8th grade · Science · Unit 5 of 13
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.
Texas Essential Knowledge and Skills (TEKS) teks student expectation: 8.11(C); 8.12(B) · the carbon cycle, and primary and secondary succession
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 Texas
In the Texas Essential Knowledge and Skills (TEKS), this is unit 5 of 13 in 8th grade Science, after Light & Radiation and before Cells & Life Processes.
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: Texas Education Agency (TEA)
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
A wildfire burns a forest. The next spring, fireweed is already growing. Why so soon?
- Succession cannot happen after a fire
- Fireweed seeds fall from clouds
- Roots, seeds and soil survived the fire
- The fire created new soil from rock
Roots, seeds and soil survived the fire
Hint: This is secondary succession, which starts with soil and seeds already in place.
Question 2
Why do we say matter is cycled in an ecosystem?
- Decomposers destroy matter
- The same atoms are used again and again
- New matter is created by producers
- Matter leaves Earth in food
The same atoms are used again and again
Hint: Matter is not created or destroyed. It moves between living things and the environment.
Question 3
How do decomposers help cycle matter?
- They turn nutrients into energy
- They break down dead matter and return nutrients to the soil
- They make new nutrients from nothing
- They remove nutrients from the ecosystem for good
They break down dead matter and return nutrients to the soil
Hint: Fungi and bacteria release nutrients so plants can use them again.
Question 4
Which process puts carbon dioxide into the air?
- respiration by living things
- photosynthesis
- evaporation
- condensation
respiration by living things
Hint: Plants and animals release carbon dioxide when they use food for energy. Burning fuels does too.
Question 5
Put the steps of the water cycle in order.
- ♨️Water evaporates from lakes and oceans
- 🌧️Rain or snow falls
- 🌊Water runs off or soaks in and collects in lakes and oceans
- ☁️Water vapor cools and condenses into clouds
Water evaporates from lakes and oceans → Water vapor cools and condenses into clouds → Rain or snow falls → Water runs off or soaks in and collects in lakes and oceans
Hint: Water evaporates, condenses into clouds, falls as precipitation and then collects, ready to evaporate again.
Question 6
Primary or secondary succession? Sort each situation.
Sort into: 🪨 primary succession · 🌱 secondary succession
- 🌋a new island formed by a volcano
- 🏖️a new sand dune
- 🌪️woodland growing back after a storm
- 🪵a logged forest left to regrow
- 🪨cooled lava with no soil
- 🔥a forest regrowing after a wildfire
- 🧊bare rock exposed by a melting glacier
- 🌾an abandoned farm field
🪨 primary succession: a new island formed by a volcano, a new sand dune, cooled lava with no soil, bare rock exposed by a melting glacier · 🌱 secondary succession: woodland growing back after a storm, a logged forest left to regrow, a forest regrowing after a wildfire, an abandoned farm field
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.