Cycling Matter Through Organisms & Environment — Practice · Grade 6 Science

Chapter: Ecosystems, Watersheds & Conservation

What this practice covers

By the end of Cycling Matter Through Organisms & Environment you should be able to:

8 questions, written answer and multiple choice, each with a worked explanation.

Vocabulary used: decomposition, respiration, evidence, system boundary, uncertainty.

Problem 1

Does the light itself become carbon matter?
Answer and explanation

No. Light supplies energy; carbon atoms come from matter such as carbon dioxide in the stated model.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 2

Do plants respire only at night?
Answer and explanation

No. Respiration occurs in plants in daytime as well; photosynthesis depends on light under the familiar green-plant model.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 3

Why should decomposer biomass be included?
Answer and explanation

Some material enters those organisms rather than all immediately becoming soil; the account needs actual pathways.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 4

What is recycled in that arrow?
Answer and explanation

Specified matter or nutrient units, not the complete original usable energy supply.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 5

Develop a complete response: Find the final stores and explain what is conserved and simplified. Include relevant evidence and one method or model limit.
Answer and explanation

Soil: 20 − 5 + 3 = 18 units. Plants: 8 + 5 − 2 = 11. Animals: 2 + 2 − 3 = 1. The total remains 30 units. These are simplified nutrient-account units, not a complete real decomposition pathway or energy total; actual stores and processes would be more detailed.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 6

Apply the unit independently: A student says decomposers return all the original food energy to plants. What distinction is missing? Give a reason and a relevant qualification.
Answer and explanation

Decomposition can return matter to usable nutrient pathways, but energy spreads through processes and thermal transfers. Plants still require an energy source such as sunlight.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 7

Which statement correctly uses decomposition in Cycling Matter Through Organisms & Environment?
  1. decomposition: Biological breakdown and transformation of organic material into other matter stores and forms.
  2. Decomposers make matter disappear.
  3. Recycling matter automatically recycles all usable energy.
  4. One illustrative result establishes every real condition and needs no further evidence.
Answer and explanation

decomposition: Biological breakdown and transformation of organic material into other matter stores and forms.

Biological breakdown and transformation of organic material into other matter stores and forms. Soil: 20 − 5 + 3 = 18 units. Plants: 8 + 5 − 2 = 11. Animals: 2 + 2 − 3 = 1. The total remains 30 units. These are simplified nutrient-account units, not a complete real decomposition pathway or energy total; actual stores and processes would be more detailed.

Problem 8

Which statement correctly uses respiration in Cycling Matter Through Organisms & Environment?
  1. Decomposers make matter disappear.
  2. respiration: Cellular processes releasing usable energy from organic material, with associated matter changes.
  3. Recycling matter automatically recycles all usable energy.
  4. One illustrative result establishes every real condition and needs no further evidence.
Answer and explanation

respiration: Cellular processes releasing usable energy from organic material, with associated matter changes.

Cellular processes releasing usable energy from organic material, with associated matter changes. Soil: 20 − 5 + 3 = 18 units. Plants: 8 + 5 − 2 = 11. Animals: 2 + 2 − 3 = 1. The total remains 30 units. These are simplified nutrient-account units, not a complete real decomposition pathway or energy total; actual stores and processes would be more detailed.

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