Beginning of Life - International Baccalaureate Biology - Lecture Slides, Slides of Biology

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3 THEORIES:

Creation:

• an omniscient power created and guides living organisms
• story found in many religions, in Christianity it is found in the book of Genesis
• cannot be proven scientifically

Chemical synthesis:

• chemicals necessary to produce life were created by reactions on Earth
• Miller-Urey exp. attempted to show part of the pathway
• there is some debate over the actual Earth conditions 4.5 b.y.a. and therefore the reactions that occurred.

How old is our earth and when

did life first appear?

• Earth about 4.6 billon years old
• Earliest life: fossil records and radiometric dating indicate that life evolved around 3. billion years ago. Picture of 180 bya fossil stromatolites from Great Slave Lake Cdn

Evolutionary theory helps to explain

1. The origins of living organisms
   • Common ancestry: organism from which all lifeevolved.
2. Microevolution: how populations change
   • Mechanisms of evolution: the causes of changeswithin a population’s gene pool
3. Macroevolution: how species diversified
   • How species are interconnected and how new speciesarise

Current Scientific debate on Evolution

• Is NOT about weather evolution exists - Body of evidence strongly suggests evolution exists - There is no sound scientific evidence to disprove theory. - Is about HOW organisms evolved - Biologists debate the mechanism of evolution (i.e. Natural selection) - Biologists also debate how species are related to each other