1. Instructor: Mrs. Nell 7 th Life Science

2. Early Thoughts About Evolution Evolution: change in the hereditary features of a species over time Species: group of organisms whose members successfully reproduce among themselves Evolution of the horse (several toes to single hoof)

3. “Theory of Acquired Characteristics” French Scientist Jean Baptiste de Lamarck In 1809 Proposed one of the first explanations as to how species evolve or change- “Theory of Acquired Characteristics”. Thought species evolve by keeping traits that their parents developed during their lives. Characteristics that were not used were lost from the species. His theory was later rejected… If a dog’s ears are cropped at birth, her offspring are not born with cropped ears.

4. “Theory of Evolution by Natural Selection” Mid 1800s, Charles Darwin developed the theory of evolution that is still accepted today. Visited the Galapagos Islands (islands in the Pacific Ocean west of the coast of Ecuador) His observations and experiments during and after his visit to the Galapagos Islands started him thinking about artificial selection in breeding plants and animals (choosing parents that had traits they wanted in the offspring). Galapagos Islands Galapagos tortoise Galapagos Land Iguana

5. The Galapagos Islands

6. Darwin’s Theory of Natural Selection Darwin theorized that individuals with traits most favorable for a specific environment survived and passed on these traits to their offspring… became known as the “Theory of Natural Selection”. (Organisms with traits best suited to their environments are more likely to survive.)

7. Factors That Govern Natural Selection 1. Organisms have more offspring than can survive.

8. Variations 2. Variations are found in individuals of a species.

9. Beneficial Variations 3) Some variations help members of a population to survive and reproduce better than others.

10. Survival of the Fittest? 4. Over time, offspring of individuals with helpful variations make up more and more of the population.

11. Gradualism Theory that evolution is a slow change of one species to another new species.

12. Punctuated Equilibrium Theory that rapid evolution of species can come about by the mutation of a few genes. In punctuated equilibrium, change comes in spurts. There is a period of very little change, and then one or a few huge changes occur, often through mutations in the genes of a few individuals. It can also be the result of other causes, such as huge and sudden changes in the environment.

13. How did the Tiger get its stripes? Maybe it was gradualismMaybe it was punctuated equilibrium A long time ago, there were a lot of tiger-like animals, but without stripes. A few, however, had markings that allowed them to blend in with the tall grasses a little bit better, so they were able to catch more food, survive, and reproduce. In the next generation, more animals were marked than in the previous generation. Very gradually, over many, many generations, stripes over the tigers' whole bodies formed and appeared in the whole population. A long time ago, there were a lot of tiger-like animals, but without stripes. One time, a mutation occurred in a few of the animals, causing a huge change: they were born with stripes! This was so helpful to survival that out of the whole population, none or almost none of those with stripes died of hunger. They lived to reproduce, and their striped offspring also did very well. Over only a few generations, the whole population was born striped.

14. Example of Natural Selection Good example of natural selection- "peppered" moths living near English industrial cities These insects have varieties that vary in wing and body coloration from light to dark. During the 19th century, sooty smoke from coal burning furnaces killed the lichen on trees and darkened the bark. When moths landed on these trees, the dark colored ones were harder to spot by birds who ate them, so they more often lived long enough to reproduce. Over generations, the environment continued to favor darker moths. As a result, they progressively became more common. By 1895, 98% of the moths in the vicinity of English cities like Manchester were mostly black. Since the 1950's, air pollution controls have significantly reduced the amount of heavy particulate air pollutants reaching the trees. As a result, lichen has grown back, making trees lighter in color. Now, natural selection favors lighter moth varieties so they have become the most common. Dark moths on light colored bark are easy targets for hungry birds but are hidden on pollution darkened trees.

15. Evidence for Evolution Fossils found and examined by scientists called paleontologists Kinds of Fossils: a) imprint of leaf, feather, or organism in rock b) cast made of minerals that filled in an animal track, mollusk shell, or other parts of an organism c) piece of wood or bone replaced by minerals d) an organism frozen in ice e) an insect or other organism trapped in plant resin (amber)

16. Sedimentary Rock Contains the most fossils Rock type formed by mud, sand, or other fine particles that settle out of a liquid Examples: limestone, sandstone, and shale

18. Determining Age of Fossils Method 1: Relative Dating Study where rock layer is- if undisturbed soil, older rock layers lie below younger rock layers. Method used to estimate the age of a fossil.

19. Determining Age of Fossils Method 2: Radioactive Dating Much more accurate in finding the age of a rock layer or fossil Uses radioactive elements (elements that give off radiation)… uranium and Carbon 14 (radioactive form of carbon) As time passes these elements give off energy as they become more stable. The more stable the elements- the older the fossil!

20. Fossil Record is Incomplete Fossils show evolution occurred, but some of the fossil record is missing. Because every living thing doesn’t or can’t become fossilized, the record will never be complete.

21. Other Evidence for Evolution Homologous structures: body parts that are similar in origin and structure A bird wing, bat wing, dolphin flipper, and human arm are homologous. Each has about the same number of bones, muscles, and blood vessels.

22. Vestigial Structures Vestigial structures: body part that is reduced in size and doesn’t seem to have a function. A blind cave salamander with eyes buried underneath the skin Dolphin’s and other whales do not have back legs, yet they have a pelvis bone where legs once existed.

23. Embryology In early stages of development- embryos have tails and gills or gill slits. Fish keep their gills, but the other organisms lose them as they continue to develop. In humans the tail disappears, while other organisms keep theirs. Embryology: the study of the development of embryos.

24. DNA Scientists can determine whether or not organisms are closely related by comparing their DNA. Organisms that are close relatives have similar DNA. Scientists have also found that hemoglobin (a protein in red blood cells that carries oxygen) is nearly identical in many primates.