Ch. 27.2 Evidence of Evolution

1. Ch. 27.2 Evidence of Evolution

2. Background info • Earth is 4.6 byo • Prokaryotes evolved ~ 3.5 bya • Eukaryotes evolved ~ 2.1 bya • Multi-cellular organisms arose ~ 700 mya • Means that only unicellular organisms existed for 80% of the time life has existed on Earth

3. Target #11- I can explain descent with modification • Descent with modification • All living things share the same fundamental characteristics • Made of cells • Take chemicals and energy from the environment • Respond to external stimuli • Reproduce • Living things are diverse because organisms are adapted to different environments and the features that enable them to survive in those environments also vary

4. Target #12- I can state the types of evidence for evolution • There are 4 types of evidence for evolution • Fossil evidence • Biogeographical evidence • Anatomical & embryological evidence • Biochemical evidence

5. Fossils: the remains and traces of past life or any other direct evidence of past life • Some can consist of hard parts of organisms • Shells • Bones • Teeth • Soft parts can be preserved based off of how the sample was preserved • Trace fossils can be preserved • Trails • Footprints • Worm casts • droppings Target #13- I can describe how fossils provide evidence for evolution

6. Target #13- cont. • The majority of fossils are embedded in sedimentary rock • Sediment are small rock particles that are a product of erosion of other rock material • Sediment, when mixed with water, creates sedimentary rock creates a recognizable layer, or strata, in the rock record

7. Paleontologists are biologists who study the fossil record and draw conclusions about the history of life • When fossils are arranged from oldest to youngest, they can provide evidence of evolutionary change through time • Example: the horse Target #13- cont.

9. Target #14- I can explain the purpose of a transitional species • Transitional species • Fossils that serve as links between groups • Example: Archaeopteryx • Lived 165 million years ago • An intermediate between reptiles and birds • Had reptile-like features: jaws, teeth, long and jointed tail • Had bird-like features: feathers and wings • Other transitional groups • Fish amphibeans reptiles

10. Biogeography: the study of the range and distribution of plants and animals in different places throughout the world • Organisms evolve in one locale and then spread to accessible regions • A different mix of plants and animals will be present whenever geography separates continents, islands, seas, etc. • Ex: marsupials in Australia Target #15- I can describe biogeography

11. Target #15- cont. • Many of these barriers arose through a process called continental drift • The positions of the continents are constantly moving • Movements create mountains, rifts & valleys, volcanoes, plateaus, etc. • The continents, although currently separate, have at many times in Earth’s history, been combined into one large landmass

12. Evidence for continental drift • A seed fern, known as Glossopteris, have been found on all the southern continents, even though they are currently separated by oceans • The fern’s presence in Antarctica is evidence that this continent was not always frozen • An early reptile (pre-dinosaur), known as the Mesosaurus, has fossils found on the eastern coast of S. America and the western coast of Africa • Appalachian Mountain range continues through North America, Canada, Iceland, and Northern Europe Target #16- I can identify evidence for continental drift

13. Target #16- cont. • Both Cacti and Spurges are plants adapted to a hot, dry environment • Both are succulent, spiny, flowering plants • Cacti grow in North America • Spurges grow in Africa • Both would do well in the others prospective climate • What is the best explanation for this phenomenon?

14. Target #17- I can describe a mass extinction • Mass extinction • An event causing the death of every member of a species • A large percentage of species become extinct in a short period of time • There have been 5 major mass extinction events • Ordovician, Devonian, Permian, Triassic, and Cretaceous periods • Permian was the worst with ~95% of all life going extinct • Following mass extinctions, the remaining groups of organisms are likely to spread out and fill the habitats vacated by those that have become extinct

15. Ordovician • An ice age at the end of the period that killed half the sea-life • Devonian • Drop in global temperatures caused glacial formation, disrupting ocean currents • 70% of all marine life went extinct • Permian • Massive volcanic eruptions • Burned large supplies of coal • Produced gigantic ash clouds • Increased temperatures, decreased oxygen • Suffocated animals • The worst extinction event in history caused 95% of Land life and 70% of ocean species go extinct • Triassic • A possible volcanic eruption or asteroid collision caused a minor extinction event • Cretaceous • Known as the K-T Boundary • Resulted in 40% of the known animal families to go extinct • Affected all dinosaurs, except birds, and most other reptiles • Caused by a gigantic asteroid impact Target #18- I can list the major mass extinctions of Earth’s history

16. Bellwork Why were mass extinctions so important in Earth’s history?

17. Target #19- I can state how anatomy of organisms is a result of common descent • Common descent offers a plausible explanation for anatomical similarities among organisms • Vertebrate forelimbs are used for many different functions • Flight, swimming, running, climbing, or swinging • All contain the same sets of bones organized in similar ways • To explain the unity, the basic forelimb plan belonged to a common ancestor • Plan was modified in the succeeding groups

19. Homologous structures • Structures that are anatomically similar • Forelimbs of humans have a similar structure to other forelimbs in other animals • Analogous structures • Structures that are not constructed similarly, nor share a common ancestry, but are a result of common environment needs • Example: wings of birds and insects…have a similar function, but have different structures and are not derived from the same ancestor Target #20- I can differentiate between homologous, analogous, and vestigial structures

22. Target #20- cont. • Vestigial structures • Anatomical features that are fully developed in one group of organisms but that are reduced in others • Examples • Ostriches have wings like other birds, but they are reduced in size • Snakes have no use for hind-limbs, but snakes still have a pelvis and leg bones • Whales & dolphins have pelvises and limb bones • Means they likely evolved from land animals • Occur because organisms inherit their anatomy from their ancestors • Exist as traces of our evolutionary history

24. The homology shared by vertebrates extends to their embryology • All vertebrates have a postanal tail and exhibit paired pharyngeal pouches • In fish and amphibians, those pouches develop into gills • In humans • 1st first pair become the cavity for the middle ear and auditory tube • 2nd pair becomes the tonsils • 3rd and 4th pairs become the thymus and parathyroid glands • Translation since both fish, amphibians, and humans have pharyngeal pouches, fish & amphibians were the common ancestor to all vertebrates Target #21- I can explain how pharyngeal pouches formed during the embryonic stage of development connect members of different vertebrate species

26. Almost all organisms use the same basic biochemical molecules • Includes DNA, ATP, and other enzymes • Organisms use the same DNA triplet code for the same 20 amino acids in their proteins • Humans share a large number of genes with much simpler organisms • Life’s diversity has come about by only a slight difference in many of the same genes and regulatory genes often found in introns and other regions of the genome Target #22- I can explain the commonalities of organism through their biochemical connections

27. The more similar the DNA sequences are between organisms, generally the more closely related the organisms are • Example comparison: • Humans and chimpanzees are about 97% similar • Example protein: • Cytochrome C used for the transport of materials across the plasma membrane in all organisms • Humans vs. monkeys: 1 amino acid difference • Humans vs. ducks: 11 amino acid difference • Humans vs. yeast: 51 amino acid difference • Data is consistent with anatomical similarities of the organisms and their relation to each other