EVOLUTION The Origin of Species E. Coleman 2010

“Evolution” means change over time. The “Theory of Evolution” says: – Living things on Earth have changed over time. – Many species that once existed are now extinct. – Many species alive today were not here when life on Earth first formed. First thought of by the ancient Greeks (in 600 BC ) but they did not try to explain HOW it happened.

Jean Baptiste Lamarck 1744-1829 First scientific attempt to explain how evolution happened came 2400 years later! In 1802 Jean LAMARCK proposed model: Evolution by Acquired Characteristics 1. More individuals are born than the environment can support - there is a struggle to survive. 2. Some individuals respond by developing traits that give them a better chance to survive. 3. When these individuals reproduce their offspring inherit their newly acquired, improved traits and develop them even further. 4. Eventually ALL members of the species have the favorable trait. Jean Baptiste Lamarck 1744-1829

1 2 3 ALL early giraffes had the same (short ) necks. Lamarck’s explanation of how the giraffe got its long neck: 1 2 3 ALL early giraffes had the same (short ) necks. 2. As giraffe population increased there wasn’t enough food within reach for all so some began stretching their necks to reach food higher in the trees. – The more they stretched, the longer their necks grew. Main Idea(s) of This Slide – Although natural selection now seems to be an obvious phenomenon that explains how species change over time, it was not always so apparent. Another scientist of Darwin’s time, Jean-Baptiste Lamarck also studied how species changed over time and had a differing hypothesis. Lamarck’s concept was that of Inheritance of acquired characteristics. According to his hypothesis, organisms acquired the characteristics they needed during their struggle for survival and passed on these “acquired characteristics” to their offspring. In this example, the giraffes needed longer necks to reach the leaves of the trees on which they fed. By stretching their necks, they were able to eat and survive. The longer necks were then passed on to their offspring when they reproduced. This hypothesis is now known to be incorrect. 3. When they reproduced they passed their longer necks on to their offspring who stretched their necks even more. – Eventually all giraffes had long necks.

Lamarck’s model was quickly discarded Lamarck’s model was quickly discarded. Scientists tried but could not find evidence to support his main ideas. All members of a species are NOT alike as Lamarck said. Great variation normally and naturally exists within a species. Organisms cannot change most of their basic physical traits at will, even if survival depends on It. They cannot “adapt” because they need to. For example giraffes cannot make their necks grow longer by stretching them! 3. Organisms can change and improve some things during their lifetimes (lifting weights to increase strength etc.) but these traits CANNOT be passed to offspring. If this man wants his future children to have small noses will it help to get a nose job?? Is there anything he could do that might help?

In 1831, Charles Darwin (failed medical student, failed divinity student, avid beetle collector) began a 5 year journey on a small ship, the H.M.S. Beagle. 90’ long 75 people 5 years Around the world! Charles Darwin 1809-1882

Purpose: survey coast of South America Darwin’s job: observe geology & biology of the area. – Kept meticulous records of observations. His observations from the Galapagos Islands led to his model of how evolution occurred. – Did NOT set out to develop a model, but couldn’t ignore what he saw. His curiosity drove him to try to explain what he had observed.

Galapagos Islands are 600 miles off west coast of Ecuador (South America). Volcanic - first rose above the ocean surface less than 15 million years ago. Why is this special? 1) Life has been there a relatively short time (compared to billions of years on the mainland!). 2) It developed in isolation from life on the mainland.

High lush island Low, desert island Darwin was surprised to find species that clearly were closely related but that had distinct differences on different islands. High lush island Low, desert island

He also discovered many species that were found nowhere else on Earth, including the world’s only swimming lizard. It was hard for him to accept the prevailing belief that all of these species had been separately created.

After returning to England Darwin spent 25 more years gathering evidence. He also studied species selectively bred by humans for desired traits - in particular, fancy pigeons and the many breeds of dogs created by 10,000 years of selective breeding.

On THE ORIGIN OF SPECIES In 1859 Darwin published his model: On THE ORIGIN OF SPECIES by Means of Natural Selection At the time he was widely criticized and ridiculed.

Darwin’s explanation of how evolution occurred: 1. More individuals are born in a species than the environment can support. There is a struggle to survive. 2. Within every species there is naturally variation. 3. Variations of some give them an advantage over others in the struggle to survive. 4. More of these individuals will survive and reproduce than will those with less favorable traits.

7. Eventually the favorable 5. Many traits are passed from parents to offspring. 6. More individuals with favorable traits reproduce, so the # of individuals with favorable traits increases in each generation. The # with less favorable traits decreases. 7. Eventually the favorable trait becomes the most common form and over many generations (and usually millions of years) such differences accumulate until a new species results.

Darwin called his model “Natural Selection” Does it sound familiar???

