Write the events about the origins of life on Earth in order from oldest to youngest

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Johnathan Knight
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1 Write the events about the origins of life on Earth in order from oldest to youngest 1. Earth forms 2. First organic molecules (such as amino acids) appear 3. First anaerobic prokaryotic cells appear 4. First photosynthetic prokaryotic cells and first aerobic prokaryotic cells appear 5. First eukaryotic cells appear 6. First multicellular organisms appear

2 Origins of Life Once thought life came from spontaneous generation, meaning that life comes from nonliving matter. This it the theory of abiogenesis (abio= not living)

3 Redi- experiment to test whether maggots (living) spontaneously generated from meat (dead)

4 Pasteur- used beef broth to prove that microorganisms cannot arise spontaneously.

5 Redi and Pasteur s experiments proved biogenesis: that life only comes from living things So if life has to come from living things, how did life first start??? Atmosphere of early Earth contained gases: hydrogen cyanide - nitrogen carbon dioxide - hydrogen carbon monoxide - water hydrogen sulfide

6 Gases reacted with energy from lightning to produce small organic molecules concentrated in primitive oceans.

In the 1950 s Miller and Urey filled a flask with hydrogen, methane, ammonia, and water to represent the early Earth and they used electric lightning

7 In the 1950 s Miller and Urey filled a flask with hydrogen, methane, ammonia, and water to represent the early Earth and they used electric lightning to stimulate the mixture. In a few days, organic compounds had formed! This suggested that life can be made from simple compounds on the primitive earth.

9 Origins of Cells The first true cells were heterotrophic prokaryotes (this is called the Heterotroph Hypothesis) They evolved the ability to do photosynthesis to make their own food Photosynthetic prokaryotes were responsible for the release of oxygen into the atmosphere Oxygen was toxic to many organisms so they died off

11 Eukaryotic cells probably arose through a symbiotic relationship between two kinds of prokaryotic cells: We believe that mitochondria and chloroplasts used to be prokaryotes (They have their own DNA)! A photosynthetic bacteria (future chloroplast) and an aerobic heterotroph (future mitochondria) found their home inside the cells This is called the Endosymbiotic Theory (that eukaryotic cells came from prokaryotic cells joining together to form a single cell).

12 To Summarize:

13 Life on Earth Two main types of life: prokaryotes: (means "before nucleus") organisms (bacteria) whose cells do not have a distinct nucleus or other internal parts enclosed in membranes. eukaryotes: (means "true nucleus") organisms whose cells have a distinct nucleus and various internal parts enclosed in membranes. Fig. 6 2 Brooks/Cole Publishing Company / ITP

15 Origins of Life Summary of the evolution of the earth and its life over the past 4.7 to 4.8 billion years. Fig. 6 5 Brooks/Cole Publishing Company / ITP

16 Evolution of Cells mutations produced new varieties of cells that co-exist. Heterotroph Hypothesis- the first cells lacked complexity and could NOT make their own food First Cell: (3.5 bya) were prokaryotic, anaerobic due to lack of oxygen in atmosphere, and heterotrophic = consumed food

17 Evolution of Cells Second cell: prokaryotic, anaerobic, photosynthetic (but produced OXYGEN) Third Cell: aerobic prokaryotic; atmosphere now filled with oxygen due to photosynthesizing prokaryotic cells

18 Evolution of Cells Endosymbiont Theory- Aerobic prokaryotes became mitochondria Photosynthetic prokaryotes became chloroplast Evidence -> chloroplast and mitochondria are the only organelles with their own DNA!

19 Funny, but not the best answer!

20 Now flip your paper over and bring up the video: How Life Began- Origins NOVA. Answer the questions while you watch. Here are two links: The video should be about 52 minutes long

Monday-Tuesday (1/7-1/8)

Monday-Tuesday (1/7-1/8) You have 4 minutes to write the following about your winter break: 3 things you did 2 places you went 1 favorite memory Geologic Time Line Contest 1. Start of the age of the dinosaurs