Evolution

The Theory of Evolution The term theory in colloquial use is closer to the concept of a “hypothesis” in science (an educated guess or hunch). In science, a theory  hypothesis. A Theory is more comprehensive than a hypothesis. National Academy of Science: “a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.”

Who’s the man? Charles Darwin Born 1809, 5th son of wealthy physician Studied medicine and natural history in Edinburgh Studied to be a clergyman at Cambridge

Voyage of the Beagle 1831: Joined the HMS Beagle on five year voyage to South America Studied geology, paleontology, plants and animals

Animals of the Galapagos Darwin could tell by the shape of the Giant Tortoises’ shells and their neck length which island they were from.

Charles Darwin’s Theory Charles Darwin – 19th century scientist Famous for Theory of Natural Selection In a population, naturally occurring variations affect which individuals survive and reproduce Natural selection - the force which acts on populations, and the best adapted organisms survive Evolution - the process by which populations change over time

Darwin’s Theory Darwin published his findings from his trip around the southern hemisphere in a book called On the Origin of Species Darwin visited the Galapagos Islands, a group of very small islands off the coast of Ecuador. Even though the islands are close together, each island has a unique climate. Darwin proposed that evolution worked by way of natural selection.

Darwin’s Theory Organisms differ, and some of this variation is heritable. Some cows produce more milk, some apple trees produce larger apples, etc. People now use artificial selection: nature provides the variation, but humans select for the variations they find useful Ex. Only breed the dogs that lose the least amount of fur.

Darwin’s Theory 2. Organisms produce more offspring than can survive, and many that do survive do not reproduce.

Does Darwin’s 2nd part still apply to humans? Many countries are prime examples of overpopulation

Darwin’s Theory 3. Because more organisms are produced than can survive, they compete for limited resources. Struggle for existence. In this struggle, predators that are faster get more prey.

Darwin’s Theory 4. Natural selection causes species to change over time. Survival of the fittest!!! (natural selection) Adaptation is any inherited characteristic that increases an organism’s chance for survivial. Those individuals best adapted to their environment will survive and reproduce.

Adaptation Great moments in evolution

Preying mantis camouflage Adaptation Preying mantis camouflage

Darwin’s Theory 5. Species alive today are descended with modification from ancestral species that lived in the distant past. All living organisms are Related to one another- common descent. Single “tree of life” links all living things (classification)

Darwin’s Finches Finches looked different on different islands Different beak shapes depending on feeding habits Finches on different islands can still interbreed but geographically isolated in the process of becoming different species

Evolution by natural selection Natural selection - force of nature that acts on populations Individuals that compete more effectively pass on their traits to the next generation Natural variation + natural selection = evolution All species could share common ancestor

Evidence of Evolution 1. Molecular Evidence Study proteins (amino acid sequences) Biologists believe that the greater the similarity between the amino acid sequences of two organisms, the closer their relationship 2. Fossils Fossil evidence can show us what older, possibly extinct organisms looked like and we can compare them to organisms known today. 3. Homologous Structures Similar bone structure can reveal evidence of evolutionary relationships. 4. Comparative Embryology The more similar organisms are in their embryological development, the more closely they are related.

Molecular Evidence The more amino acids that are the same, the closer the evolutionary relationship between the organisms. Hemoglobin, protein in blood, is often looked at for comparisons – all of these organisms have blood.

Fossils Radioactive dating gives relatively exact dates for fossils. If undisturbed, the older fossils will be found deeper in the ground than younger fossils.

Homologous Structures Structures have different mature forms , but from the same type of tissue. Suggests common ancestor. Analogous structures: Similar in function, but not from the same ancestor.

Embryology Embryological development The developing embryos of many very different organisms are surprisingly similar in their early stages.

Ideas that shaped Darwin’s theory At the time Darwin was doing his research, the majority of people in the world though that the earth was only a few thousand years old. 5 main scientists helped shape our modern theory of evolution.

Classification of Species Carl Linnaeus (1700s) Identify relationships between groups of organisms Species: groups of organisms based on physical resemblances and ability to interbreed Created system of classification - taxonomy Canidae Canis Vulpes familiaris lupus vulpes fulva Dog Wolf European fox American fox Family Genus Species Common name

How old is the earth? James Hutton and Charles Lyell, both geologists, helped scientists realize that the earth is many millions of years old. Contrary to popular religious beliefs at the time. James Hutton Charles Lyell

Lamarck’s Theory of Evolution Jean-Baptiste Lamarck – French naturalist By the use or disuse of organs, organisms acquired or lost certain traits during their lifetime. Organisms pass on acquired characteristics to next generation Organisms adapt to different environments, causing branching of species “Use it or lose it”

Lamarck’s Theory of Evolution

How are species selected in nature? Insight from Thomas Malthus: struggle for existence Constant pressure of expanding population for resources If the population keeps growing unchecked, humans would run out of living space and food (1798). He felt the only thing that could limit population growth would be war, famine and disease. Was he correct?

Major Misconception About Evolution Evolution has never been observed. Peppered moths during industrial revolution. Change has been directly observed. Antibiotic Resistance Flu Vaccines Creation of new species of bacteria has been directly observed.