7th grade · Science · Unit 15 of 16
Natural Selection
How species adapt and change
What your child practices
Variation, inherited versus acquired traits, adaptations, and how natural selection changes populations over generations, with fossils and other evidence. Includes reading data from a predator–prey model.
Alabama Course of Study content standard: 7.15; 7.17 · how natural selection changes the traits of a population over generations
How we explain it
Children can open this short lesson before they practice.
- Inherited traits come from parents in genes. Acquired traits are learned or gained during one life and are not passed on.
- Members of a species vary. Those best suited to their surroundings survive and have more young.
- Over many generations, the helpful traits become more common in the population.
Example: Mice live on dark soil, and owls hunt them by sight. Which mice will become more common? Owls spot light mice more easily on dark soil. Dark mice survive and have more young. Their color is inherited, so it spreads. Answer: dark mice
Natural Selection in Alabama
In the Alabama Course of Study, this is unit 15 of 16 in 7th grade Science, after Species & Hybrids and before Natural Selection.
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
What is a mutation?
🧬- An injury that heals over time
- A trait learned from a parent
- A change in an organism's DNA that can create a new trait
- A type of fossil
A change in an organism's DNA that can create a new trait
Hint: Mutations are one source of new variation. Natural selection then acts on that variation.
Question 2
A cactus has thick stems that store water and spines instead of leaves. These are adaptations to…
🌵- a freshwater pond
- a shady rainforest floor
- a cold ocean
- a hot, dry desert
a hot, dry desert
Hint: Storing water and losing less of it through leaves helps a plant where rain is rare.
Question 3
Inherited or acquired? Sort each trait.
Sort into: 🧬 inherited (in the genes) · 🏋️ acquired during life
- 👁️a person's natural eye color
- 🐅a tiger's stripe pattern
- 🩹a scar from a cut
- 🐕a dog that learned to sit
- 🚲knowing how to ride a bike
- 🌺a flower's petal color
- 🐦a finch's beak shape
- 🌳a branch bent by strong winds
🧬 inherited (in the genes): a person's natural eye color, a tiger's stripe pattern, a flower's petal color, a finch's beak shape · 🏋️ acquired during life: a scar from a cut, a dog that learned to sit, knowing how to ride a bike, a branch bent by strong winds
Hint: Inherited traits are passed from parents to offspring in their genes. Acquired traits are gained during one organism's life and are not passed on to its offspring.
Question 4
Which scientist proposed the theory of evolution by natural selection after studying finches, tortoises and other species?
🐢- Charles Darwin
- Dmitri Mendeleev
- Marie Curie
- Isaac Newton
Charles Darwin
Hint: He sailed on HMS Beagle to the Galápagos Islands. Alfred Russel Wallace came up with the same idea on his own.
Question 5
A class modeled beetles living on dark brown soil. Birds hunt them by sight. What best explains the pattern in the table?
A sample of 100 beetles in each generation Generation Green beetles Brown beetles 1 51 49 2 43 57 3 31 69 4 21 79 - The beetles decide to have brown offspring so they can hide
- Brown beetles are harder for birds to spot, so more survive and reproduce
- Green beetles change color during their lives to match the ground
- Birds cannot see any of the beetles at all
Brown beetles are harder for birds to spot, so more survive and reproduce
Hint: Individuals can't change their inherited color. Those that blend in are eaten less, so they live to pass their color on to more offspring.
Question 6
Bacteria are treated with an antibiotic. A few have a trait that lets them survive it. What happens over many generations?
🧫- Nothing changes in the population
- All bacteria disappear forever
- The bacteria learn to resist the drug on purpose
- Antibiotic-resistant bacteria become more common
Antibiotic-resistant bacteria become more common
Hint: The survivors reproduce and pass on their resistance. This is natural selection happening fast.