Why Evolution Works

1. Why Evolution Works ‘Tis crazy!!!!!!!!!!!!!!!!!!

2. Evolutionary Biology is not just Biology!?!?!?!?!?! • Nope! There’s anthropology, astrophysics, chemistry, geology, physics, math, and other scientific stuff that the packet deems unimportant!

3. Origins of Universe Made Evolution Work (it’s actually really cool) • In the 1920’s the telescope at Mount Wilson Observatory outside L.A. found that the faint light scattered in the sky was actually separate galaxies. Que????!! • By studying the light emitted from the stars from these galaxies Astrophysicists found that the galaxies were moving away from each other so the universe is expanding. Que?!?!?!?! X2

4. Thus the “Big Bang” Theory was thought up by Georges Lamaitre • This is when the universe was originally compressed into an infinitesimally small, infinitely dense, and hot little speck that began to expand and then cooled to a point when the elementary particles became stable and there is a lot of random evidence to support this like the temperature of space and its radiation. • Then dust gathered through gravity and made stars through the fusion of hydrogen into helium. • Astrophysicists also saw that some stars formed with spinning disks of matter around them which then condensed into planetesimals and then planets and moons and asteroids depending on their size. The Milky Way formed through this process.

5. Astrophysicists and Geologists found crazy ways of Dating the Age of Things • By measuring the distance between galaxies and the rate at which they are separating Astrophysicists can find that the universe is 14 billion years old!!!!! • They can also measure the background radiation to date the universe and they got similar results. • They also found that the Milky Way formed a few hundred million years after the universe formed. • Radioactive elements in meteorites indicate that our planet formed between 4.5-4.6 billion years ago • At this point in time lots of asteroids and comets attacked the Earth scaring dust into the atmosphere which then turned into the moon. • Geologists know this from zircon crystals that are 4.4 billion years old.

6. Funny Blurb Thing #1 Radiometric Dating!!!!! • Modern Cosmology says protons neutrons and electrons formed once the universe cooled and then came together to make Hydrogen, Helium, and Lithium. • All other elements were formed through stars smashing these elements together for fun (or when they got really angry and made supernovas). • Some atoms are radioactive and decay into radioactive and non-radioactive atoms by throwing off subatomic particles and energy. Radioactive atoms decay in a certain amount of time for half of it to decay (called a half-life). By comparing the amount of the radioactive element and its decay product around it scientists can determine when the material formed and its age.

7. Living Things Came about in the First Billion years of Earth’s History • Paleontologists found layered rocks known as stromatolites that are supposedly made by bacteria 3.4 billion years ago. • They also found cyanobacteria (blue-green algae) that are nearly 3.5 billion years old but life also appeared much earlier. • In the 1950s hundreds of lab experiments showed that DNA, molecules that make proteins, and cell membrane molecules could be formed through reactions between water and volcanic gasses. They also found these elements in meteorites and floating in outer space.

8. Three Conditions For Life • 1) Groups of Molecules that could reproduce by themselves needed to come together. • 2) Copies of these molecules must have variation. • 3) These variations must be heritable.

9. RNA Might Have Met those Conditions • Researchers discovered that some RNA molecules can catalyze the rate of some reactions including the replication of other RNA molecules • If RNA could reproduce itself it could form the basis of a very simple living organism when packaged in vesicles (cell membrane) and form “Protocells” • Changes in these molecules could lead to variants that could replicate more efficiently in certain environments. • Thus Natural selection started choosing protocells that then became more complex into the organisms of today.

