Lessons · Teaching · adaptation, and how it comes about
Adaptations are not chosen, and individuals do not acquire them
An adaptation is a feature that helps an organism survive and reproduce where it lives. Variation already exists in a population; the individuals whose variations suit the conditions leave more offspring, so the feature becomes commoner over generations.
Hone is a place to practise a career, one idea a day. This is one of its lessons, written out in full and free to read without an account.
In beta. This lesson was written for Hone and has not yet been checked by a state certification officer. Practice material, not professional advice. What that means.
What it is for
'The giraffe stretched its neck to reach the leaves' is the explanation almost every child arrives with and many adults keep. The correction is not a detail: individuals do not change to suit their surroundings, populations shift because some individuals already differed.
How to think about it
Phrase every explanation at the level of the population and across generations, never the individual within its life. Not 'it grew a thicker coat', but 'the ones already thicker-coated survived more winters and had more young'.
Worked example
Variation exists first: some individuals differ before the conditions changeNothing is invented on demand.
Conditions favour some variants, which survive and reproduce moreSurvival is only half of it; reproduction is the half that counts.
The feature becomes commoner in the population over generationsThe population changes. No individual did.
A structural adaptation is a body part; a behavioural one is a thing done, like migratingBoth are examined, and both arise the same way.
Your turn
Name the thing that must already exist in a population before conditions can favour anything.
Conditions can only act on the that is already there
Solve one, graded on the server
The trap
Saying an organism adapted during its life. A person who tans has not adapted in this sense and will not pass a tan to a child. Adaptation is a change in a population across generations.