Aim 63: EVOLUTION: What is it? Where do scientists look for evidence?

1. Aim 63: EVOLUTION: What is it? Where do scientists look for evidence? Evolution -_____________________________________________________________ ______________________________________________________________________ Evolutionary changes may occur in the ________________________, _________________________, and ________________________ over time. Classify the following characteristics. Mark them with an S, F, or B. ___ Burying eggs. ___ Building nests. ____ Storing fat in cells. ____ Males competing for females. ___ Long necks. ___ Webbed feet. ____White fur. ____ Making poison to kill predators ___ Hunting in packs. ___Digesting milk. ____ Excellent night vision. ____ Using hormones for regulation. Evolution is a theory. A THEORY is an explanation, supported by observations or experiments, that can be used to accurately explain related occurrences and can be used to predict outcomes. Ie A theory is an explanation that is backed up with evidence. The Theory of Evolution attempts to explain: • how such a huge __________________________________ came to exist on planet Earth. • why there are many ____________________________ between the species that do exist. • what happened over time to produce the history of species on Earth as seen in the __________ __________.

2. Aim 63: EVOLUTION: What is it? Where do scientists look for evidence? Evolution- THE CHANGE OF SPECIES OVER TIME; THE IDEA THAT EARTH’S PRESENT DAY SPECIES DEVELOPED FROM EARLIER, DISTINCTLY DIFFERENT SPECIES. Evolutionary changes may occur in the STRUCTURE, FUNCTION, andBEHAVIOR over time. Classify the following characteristics. Mark them with an S, F, or B. ___ Burying eggs. ___ Building nests. ____ Storing fat in cells. ____ Males competing for females. ___ Long necks. ___ Webbed feet. ____White fur. ____ Making poison to kill predators ___ Hunting in packs. ___Digesting milk. ____ Excellent night vision. ____ Using hormones for regulation. Evolution is a theory. A THEORY is an explanation, supported by observations or experiments, that can be used to accurately explain related occurrences and can be used to predict outcomes. Ie A theory is an explanation that is backed up with evidence. The Theory of Evolution attempts to explain: • how such a huge __________________________________ came to exist on planet Earth. • why there are many ____________________________ between the species that do exist. • what happened over time to produce the history of species on Earth as seen in the __________ __________.

3. Aim 63: EVOLUTION: What is it? Where do scientists look for evidence? Evolution- THE CHANGE OF SPECIES OVER TIME; THE IDEA THAT EARTH’S PRESENT DAY SPECIES DEVELOPED FROM EARLIER, DISTINCTLY DIFFERENT SPECIES. Evolutionary changes may occur in the STRUCTURE, FUNCTION, andBEHAVIOR over time. Classify the following characteristics. Mark them with an S, F, or B. B Burying eggs. B Building nests. F Storing fat in cells. B Males competing for females. S Long necks. S Webbed feet. S White fur. F Making poison to kill predators B Hunting in packs. FDigesting milk. F Excellent night vision. F Using hormones for regulation. Evolution is a theory. A THEORY is an explanation, supported by observations or experiments, that can be used to accurately explain related occurrences and can be used to predict outcomes. Ie A theory is an explanation that is backed up with evidence. The Theory of Evolution attempts to explain: • how such a huge __________________________________ came to exist on planet Earth. • why there are many ____________________________ between the species that do exist. • what happened over time to produce the history of species on Earth as seen in the __________ __________.

4. Aim 63: EVOLUTION: What is it? Where do scientists look for evidence? Evolution- THE CHANGE OF SPECIES OVER TIME; THE IDEA THAT EARTH’S PRESENT DAY SPECIES DEVELOPED FROM EARLIER, DISTINCTLY DIFFERENT SPECIES. Evolutionary changes may occur in the STRUCTURE, FUNCTION, andBEHAVIOR over time. Classify the following characteristics. Mark them with an S, F, or B. B Burying eggs. B Building nests. F Storing fat in cells. B Males competing for females. S Long necks. S Webbed feet. S White fur. F Making poison to kill predators B Hunting in packs. FDigesting milk. F Excellent night vision. F Using hormones for regulation. Evolution is a theory. A THEORY is an explanation, supported by observations or experiments, that can be used to accurately explain related occurrences and can be used to predict outcomes. Ie A theory is an explanation that is backed up with evidence. The Theory of Evolution attempts to explain: • how such a huge VARIETY OF SPECIES came to exist on planet Earth. • why there are many SIMILARITIES between the species that do exist. • what happened to produce the species on Earth as seen in the FOSSIL RECORD.

6. For evolution to occur, lots and lots of TIME is required because evolutionary changes occur slowly. Evolutionary theorists believe the age of the earth to be ~ 4.5 BILLION yrs old, with unicellular life existing for the last ~3.5 BILLION yrs and multicellular organisms for the last ~ 1BILLION yrs. These dates have been determined using several dating methods. Carbon dating compares the ratio of C12 to C14 in fossil samples. It is only accurate for specimens up to 50,000 yrs. Radioactive dating compares ratios of two elements. Potassium decays into argon over time, so K-Ar ratios are used to date fossils. Index fossils are also used to date specimens. Index fossils are fossils of species that are known to be very common during a time period. So, when rocks or other fossils are found near them it is supposed that they are of the same age as the index fossils.

