4 From Chemistry to Energy to Life Part C PowerPoint® Slides prepared by Jay Withgott and Kristy Manning Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Fossil record Fossil = imprint in rock of a dead organism The fossil record teaches us much of what we know of life on the planet over the past 3.5 billion years.

Fossil record The fossil record shows that: • Species today are a tiny fraction of all that ever lived. • Earlier organisms evolved into later ones. • The number of species has increased through time. • Episodes of mass extinction have occurred. • Eukaryotes are only ~600 million years old.

History of life By studying present-day organisms or their genes, we can infer relationships among organisms and decipher life’s history. Life’s complete phylogeny is the “tree of life.”

How did life originate? Several hypotheses are competing: Heterotrophic hypothesis (primordial soup): interactions in early soup of organic chemicals Extraterrestrial hypothesis (seeds from space): microbes from elsewhere arrived on meteorites Chemoautotrophic hypothesis (life from the deep): first life from deep-sea hydrothermal vents

Conclusion: Carbon-based life has flourished on Earth for over 3 billion years. Scientists are trying to understand its origin. Deciphering the origins of life requires understanding energy, energy flow, and chemistry.

Conclusion Energy and chemistry are tied to nearly every important process in environmental science. Chemistry can also be a tool for finding solutions to environmental problems. Knowledge of chemistry is relevant to agriculture, water resource management, energy policy, toxicology, and climate change.

QUESTION: Review Which of the following is a heterotroph? a. Pine tree b. Photosynthetic algae c. Squid d. Hydrogen sulfide Answer: c

QUESTION: Review The second law of thermodynamics states that…? a. Energy cannot be created or destroyed b. Things tend to move toward a less-ordered state c. Matter tends to remain stable d. Potential and kinetic energy are interchangeable Answer: b

QUESTION: Review Which of these does the fossil record NOT demonstrate? a. There have been mass extinction episodes. b. Most organisms that ever lived are now extinct. c. Animals originated before plants, and plants before bacteria. d. Numbers of species have increased through time. Answer: c

QUESTION: Weighing the Issues If there was an oil spill on your campus, would you recommend bioremediation? a. Yes, because it is environmentally most desirable. b. No, because it is less tested than traditional methods. c. It depends. (on what factors…?) Answer: any

QUESTION: Interpreting Graphs and Data A molecule of the hydrocarbon ethane contains…? a. 2 carbon atoms and 6 hydrogen atoms b. 2 carbon molecules and 6 hydrogen enzymes c. Carbon and hydrogen DNA d. Eight different isotopes Answer: a

QUESTION: Interpreting Graphs and Data Which is listed from most acidic to most basic? a. Ammonia, baking soda, lemon juice b. Stomach acid, soft soap, HCl c. Acid rain, NaOH, pure water d. HCl, acid rain, ammonia Answer: d

QUESTION: Viewpoints How do you think life on Earth began? a. With a mix of organic compounds in a primordial soup on Earth’s surface b. With the entrance of microbes from other planets on meteorites falling to Earth c. In deep-sea hydrothermal vents Answer: any