Individuals have variations within their heritable traits. The population will not only evolve (change in its genetic makeup and inherited traits), but will evolve in such a way that it becomes adapted, or better-suited, to its environment.

In natural selection, what must be true of traits that are passed down through generations? Could natural selection work on a trait that is not heritable? No because there would be no new traits to be passed down. Could natural selection work on a population that has no variation?

The theory of natural selection states that: the best-adapted individuals survive and reproduce, contributing the most genes to the next generation.

Inherited traits are influenced by genes, which are passed on to offspring and future generations. Natural selection means that traits that offer an advantage will most likely be passed on to offspring; individuals with those traits have a better chance of surviving. Evolution occurs by natural selection.

Q. Why are advantageous traits more likely to be passed onto offspring? Because they are more likely to survive and reproduce. Because they come from dominant alleles.

Both groups of scientists agree that natural selection is the single most important factor in evolutionary changes in species. Whether the change is slow and gradual or punctuated and rapid, one thing is certain: Organisms have evolved over time.

There are five lines of evidence that support evolution: the fossil record, biogeography, comparative anatomy, comparative embryology, and molecular biology.

Five different forces have influenced human evolution: natural selection, random genetic drift, mutation, population mating structure, and culture. All evolutionary biologists agree on the first three of these forces, although there have been disputes at times about the relative importance of each force.

Describe the four basic causes of evolution: natural selection, mutation, genetic drift, and gene flow.

There are two general classes of evolutionary change: microevolution and macroevolution. Microevolutionary processes are changes in allele frequencies in a population over time. Three main mechanisms cause allele frequency change: natural selection, genetic drift, and gene flow.

Groups of species undergo various kinds of natural selection and, over time, may engage in several patterns of evolution: convergent evolution, divergent evolution, parallel evolution, and coevolution.

There Are Six Important Patterns of Macroevolution:

• Mass Extinctions.
• Adaptive Radiation.
• Convergent Evolution.
• Coevolution.
• Punctuated Equilibrium.
• Developmental Gene Changes.

Coevolution, the process of reciprocal evolutionary change that occurs between pairs of species or among groups of species as they interact with one another. The activity of each species that participates in the interaction applies selection pressure on the others.

A scientific theory stands until proven wrong — it is never proven correct. The Darwinian theory of evolution has withstood the test of time and thousands of scientific experiments; nothing has disproved it since Darwin first proposed it more than 150 years ago.

Perhaps the most persuasive fossil evidence for evolution is the consistency of the sequence of fossils from early to recent. Nowhere on Earth do we find, for example, mammals in Devonian (the age of fishes) strata, or human fossils coexisting with dinosaur remains.