7th grade · Science · Unit 6 of 10
Ecosystems
Living and non-living parts
What your child practices
Biotic and abiotic parts of an ecosystem, how they interact, and the limiting factors and carrying capacity that decide how many organisms an ecosystem can support.
Minnesota K-12 Academic Standards benchmark: 7L.2.1.1.1; 7L.4.1.2.1 · how resources affect populations, and how changes to an ecosystem affect them
How we explain it
Children can open this short lesson before they practice.
- An ecosystem is living things (biotic) and their non-living surroundings (abiotic) interacting.
- Abiotic parts include water, light, soil and temperature.
- A limiting factor, such as food or space, caps how many organisms an area can support: its carrying capacity.
Example: Is sunlight a biotic or an abiotic part of a pond ecosystem? Biotic means living or once living. Sunlight is not alive. Answer: abiotic
Ecosystems in Minnesota
In the Minnesota K-12 Academic Standards, this is unit 6 of 10 in 7th grade Science, after How Plants Work and before Food Chains & Energy.
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.
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
Which is a biotic limiting factor for a population of rabbits?
- predators such as foxes
- the hours of daylight
- the air temperature
- the amount of rainfall
predators such as foxes
Hint: Biotic limiting factors are living things, such as predators, disease and competitors.
Question 2
Which is the best example of a limiting factor that is not about food?
- a shortage of nesting sites for cavity-nesting birds
- an increase in plant growth
- more insects hatching in spring
- a long, warm summer with plenty of rain
a shortage of nesting sites for cavity-nesting birds
Hint: Space and shelter limit populations as well as food.
Question 3
Lake water warms during a heat wave and holds less dissolved oxygen. How might this affect fish?
- Fish that need a lot of oxygen may struggle to survive
- Fish are not affected at all
- Fish breathe more easily
- All fish grow faster
Fish that need a lot of oxygen may struggle to survive
Hint: Warm water holds less dissolved oxygen, an abiotic factor that fish need.
Question 4
Biotic or abiotic? Sort each part of an ecosystem.
Sort into: 🌱 biotic (living) · 🪨 abiotic (non-living)
- 🌳a maple tree
- 🐸a frog
- 🦠bacteria in the soil
- 🪨a boulder
- 🌬️wind
- 🌡️the temperature
- 🦫a beaver
- ☀️sunlight
🌱 biotic (living): a maple tree, a frog, bacteria in the soil, a beaver · 🪨 abiotic (non-living): a boulder, wind, the temperature, sunlight
Hint: Biotic parts are living things (plants, animals, fungi, bacteria). Abiotic parts are the non-living things, such as sunlight, water, air, rock and temperature.
Question 5
A deer population grows larger than its food supply. What is most likely to happen next?
- The deer stop needing food
- The population keeps rising forever
- Some deer starve and the population drops
- The food supply grows to match the deer
Some deer starve and the population drops
Hint: When a population passes the carrying capacity, limiting factors push it back down.
Question 6
Why can a small pond support fewer fish than a large lake?
- Fish need less food in ponds
- It has less space, food and dissolved oxygen
- Pond fish are always larger
- Ponds have no producers
It has less space, food and dissolved oxygen
Hint: A bigger ecosystem has more of the resources that limit a population.