History of Life Chapter 14

Biogenesis All living things come from other living things

Spontaneous generation The idea that living things could also arise from nonliving things.

Francesco Redi His experiments showed that maggots came from flies One open jar and one closed jar Meat had maggots in the open jar but not the closed jar

Lazzaro Spallanzani His experiments showed that microorganisms are in the air around us. Boiled broth in two flasks – covered one and left the other open – microorganisms appeared in the open flask

Louis Pasteur His experiments helped to prove biogenesis and get rid of the idea of spontaneous generation. Used curved neck flasks and broth

EARTH’S HISTORY

The Formation of Earth The estimated age of earth is about 4 billion years old. This was determined by studying the many layers of earth surface.

Radiometric dating Method for determining the age of materials

Isotopes Atoms of the same element that differ in the number of neutrons they contain. Most elements have several isotopes. Mass number of an isotope is the total number of protons and neutrons in the nucleus Isotopes are designated by their chemical name followed by their mass number. Example: carbon exists as both carbon-12 and carbon-14

Radioactive decay – the nuclei of an isotope release particles or radiant energy, or both, until the nuclei become stable. Such isotopes are called radioactive isotopes. Half-life – the length of time it takes for one-half of any size sample of an isotope to decay to a stable form.

Alexander Oparin and John Haldane Hypothesized about how the first organic compounds were assembled from earth’s early atomosphere Ammonia (NH3), H2 (g), water vapor, and compounds made of hydrogen and carbon, like methane (CH4) At high temperatures, these gases might have formed simple organic compounds such as amino acids. Over time, these compounds would have (in water) entered complex chemical reactions fueled by lightning and UV rays.

Stanley Miller and Harold Urey Used Oparin’s hypothesis to set up an experiment and synthesize organic compounds including amino acids in the lab Oparin had the hypotheses but didn’t do the experiment. Were able to produce a variety of organic compounds including amino acids. Under water hot springs- CO2 and O2 mess things up

Sidney Fox Research on physical structures that may have given rise to the first cells Cell like structures form spontaneously in the lab from solutions of simple organic chemicals

Microspheres – spherical in shape and are composed of many protein molecules that are organized as a membrane Coacervates – collections of droplets that are composed of molecules of different types, including lipids, amino acids, and sugars .

These studies suggest that the gap between the nonliving chemical compounds and cellular life may not be quite as wide as previously thought However, microspheres and coacervates do not have all of the properties of life. This creates the “container” to support life. Hot clay- don’t need genes to create life supporting structures

THE FIRST LIFE FORMS

The First Cells The first cells were probably anaerobic, heterotrophic prokaryotes

The First Cells Archaea – related group of unicellular organisms, many of which thrive under extremely harsh environmental conditions Many species of archaea are autotrophs that obtain energy by chemosynthesis instead of photosynthesis

The First Cells Some forms of life had become photosynthetic by 3 billion years ago Oxygen is a byproduct of photosynthesis Ozone formed in the upper atmosphere to help protect the earth from ultraviolet radiation

The First Eukaryotes Endosymbiosis – about 1.5 to 2 billions years ago, a type of small aerobic prokaryote was engulfed by and began to live and reproduce inside a larger, anaerobic prokaryote. The eukaryotes provided a beneficial environment, and the prokaryotes provided a method of energy synthesis.