Ocean - Session II.2 Where do marine species live?


By examining the cards showing a selection of marine species and their habitats, the pupils will discover that large zones can be delineated in the oceans. They will also notice that certain species migrate (horizontally or vertically) over the course of their lives or even over the course of one day.

Key ideas

  • Species adapt to a variety of environments
  • Marine species have colonised various environments with a wide range of characteristics and constraints (depth, access to the light of day, distance from the coast, zones that alternate between being submerged and exposed, etc.).
  • Some species change environments throughout their development, or during the day
  • Species can be characterised by their living environment
    • Some species live on the coast, others on the continental shelf, while still others live in open water (oceanic zone)
    • Some species evolve in open water (pelagic species) and others near the bottom (benthic species)
    • Some pelagic species are unable to swim against the current (these are grouped under the term “plankton”)

Inquiry methods

Document review


For the entire class

For each group of pupils

  • One set of cards: A, B or C
    • Set A (Worksheet 12): cards 1, 4, 7, 10, 13, 14, 16, 19, 22, 24, 25, 28
    • Set B (Worksheet 13): cards 1, 2, 5, 8, 11, 14, 17, 20, 23, 24, 26, 29
    • Set C (Worksheet 14): cards 1, 3, 6, 9, 12, 14, 15, 18, 21, 24, 27, 30

For each pupil


Zones, tide, sea spray, abysses. Possibly: benthic, pelagic



Introductory Question

The teacher asks the entire class: Where in the ocean are living creatures found? If Session II.1 has already been completed, the teacher can remind them that the habitable volume of the ocean is 300 times that of dry land. The pupils will make their guesses, suggesting for example that certain living creatures are found on the bottom, that others swim in open water, or even that living creatures can be found at great depths (they are often familiar with the existence of abysses).

Example in a 3rd grade class: “Where in the oceans can we find living creatures?         On the ocean floor (depths);  On the edge; On the sand and rocks; On plants (algae);    In open water and offshore; In underwater grottos, coral reefs”

In order to enliven the debate, the teacher can bring up the littoral zone or even the tidal zone, which is sometimes submerged and sometimes exposed. Children are often familiar with these areas without thinking of them immediately. After this debate, the question, “where does the ocean stop” might be asked as certain zones on land are intimately tied to the ocean.

Research (Document Review)

In order to explore further, the teacher will then distribute to each group of pupils one of the sets of cards (A – Worksheet 12, B – Worksheet 13, or C – Worksheet 14), which present certain marine species with some of their characteristics, including their living environment. Each pupil will also receive a copy of Worksheet 11 which shows the topography of the sea floor. The nature and content of the documents will be briefly explained so that each pupil can fully understand what they are.

The teacher will then give the instructions: Using the set of cards your group has received and the information you have on the habitat preferences of each species:

  • On Worksheet 11, draw arrows to indicate the space occupied by each species. The arrows can be horizontal or vertical: the arrows corresponding to the species in cards 1, 14, and 24 are given as examples. Write the number of the species you are drawing the arrow for in a circle.
  • For each aquatic species: colour the circle in green if it lives on the bottom or in yellow if it swims in open water.
  • Do you notice any clear correlations between oceanic space and the characteristics of the species?

Teacher’s Notes:

  • If the teacher wishes, a time for exploring, reading and playing with the cards (20 to 30 minutes) can be organised before the session. This approach allows for a greater fluidity during the session itself because the pupils will already be familiar with the images and the vocabulary and won't be facing the unknown. They will benefit even more from this if the teacher plans on completing the other sessions in the module using these cards.
  • On Worksheet 11, the distances are purposefully not to scale in order to better show the images.
  • Let the pupils know that when the species live in shallow water, it is not necessary to use a vertical arrow to represent these: a horizontal arrow will suffice. Similarly, when a species can be found throughout the ocean but the depth of its habitat is what interests us, it is not necessary to draw a horizontal arrow; a vertical arrow is enough. Species 14 and 24 were chosen as examples (already filled out on Worksheet 11) to illustrate these two situations.
  • The pupils are divided into groups so that they need only handle a subset of the entire set received by the class. While the discussion around the spatial (and temporal) division of species is carried out by the group, it is preferable that each pupil complete Worksheet 11 on their own, in order to keep an individual record of this activity.
  • It is similarly suggested that each pupil has their own complete set of species cards, given in Worksheet 15.
  • These cards will be used again in sessions II.3, II.4 and II.5. Providing one or several laminated sets for the class could be a good investment.
  • If the pupils are not familiar with the scale indicators given on the cards, the teacher should take a moment to explain the concept (it is not the “length” of the organism, as some pupils sometimes believe).
  • A variant could be proposed, which would consist in having the pupils complete the activity as a “role-playing game”: “Imagine that you are in charge of drawing a map showing the distribution of the species living in the ocean. In order to do this, researchers specialised in various groups of living creatures have sent you data. It’s up to you to compile this data to create the map!” 

Group Discussion and Conclusion

Each pupil will receive a copy of Worksheet 15, which has the entire set of species cards. The teacher will post the poster-size version on the board and each group will share its ideas, discussing them collectively, then adding them to the poster (here are the answers).

The class will likely notice certain zones in particular:

The horizontally-defined zones:

  • The zone which is never submerged but is affected by sea spray
  • The zone which is sometimes submerged and sometime exposed, depending on the tides, called “intertidal zone,” “littoral zone” or sometimes “foreshore”
  • The zone close to the coast, which is shallow and above the continental shelf
  • The oceanic zone, which is past the continental shelf (“offshore”) and deeper

The vertically-defined zones:

  • The surface-level zone of the ocean which receives sunlight during the day, called the “photic zone” (it receives photons, which are particles that make up light)
  • The deepest zone, which does not receive sunlight and is called the "aphotic zone” ("without photons"). Once they reach depths of 200m, ocean regions are called abysses.

Each species seems to have a preferred habitat within oceanic space, which includes the portion of dry land that is exposed to sea spray. It appears that all three dimensions of space are much more utilised in the ocean than on land: depth plays a key role in species distribution.

Some pupils will no doubt notice that certain species are able to migrate from one zone to another, either over a long period of time (like sole, which make one round trip per year between deep and shallow waters) or shorter periods of time (like zooplankton, which make daily round trips between sunlit and dark zones). It also seems that certain species live on the sea floor, some of which are affixed there (like mussels) and others which also swim in open water. The former are called “benthic” and the latter “pelagic.”

Using these ideas as a starting point, the class will come up with a collective conclusion that will be written in their science logbook.

Science note and teacher’s note:

  • This division of oceanic space is purposefully simplified compared to what is used in scientific vocabulary, which divides the pelagic zone into 5 sub-zones (from shallowest to deepest): epipelagic (from the surface to approximately 200 m/650 ft), mesopelagic (approximately 200 m/650 ft to 1,000 m/3,300 ft), bathypelagic (approximately 1,000 m / 3,300 ft to 2,000 m/6,600 ft), abyssopelagic (approximately 2,000 m / 6,600 ft to 6,000 m/20,000 ft) and hadopelagic (beyond 6,000 m/20,000 ft).
  • The “scientific” names of some of these divisions are used in the session since it can be useful to learn these terms in order to facilitate later discussions. Using the term “foreshore,” for instance, will make it easier later in the module than referring to “the zone that is sometimes exposed and sometimes submerged depending on the tides.”

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