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Understanding Evolution
Fossil evidence. Nicholas Steno’s anatomical drawing of an extant shark (left) and a fossil shark tooth (right). The fossil record provides snapshots of the past which, when assembled, illustrate a panorama of evolutionary change over the past 3.5 billion years.
Lines of evidence: The science of evolution. Grade Level (s): 6-8. 9-12. Source: UC Museum of Paleontology. Resource type: Tutorial. Time: 30-40 minutes.
The timing of many evolutionary and geologic events on Earth has been determined through two complementary lines of evidence: relative dating and absolute (numerical or radiometric) dating. This evidence makes it clear that life is very old and places a timescale on the pace of evolutionary change, diversification, and extinction.
A fossil that shows an intermediate state between an ancestral trait and that of its later descendants is said to bear a transitional feature. The fossil record includes many examples of transitional features, providing an abundance of evidence for evolutionary change over time. Transitions in whale evolution.
Based on decades of accumulated evidence, the scientific community supports Margulis’s ideas: endosymbiosis is the best explanation for the evolution of the eukaryotic cell. What’s more, the evidence for endosymbiosis applies not only to mitochondria, but to other cellular organelles as well.
Evolution 101. An introduction to evolution: what is evolution and how does it work? The history of life: looking at the patterns – Change over time and shared ancestors; Mechanisms: the processes of evolution – Selection, mutation, migration, and more; Microevolution – Evolution within a population; Speciation – How new species arise
From land to water: The origin of whales, dolphins, and porpoises.Evolution: Education & Outreach 2:272-288. Compared to other early whales, like Indohyus and Pakicetus, Ambulocetus looks like it lived a more aquatic lifestyle. Its legs are shorter, and its hands and feet are enlarged like paddles.
Artificial selection is an evolutionary process in which humans consciously select for or against particular features in organisms – for example, by choosing which individuals to save seeds from or breed from one generation to the next.
Evolution 101. An introduction to evolution: what is evolution and how does it work? The history of life: looking at the patterns – Change over time and shared ancestors; Mechanisms: the processes of evolution – Selection, mutation, migration, and more; Microevolution – Evolution within a population; Speciation – How new species arise