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Biology

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Sample exercises

Grades K–3 · Cells & microscopy

Which is a living thing?

  1. A rolling stone.
  2. A bean plant.
  3. A toy car.
Answer and explanation

A bean plant.

A plant carries out life processes even though it does not walk.

Grades K–3 · Cells & microscopy

Does a moving toy prove that all moving objects are alive?

  1. No.
  2. Yes.
  3. Only if it moves quickly.
Answer and explanation

No.

Movement can have a nonliving cause such as a motor.

Grades K–3 · Cells & microscopy

Name two observations that could help describe a growing plant over time.

Answer and explanation

Its height increases and new leaves appear.

Accept relevant observable changes without claiming that one observation proves every life process.

Grades K–3 · Cells & microscopy

A plant has 3 leaves, then grows 2 new leaves and loses none. How many leaves does it have?

Answer and explanation

5

Add the two new leaves to the three existing leaves: 3 + 2 = 5.

Grades K–3 · Cells & microscopy

Why is a tree still living while standing in one place?

  1. It is secretly a rock.
  2. Only animals can be alive.
  3. Walking is not required for life.
Answer and explanation

Walking is not required for life.

Plants have growth, metabolism and other life processes.

Grades K–3 · Cells & microscopy

Why should an unfamiliar berry not be tasted during a nature observation?

Answer and explanation

It may be harmful; observe without eating unknown plants.

A simple safety explanation is sufficient.

Study notes

Actual size from an image

Magnification is image size divided by actual size. Convert millimetres to micrometres consistently.

Grades 7–11

Quadrat density estimate

Divide the total counted organisms by the total sampled area. Density is not the same as total population size.

Grades 8–11

Germination percentage

Divide germinated seeds by all tested seeds, including those that did not germinate.

Grades 5–9

Population balance

Add births and immigration; subtract deaths and emigration. All counts refer to the same interval.

Grades 8–12

Surface-area to volume ratio

For a cube, surface area is 6a² and volume is a³. Their ratio decreases as side length increases.

Grades 8–11

DNA base-percentage model

In the stated double-stranded DNA model, A = T and C = G; all four percentages sum to 100.

Grades 9–12

Diploid to haploid

In the stated standard model, meiosis reduces two chromosome sets to one. Do not substitute a universal species count.

Grades 9–12

Expected counts in Aa × Aa

For the simple Aa × Aa model, P(aa) = 1/4. An expected count is not a guaranteed outcome in a finite sample.

Grades 9–12

Percentage mass change

Use initial mass in the denominator. A negative percentage represents a decrease from the starting mass.

Grades 8–11

Food-web transfer model

Convert the supplied transfer efficiency to a fraction. Do not assume that all food webs have a fixed 10% efficiency.

Grades 7–11

Michaelis-Menten model rate

Assume the stated steady-state model applies; Vmax and v share units, and Km and substrate concentration share units.

University

Instantaneous logistic growth

This deterministic model assumes constant r and carrying capacity K; it is not a guaranteed population forecast.

University