1. Evolution Patterns Coevolution: A change in two or more species in close association with each other. plants and the animals that help pollinate them Convergent Evolution: Similar phenotypes are selected by the environment. dolphin vs. sharks – fins, streamlined body Macroevolution: changes of many different species over extremely long periods of time.

2. Evolution Patterns Divergent Evolution: two or more related populations become more and more dissimilar. -Often the result of habitat change -Can result in the formation of a new species Human Intervention can speed this up with “Artificial Selection” (e.g. Dog breeding)

3. Evolution and Populations Variations and Trends of Natural Selection Traits of organisms are often studied by “Populations” Population – a collection of individuals of the same species that routinely interbreeds. It is the smallest unit in which evolution occurs. Phenotypes will vary within a population. Variations happen because of: –Random fusion of gametes –Recombination/crossing-over –Mutations If a trait is graphed for a large number of individuals, it will follow the bell-curve trend: Bell Curve

4. Evolution & Populations Stabilizing Selection – The individuals in the population that have the average form of the trait are best adapted for the environment and succeed in reproduction. The center of the bell-curve is more prominent. Something like body size is an example. Directional Selection – The individuals in the population that have one of the extreme versions of the trait are best adapted for the environment and succeed in reproduction. The hump in the bell curve shifts either direction. Tongue length of anteaters is an example. Variations and the process of natural selection can potentially change the population’s most common phenotype and therefore affect the bell curve. The four primary types of “selection” are provided. Bell Curves

5. Evolution & Populations Disruptive Selection – The individuals in the population that have EITHER extreme from the average trait are best adapted for the environment and succeed in reproduction. The bell curve splits and almost becomes 2 curves. Shell color in limpets. Bell Curve Sexual Selection – The female of an organism can choose a mate specifically because of certain traits. Selection is successful reproducers, not successful survivors!

6. Evolution: People & Theories Jean Baptiste de Lamarck (1744-1829) Acquired traits passed to offspring – the webbed foot of a water bird being created from stretching membranes between birds toes would be passed on to offspring. Use or lose – if an organism did not use a part of its body (tail) it would produce offspring with smaller versions of that part until it didn’t have that part at all. His theories were easy to disprove; the described phenotypes were not always genetically carried on. He does get credit for saying that organisms must change over time and the newer organisms were modified versions of previous organisms.

7. Evolution: People & Theories Charles Darwin (1809-1882) He provided the basis of modern evolutionary theory. HMS Beagle – Darwin worked on a 5-year voyage as a naturalist. Traveled to South America and the South Pacific. He collected specimens and took detailed notes – often requesting to be left at ports along the way. QUALITATIVE OBSERVATIONS! Galapagos Islands were especially important! Because of GEOGRAPHIC ISOLATION, many of the plants and animals were unique to the island.

8. Evolution: People & Theories Specifically he studied 13 types of finches. They all had different beaks related to their primary food source; all were obviously descendents from an original. Darwin understood these animals had to have changed over time. He wasn’t sure how. The finch offspring had only been adapting for what was a relatively “short” geologic time. He concluded: over many millions of years, large differences in all known organisms could have occurred.

9. Evolution: People & Theories Research after his journey inspired Darwin to publish: “The Origin of Species” – 1858; which contained his ideas of evolution and natural selection. Summarized in two theories: 1.Decent with modification  All species had descended from one (or a few) original types of life; a “common ancestor”. Newer forms of the organism seen in the fossil record are modified versions of the older species found. 2.Modification by Natural Selection  a trait is beneficial to the reproductive success of an organism AND is inherited by offspring. This is “adaptation” occurring; the resulting change in genes of a population s evolution.

10. Evolution Theory: Natural Selection Natural Selection – organisms best suited to their environment reproduce more successfully than others. Therefore, the population with the most favorable traits increases in number. Natural Selection is not an “active process”; favorable traits are relative to the environment of an organism, and varied. What’s good for some is not good for all!

11. Evidences of Evolution 1. Anatomy Homologous Features (see next page) Organisms can have parts that look different and serve different functions BUT are still similar in skeletal structure and development processes. These are called Homologous Features Vestigial Structures – feature useful to an organism’s ancestor but not the modern carrier of the feature. These were functional features at some point. (Tail bones in humans; leg bones in sperm whales)

12. Evidences of Evolution 1. Anatomy (cont.) (opposite homologous) Analogous Features – serve identical functions and appear similar on both organisms. Analogous features have very different developmental patterns and internal anatomy. Wings: Birds vs. Insects 2. Embryology States that in early stages of development, different vertebrate embryos are very similar looking. Means it is evidence of a common ancestry.

13. 3. Macromolecules Darwin hypothesized that the more similar looking organisms were, the more recently they shared a common ancestor. We can now study these similarities at a molecular level: DNA and related proteins. For instance, proteins responsible for similar functions (hemoglobin) are found in many similar species. Differences in the amino acids found in homologous proteins are directly proportional to the length of time since they shared an ancestor. Evidences of Evolution DNA works like a clock – the more similarities in DNA, the more recently they shared the common ancestor.