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Chapter 19.1 & 19.3 1.  The ideas presented here are hypotheses.  The evidence for life’s origin’s are speculative and difficult to find (since these.

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Presentation on theme: "Chapter 19.1 & 19.3 1.  The ideas presented here are hypotheses.  The evidence for life’s origin’s are speculative and difficult to find (since these."— Presentation transcript:

1 Chapter 19.1 &

2  The ideas presented here are hypotheses.  The evidence for life’s origin’s are speculative and difficult to find (since these events occurred much further back in Earth’s history) 2

3  Early Scientists hypothesized that the Earth’s early atmosphere was rich in ammonia, methane, water vapor, and hydrogen.  Earth’s atmosphere lacked oxygen 3

4  Step 1: Formation of the building blocks of life  Step 2: Formation of cells  Step 3: Formation of a reliable CODE for building proteins 4

5  Can the components of living organisms form all by themselves from simple chemicals? YES  The Miller-Urey experiment demonstrated how cells formed all by themselves. 5

6  Miller-Urey Experiment:  Miller and Urey placed Ammonia, Water, Methane, and Hydrogen gases into a device.  To simulate lightening they used electrical sparks. Heat could also be used  They found organic molecules in the device after 3 days. (fats/lipids & amino acids). 6

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8  The Miller-Urey experiment did NOT yield living organisms … so how did the first cells form?  Experiments show that membranes can form by themselves when lipids (fats) are added to water. 8

9  Cells may have formed on their own, but eventually cells would need to replicate and pass on their ability to make proteins to offspring cells.  Some evidence exists that the earliest code for building proteins may have been an RNA code. 9

10  RNA can code for building proteins as well as serving as enzymes to speed up other reactions.  Later, a DNA code developed which was more stable and held the protein code longer. 10

11  Earth is 4.6 billion years old  Fossil evidence indicates that the earliest life on Earth might have existed 3.5 billion years ago…………  Suggesting that it took approximately 1.1 billion years for life to evolve 11

12  Stramatolites or mats of Cyanobacteria 12

13  The earliest life forms on Earth were prokaryotic.(before the nucleus)  They were also almost certainly heterotrophs early on. 13

14  Development #1: Autotrophy  Development #2: Evolution of Eukaryotic cells  Development #3: Evolution of Multicellular Organisms 14

15  Autotrophs make their own food by the process of photosynthesis.  The byproduct that autotrophs release into the atmosphere is oxygen. 15

16  Cyanobacteria were photosynthetic organisms that began adding oxygen to the atmosphere. 16

17  Over time oxygen built up in the atmosphere, eventually forming the Ozone Layer O 3  The Ozone Layer blocked UV rays to allow for land life 17

18  The evolution of some eukaryotic organelles such as chloroplasts and mitochondria can be explained by the endosymbiotic theory. 18

19  Endosymbiotic Theory: 1. Large Prokaryotic Cells engulfed Smaller aerobic bacteria and cyanobacteria, which then began to live inside the larger cells. 2. Aerobic bacteria are thought to give rise to the mitochondria. 3. Cyanobacteria (contain chlorophyll) are thought to give rise to chloroplasts. 19

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21  Evidence that supports the Endosymbiotic Theory: 1. Size & Structure: Mitochondria & Chloroplasts are the same size as most bacteria 2. Genetic Material: Mitochondria & Chloroplasts contain DNA different from the nucleus 3. Reproduction: Mitochondria and Chloroplasts reproduce similarly to bacteria (binary fission) 21

22  Only organisms made of eukaryotic cells can be multicellular  Multicellularity first developed in protists in Precambrian Time 22

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