7th grade · Science · Unit 4 of 10
Cycles & Succession
Matter cycles; land regrows
What your child practices
How water, carbon and nitrogen are cycled through ecosystems, why cycling supports sustainability, and the difference between primary and secondary succession.
Maine Learning Results learning standard: MS-LS2-3; MS-LS2-4 · matter cycling in ecosystems and how ecosystems change after disturbances
How we explain it
Children can open this short lesson before they practice.
- Water, carbon and nitrogen are reused over and over as they cycle between living things, air, water and soil.
- Primary succession starts on bare rock with no soil, with pioneer species such as lichens.
- Secondary succession happens where soil is left, such as after a fire or on an old field.
Example: A forest grows back after a wildfire. Primary or secondary succession? The fire left the soil behind. Life returns on existing soil. Answer: secondary succession
Cycles & Succession in Maine
In the Maine Learning Results, this is unit 4 of 10 in 7th grade Science, after Food Chains & Energy and before Particles & Mixtures.
Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.
Source: Maine Department of Education
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
Put the stages of primary succession in order.
- 🌲A mature forest develops
- 🌿Lichens and mosses grow
- 🪨Bare rock
- 🌾Soil builds up and grasses grow
Bare rock → Lichens and mosses grow → Soil builds up and grasses grow → A mature forest develops
Hint: Bare rock, then lichens and mosses, then soil and grasses, then shrubs, then forest.
Question 2
Water vapor cools and turns into tiny droplets in clouds. This is called…
- condensation
- precipitation
- runoff
- evaporation
condensation
Hint: A gas turning into a liquid is condensation.
Question 3
Burning coal and oil mainly moves carbon from…
- the Sun into the Earth
- plants into the soil
- the atmosphere into the ocean floor
- underground deposits into the atmosphere
underground deposits into the atmosphere
Hint: Fossil fuels hold carbon from ancient living things. Burning releases it as carbon dioxide.
Question 4
Primary or secondary succession? Sort each situation.
Sort into: 🪨 primary succession · 🌱 secondary succession
- 🏖️a new sand dune
- 🌪️woodland growing back after a storm
- 🌋a new island formed by a volcano
- 🧊bare rock exposed by a melting glacier
- 🪵a logged forest left to regrow
- 🪨cooled lava with no soil
- 🌾an abandoned farm field
- 🔥a forest regrowing after a wildfire
🪨 primary succession: a new sand dune, a new island formed by a volcano, bare rock exposed by a melting glacier, cooled lava with no soil · 🌱 secondary succession: woodland growing back after a storm, a logged forest left to regrow, an abandoned farm field, a forest regrowing after a wildfire
Hint: Primary succession starts on bare rock or new land with no soil. Secondary succession starts where soil and seeds are still there, such as after a fire or when a field is left alone.
Question 5
Which are usually the first living things to grow on bare rock?
- lichens
- tall shrubs
- deer
- oak trees
lichens
Hint: Lichens and mosses are pioneer species that can live where there is almost no soil.
Question 6
Which statement about succession is true?
- It always ends in a desert
- It never happens after fires
- It happens only in water
- Communities change over time in a fairly predictable pattern
Communities change over time in a fairly predictable pattern
Hint: Simple, fast-growing species come first and are later replaced by larger, longer-lived ones.