Evolution by Natural Selection Hour 2, 2-23-2011

Why should we study evolution?

Important Terms Evolution Artificial selection Natural selection Variation Competition Adaptation

What is a Theory? Theory- a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses

Evolution by Natural Selection is a theory Evolution (or change in organisms over time) is a scientific theory; it is a well-substantiated explanation of an aspect of the natural world that incorporates facts (observable phenomena) such as virus and bacterial adaptations, inferences (geological processes have always been happening at a constant rate in the history of the Earth), and tested hypotheses (evolutionary relationships echoed in DNA analysis).

Age of the Earth Earth is about 4.5 billion years old Geologists confirmed this approximate date through determining the age of rock formations and the time it would take for them to form

Why does it matter how old the Earth is?

Time is important: If weathering and other geological processes have been happening at the same rate for a very long time (or always) then the Earth must be several billion years old to account for the formations. Other ways we know: Chemical analysis of ice cores radio active fluorine

Evolution Change in organisms over time These changes are seen in populations not in individuals

Charles Darwin On the Origin of Species in 1859. Darwin supplied evidence that evolution has occurred. He also explained his ideas about how (mechanism) evolution occurs.

Darwin’s theory was based on artificial selection Darwin’s theory was based on artificial selection. In artificial selection, nature provided the variation, and humans selected those variations that they found useful. For example, animal breeders used only the largest hogs, fastest horses, or cows that produced the most milk for breeding.

Artificial Selection Natural Selection Variation in traits exists Breeder selects favorable traits in organism Breeder mates animals with the favorable traits more than other organisms Desired traits become more common in population Variation in traits exists Nature “selects” favorable traits in organism because some of these trait give a reproductive or survival advantage Organisms with favorable traits survive better and have more offspring Traits that give a reproductive/survival advantage become more common in population

Why do both forms of selection require variation?

Sources of variation Genetic Shuffling in Anaphase I of meiosis Mutation to DNA passed down to offspring (very rare!)

What is competition?

Competition Competition is a struggle for limited resources in which there can only be one or a few “winners” On Earth we have a finite number of resources; there are many more organisms than resources. A struggle for survival results, the organisms that get the resources will live and pass on their genes to the next generation. Besides limited resources; what are some other challenges organisms must face to survive and reproduce?

Adaptations Traits that provide some type of advantage to organisms in the struggle for survival are called adaptations. There are recognizable patterns to the way organisms adapt

Predict what will happen to a bunny population with a brown fur mutation in an equatorial environment.

Convergence Unrelated species respond to environmental pressures with similar functional adaptations

Divergence Humans DID NOT come from apes, rather both species had a common ancestor long ago IDA

Draw a diagram of how scientist would describe the relationship between Ida, humans and apes.

Adaptive Radiation Adaptive radiation is the pattern of adaptation that isolates a species into two separate lineages

Co-Evolution Co-evolution is when a species directly influences the evolution of another species and both populations evolve in parallel.