Week 6 · Theme 1 Systems, Unit 1 Interactions of Organisms, Concept 1.3 Changes in Food Webs (B) · 3 lessons
3
Plastic and the Red Sea
Discovery Education Science P5: Term 1, Unit 1, pp. 90–99
GoalExplain how plastic and microplastics harm food webs, and describe ways people protect the sea.
New words
microplastics · plastic pieces smaller than 5 mmsingle-use plastic · plastic made to be used once, such as a bag or a straw, and then thrown awayrestoration · repairing a damaged habitat so living things can return
Explanation
Plastic does not rot like leaves do. Sunlight and waves break it into smaller and smaller pieces, and pieces smaller than 5 mm are called microplastics. Many sea animals cannot tell plastic from food. A turtle may take a floating bag for a jellyfish. Plastic is not nutritious, and it can be sharp. Corals take in tiny pieces with their food. So plastic can harm several links of a food web. People can help. In Egypt, some coastal communities near the Red Sea reefs have limited single-use plastic: they use cloth bags and wooden forks instead. Volunteers clean beaches. Restoration projects grow small pieces of coral in a nursery and return them to the reef. A scientific explanation of a change to a food web uses a claim, evidence and reasoning.
plastic bag in the sea→breaks into microplastics→animals and corals take them in→harm moves along the food web
Worked examples
Piece
Size
Microplastic?
1
2 mm
yes
2
4 mm
yes
3
8 mm
no
4
12 mm
no
Hana sorts pieces of plastic she finds in a picture of a beach by their size. Only those smaller than 5 mm are microplastics.
A village near the Red Sea limits single-use plastic. Cloth bags and wooden forks replace plastic ones, so less plastic reaches the water.
Part
What it says
Claim
Plastic in the sea can harm a whole food web.
Evidence
Turtles eat plastic bags by mistake, and corals take in microplastics.
Reasoning
Turtles and corals are links in the web. If they are harmed, the animals that depend on them are harmed too.
A claim, evidence and reasoning about a change in a food web:
Class activity
Plastic audit (a grown-up helps). For one day, make a tally of the single-use plastic items your family throws away: bags, bottles, wrappers, straws. Do not touch dirty rubbish; look and ask. For each item write a reusable or plastic-free choice, such as a cloth bag or a refillable bottle. Which choice could your family start this week?
Practice
1
What are microplastics?
Plastic pieces smaller than 5 mm.
2
Which pieces are microplastics? Say the letters.
Piece
Size
A
3 mm
B
9 mm
C
1 mm
D
15 mm
A and C: 3 mm and 1 mm are smaller than 5 mm.
3
Why do sea turtles sometimes eat plastic bags?
They mistake a floating bag for a jellyfish, which they eat.
4
Name two things people can do to protect reefs and the sea from plastic.
Any two: use cloth bags and wooden forks, limit single-use plastic, clean beaches, help restore corals.