10. Fossils do Important Things • In the 19th Century, naturalists saw that older rocks are found lower than newer rocks in the earth’s crust. Thus older fossils are farther down in the earth’s crust. • Thus naturalists proposed that organisms changed over time. But Darwin and Alfred Russel Wallace were the first to identify the reason for it: Natural Selection (Darwin called it “descent of modification”)

11. Darwin was Really SMART • When he published On the Origin of Species paleontology was still undeveloped. So he spent 20 years gathering evidence and considered problems with his view despite the inadequacy of his fossil record and rare intermediate forms. • Since then Paleontologists have found many intermediate forms along with sedimentary rocks (between 540-635 million years old) with soft bodied multi-cellular organisms and tracks that seem to show the existence of wormlike creatures as early as 1 billion years ago. • Many of these organisms are probably intermediate forms between single celled organisms and big, hard-bodied organisms that are abundant in the fossil record starting 540 million years ago. Also these hard-bodied organisms are transitions between soft bodied organisms and major evolutionary lineages such as fish, arthropods, mollusks.

12. Crazy Transitional Organisms • Tiktaalik is a notable transition between fish and early tetrapods. Fossils from 330 million years ago show the evolution of large amphibians into early tetrapods. Skeletons from 230 million years ago show dinosaurs evolving from a lineage of reptiles. • Another example of a transitional form is Archaeopteryx, a 155 millionyear old fossil of a skeleton similar to small dinosaur but also had feathers and wings. • More of these birdlike fossils were found in China and are about 110 million years old and have tails and clawed appendages.

13. Similar Features Usually Means Common Ancestry • Each species on Earth is a product of evolutionary lineage. • Any two species today can have their evolutionary lineages traced back until their lineages intersect which is where their most recent common ancestor appeared in time. • So Humans and Chimps evolved from a common ancestor, Humans did not evolve from chimps!!! • If the common ancestor of two species is fairly recent then those two species will share physical features and behaviors. This means that all organisms share some traits because we all have a common ancestor.

14. Homologies and……………. Analogies? • Biologists call similar structures that arise from common ancestry Homologies. They investigate homologies to connect today’s organisms with common ancestors. • Sometimes different lineages independently evolve similar structures which we call Analogous structures (Analogies). These look like homologies but stem from similar environments, not common ancestry.

15. I CAN FLY!!!!!!!!!!!!! Flying squirrel Flying lemur

16. Evolution and Geographic Distribution • Example 500 species of Drosophila and Scaptomyza live only on Hawaii. Why is this true? • Hawaiian Islands are the tops of mid-ocean volcanoes and thus have never been connected to land. So all plants and animals on the Hawaiian Islands are descended from those that traveled there from other places. In the case of the Hawaiian flies they were all descended from one ancestral species that first came to the islands.

17. The Hawaiian Lord of the Flies • The initial ancestors of the flies faced conditions favorable for rapid speciation. • Individual species repeatedly served as ancestors for multiple other species as groups of flies occupied habitats with different altitudes, amount of precipitation, plants, and soils. Also these groups, or even a single fertilized female went to other islands giving rise to different species because of the different environments. • These different species were also able to fill ecological niches that were already filled on the continents and thus it was easier for them to go through rapid speciation.

18. More examples of Species Distribution • Mammals that lived on North and South America are another example. When North and South were connected these mammals evolved similarly. • But then the land decided to break apart and thus these mammals decided to evolve differently. On South America ant-eaters, sloths, and armadillos evolved while horses, bats, and wolves evolved on North America. • Then when North and South America finally made up about 3 million years ago the different mammals migrated across to the different continents.

19. Funny Blurb Thing #2 Picture Winged Drosphilids • The Hawaiian Drosphilids are an example of “Adaptive Radiation” which is when one ancestral species gives rise to lots of new species in a short period of time. • Biologists focus specifically on 100 of these species that have pigmented markings on their wings which are known as Picture Winged Drosphilids. These flies carry a remarkable record of the groups evolutionary history. • The cells of the salivary glands in the larvae of these Drosphilids there are special chromosomes called polytene chromosomes. • These chromosomes have alternating dark and light bands of different sizes which makes it easy to see the chromosomal rearrangement called inversion. • Biologists use the changes in the chromosome pattern to find out the sequence of which species went from the older islands to the newer islands.

