What Evolution Claims, and What It Rests On

Lesson Goal

Students will explain variation, overproduction and natural selection, compare Lamarck's and Darwin's ideas, describe gradualism and punctuated equilibrium as two views of rate, and sort statements into what has been observed and what is a claim about origins.

Side by Side, Not Blended

This unit follows the site's rule for the origin question. What can be watched and measured is taught exactly as the textbook teaches it. The question of where all living things came from is named as a different kind of question, and both answers are given in their own words: common descent, which is the textbook's view, and creation, which is what Genesis 1 says.

The student is asked to sort statements into observed and origin claim, and is never asked to pick a side. Keeping the two apart is the honest way to study the subject, and the lesson says so out loud.

Key Concepts

Natural selection can be observed. Individuals in a population vary, more are born than can survive, those with helpful variations survive and reproduce more, and the helpful variations become more common. Both of the answers in this lesson accept that.

Whether this process, carried on for millions of years, accounts for all living things coming from one ancestor is the origin question, and that's the part nobody watched.

Added From the Record

The year of Darwin's book (1859), the dates of the voyage, and the finch-beak result from the 1977 drought are added from the historical record. The book's own parts are the kittens, the pumpkin seeds, the pigeons, Lamarck's bodybuilder, the two views of rate, and the horse fossils.

Key Vocabulary

Species

A group of living things that can breed together and have fertile young.

Population

A group of one species living in one area.

Variation

The differences between individuals of the same kind, like kittens in a litter.

Natural selection

The process in which individuals with helpful variations survive and reproduce more, so those variations become more common.

Evolution

In its smaller meaning, a change in a population's inherited traits over generations. The same word is also used for the larger claim of one common ancestor.

Gradualism

The view that change is slow and steady, with many small in-between steps.

Punctuated equilibrium

The view that long stretches of little change are broken by short bursts of quick change.