CHAPTER 02 · Read Cosmos
Natural selection and evolution
Do complex organisms necessarily have to be complete at once?
Explore this chapter ↗Let's begin! The experience allows you to directly interact with the scenes and observation tools.
How selection shapes the diversity of life
Chapter 2 does not treat life as an exception separate from the universe. It begins with people selectively breeding plants and animals, then asks how differences can also accumulate over generations in nature.
Natural selection is not a story of individuals creating the traits they need. When differences are inherited and reproductive success varies with the environment, the composition of a population changes.
OBSERVE · Start with evidence
Three pieces of evidence
- Individuals within a population have different traits.
- Some of these differences are passed on to offspring.
- When reproductive success differs in an environment, the proportions of traits in the next generation change.
Placing the Complexity of Life in Time
Commentary following selection and the continuity of life in chapter 2 of the original book. The activity uses a simplified population model; it does not recreate the origin of life.
Difference first, then selection
Without variation within a population, or without differences passing to the next generation, the changes in this activity would be difficult to explain. Distinguish variation from inheritance before discussing natural selection.
The environment is not a designer who orders the desired characteristics for individuals. Reframe the story by asking how existing differences lead to reproductive differences under certain conditions.
Questions to ConsiderIf the number of dark individuals has increased, what would you investigate?
Human selection and natural selection
Selecting and breeding individuals with desired traits makes you think about the power of generational change. However, this does not necessarily mean that someone with the same purpose must exist for natural selection to occur.
When reading analogies, indicate both the similarities and differences. While cumulative genetic differences are useful, transferring the existence of a selector who has pre-defined goals changes the explanation.
Questions to ConsiderIf you were to apply the example of artificial selection to natural selection, what would you leave behind?
The beginning of life and the changes in life.
Describing how a living group changes and describing how the initial living system was formed are different things. The experimental results showing that organic molecules were created do not necessarily mean that the entire living cell was created.
The connection between matter from stars, molecules needed for life, replication and metabolism, and changes across generations. However, one step does not automatically solve the next step. Please read both the wonder of the connection and the remaining problems together.
Questions to ConsiderHow would you report on the experiment in which organic molecules were created?
Discoveries and their limits
Evolution is not a ladder leading to humans. It is the history of life that has diverged from a common ancestor and changed in the environment and through chance. The emergence of the first life is a separate question.
Connect mutation, heredity, and selection in a single sentence, then leave the question of origin unanswered by the explanation.
Explore this chapter ↗Evidence and further reading
If we want to explain the order of nature, can we discard even the shapes that we find beautiful?