20. Funny Blurb Thing #3 Limbs in Early Tetrapods • Biologists have discovered the sections of DNA that code for the formation of body parts which are known as Hox genes. • All mammals have 39 Hox genes. Hox genes control the function of other types of genes and one Hox gene can control multiple sets of genes that control different parts of the body. • Hox genes are also involved with the development of anatomical features in both invertebrates and vertebrates. They are expressed in different patterns and these different patterns result in the formation of toes and fingers to the formation of fins and wings. • Changes in these genes are likely to be involved in the evolution of Tiktaalik.

21. Funny Blurb Thing #4 Evolution of Whales and Dolphins and Porpoises. • Fossils and molecular evidence allow biologist to reconstruct detailed evolutionary histories. • For example fossils in Asia revealed that 50 million years ago organisms moved from life on land to first hunt in marine environments and then live in them. • This fossil evidence accords with genetic findings that whales, dolphins, and porpoises descended from terrestrial mammals known as artiodactyls, which include sheep, goats, and giraffes. • Studies of DNA regulatory regions of modern porpoises have revealed the molecular changes that caused their ancestors to lose their hind legs and develop streamlined bodies.

22. Molecular Biology Shows Crazy Changes in Genetics • DNA ispassed from one generation to the next directly form parent to offspring (in asexual organisms) or through a sperm and egg cell from a mother and father(sexual reproduction). • Changes in the nucleotide sequence of DNA from one generation to the next are due to mutations, if the mutations are beneficial then the DNA sequences are likely to sweep through a population over multiple generations. • Neutral mutations have no effect at all and thus can be maintained within a population. • So DNA contains a record of past genetic changes.

23. DNA Shows Common Ancestry • Biologists can uncover genetic changes that have occurred since two organisms shared a common ancestor. • If the two organisms share a recent common ancestor then their DNA sequences will be fairly similar. • In opposition if they share an old common ancestor they will have more differences in their DNA sequences. • Yet there will always be similarities in the DNA sequences of all living things sine we all share a common ancestor.

24. Changes in Biological Molecules make Weird Stuff Happen • An example of this is that biologists have been examining regulatory protein that cause genes to turn off and on as an organism develops in an egg. • Changes in the proteins, the DNA regions that they attach to, or in small RNA molecules can have a dramatic effect on the anatomy and function of an organism. • These changes could be responsible for the development of limbs from fins in early tetrapods • Also biologists have discovered very similar sets of regulatory proteins in organisms such as fleas, mice, and humans. Despite the many millions of years of separation from the common ancestors. • DNA Evidence suggests that basic mechanisms controlling biological form became established before/during the evolution of multi-celled organisms and haven’t changed much since.

25. We Evolved WITH Apes (Who Knew?) • Today there is no scientific doubt that humans have evolved with close ancestry with primates and we evolved because of the same forces applied on us and other organisms. • Based on DNA evidence the common ancestor between humans and chimps lived about 6-7 million years ago in Africa. • The evolutionary tree leading from chimps to modern day humans contains many side branches containing human like species that weren’t as good as us.

26. Lame Human-ish Species that DIED • 4.1 million years ago a species of the genus Australopithecus showed up on Africa (Lucy is this species). The brain of the adult of this species is like that of modern apes and it seems to have spent some time climbing in trees, indicated by its short legs and features in the arms. They also walked upright so that’s special. • 2.3 million years ago the first of the Homo genus arrived. Homo habilis (handy man) and these guys had a 50% larger brain than Lucy did. For reference the earliest stone tools appear 2.6 million years ago. • 1.8 million years ago Homo erectus (upright man) came about and then traveled to Eurasia because they got restless. • Then 200,000 years ago Homo sapiens evolved in Africa and then they traveled everywhere and beat up all the other Homos because they were lame and cramped our style!

27. The END of Part 1 There is still about 2/3s to go I know this is really long.