Charles Darwin: Evolution and the Story of Our Species
5 The Living Environment
Evolution of Life
For Grades: 6-8
Learning Goal 1
Small differences between parents and offspring can accumulate (through selective breeding) in successive generations so that descendants are very different from their ancestors.
Learning Goal 2a
Individual organisms with certain traits are more likely than others to survive and have offspring.
Learning Goal 2b
Changes in environmental conditions can affect the survival of individual organisms and entire species.
For Grades: 9-12
Learning Goal 1
The basic idea of biological evolution is that the earth's present-day species are descended from earlier, distinctly different species.
Learning Goal 3
Natural selection provides the following mechanism for evolution: Some variation in heritable characteristics exists within every species; some of these characteristics give individuals an advantage over others in surviving and reproducing; and the advantaged offspring, in turn, are more likely than others to survive and reproduce. As a result, the proportion of individuals that have advantageous characteristics will increase.
Learning Goal 4b
Heritable characteristics influence how likely an organism is to survive and reproduce.
Learning Goal 6a
Natural selection leads to organisms that are well-suited for survival in particular environments.
Learning Goal 6b
Chance alone can result in the persistence of some heritable characteristics having no survival or reproductive advantage or disadvantage for the organism.
Learning Goal 7
Modern ideas about evolution and heredity provide a scientific explanation for the history of life on Earth as depicted in the fossil record and in the similarities evident within the diversity of existing organisms.
Learning Goal 8
Life on earth is thought to have begun as simple, one-celled organisms about four billion years ago. Once cells with nuclei developed about a billion years ago, increasingly complex multi-cellular organisms evolved.
Learning Goal 9
Evolution builds on what already exists, so the more variety there is, the more there can be in the future. But evolution does not necessitate long-term progress in some set direction. Evolutionary change appears to be like the growth of a bush: Some branches survive from the beginning with little or no change; many die out altogether; and others branch repeatedly, sometimes giving rise to more complex organisms.
Learning Goal 10
The continuing operation of natural selection on new characteristics and in diverse and changing environments, over and over again for millions of years, has produced a succession of diverse new species.