Natural selection is the process by which individuals with traits better suited to their environment are more likely to survive and reproduce, passing those advantageous traits to offspring. Over many generations, this can cause a population to change (evolve). It requires variation within a population, a struggle for survival (limited resources), and traits being heritable — passed from parents to offspring.
Example
In a population of moths living on trees, if darker moths are better camouflaged from predators than lighter ones, darker moths survive and reproduce more often — over many generations, the population would likely shift toward more dark-coloured moths, an example of natural selection.
Key terms
Natural selection:
The process by which better-suited individuals are more likely to survive and reproduce.
Variation:
Differences in traits among individuals in a population.
Adaptation:
A trait that improves an organism's survival or reproduction in its environment.
Questions
1. Natural selection is the process by which:
Better-suited individuals are more likely to survive and reproduce
All individuals survive equally, regardless of traits
Traits never change across generations
Organisms choose their own traits deliberately
2. Variation refers to:
Differences in traits among individuals
Every individual being identical
A single fixed trait for a species
A type of chromosome only
3. An adaptation is a trait that:
Improves survival or reproduction in an environment
Always harms an organism
Has no effect on survival
Only appears in plants
4. Natural selection requires traits to be:
Heritable, passed from parents to offspring
Chosen deliberately by the organism
Completely random with no pattern
Impossible to pass on
5. Natural selection was famously described by:
Charles Darwin
Isaac Newton
Albert Einstein
Gregor Mendel only
6. Darker moths surviving better on dark tree bark, due to camouflage, is an example of:
Natural selection
Random chance with no pattern
No selection occurring at all
An impossible scenario
7. Over many generations, natural selection can cause a population to:
Evolve (change over time)
Stay exactly identical forever
Disappear instantly
Reverse all previous traits immediately
8. Why does natural selection require variation within a population?
Without differences between individuals, there would be no different survival advantage to select for
Variation has no role in natural selection
All individuals must be identical for selection to work
Natural selection works the same with or without variation
9. A "struggle for survival" in natural selection refers to:
Competition for limited resources like food and space
Organisms actively fighting each other physically at all times
A concept with no real biological basis
Only applying to predators, never prey
10. Antibiotic-resistant bacteria becoming more common after repeated antibiotic use is an example of:
Natural selection acting on bacterial populations
A random, unrelated coincidence
Bacteria choosing to resist antibiotics on purpose
Something unrelated to evolution
11. Individuals with a helpful adaptation are more likely to:
Survive and pass on their traits to offspring
Always die before reproducing
Have no advantage over other individuals
Immediately change species
12. Why is natural selection considered a gradual process rather than a sudden change?
It typically requires many generations for advantageous traits to become common in a population
Natural selection always happens within a single generation
Populations change instantly with no generational process
Time has no role in natural selection
13. A trait that offers no survival or reproductive advantage is:
Less likely to be specifically favoured by natural selection
Always eliminated instantly
Guaranteed to become dominant
The only type of trait that exists
14. Species adapted to a stable environment for a long time may struggle if the environment suddenly changes because:
Their existing adaptations may no longer offer the same survival advantage
Adaptations always remain useful no matter how the environment changes
Environmental change has no connection to survival
Species can instantly adapt to any new environment
15. Why might isolated populations of the same species (e.g. on separate islands) evolve differently over time?
Different environments can favour different traits through natural selection in each location
Isolated populations always evolve identically regardless of environment
Geography has no influence on natural selection
Only one population can ever experience natural selection at a time
16. Why is the peppered moth (which shifted from light to dark colouring during increased industrial pollution in England) often used as a classic example of natural selection?
It shows a clear, observed shift in a population's traits linked to a specific environmental change
The peppered moth never actually changed colour at any point
This example has no connection to natural selection
Industrial pollution has no relationship to moth camouflage
17. Why doesn't natural selection work toward a "perfect" organism, but rather one suited to its current environment?
Selection favours whatever traits work best for current conditions, which can change over time
Natural selection always produces one single ideal organism for all environments
Perfection is a concept that applies directly to natural selection
Environmental conditions never change, so perfection would be fixed
18. Why can natural selection only act on traits that already exist as variation within a population, not create entirely new traits instantly?
Selection works by favouring existing heritable differences, not generating brand new traits on demand
Natural selection can create any new trait instantly on demand
Variation is not required for natural selection to occur
All traits appear for the first time by natural selection alone
19. Why might a species with very low genetic variation be more vulnerable to extinction if their environment changes?
Fewer different traits mean less chance that some individuals will have what it takes to survive the new conditions
Low variation always makes a species stronger and more resilient
Genetic variation has no connection to a species' survival chances
A species with no variation is always the most likely to survive change
20. Why is natural selection considered different from an organism actively "choosing" to adapt during its own lifetime?
Natural selection acts across generations on existing heritable variation, not through an individual's deliberate choices
Organisms can choose to instantly develop any adaptation they want
Natural selection and deliberate choice are the exact same process
Adaptation always happens within a single organism's lifetime by choice
21. Why might a rapidly reproducing organism (like bacteria) show evidence of natural selection more quickly than a slowly reproducing one (like elephants)?
More generations occurring in a shorter time gives natural selection more opportunities to act
Reproduction rate has no connection to how quickly natural selection can be observed
Slowly reproducing organisms always evolve faster than rapidly reproducing ones
Natural selection requires a fixed amount of real time, regardless of generations
Answer key (parent copy)
1. Better-suited individuals are more likely to survive and reproduce
2. Differences in traits among individuals
3. Improves survival or reproduction in an environment
4. Heritable, passed from parents to offspring
5. Charles Darwin
6. Natural selection
7. Evolve (change over time)
8. Without differences between individuals, there would be no different survival advantage to select for
9. Competition for limited resources like food and space
10. Natural selection acting on bacterial populations
11. Survive and pass on their traits to offspring
12. It typically requires many generations for advantageous traits to become common in a population
13. Less likely to be specifically favoured by natural selection
14. Their existing adaptations may no longer offer the same survival advantage
15. Different environments can favour different traits through natural selection in each location
16. It shows a clear, observed shift in a population's traits linked to a specific environmental change
17. Selection favours whatever traits work best for current conditions, which can change over time
18. Selection works by favouring existing heritable differences, not generating brand new traits on demand
19. Fewer different traits mean less chance that some individuals will have what it takes to survive the new conditions
20. Natural selection acts across generations on existing heritable variation, not through an individual's deliberate choices
21. More generations occurring in a shorter time gives natural selection more opportunities to act