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Following a Chain of Causes is a free printable Grade 4 English worksheet on holding a multi-step causal chain together, aligned to Common Core standard RI.4.10. It prints 2 questions with an answer key on its own sheet of paper, in 25 versions that each ask different questions, so no two pupils in the class work from the same page. Print it from the browser or download it as a PDF — no account, no email.

Set 20 of 25 · the same problems every time you open this link.

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Set 1 has all 25 in a single PDF. All 25 sets ask different questions.

Following a Chain of Causes

RI.4.10

NameDate

Read the text, then answer the questions.

1.Read the text, then answer the questions.

Lichen

A lichen is not one organism. It is a fungus and an alga living as one body. The fungus provides the structure and holds water. The alga photosynthesises and makes sugar. Separated, the fungus starves and the alga dries out. Because it needs no soil, a lichen can grow on bare rock, on gravestones and on the roofs of cars that have not moved for a decade. Lichens grow extremely slowly — some crustose species less than a millimetre a year. Scientists use that rate to date rock surfaces, a method called lichenometry. Lichens also absorb whatever is in the air. Where the air is dirty, they disappear, which makes them a living measure of pollution.

  1. 1. Why can a lichen colonise bare rock before anything else?
  2. 2. Summarise this text.
  3. 3. Explain the relationship between the fungus and the alga.
2.Read the text, then answer the questions.

What a Coral Reef Is

A coral reef looks like rock and is built by animals. A coral polyp is a soft creature the size of a pinhead. It draws calcium from the sea water and builds a hard cup around itself. Millions of polyps, cup upon cup, become a reef. Inside each polyp live tiny algae. The algae make food from sunlight and pass most of it to the polyp. In exchange they get shelter and the polyp's waste. Neither could build a reef alone. When the water gets too warm, the polyps expel the algae. Without them the coral turns white and starves. That is what bleaching means. A reef takes centuries to build and can bleach in a single hot summer.

  1. 1. Explain the relationship between the polyp and the algae.
  2. 2. Summarise this text.
  3. 3. Put these in order: the coral turns white, the water warms, the polyps expel the algae.

LessonPrint · RI.4.10 · Set 20 · free to copy for classroom use

Answer key — Following a Chain of Causes

Set 20. Prints on its own sheet.

  1. 1.1. Because it needs no soil — the fungus holds water and the alga makes food. 2. A lichen is a fungus and an alga living as one body, able to grow on bare rock, so slow it can date surfaces and so sensitive it measures air pollution. 3. The fungus gives structure and water, the alga makes sugar; separated, the fungus starves and the alga dries out.
  2. 2.1. The algae make food from sunlight and give most of it to the polyp; the polyp gives them shelter and its waste. Neither builds a reef alone. 2. Coral reefs are built by pinhead-sized polyps that make calcium cups and live in partnership with algae, and warm water breaks that partnership and bleaches the reef. 3. The water warms, the polyps expel the algae, the coral turns white.

Last reviewed 2026-09-05. Aligned to RI.4.10 of the Common Core State Standards for English language arts.