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Natural Selection occurs through a sequence of events:
Natural Selection occurs through a sequence of events:
Overproduction of offspring results in...
Competition among organisms for limited resources.
Variations among the organisms exist due to mutation or sexual reproduction.
Adaptations are variations that are beneficial to the survival of an organism.
Natural Selection occurs when NATURE SELECTS the organisms that are most fit to their environments to survive and reproduce. This results in the desirable traits becoming more numerous in successive generations. This is called Survival of the Fittest. A selecting agent is a factor in the environment that is putting pressure on a population, influencing the survival of particular traits.
Populations evolve, individuals do not. Individual organisms are born with specific genes and traits that do not change over their lives.
Populations evolve, individuals do not. Individual organisms are born with specific genes and traits that do not change over their lives.
Evidence for Evolution
Evidence for Evolution
Fossil evidence provides scientists with a record of ancient life and the changes in species over time. Although paleontologists do not have fossils for all of the changes that have occurred, they can still understand the overall picture of how most groups evolved. Also, gaps in the fossil record are still being filled in as paleontologists continue to discover ancient species.
Comparing Anatomy of species suggests that they have common ancestors when the arrangement of bones or other structures are similar, such as the arrangement of bones in the limbs of various vertebrates. These common structures or arrangement of structures are called homologous structures.
Vestigial structures are parts of an organism that no longer serve a necessary function, such as our appendix or tailbone. These structures suggest that organisms decended from another species that had a use for them.
Comparing embryos of organisms shows that closely-related organisms look similar for longer during embryonic development. This strongly suggests that they have a recent common ancestor when compared to less-related organisms' embryos.
Comparing DNA sequences of species also suggest that they have common ancestors. The more DNA nucleotides that two species have in common in specific genes, the more related the two species are and suggests that they have a more recent common ancestor. For example, humans and our closest-related species the chimpanzee have 98% of our nucleotides in common.
Some people become anxious when discussing evolution through natural selection, and it's important to understand the concepts before engaging in debate. For instance, the idea that humans "came from chimps" is not a part of the theory of natural selection. Quite simply, humans and chimps are cousins. Both species have descended from an extinct common ancestor. Oversimplifying the concepts that Charles Darwin introduced causes confusion and misunderstanding. Here are some other common misconceptions about evolution:
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