Evolution is often misunderstood because everyday language and scientific language use some of the same words differently. This lesson clarifies what scientists mean by a theory and explains why evolution describes changes in populations across generations, not changes in individual organisms during their lifetimes.
In everyday conversation, theory can mean a guess or an untested idea. In science, a theory is a broad explanation that has been extensively tested and supported by evidence. Theories such as the theory of gravity and the theory of evolution explain patterns scientists observe in the natural world.
All flashcards
What is a scientific theory?
A broad explanation of natural phenomena that has been extensively tested and supported by evidence. It can be refined when new evidence becomes available.
What is a scientific hypothesis?
A proposed explanation that can be tested and may gain support or be rejected through evidence.
What is evolution?
A change in the genetic composition of a population over generations, often involving differences in reproductive success among individuals with heritable traits.
How is development different from evolution?
Development describes changes in an individual during its lifetime. Evolution describes changes in populations across generations.
How can natural selection change average bill size in finches?
If bill-size differences are heritable and some sizes lead to greater reproductive success, those traits can become more common over generations, shifting the population average.
Quiz questions
What does the word theory mean in a scientific context?Answer: A broad explanation extensively tested and supported by evidence.
How does a scientific hypothesis differ from a scientific theory?Answer: A hypothesis is testable; a theory is extensively tested and well supported.
What changes when a population evolves?Answer: Its genetic composition changes over generations.
Finches with heritable traits associated with larger bills leave more offspring. What can happen over generations?Answer: Larger-bill traits can become more common, shifting the population average.
Why is a change in an individual finch's bill as it ages not evolution?Answer: It is development within an individual, not population change across generations.
Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.