02-28 Origin and Diversity of Life key

02-28 Origin and Diversity of Life key - Biology 105 Origin...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Biology 105 Origin and Diversity of Life I. Origin of Life A. Science provides evidence to explain the origin of life, using ideas of evolution and knowledge of chemistry and physics. B. To understand how life could have evolved, we need to know what the very early Earth was like. 1. The Earth was formed about 4.5 bya (billion years ago), and conditions then were very different than they are now. a. The atmosphere was thought to include hydrogen gas, ammonia, methane, carbon dioxide, carbon monoxide, and water vapor, but no oxygen. b. There were severe storms with lightning, strong UV light, and constant volcanic eruptions supplying energy to these atmospheric chemicals. c. A Russian scientist, Oparin, hypothesized that these atmospheric gasses, when given energy, would react to form organic (cellular) molecules. d. This hypothesis was tested by an American scientist, Miller. He put the gasses into an apparatus with circulating water and used sparks to simulate lightning. In only a few weeks he succeeded in making many organic molecules, similar to those found in cells, in his 'primitive Earth' apparatus. C. Scientists now believe that similar cellular molecules were in fact formed on the primitive Earth and slowly built up in the oceans, forming a mixture called the “primordial soup”. Somehow primitive cells evolved in the primordial soup and lived by eating these molecules. 1. Nobody knows quite how this happened, but natural selection clearly would have played a big role. Cells or even proto-cells that were good at getting what they needed would persist and reproduce, while others would fall apart or be eaten. a. The requirements needed to make a cell out of non-living materials seem to be: i. a boundary, or membrane, between the cell and its environment ii. controlled chemical activity, or some sort of metabolism, in the cell, and iii. a way to store and use the biological information needed to produce the metabolic enzymes and membrane (there is evidence that this was RNA in the first cells) b. Once a cell had achieved all of these, it could be considered alive. However, evolution could occur even in the pre-living state, and maybe helped cells become alive. 2. The first primitive cells formed in this way were anaerobic (non oxygen-using), procaryotic cells -- small primitive cells lacking a nucleus or other internal parts, like bacteria today. D. After these first prokaryotic cells evolved, the Earth's first ecological crisis occurred. Cells were consuming the organic molecules much faster than they could be made. Even if the cells could eat each other, they were still limited by the original small supply of abiotically-formed organic molecules. The future of life on Earth appeared extremely limited.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 3

02-28 Origin and Diversity of Life key - Biology 105 Origin...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online