Wolodkowicz Biology 1H

Chapter 15 Evidence of Evolution

Evolution: Theory that species change over time, or the change in the genetic make-up of a population over a period of time. Two ways of observing Evolution: Through Indirect Evidence and Direct Evidence. I. Indirect Evidence of Evolution- Evidence for evolution by observing the history of the earth. A. Fossils- traces of once-living organisms usually found imbedded in rock (sedimentary rock). (Indirect because we are not seeing a creature change before our eyes but rather studying the change of creatures through millions of years.) Examples of fossils: hard parts of an organism such as bones, shells, molds (impression of the organism), casts (cast forms around dead creature, creature decomposes, cast is left). 1. Dating fossils a. Rock Sedimentation or the law of superposition- in a rock layer or stratum, the oldest rocks or fossils are found at the bottom while the newer rocks or fossils are found toward the top.

b. Radioactive Carbon Dating- Living organisms are made of both C12 and

C14. Carbon 14 is radioactive. Scientists can determine the amount of

C14 in your body to determine your age. This is because C14 has a ½ life

of 5,568 yrs. Thus if ½ of your C14 is gone you have lived 5,568 yrs. C14 can be used to measure fossils up to 50,000 yrs. Old. 2. Fossil Record- worldwide standard developed by scientists that records layers of sedimentary rock and the fossils they contain. 3. By observing the fossil record from oldest to most recent, one notes: a change from all organisms living in a marine environment, to living on land, a change from simple, one celled organisms, to multicellular organisms, intermediate organisms (amphibians), and it takes much time for evolution to occur. B. Evidence from living organisms- to determine if a species has evolved, scientist compare, common ancestry, structure, embryonic development, vestigial structures, and biochemistry. 1. Common Ancestry- scientists can show that a group of living species may have come from a common ancestor. 2. Structures of organisms: 2 types a. Homologous Structures- Structures that are similar, but have different functions. Shows that these organisms have the same ancestor. Ex: Whale’s flipper is similar in structure to a human but the Whale’s flipper is for swimming. b. Analogous Structures- structures that have similar function, but differ in structure (does not necessarily show 2 that the organisms come from a similar ancestor): insect wing, no skeleton, veins support it, bat has an internal skeleton and covered by muscle and skin. 3. Embryonic Development- Early stages of development very similar in a fish, human, pig (tail & gills). Ernst Haeckel stated the famous quote in Biology: “Ontogeny recapitulates phylogeny” which means: embryonic development repeats evolutionary history 4. Vestigial Organs- an organ or part of an organism that at the present does not appear to have a function. Ex. Appendix and coccyx. Organisms with vestigial structures share a common ancestry with organisms in which they have the same homologous structure. Wolodkowicz Biology 1H

5. Comparative biochemistry- similar organisms have similar DNA and amino acid sequences. Ex. Only one amino acid difference in the sequence for hemoglobin (protein in the blood) in apes and humans. II. Direct Evidence of Evolution- Evidence of Evolution that one can visually observe over time. A. Microevolution- small observable changes in evolution. 1. Changes in genetic make-up- the organism whose genetic make-up will aid in its survival will reproduce & pass on those traits. Ex. When one takes 2 antibiotics, the antibiotics will kill most of the bacteria, but if just one bacterium is resistant to the antibiotics (different genetic make-up), it will survive and reproduce more bacteria resistant to the antibiotic…they have evolved. 2. Observations in nature- Ex. Peppered moths. Peppered moths lived in wooded areas of England. Prior to 1848, they were light gray with dark markings. A few were black. The black were easy pray for birds. After 1898, Industrial Revolution caused soot to cover trees. The numbers of black moths increased, the number of gray moths decreased (Industrial Melanism). III. Early Evolutionary Theory A. Jean Baptiste de Lamarck (1744-1829)- Created a theory of evolution based on the inheritance of acquired characteristics. Ex. He believed that giraffes originally had short necks. But food was scarce so they reached for leaves in tall trees. In doing this they stretched their necks. Their offspring then inherited this trait. This is not supported. Special use of a body part does not change the genetic make-up of that part. B. Charles Darwin (1809-1882) (Father of Evolution) - Darwin was a naturalist (study living organisms) and in 1831 was selected to be the naturalist on the voyage of the HMS Beagle, a British ship chartered for a five-year mapping and collecting expedition to South America and the South Pacific. One of the places he visited was the Galapagos Islands (Islands off of South America). 1. Studied 14 different species (definition of a species is that members of a species can breed and produce fertile offspring (Donkey with a Horse= Mule) Finches- He observed that the different species all were very similar (homologous- similar ancestor) except that they had different beak structures based on environment and diet. Ex: Warbler finch –slender, pointed bill, feeds on small insects, lives in trees. Medium ground finch- very powerful, heavy bill, good for crushing, feeds on large seeds and nuts, lives on the ground. 2. Darwin using his discoveries wrote The Origin of Species in which he based his theory of evolution on Natural selection: Conditions in nature determine which organisms survive and reproduce. Ex: An antelope born with one leg shorter then the other 4 cannot run as fast as the other antelopes. He will thus be more likely to get caught and eaten. Thus, only the strong will survive and pass on their genes. In terms of giraffes: The giraffes with the longer necks were able to survive and pass on their genes (could reach the leaves of tall trees). While the giraffes with short necks starved and did not pass on their genes. Darwin’s additional ideas based on natural selection: a. Populations produce more offspring than are likely to survive. b. Variation- individuals in populations vary and these variations are inherited. c. Survival of the fittest- the strongest will survive and the weak will perish. d. Organisms within a species are not identical. Some are more likely to survive then others. These individuals will be better suited to survive and pass on their traits. Wolodkowicz Biology 1H