Biology by Bradford
7.2.A, 7.2.BThree kinds of selection
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7.2 Natural Selection: revision map
The subtopic in the middle and five tasks round it: label a diagram, complete two tables and fill 10 gaps. Every box rests on a learning objective of the topic in the AP Biology course and exam description. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.
Natural Selection
AP Biology ยท Unit 7 Natural SelectionHover over a box to see it. Untick it to leave it off this sheet and its printout.
Name7.2.BChoosing mates
In , individuals with traits that attract mates or win contests leave more offspring. This can give males bright colors or large antlers, though these traits may cost survival. Because the trait is expressed in one sex and helps reproduction, selection can favor it even if it makes an animal easier for predators to find.
7.2.BFitness is measured in offspring
| Individual | Lives to | Offspring | Fitness |
|---|---|---|---|
| Rabbit A | 8 years | 2 | low |
| Rabbit B | 3 years |
Fitness depends on the number of offspring that survive to reproduce, not on strength or age.
Topic 7.2Natural Selection
7.2.ATypes of selection
| Type | Favors | Result | Example |
|---|---|---|---|
| the average phenotype | range narrows | human birth weight | |
| one extreme | the mean shifts | antibiotic resistance in bacteria | |
| both extremes | two peaks form | finches with small or large beaks when seeds are small or large only |
7.2.ASelection pressures
A selection pressure is any factor that affects survival or reproduction. It can be , such as temperature or drought, or biotic, such as predators, disease or competition for food and mates. A trait is only an advantage in a particular environment: dark fur is favored on dark soil but not on snow, and if the environment changes, so does the direction of selection.
Word bank 12abioticDirectionaldirectional selectionDisruptivedisruptive selectionhighsexual selectionStabilizingstabilizing selection
Answer key
Every box on the sheet with its gaps filled in, as the subtopic reads in full.
LabelThree kinds of selection
- stabilizing selection
- directional selection
- disruptive selection
TableTypes of selection
Type Favors Result Example Stabilizing the average phenotype range narrows human birth weight Directional one extreme the mean shifts antibiotic resistance in bacteria Disruptive both extremes two peaks form finches with small or large beaks when seeds are small or large only GapsSelection pressures
A selection pressure is any factor that affects survival or reproduction. It can be abiotic, such as temperature or drought, or biotic, such as predators, disease or competition for food and mates. A trait is only an advantage in a particular environment: dark fur is favored on dark soil but not on snow, and if the environment changes, so does the direction of selection.
GapsChoosing mates
In sexual selection, individuals with traits that attract mates or win contests leave more offspring. This can give males bright colors or large antlers, though these traits may cost survival. Because the trait is expressed in one sex and helps reproduction, selection can favor it even if it makes an animal easier for predators to find.
TableFitness is measured in offspring
Individual Lives to Offspring Fitness Rabbit A 8 years 2 low Rabbit B 3 years 12 high Fitness depends on the number of offspring that survive to reproduce, not on strength or age.