7. Where do scientists look for evidence of evolution, or to try to determine what species changed or evolved into the species we have on earth today or to try to determine which species on earth are the most closely related, or which have evolved from a COMMON ANCESTOR? • FOSSILS(FOSSILRECORD) - the remains of living things preserved in rock or other materials. There are many types: • MOLD FOSSIL - an indentation left in SEDIMENTARY rock. When the organism dies it is covered by sediments that harden into rock. When the organism decomposes the fossil remains. • CAST FOSSIL - when the empty mold fills in with another substance and hardens • AMBER - organisms are preserved in tree sap (Remember Jurassic Park?) • REPLACEMENT or PETRIFICATION - the organic molecules of the specimen are replaced by minerals • IMPRINT or TRACE FOSSIL - footprints, or other indentations made by the organism • Organisms have also been preserved in ice, acidic bogs, or as a black carbon print.

8. MOLD FOSSIL

9. CAST FOSSILS

10. A mosquito fossilized in AMBER, the sap or resin of a plant. Amber has preserved many insects and even small animals.

11. PETRIFIED WOOD- the organic molecules of the wood have been replaced by inorganic mineral molecules, and the structures of the wood are preserved. (Is sometimes called replacement fossilization.)

13. IMPRINT FOSSIL

14. The woolly mammoth, an extinct mammal. Specimens have been preserved in the ice of the arctic.

15. A human fossil preserved in the acid conditions of a peat bog.

16. CARBON FOSSIL

18. 2. Comparative ANATOMY • HOMOLOGOUSSTRUCTURES - organs or appendages from different species that seem to have a common origin or similar structure.(but they aren’t necessarily used for the same function) Examples: bat wing, bird wing, whale flipper, human arm/hand, lizard paw • VESTIGIALSTRUCTURES - organs or appendages that have no current function, they are thought to have had a function in earlier forms of the organism Examples: human appendix, nipples on males, leg bones on snakes • Analogous structuresare also studied. These are appendages that have the same function but they aren’t formed in the same way, the structure is different in different species (Example: Fly wings and bat wings are both for flying but they don’t look similar in structure.)

19. HOMOLOGOUS STRUCTURES have similar structure but may NOT be used for the same function.

20. bat turtle dolphin bird human horse

21. VESTIGIAL STRUCTURES – body parts that seem to have no function but are thought to have had a function in previous times. (They are a VESTIGE of the past.)

22. Analogous structures – they are used for the same function, but they don’t have the same structure.

23. 3. Comparative EMBRYOLOGY • Developing organisms of different species have similarities in their earliest stages. It is difficult to distinguish an embryo of a chicken from that of a turtle or pig or rabbit.

24. In COMPARATIVE EMBRYOLOGY scientists examine embryos from different species looking for evidence that they evolved from a COMMON ANCESTER. Do you have any guesses about what species are represented by these embryos?

25. Any guesses now?

28. 4. Comparative Cytology – similarities in the cell parts and cell functions of different species. (Note: the prefix cyt- = cell) Examples: plant cells have cell walls and chloroplasts, bacterial cells have cell walls but they don’t have a nucleus, animal cells have centrioles

29. 5. Comparative Biochemistry – similarities in different species in their molecules of DNA, ENZYMES, PROTEINS, and HORMONES or in the chemical reactions or chemical processes they can perform, such as photosynthesis, aerobic respiration, anaerobic respiration • Similarities in Comparative Anatomy, Comparative Biochemistry, Comparative Embryology, and Comparative Cytology are used to try to determine how closely two species on earth may be and to look for • the COMMONANCESTOR of two or more species. Ie, If you go back far enough in the history of horses and goats, at what point will you find the common ancestor they both evolved from?

30. Aim 64: Patterns of Evolution • The basic idea of biological evolution is that the huge variety of Earth’s present-day species developed from earlier, simpler, distinctly different species. It attempts to explain why there are many similarities between the different species and how the different species came to exist on Earth. • However, evolution does not necessarily have to show long-term progress in the evolution of new species in any set direction.

31. Evolutionary changes appear to be like the growth of a bush: • Some species survive from the beginning with little or no change because they were WELL-ADAPTED to their environment and/or their environment didn’t change. (The horseshoe crab is an example of a species that has not changed much over time.) • Some species die out because of sudden CHANGE in their ENVIRONMENT and they were not WELL-ADAPTED to the new conditions. (Fossils indicate that many species have already become extinct; most of the species that have lived on Earth have already become extinct.) • Other species branch repeatedly through the process of evolution and speciation, giving rise to new, different and even more complex organisms.

