGSS Lead States. 2013. Next Generation Science Standards: For States, By States. Washington, DC: The National Academies Press. Neither WestEd nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.