History of Life On Earth

1. History of Life On Earth EQ: What does science tell us about evolutionary biology, the unity and diversity of organisms on Earth and how present populations are changing? Phoenix Curriculum Guide Essential Standard 6.3, Secondary Standard 6.5 Analyze scientific evidence (e.g. fossil record, geographical distribution, physiology) that support the theory of evolution through natural selection. Describe the history of life on Earth including major events that support the theory of evolution.

2. Origin of the Earth Theory • Most scientists generally believe that the Earth was not always here. • Instead, like all things on it, the Earth itself was “born.”

3. Origin of the Earth Theory • Many scientists believe that planet Earth began from the Big Bang Theory-a huge cosmic explosion caused massive clouds of dust and gases to form in space. • This occurred around 12 billion years ago

4. Origin of the Earth Theory • The gases cooled and condensed and the solid Earth and other bodies were formed. • How old is our earth? The Earth is estimated to be about 4.6 billion years old.

5. What are the Origin of Life on Earth theories? • Three theories attempt to explain how life began: • Extraterrestrial Origin: life was brought to Earth by a meteorite or asteroid • Divine Origin: life was placed on Earth by a superior creator (god or gods) • Spontaneous Origin: life had a natural and automatic beginning; nonliving matter became living organisms over a very long time period

6. What are some Chemicals needed for Life? • The ancient atmosphere did not have oxygen. There was no ozone. • The first gases included methane (CH4) and ammonia (NH3). • In the 1920’s, a Russian scientist named A. I. Oparin hypothesized that life started from inorganic molecules built with amino acids to form complex polymers (like proteins). • Miller- Urey experiment provided evidence that organic molecules could be formed from inorganic parts.

7. What are some Chemicals needed for Life? • Early earth was hot, gaseous and unlivable for life forms. • In 1953, an American scientist, Stanley Miller, mixed these inorganic compounds with water vapor and electricity. - Guess what formed? Amino Acids = proteins • These reactions took place in protected environments of bubbles along ocean shorelines (protocells) Protocells- “primitive cells” that are believed to be the 1st cells on earth

8. What are the Earliest Living Cells? • The first living cells on the fossil record (the oldest fossils) were bacteria or prokaryotes • The first cells appeared about 3.5 billion years ago • The earliest cells were autotrophic prokaryotes (no nuclei) • Endosymbiotic Theory: Prokaryotic cells changed into Eukaryotic cells • How did this happen: One Prokaryotic cell engulfed (ate) 1 Prokaryotic cell that could do Aerobic Cellular Respiration and ate 1 more that could photosynthesize.

9. How did Scientists gather all of this information? Paleontology: Through the study of fossils and the world surrounding these fossils. -An evolutionist study these fossils and their species within certain populations.

10. What are Fossils and Geological Time? Fossil- evidence that an organism has lived some time in the past. Paleontologist-a scientist who studies the past and/or ancient life. Geographic Distribution: the movement of a species in a geographical area.

11. What are Fossils and Geological Time? Scientists date the rocks to determine the age of the fossil. Some ways of doing this are: • Relative dating: When you compare the depth of the layerof rock the fossil was formed in relative to other layers of rock. • Law of Superposition: that the oldest rock layers are furthest toward the bottom, and the youngest rock layers are closest to the top. • Radiometric (radioactive)dating: Uses isotopes. • Absolute Dating: A specific time period for a certain layer.

12. Geological Time – determined by the fossil record. • The best current estimate for the age of the earth is 4.5 billion years.

13. How is Geological time measured? Scale: a representation of how time has passed. Era: a certain amount of time. Period: a specific amount of time within an era.

14. What is the law of Original Horizontality? First proposed by Danish geological pioneer Nicholas Steno in the 17th Century. Proposed that sediment (sand, rock) is originally deposited horizontally. It is then moved later by outside forces (crustal disturbances).

15. Relative dating • Simply counting the layers of rock above the fossil. 1 million years old  2 million years old  3 million years old  4 million years old  5 million years old 

16. Absolute Dating Absolute Dating gives a specific time period for a certain layer.

17. Radiometric Dating • Technique involves using radioactive isotopes, which are atoms with unstable nuclei that break down (decay) over time, giving off radiation. • Most fossils cannot be directly radiometrically dated. • Most dates are for volcanic or igneous rocks, or metamorphic rocks that are closely associated with sedimentary rocks.

18. How did Paleontologists know some species are related? • Embryology: The study of Embryos. -Embryos: unborn or unhatched animal or earliest form before human baby. • Many traits of one animal appear in another animal. That is between reptiles, mammals, birds, fish, and more! -Example: Both fish and human embryos have gill slits. • In fish, gill slits turn into actual gills. • In humans, gill slits will disappear before birth.

19. How can offspring be related to ancestor physiologically ? • Homologous Structure: An organ or bone that is the same shape (structure) among different animals. • Analogous Structure: An organ or bone that do the same thing, but have different shape (structure). • Vestigial Structure: An organ or bone that animals have grown out of. Organisms could have needed these in the past, but not anymore.

20. How do all species begin to evolve? • Convergent Evolution: When two species that do not look similar, start to have similar traits due to their similar environments. • Divergent Evolution: When two species stem from one common ancestor start to evolve and look more different from each other.

21. How do all species begin to evolve? Punctuated Equilibrium: The change or evolution of species that comes in spurts that are caused by mutations in the DNA. Gradualism: Over a certain period of time, a certain species will change or evolve with very small changes.

22. How did these organisms become fossils? Fossilization: Only a few organisms can become fossils. To become a fossil: • Organisms usually have to be buried in mud, sand or clay as soon as they die. • Most fossils are found in sedimentary rock because these rocks form at relatively low temperatures and pressures that may prevent damage to the organism. • Metamorphic rock and igneous rock undergo very physically demanding transformations that can incinerate and destroy organisms.

23. What are different types of Fossils? • Trace Fossils: Are the markings of animal activities. • Molds: When an organism is buried, it can decay, leaving an empty space in the rock that is the exact shape of the organism. • Amber-preserved or Frozen Fossils: Sometimes an entire, intact organism can be found frozen in ice or preserved in fossilized tree sap, such as amber. • Petrified / Permineralized Fossils: The hard parts of organisms are sometimes penetrated and replaced by minerals, atom – for – atom. When the minerals harden, an exact stone copy of the original organism is produced. • Casts: When a mold of an organism is created, it often becomes filled by minerals in the surrounding rock, producing a replica of the original organism.

24. When did life began? • Life began in the Precambrian era. • Fish and Reptiles developed during the Paleozoic era. • Dinosaurs were seen in the Mesozoic era. • We currently live in the Cenozoic era.

25. Geological Time Scale

26. Summary • ___1. Law of Superposition a. Prokaryotic cells changed into Eukaryotic cells • ___2. Gradualism b. Older rocks on the bottom, and younger rocks to the top. • ___3. Divergent Evolution c. A certain species will change slowly over time. • ___4. Endosymbiotic Theory d. When two species from the ancestor will start evolve. • .