LaMarck vs. Darwin

What is a Theory? Theory – the most probable explanation for a large set of data based on the best available evidence Theories are used to make predictions about new data

Jean Baptiste LaMarck’s Theory Believed change occurs over time within a single generation Inheritance of Acquired Characteristics acquired changes were passed to offspring Law of Use and Disuse If a body part were used, it got stronger If a body part was not used, it got smaller

LaMarck’s Theory of Evolution Traits acquired during one’s lifetime would be passed to offspring. Clipped ears of dogs could be passed to offspring!

LaMarck’s Mistake Reminder from genetics – Traits are passed through genes. Lamarck did not know how traits were inherited. Genes are not changed by activities in life Genes are changed through DNA mutations that are passed onto offspring

Voyage of the Beagle Charles Darwin HMS Beagle, 1831 for 5 year voyage around world Avid collector of flora & fauna Astounded by variety of life

Voyage of the Beagle During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time

Darwin’s Belief’s Survival of the Fittest OR Natural Selection Food and resources are limited There are too many organisms, so they will compete to survive. Not all offspring will survive; only those best suited to environment survive.

Darwin’s Giraffes Giraffes with a variety of neck lengths existed. The giraffes had to compete for food. Short necks could not reach upper branches, limiting their food supply and causing them to die Long neck giraffes survived because they were able to reach the food Long neck giraffes reproduce and pass on genes.

So What is a Good Definition of Evolution? Evolution is the slow, gradual change in a population of organisms over many generations of time The change of a genetic population through successive generations The change of a species over time.

Natural Selection Selective pressure can occur from several factors: Resource limitation Predation Industry (Environment) Social influence (Society)

Classic Example Peppered moths