Notes for Understanding Evolution - Chapter 14

Click link to return to Biology 409 Schedule
or back to Chapter 13 or ahead to Chapter 15

General guide on these review questions here

Notes for Chapter 14: Origin of Life

Collection of relevant links from Biology 404

Introduction

Formation of the Solar System

Life on Planetary Surfaces

Reconstructing the Origin of Life

Toward the First Living Cell



[Black Smoker] [Riftia]
Visit the Source of the Images of the Deep Sea Hot "Black Smoker" Vent
and the Gutless Hot Vent Worms, Riftia, Hosts of Chemosynthetic Symbiotic
Microbes, at Nova's Living at Extremes Website


Where Did Life Evolve?

Living Things

Energy and Life

Links last updated 7/19/02 © D.J. Eernisse 1998-2002

Introduction


I. Primitive Earth

RQUE14.1: Using the above links and the text, describe how conditions on Earth are thought to have differed when life as we know it first originated.

II. Experimental Synthesis of Organic Compounds

RQUE14.2: What is the significance of experiments of the sort pioneered by Dr. Stanley Miller?

RQUE14.3: All three domains of life use DNA to store the codes necessary for their continued success. So why is RNA now considered to have been the first genetic material, and what does this have to do with molecules known as ribozymes?

III. Life's Beginnings

RQUE14.4: One common fallacy about the origins of life is that all aspects we see shared in common in organisms today must have evolved simultaneously in order for the organism to have been capable of surviving. However, the last common ancestor of organisms alive today had already descended from a long lineage of simpler organisms. What were the first self-replicating precursors to organisms, and where were they likely to have been found? What are some of the steps that would have been necessary before this more complicated organism could have existed? Why is natural selection vitally important in countering the naïve view* that this transition is expected to have happened by chance alone, and so the evolution of life is regarded as a highly improbable scenario.

*Here is one example of this sort of argument, from this website:

Much of the populist evolutionary propaganda resembles the following hypothetical theory for the origin of a car:

‘Design is an unscientific explanation, so we must find a naturalistic explanation instead. Now, experiments have shown that one of the important building blocks of the car — iron — can be produced by heating naturally occurring minerals like hematite to temperatures which are found in some locations on earth. What’s more, iron can be shown to form thin sheets under pressures which are known to occur in certain geological formations ….’

If this seems far-fetched, then note that even the simplest self-reproducing cell, which has 482 genes, has a vastly higher information content than a car, yet self-reproduction is a pre-requisite for neo-Darwinian evolution.

IV. Retrograde Evolution

RQUE14.5: What is Norman Horowitz's notion of retrograde evolution and why is it billed as "ingenious" by the text authors?

V. Autotrophic Existence

RQUE14.6: Perhaps the greatest innovation in the history of life was an adaptation by cyanobacteria. (referred to in the text incorrectly by their old-fashioned name, blue-green algae). Cyanobacteria were the first organisms to manage to use the hydrogen in readily available water as their hydrogen source for photosynthesis. The problem before this was that removing hydrogen from oxygen releases free oxygen, which is highly oxidative, and would tend to rip cells apart without protection. Cyanobacteria do this with the help of an enzyme, SOD, which delivers oxygen safely to the cell surface, where it is discharged. So why is this so important in the history of life, presenting new opportunities but also leading to a "pollution crisis"?

VI. Prokaryotic and Eukaryotic Cells

RQUE14.7: Contrast eukaryotes with other life forms. What primary shared-derived similarities do eukaryotes share with each other that are lacking in other life forms, and what were the implications of the evolution of these new eukaryotic features? Careful, mitochondria and chloroplasts are present in only some eukaryotes, and probably were not present in the common ancestor of all eukaryotes -- they were later additions, despite what is implied in the text.

 

PBS Link: Example of modern-day symbiosis - Ancient Farmers of the Amazon 

VII. Organelles and Evolution

RQUE14.8: Describe the endosymbiotic hypothesis for the origin of mitochondria and chloroplasts in eukaryotes, and review the primary evidence for this hypothesis. (Note: Fig. 14.5 shows a similar hypothesis for the origin of the nucleus and ER, which is not a very popular hypothesis, to my knowledge.)

VIII. Classification of Organisms

RQUE14.9: Non-eukaryotes used to be grouped together by the paraphyletic name, "prokaryotes" but Carl Woese and most biologists today have divided them into two life domains. Why, and what implications does this have? What is wrong with Whittaker's older 5-Kingdom system, which is so popular among textbook authors? (The links provided above and the Chapter 13 notes should be helpful.)

 

Click link to return to Biology 409 Schedule
or back to Chapter 13 or ahead to Chapter 15

This page created 6/8/02 © D.J. Eernisse, Last Modified 7/19/02, Links Last Completely Checked 6/8/02