16.3 Darwin Presents His Case
Under what conditions does natural selection occur?- What does Darwin's mechanism for evolution suggest about living and extinct species?
adaptation
fitness
natural selection
Preview Visuals Before you read this lesson, look at Figure 16–10. Read the information in the figure, and then write three questions you have about it. As you read, answer your questions.
THINK ABOUT IT Soon after reading Malthus and thinking about artificial selection, Darwin worked out the main points of his theory about natural selection. Most of his scientific friends considered Darwin's arguments to be brilliant, and they urged him to publish them. But although he wrote up a complete draft of his ideas, he put the work aside and didn't publish it for another 20 years. Why? Darwin knew that many scientists, including some of Darwin's own teachers, had ridiculed Lamarck's ideas. Darwin also knew that his own theory was just as radical, so he wanted to gather as much evidence as he could to support his ideas before he made them public.
Then, in 1858, Darwin reviewed an essay by Alfred Russel Wallace, an English naturalist working in Malaysia. Wallace's thoughts about evolution were almost identical to Darwin's! Not wanting to get “scooped,” Darwin decided to move forward with his own work. Wallace's essay was presented together with some of Darwin's observations at a scientific meeting in 1858. The next year, Darwin published his first complete work on evolution: On the Origin of Species.
Evolution by Natural Selection
Under what conditions does natural selection occur?
Darwin's great contribution was to describe a process in nature—a scientific mechanism—that could operate like artificial selection. In On the Origin of Species, he combined his own thoughts with ideas from Malthus and Lamarck.
The Struggle for Existence After reading Malthus, Darwin realized that if more individuals are produced than can survive, members of a population must compete to obtain food, living space, and other limited necessities of life. Darwin described this as the struggle for existence. But which individuals come out on top in this struggle?
Variation and Adaptation Here's where individual variation plays a vital role. Darwin knew that individuals have natural variations among their heritable traits. He hypothesized that some of those variants are better suited to life in their environment than others. Members of a predatory species that are faster or have longer claws or sharper teeth can catch more prey. And members of a prey species that are faster or better camouflaged can avoid being caught.
Table of Contents
- Formulas and Equations
- Applying Formulas and Equations
- Mean, Median, and Mode
- Estimation
- Using Measurements in Calculations
- Effects of Measurement Errors
- Accuracy
- Precision
- Comparing Accuracy and Precision
- Significant Figures
- Calculating With Significant Figures
- Scientific Notation
- Calculating With Scientific Notation
- Dimensional Analysis
- Applying Dimensional Analysis