"nothing in biology makes sense except in the light of evolution” Photo by “davemee” flickr creative commons "nothing in biology makes sense except in the light of evolution” ~Theodosius Dobzhansky (1900-1975)

In science, theories are statements or models that have been confirmed many times through tests and observations.

They explain a wide variety of data and observations In science, the term "Theory" does not express doubt. They explain a wide variety of data and observations They can be used to make predictions They are not absolute, can be changed as new evidence is found

Why do the embryos of animals look very similar at an early stage? Why do so many different animals have the same structures, the arm bones in a human are the same bones as a flipper in a whale? Why is the sequence of DNA very similar in some groups of organisms but not in others? Why do the embryos of animals look very similar at an early stage?

Photo courtesy of Swamibu, Flickr Creative Commons

Jean-Baptiste Lamarck (1744-1829) French soldier and scientist Lamarke's Theory of Acquired Characteristics-1802 Some thought that you would gain or lose features if you overused or didn't use them, and that you pass these new traits to your offspring. In 1801, he published Système des animaux sans vertèbres, a major work on the classification of invertebrates, a term he coined. In an 1802 publication, he became one of the first to use the term biology in its modern sense.[3][4] Lamarck continued his work as a premier authority on invertebrate zoology. He is remembered, at least in malacology, as a taxonomist of considerable stature. Jean-Baptiste Lamarck (1744-1829) French soldier and scientist

Examples – THEORY PROVEN WRONG!! A lizard who didn’t use its legs would eventually not have legs and its offspring would not have legs. A giraffe stretched its neck to reach higher leaves and that stretched neck would be inherited by its offspring THEORY PROVEN WRONG!! Why? If you are in a car accident and your leg has to be amputated, does this mean that your offspring will only have 1 leg? Photo courtesy of ucumari, creative commons, flickr

Charles Darwin developed the THEORY OF EVOLUTION BY NATURAL SELECTION It explained how organisms changed over time  (ADAPTED) 1809 - 1882

More on Darwin Darwin was a naturalist (what we today call biologists) He traveled the world and made observations and sketches of many species His most famous travels were aboard the H.M.S. Beagle where he traveled to the Galapagos Islands

Marine Iguana, photo courtesy of mtchm, flickr creative commons Blue-footed booby, photo courtesy of stirwise, flickr creative commons

He noticed tortoises with different shaped shells Finch, photo courtesy of stirwise, flickr, creative commons Giant tortoise, photo courtesy of Planetgordon, flickr creative commons

Darwin noted that there existed many finches on the islands, but while they had similarities, each was adapted to eating a particular type of island food He concluded that the finches all came from one ancestral species and evolved into many new species sooo . . . . . . The shapes of the beaks were adapted for eating a particular type of food. Cactus finch, photo courtesy of zrim, flickr creative commons

Darwin published this work to explain the variety of species that exist on the planet He proposed the “Theory of Evolution by Natural Selection”

1. Variation exists among individuals in a species. 2 1. Variation exists among individuals in a species. 2. Individuals will compete for resources (food, mates, and space) 3. Competition would lead to the death of some individuals while others would survive 4. Individuals that had advantageous variations are more likely to survive and reproduce. This process came to be known as Natural Selection The favorable variations are called Adaptations Photo courtesy of digitalART2, flickr creative commons

Say in a species of blob… Say in a species of blob….there exists blobs of all shapes and sizes (variation) Blobs eat the little purple organisms that live underground and on the surface.

During a particularly hot year, food became less abundant (competition), blobs that had the ability to dig into the soil to get food had a better chance of survival. Many blobs died that year…….

The ones that survived mated and passed their genes to the next generation. (reproduction)

The next generation had more blobs with the pointed noses The next generation had more blobs with the pointed noses. That is NATURAL SELECTION or survival of the fittest. Variation Competition Survival Reproduction

Fossil Evidence Shows numbers extinct animals Shows similarities between extinct animals and animals that are alive today The earth’s layers show a time scale of species and when they appeared on earth (and when they died out)

Dinosaurs have always fascinated us, movies such as Jurassic Park capitalize on that fascination. How do we know what dinosaurs looked like? We create a picture based on the bones we find (fossils) and use modern reptiles to guess at their texture and skin color.

Homologous structures also known as Anatomical evidence – these are parts of the body that are similar, but have different functions ex. The flippers of whales, and the wings of birds All forelimbs of vertebrates have the same pattern of bones •This shows evidence of common ancestry

Vestigial Organs – these are organs or parts that seem to have no function Whales have pelvic bones that do not attach to legs Snakes have a tiny pelvic bone and limb bones Humans have a tail bone

Biochemistry and DNA (Molecular Evidence) When comparing the DNA of one species to another, more similarities are found in species that are more closely related. Lion photo credit: ucumari Tiger photo credit: digitalART2

Embryological Development Embryos of different species develop in almost identical ways. Human fetus at 8 weeks

Direct observation of species change Bacteria become resistant to antibiotics Wolves were bred over many generations to become dogs (artificial selection) • and then bred further to create a variety of breeds Artificial selection experiments are also the foundation of agricultural improvement over the past 10,000 years.

Direct observation of species change