Ch. 26 - Chapter 26 The Tree of Life An Introduction to...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 26 The Tree of Life An Introduction to Biological Diversity Book Notes Overview – Changing Life on a changing Earth 26.1 – Conditions on Early Earth Made the Origin of Life Possible 26.2 – The Fossil Record Chronicles Life on Earth 26.3 – As Prokaryotes Evolved, they Exploited and Changed Youth Earth 26.4 – Eukaryotic Cells Arose from Symbioses and Genetic Exchanges between Prokaryotes 26.5 – Multicellularity Evolved Several Times in Eukaryotes 26.6 – New Information had revised our Understanding of the Tree of Life Key Terms
Background image of page 1

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

View Full DocumentRight Arrow Icon
Overview 1. Life is a continuum extending from the earliest organisms to the great variety of species that exist today 2. Interactions between organisms and the environment have shaped life on earth 3. Geological events that alter environments change the course of biological evolution 4. Conversely, life changes the planet that it inhabits 5. Geological history and biological history have been episodic marked by what were in essence revolutions that opened many new ways of life Section 26.1 1. Most biologist now think there is at least a credible hypothesis that chemical and physical processes on early Earth produced very simple cells through a sequence of stages 2. According to one hypothetical scenario there were four main stages in the process: 1. Abiotic synthesis of organic molecules 2. Joining of these small molecules into polymers (i.e. proteins) 3. Packing of these molecules into “protobionts” 4. Origin of self-replicating molecules (made inheritance possible) 3. Synthesis of Organic Compounds on Early Earth 1. Earth formed about 4.6 billion years ago along with the rest of the solar system and was bombarded with chunk of rocks and ice for the 1 st few hundred million years 2. Earth’s early atmosphere contained water vapor and many chemicals released by volcanic eruptions, as the earth cooled, water vapor condensed into the oceans 3. Laboratory experiments simulation an early Earth atmosphere have produced organic molecules from inorganic precursors, but the existence of such an atmosphere on early Earth is unlikely 4. Instead of forming in the atmosphere the first organic compounds on Earth may have been synthesized near submerged volcanoes and deep-sea vents 4. Extraterrestrial Sources of Organic Compounds 1. Some of the organic compounds from which the first life on Earth arose may have come from space
Background image of page 2
2. Carbon compounds have been found in some of the meteorites that have landed on Earth 5. Looking Outside Earth for Clues about the Origins of Life 1. The possibility that life is not restricted to Earth is becoming more accessible to scientific testing 6. Abiotic Synthesis of Polymers and Protobionts 1. Small organic molecules polymerize when they are concentrated on hot sand, clay, or rock 2. Protobionts are aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure 1. Laboratory experiments demonstrate that protobionts could have formed spontaneously from abiotically produced organic compounds
Background image of page 3

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

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 10

Ch. 26 - Chapter 26 The Tree of Life An Introduction to...

This preview shows document pages 1 - 4. Sign up to view the full document.

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