33. Biological classifications are based on how organisms are related based on their common ancestry which is determined by examining their structures, and more importantly their DNA. • All living things are classified into one of the 6 Kingdoms: Animal, Plant, Fungi, Protista, Monera, Archebacteria. • Kingdoms are divided into Phylums, then Classes, Orders, Families, Genus and finally Species, the narrowest classification. Remember only organisms of the same species can successfully reproduce. • Organisms are named by their Genus species, • Example: Homo sapiens Genus=Homo, species= sapiens cats are Felis Sylvestris. • Classification for housecats: Kingdom Animal, Phylum Chordate, Class Mammal, Order Carnivore, • Family Felidae, Genus Felis, Species sylvestris

34. Classification for housecats: • Kingdom Animal, • Phylum Chordate, • Class Mammal, • Order Carnivore, • Family Felidae, • Genus Felis, • Species sylvestris • Housecat = Felis sylvestris • (Note the Genus always has a capital letter but the species gets a lower case letter.)

35. Aim 65: Two Theories on the Rate of Evolution Scientists do not agree about the rate of change or how quickly evolution of a species can occur. GRADUALISM - the theory that evolution occurs gradually, slowly, and continuously. There are a few examples where the fossil record seems to support this idea. Darwin himself described the rate of evolution as gradual. PUNCTUATEDEQUILIBRIUM - this theory states that organisms remain the same for long periods of time (many thousands or millions of years) and then in a relatively short period of time ( a few thousands of years) this equilibrium is interrupted by the appearance of a new species. Ie long periods of equilibrium are interrupted, or punctuated, by short periods or bursts of rapid evolution of species. Modern scientists believe the fossil record supports this last idea. They believe the fossil record for some organisms shows no change for millions of years and then suddenly new species appearing. They say the transitional forms are missing in the fossil record because the evolution occurred rapidly leaving few fossils. Scientists speculate that major geological changes or major climate changes might spur on the periods of rapid change.

36. Aim 66: Explaining how evolution could occur: Natural Selection The basic theory of biological evolution states that the Earth’s present-day species developed from earlier, distinctly different species. Modern Evolutionary Theory attempts to explain how that could happen through a process of Natural Selection.

37. Charles Darwin became known for his writings, On the Origins of Species, on the concept of Natural Selection. He did not, however, include the study of genetics in his explanations because little was known of genetics in his time period (mid-1800s.) The modern theory of evolution includes both Darwin’s ideas of Natural Selection and explanations based on our current knowledge of genetics.

38. Darwin took a 5 year voyage around the world and studied and collected species. He had a second voyage also. He spent time in the Galapagos Islands. Darwin went back to England to think about what he had seen for many years. He wrote On the Origin of Species which explained his thoughts on Natural Selection.

39. Natural Selection is an explanation of how new species could evolve. It is based on the following principles. • OVERPRODUCTION – more offspring are produced than the environment can support. ( Everyone won’t survive. Some will die from lack of food, water, space, shelter; some will be eaten or die of diseases) • COMPETITION - organisms compete for limited resources in the environment, there is often not enough food, water, space or shelter for everyone soThere is a struggle for survival. • ‼ VARIATION - differences in traits within a species exist, These differences can be in the structure, the behavior, and/or the function of the individuals.; (some are lighter, or taller, or thinner, faster, less hairy, more aggressive, get up earlier, have more enzymes, see better in the dark, digest fewer substances, have fewer babies, nurse babies longer, have a curved tail, a longer neck, a thinner beak, a softer call, grow slower, etc, etc, etc,) Darwin could not explain how these differences came to be, but you should know from your studies of genetics and reproduction how the variation comes to be. • ADAPTATION - individuals who survive are the ones best adapted because they have variations that are the best suited for their environment. So, Survival of the Fittest really means, Suvival of the Best Adapted. Characteristics or traits that are best suited are said to have a HIGHADAPTIVE VALUE, traits that are not suited to the environment have a LOW ADAPTIVE VALUE.

40. USING GIRAFFES AS AN EXAMPLE

41. OVERPRODUCTION Many baby giraffes are born.

42. COMPETITION As they grow up they compete for food, water, and shelter.

43. VARIATION Some of the giraffes have short necks, and some have medium necks and some have long necks.

44. ADAPTATION The food is mostly found up high for a few years. The giraffes with longer necks are better adapted to this environment and get more food and are healthy. The long neck giraffes mate and have long-necked babies. The next year there will be more long-necked giraffes than before. The short-necked giraffes are not well-adapted to this environment. They die or don’t find mates and their numbers decrease in the population.

45. As a result of the above principles, the following could occur over time: Individual organisms best adapted to the environment will live to adulthood in greater numbers than those less adapted. They will pass the adaptive trait(s) to their offspring through their genes. Over time,the proportion of individuals with the adaptive trait will INCREASE and the proportion of those without the adaptive trait(s) will DECREASE. So, the environment ‘selects’ who will live to reproduce and who will die. The environment or nature does not cause the organisms to have adaptive traits, the traits come from their genes, but nature selects which traits are the best or most useful for survival. This is natural selection.

46. According to modern evolutionary theory new species could also come into existence through this mechanism. SPECIATION - when a new species arises through natural selection due to either dramatic changes in the environment, or slow but gradual changes in the environment over an expanse of time. Isolation of populations with different traits is essential for new species to arise.

47. Remember: Behaviors can evolve as well as Structures or Functions

48. Also, organisms do NOT obtain adaptive traits because they NEED them. They obtain them through mutation or new genetic combinations.