The Voyage of the H.M.S. The Voyage of the H.M.S. BeagleBeagle

•In 1831, Charles Darwin set sail from England aboard the H.M.S. Beagle on a voyage around the world.

•Darwin collected numerous plant and animal specimens for his collection.

•He studied the specimens, read the latest scientific publications, and recorded his observations/thoughts in notebooks.

Darwin and the Galapagos Darwin and the Galapagos IslandsIslands

•Darwin observed that the Galápagos Islands were in close proximity, but had very different climates and corresponding differences in vegetation.

•Accordingly, he observed that the characteristics of many animals and plants varied noticeably among the different islands.

Darwin’s Darwin’s Contribution to Contribution to

ScienceScience

•Darwin’s evidence led him to propose a revolutionary hypothesis pertaining to the way life changes over time.

•This hypothesis has become the theory of evolution. It was presented in his book, On the Origin of Species, published in 1859.

Darwin’s Case: Key Idea #1Darwin’s Case: Key Idea #1Variation Within SpeciesVariation Within Species

• Members within a species vary from one another in important ways.

• At the time, variations were thought to be unimportant, minor defects.

• Darwin argued that this variation is significant.

Darwin’s Case: Key Idea #1Darwin’s Case: Key Idea #1Variation Within SpeciesVariation Within Species

•Darwin realized that high birth rates and a shortage of life's basic resources (food, water, and shelter) inevitably force organisms to compete for resources.

•Competition, both within and among species exists in almost all natural environments.

•This struggle is ultimately reflected by reproductive success

Darwin’s Case: Key Idea #2Darwin’s Case: Key Idea #2The Struggle For ExistenceThe Struggle For Existence

Darwin’s Case: Key Idea #2Darwin’s Case: Key Idea #2The Struggle For ExistenceThe Struggle For Existence

► Characteristics exhibited by Characteristics exhibited by one parent, whether one parent, whether beneficial or harmful, are beneficial or harmful, are passed down from one passed down from one generation to the next generation to the next (assuming that organism is (assuming that organism is able to reproduce).able to reproduce).

►Modern Modern GeneticsGenetics presents presents a mechanism for a mechanism for heredityheredity..

Darwin’s Case: Key Idea #3Darwin’s Case: Key Idea #3TheThe Inheritance of TraitsInheritance of Traits

Darwin’s Case: Key Idea #3Darwin’s Case: Key Idea #3TheThe Inheritance of TraitsInheritance of Traits

Darwin’s Influences: Darwin’s Influences: Thomas MathusThomas Mathus

Mathus’ An Essay on the Principle of Population emphasized that population growth will always overwhelm growth in food, creating inevitable states of hunger, disease, and competition. This perpetual struggle for survival caught Darwin’s attention, and he applied it to biology.

Darwin argued that some of the competitors in Malthus' perpetual struggle scenario would be better equipped to survive. Those that were less able would die out, leaving only those with the more desirable traits.

Darwin’s Influences: Darwin’s Influences: Charles Charles LyellLyell

► The world’s most The world’s most renowned geologist of renowned geologist of the day and author of the day and author of author of author of Principles of Principles of GeologyGeology, , prompted prompted Darwin to think of Darwin to think of evolution as a slow evolution as a slow process in which small process in which small changes gradually changes gradually accumulate over accumulate over immense spans of time…immense spans of time…

Darwin’s Influences:Darwin’s Influences:Jean-Babtiste LamarkJean-Babtiste Lamark

► Lamarck's proposed the first truly cohesive Lamarck's proposed the first truly cohesive theory of evolution, in which all organisms theory of evolution, in which all organisms had an innate tendency toward perfection.had an innate tendency toward perfection.

► He correctly argued that species change He correctly argued that species change over time, and that environmental forces over time, and that environmental forces adapted them to local environments. adapted them to local environments.

► Lamarck is widely remembered for his Lamarck is widely remembered for his inaccurate theory of inaccurate theory of inheritance of inheritance of acquired characteristics acquired characteristics in which the in which the use and disuse use and disuse of physiologic features of physiologic features differentiated organisms over time.differentiated organisms over time.

What Darwin What Darwin Couldn’t Couldn’t KnowKnow….….

► Although Darwin had no way of knowing, Although Darwin had no way of knowing, there is a genetic mechanism for phenotypic there is a genetic mechanism for phenotypic change in species over time.change in species over time.

► Can you guess what this is?Can you guess what this is?

Sweet!

Putting it all Together…Putting it all Together…Survival of the FittestSurvival of the Fittest

•The ability of an organism to survive and reproduce in its specific environment is fitness. •Darwin proposed that fitness is the result of adaptations.

•An adaptation is any inherited characteristic that increases an organism's chance of survival.

Survival of the Fittest Survival of the Fittest (cont.)(cont.)

•Beneficial adaptations better suit organisms to their environment, and in turn, they’re better able to survive and reproduce.

•Individuals with characteristics that are not well suited to their environment either die or leave few offspring.

Natural Selection: Natural Selection: Decent with ModificationDecent with Modification

•Natural selection yields organisms that display different structures, establish different niches, and/or occupy different habitats.

•Every living species has descended, with changes, from other species over time. •Darwin referred to this principle as descent with modification.

Natural Selection in Natural Selection in ActionAction

•Darwin wondered if animals living on different islands had once been members of the same species.

•These separate species would have evolved from an original South American ancestor species.

•His observations of finches, tortoises, iguanas, and other animals supported his hypothesis.

Galapagos TortoisesGalapagos Tortoises

Natural Selection in Action: Natural Selection in Action: Industrial Melanism and the Peppered Industrial Melanism and the Peppered

MothMoth

► Coal burning during the Coal burning during the industrial revolution industrial revolution caused the trees in caused the trees in nearby forests to turn nearby forests to turn dark with soot.dark with soot.

► Within a short time Within a short time period, the peppered period, the peppered moth responded…moth responded…

► Explain…Explain…

3 Key Misconceptions about3 Key Misconceptions about Darwin’s Theory Darwin’s Theory

► Why is this statement false? Why is this statement false? ► How can you change it to make How can you change it to make

it accurate?it accurate?

“Child Please!”

“survival of the fittest means only the strongest

and fastest survive”…

3 Key Misconceptions about3 Key Misconceptions about Darwin’s Theory Darwin’s Theory

“Say What?”

► Why is this statement false? Why is this statement false? ► How can you change it to How can you change it to

make it accurate?make it accurate?

“Natural selection is random”…

3 Key Misconceptions about3 Key Misconceptions about Darwin’s Theory Darwin’s Theory

“Oh No you

didn’t”

► Why is this statement false? Why is this statement false? ► How can you change it to How can you change it to

make it accurate?make it accurate?

“Organisms can evolve over their

lifetimes”…