Year 7 Science · Unit 1 · Lesson 01

What Is Life?

Challenge Worksheet

Name

Date

Class

Learning Goals

Rigorously apply MRS GREN to evaluate ambiguous or unusual cases.
Distinguish superficial similarities to life from the full set of characteristics.
Construct a well-reasoned scientific argument about what counts as "alive".

Go Deeper

What if…?

Scenario

In 2031, a NASA rover named Ares IV discovers an unusual crystal formation in the subsurface of Mars. The crystals grow in size over several weeks by drawing minerals from the surrounding rock. They release a small amount of heat during this process — similar to the way living cells release heat during respiration. Under repeated observation, larger crystals eventually fracture along precise fault lines, producing two or three smaller crystals that then continue to grow independently — which appears similar to reproduction. A journalist covering the mission publishes the headline: "Life found on Mars — alien crystals grow and reproduce."

The NASA team is not so sure. They note that the crystals show no response to light, temperature changes, or touch; they do not appear to take in any organic nutrients; and no internal structure resembling a cell has been detected under the electron microscope.

Using all seven MRS GREN characteristics, evaluate whether the Martian crystals should be classified as living. Clearly identify which characteristics the crystals appear to meet, which they fail, and whether the journalist's headline is scientifically justified. Use scientific terms in your answer.

Challenge 4 marks

Show What You Know

1. Evaluate whether a virus should be classified as a living thing. In your answer, identify at least three MRS GREN characteristics that viruses fail when outside a host cell, and explain what the "grey area" status of viruses tells us about the limitations of MRS GREN as a classification system.

Challenge 4 marks

2. Scientists must agree on a shared definition of "life" before they can search for it on other planets. Explain why using MRS GREN is more useful than relying on a single characteristic (for example, movement) when deciding whether an extraterrestrial object is alive. In your answer, include a specific example of something non-living that could be mistakenly called alive if only one characteristic were checked.

Challenge 3 marks

Wrap Up

In one sentence, what was the main idea of this lesson?