Grade 8 · Science · Unit 9 of 9
Life in Lakes & Oceans
What helps and harms life in fresh and salt water
What your child practises
Producers, food webs, nutrients, oxygen, light and temperature in lakes and oceans, how fishing, fertilizer runoff, dams and invasive species change aquatic life, with Saskatchewan lake examples.
Saskatchewan Curriculum outcome: WS8.3 · natural factors and human practices that affect productivity and species distribution in marine and fresh water environments
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
If walleye are overfished, what could happen to the smaller fish they eat?
🕸️- they would vanish at once
- their numbers could rise at first
- they would turn into walleye
- nothing could change
Show answer
their numbers could rise at first
Hint: Removing a predator affects the whole food web.
Question 2
What is the main difference between fresh water and ocean water?
🧂- ocean water has much more dissolved salt
- fresh water is salty
- fresh water is warmer
- ocean water has no fish
Show answer
ocean water has much more dissolved salt
Hint: Fresh water has very little salt.
Question 3
How do fish limits help a lake?
📏- they keep enough fish to breed and replace themselves
- they cool the water
- they make fish bigger every year
- they stop the lake from freezing
Show answer
they keep enough fish to breed and replace themselves
Hint: Rules on size and number caught protect fish populations.
Question 4
What can too many nutrients in a lake cause?
🟢- more ice
- clearer water
- more sunlight
- a large algae bloom
Show answer
a large algae bloom
Hint: Fertilizer and sewage can wash nutrients into lakes.
Question 5
Why can adding shoreline plants help a lake's health?
🌿- they make algae
- they heat the water
- they filter runoff and give fish and birds shelter
- they stop the wind
Show answer
they filter runoff and give fish and birds shelter
Hint: Shore plants act as natural filters.
Question 6
Is it a natural factor or a human practice? Tap a factor, then tap its basket.
Sort into: 🌿 natural factor · 🎣 human practice
- 🏗️building a dam
- ☀️amount of sunlight
- 🧪fertilizer runoff
- 🐟releasing invasive species
- 🏞️nutrients from rivers
- 🌡️water temperature
Show answer
🌿 natural factor: amount of sunlight, nutrients from rivers, water temperature · 🎣 human practice: building a dam, fertilizer runoff, releasing invasive species
Hint: Sunlight, water temperature and a river's nutrients are natural. Fertilizer runoff, overfishing and dams are human practices.