How Darwin explained the giraffe’s long neck: 2 3 1 Ancestral giraffes had necks of various lengths. 2. When food became scarce, longer-necked individuals could reach more food sources so they survived in greater numbers than those with shorter necks, many of whom starved and died. Main Idea(s) of This Slide – According to Darwin’s hypothesis of natural selection, the giraffes originally had varying neck lengths. Those individuals whose necks were long enough to reach the leaves survived while those with shorter necks did not survive. Only those surviving individuals (those with longer necks) were able to pass their genes onto their offspring and so, over time, the population had changed and only longer necked giraffes existed. Darwin’s theory relies upon variation within a population and natural selective forces favoring some of those individuals more than others. The theory of natural selection remains the best explanation for almost all of the characteristics seen in the biological world today. – more long necks survived, so more reproduced and passed the long-necked trait to their offspring. – each generation had more long and fewer short necks than the one before. 3. Eventually after many generations and millions of years ALL giraffes had long necks.

Unlike Lamarck, the ideas in Darwin’s model were found to be consistent with observations and scientific evidence. In fact they continue to be supported by all evidence gathered in the 150 years since they were first published. This includes hundreds of thousands of experiments, studies, archeological finds, and facts. Scientists are so confident that Darwin’s model is correct that it is now called a THEORY - The Theory of Evolution by Natural Selection.

Warm Up If you get an infection, and are given an antibiotic, and you get better. Then you get a second infection, and you are given the same medicine, but you don’t get better. What happened? Use natural selection to describe the process.

Meaning of THEORY in science: a comprehensive model that takes into account all known evidence (facts, observations as well as scientific laws) and explains a wide range of natural phenomena. Theories are the models scientists are MOST certain about. Must be supported by MANY different lines of evidence. Must be changed if new evidence is discovered. Must provide a reliable basis for scientists to make and test predictions. THEORY Scientific Laws All Facts All Observations Just 3 theories organize all knowledge in Biology:

CELLTHEORY - all living things are made of cells. (1838) CENTRAL DOGMA - explains what DNA and RNA do and how they do it. (1958) THEORY OF EVOLUTION by NATURAL SELECTION (1859)

MANY LINES OF EVIDENCE SUPPORT DARWIN’S THEORY: 1. FOSSILS

Even in Darwin’s day, change in life forms over time was apparent in fossils found in different layers of rock. This type of dating is referred to as relative dating. NEWER   OLDER Today isotope dating: called absolute dating and DNA analysis allow precise determination of fossil age. Most results agree with earlier studies based on layering alone.

Histories of many species have been reconstructed using layering and other forms of dating.

SIMILARITY OF EMBRYOS 2)Another evidence: Embryology LEMUR PIG HUMAN Which is a human? A lemur? A pig? LEMUR PIG HUMAN

All living things have the same make-up at the molecular level. 3. MOLECULAR EVIDENCE Main Idea(s) of This Slide – Cytochrome C is a protein produced in all of the organisms included in this slide, but there are variations between the amino acid sequence between each species. This slide depicts the number of amino acid differences between the cytochrome c of each of these organisms. Using this evidence, it is easy to compare the relative ancestral relationship between these species. The cytochrome C of humans and chimpanzees are almost identical, indicating close relationship. The cytochrome C of a moth, however, has many differences in it’s sequence and indicates a more distant relationship. The relationship found using this method “matches” the same ancestral relationship found using other types of evidence (fossil, embryological, etc.). All living things have the same make-up at the molecular level.

4. ANATOMICAL EVIDENCE Anatomical similarities reveal common ancestry. Example: All vertebrate forelimbs contain the same set of bones (they’re “homologous”). Main Idea(s) of This Slide – Anatomical structures of various species provide strong support for the Theory of Evolution. When looking at the limb bones of various organisms (as seen here), homologous structures are present in each. This similarity in design supports the fact that these organisms shared a common ancestor and that their structures evolved differently depending on the environmental pressures exerted on them. In this slide the limb bones are compared from the following species; Bird, bat, whale, cat, horse, and human. Note that in each of these highly different animals, the same bones (homologous bones) are found in varying lengths and shapes as indicated by the color coding.

5. DNA EVIDENCE Every organism’s DNA is unique. But most of our DNA is the same as all living things. The more closely related organisms are, the more of their DNA that is the same.

96% of Chimp and Human DNA is identical !

PREDICTIONS THAT FOLLOW FROM DARWIN’S THEORY OF NATURAL SELECTION: 1. There should be fewer and fewer species as we go back toward the beginning of life 3.5 billion years ago. 2. Earlier organisms should be simpler than modern ones. As organisms evolved they became more complex. 3. We should see evidence of life forms that are no longer found on Earth. 4. There should be differences between these organisms and modern organisms. 5. All organisms should have some characteristics in common. 6. Some organisms will be “in-between”, i.e. have traits that make them hard to classify.

ALL of these predictions have been tested and supported. The Theory of Evolution by Natural Selection as proposed by Charles Darwin (and Ms. Lopez’s fabulous Biology students ! ) is supported by all credible scientific evidence collected before and since.

CHECK YOUR UNDERSTANDING: 1. Would you expect individual organisms to “evolve” in their lifetime? 2. What does evolve over time? 3. What “force” shapes the characteristics of species - in other words, what “selects” traits? 4. What might cause evolution to“speed up” - that is, cause species to change more rapidly? 5. What was the original cause of variation within species? NO! SPECIES EVOLVE! THE ENVIRONMENT DRASTIC CHANGE IN ENVIRONMENT MUTATION