Lesson 1: Oceans and Seas

Lesson 2: Coral Reefs

Lesson 3: Algae

Lesson 4: Marine Biodiversity



Learning objectives

By the end of this lesson, the students will be able to:

  • understand that marine biodiversity is the variety of life in our oceans and seas
  • appreciate the interconnectedness of marine organisms in the food chains
  • reflect on how all people and societies benefit from biodiversity as a source of food, medicines, clean water and air, raw materials, jobs and income.



What is biodiversity?
  • Biodiversity is the short form of 'biological diversity' which is the variety of all forms of life on the planet. It includes microorganisms, plants, animals and humans, and the places where they live – the ecosystems.
  • The ocean biodiversity is the variety of life in the oceans and seas. From the smallest plankton to huge whales, our oceans and seas contain over 230 thousand species.
How are organisms interconnected?
Curious facts

Biodiversity is the result of two thousand million years of evolution of life on the Earth.

The Convention on biological diversity is an international treaty to sustain the rich diversity of life on the Earth.

The United Nations declared 2010 the International Year of Biodiversity.

  • Biodiversity is sometimes called the web of life because all creatures, on land and in oceans, are naturally interconnected, interact with each other and form multiple food chains. Food chain is a chain where each organism feeds on the preceding organism.
Marine food chain: who eats whom?
  • Phytoplankton - microscopic plants that make their own food from sunlight - is the first feeding level.
  • They are followed by zooplankton - tiny sea animals, such as krill, copepods, jellyfish, worms - which feeds on the phytoplankton.
  • Zooplankton is then eaten by small fish such as mackerel, herring, as well as crustaceans (crabs, shrimp, lobsters), molluscs (clams, scallops) and squid.
  • Small fish and crustaceans are eaten by big fish (swordfish, tuna, octopus, shark, whale) and penguins, seals, polar bears.
Celebrating biodiversity
  • All organisms in all the oceans make a big difference to our world. Thanks to them we can benefit from highly nutritious fish as food; oxygen to breathe; jobs for work and money; even beaches for holidays and fun. Without this immensely rich biodiversity, we risk decreasing the number of fish, increasing negative climate change effects, destroying aquatic habitats.


Biodiversity mix (energizer)
  1. Ask the students to arrange their chairs in a circle and sit down. Explain that the circle represents the ocean.
  2. Walk around the circle and give each player a name: "Plankton", "Fish", "Sea turtle" or "Seabird".
  3. Choose one player to stand in the middle. Remove the empty chair.
  4. When the player calls one of the names (for example, "Seabirds!") eveyone with that name have to run and change places. The central player must also try to get into someone’s place while the other children are moving.
  5. The person left without a place goes in the middle and calls the next name, for example “Sea turtles!”. He or she can also call “Biodiversity!” In this case, everyone should run and change places.
  6. Discuss how all forms of life – plants, birds, fish, mammals – live together in one ecosystem and interact with each other.
Ocean biodiversity collage
  1. Draw big letters from the word “biodiversity” on 12 sheets of paper and mix them. Do not tell the word to the children.
  2. Divide them into 12 groups and ask each group to decorate each letter with pictures of the ocean wildlife: fish, animals, seabirds, algae, corals. Pictures can be drawn or taken from newspapers, magazines, postcards and brochures.
  3. Then ask the groups to work all together to make a word.
  4. Display the collage on the board or on the wall and discuss the role of ocean biodiversity.
Ocean biodiversity relay
  1. Divide the group into two teams, draw a line on the floor and tell them to stand in two lines behind it.
  2. On your signal the first players in both teams run to the table, grab a marker and write a name of a fish, a water animal or any word that comes to his mind when he thinks about ocean biodiversity.
  3. Then they hold up the paper and run back to their teams.
  4. The teams should shout all the letters in the word: e.g. T-U-N-A
  5. The players should jump up for every vowel and squat for every consonant.
  6. The next player then does the same.
  7. The team that arrives to finish first wins.
Marine food chain
  1. Write the names of marine species and their description on separate cards of paper. Mix them up and distribute to the students. Explain that they are to read their card out and match the names of the creatures with their description.
  2. Once all the species are identified, students work in small groups creating some examples of aquatic food chains. They can use the cards or make the drawings. Explain that one species can be part of several food chains because most organisms eat more than one type of food and can be eaten by more than one type of predator.
  3. Discuss with students how human activity can affect marine biodiversity and food chains in both positive and negative ways.
Marine food chain worksheet (PDF  - 127 KB)

Ask an expert

Invite a fisheries officer, a biologist, a researcher or any other person who works with the oceans to come to your school and talk about the ocean biodiversity. Prepare some questions to ask the presenter in advance. If you live in a coastal area organize a school visit to the ocean or sea together with the expert.