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14.5: Lesson 14.4: Ocean Life

Difficulty Level: At Grade Created by: CK-12

Key Concepts

  • Types of ocean organisms (plankton, nekton, and benthos)
  • Marine food chains

Lesson Objectives

  • Identify three major groups of marine life.
  • Describe marine food chains.

Lesson Vocabulary

  • benthos: major group of marine organisms consisting of organisms that live on the ocean floor
  • marine organism: ocean organism, adapted for life in salt water
  • nekton: major group of marine organisms consisting of organisms such as fish that swim through the water
  • phytoplankton: “plant-like” plankton such as algae that make food by photosynthesis
  • plankton: major group of marine organisms consisting mainly of microscopic organisms that are suspended in the water of the photic zone; include phytoplankton and zooplankton
  • zooplankton: “animal-like” plankton that consume phytoplankton

Teaching Strategies

Introducing the Lesson

To introduce life in the ocean, show the entertaining and amazing video “Underwater Astonishments” at the URL below. Students will see a diversity of astonishing ways that ocean organisms have adapted to their aquatic environments.


Building Science Skills

Continue the theme of underwater adaptations with the activity at the following URL. Students will review what animal adaptations are, identify marine animal adaptations in photographs, and predict how types of adaptations vary with ocean habitats.



The intertidal zone presents a unique set of challenges for the organisms that live there. Conditions keep changing dramatically as the tide goes in and out. Students can investigate adaptations of organisms in the intertidal zone with the activity at the URL below.


Building Science Skills

Students can explore marine organisms with a focus on coral reefs by doing the activity at the URL below. The main goal of their investigation is to identify the major functions that organisms must perform in a coral reef ecosystem. Specific objectives include comparing and contrasting coral reefs in shallow and deep water; explaining the importance of physical factors in coral reef ecosystems; and inferring the fundamental source of energy in a deep-water coral reef ecosystem.


Differentiated Instruction

Suggest that students make a compare/contrast table for the three major groups of marine organisms: plankton, nekton, and benthos. They should where the organisms live, how they move, and examples of each group of organisms.


Ask students to create a two- or three-dimensional model of a hydrothermal vent food chain. It should include organisms to fill at least three tropic levels, and the organisms and their trophic levels should be identified. Have the students display their model in the classroom.

Science Inquiry

Use the inquiry activity below to test students’ ability to apply knowledge of ocean zones to living things. In the activity, students will create a diagram of the ocean zones and their features. Then they will use critical thinking skills to determine where in the ocean each organism lives based on its limits for survival.


Common Misconceptions

There are many common misconceptions about the classification of ocean organisms. For example, students commonly think that most organisms in the ocean are animals and that most of the animals are vertebrates. Several other misconceptions about the classification of ocean organisms are listed below. Share these misconceptions with the class. Then assign each of the organisms named in the list to a different student. Have the students find out how the organisms are actually classified and why they are classified this way. Tell them to report back to the class with the correct information.

  • Algae are plants.
  • Sponges, corals, anemones, and sea cucumbers are plants.
  • Starfish and jellyfish are fish.
  • Whales are fish.
  • Sharks are not fish.

Reinforce and Review

Lesson Worksheets

Copy and distribute the lesson worksheets in the CK-12 Earth Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content.

Lesson Review Questions

Have students answer the Review Questions listed at the end of the lesson in the FlexBook® student edition.

Lesson Quiz

Check students’ mastery of the lesson with Lesson 14.4 Quiz in CK-12 Earth Science for Middle School Quizzes and Tests.

Points to Consider

This chapter describes how the oceans influence Earth’s atmosphere. What else do you know about the atmosphere? For example, what gases does it contain?

The ocean is divided into zones. Do you think the atmosphere is divided into zones as well?

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