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8th grade · Science · Unit 7 of 9

Natural Selection

Variation, survival and populations changing over time.

What your child practices

Practices how variation in traits leads some individuals to survive and reproduce more, how populations change over generations, and how artificial selection works.

Arizona Academic Standards learning standard: 8.L4U1.11; 8.L4U1.12 · natural selection and how new species arise

How we explain it

Children can open this short lesson before they practice.

  1. Individuals vary. Those with helpful traits survive and reproduce more.
  2. Over generations, helpful traits become more common: natural selection.
  3. In artificial selection, people choose which plants or animals breed, like dog breeds.

Example: Farmers breed only the cows that give the most milk. What is this? People, not nature, are choosing. Choosing by people is artificial selection. Answer: artificial selection

Natural Selection in Arizona

In the Arizona Academic Standards, this is unit 7 of 9 in 8th grade Science, after Genes & Heredity and before Earth's History & Fossils.

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: Arizona 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.

  1. Question 1

    Natural selection requires…

    • variation in traits
    • unlimited food
    • no reproduction
    • identical individuals

  2. Question 2

    Organisms usually produce more offspring than can survive. This leads to…

    • identical offspring
    • no predators
    • competition for resources
    • unlimited food

  3. Question 3

    Peppered moths got darker when trees were sooty because…

    • moths painted themselves
    • dark moths were harder for birds to see
    • light moths flew away forever
    • soot dyed them

  4. Question 4

    Over many generations, helpful traits become…

    • more common
    • extinct always
    • less common
    • invisible

  5. Question 5

    Finches with different beaks on different islands show…

    • random paint
    • no variation
    • adaptation to different foods
    • same diets

  6. Question 6

    Why does finishing antibiotics as prescribed matter?

    • Bacteria need it to grow
    • It has no effect
    • It makes bacteria stronger always
    • Stopping early can leave resistant bacteria to multiply

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