The Origin of Life Notes: Chapter 14
Origin of Life outline A. Background Age of earth Life began when/where Fossil Relative dating Radioactive dating B. Spontaneous generation 1. Redi: 2. Pasteur C. Biogenesis D. First cells E. Endosymbiont theory
The Beginning: Earth is about 4.4 billion years old Life began on Earth about 3.5 billion years ago in the ocean
Evidence of Life: Fossils: Evidence of an organism that lived long ago, can include remains or imprints of organism in sedimentary rock (clay, mud)
A Protoceratops drinking at a river falls into the water and drowns Sediments from upstream rapidly cover the body, slowing its decomposition. Minerals from the sediments seep into the body. Over time, additional layers of sediment compress the sediments around the body, forming rock. Minerals eventually replace all the body’s bone material. Earth movements or erosion may expose the fossil millions of years after it formed.
2 Methods for Determining a Fossil’s Age: Relative Dating: lower rocks are older than higher ones
Relative Dating:
2 Methods for Determining a Fossil’s Age Radiometric Dating--Used to find specific age of a fossil As fossils age, elements in fossil decay Scientists measure the amount of decay with radioactive isotopes to determine age.
Radiometric Dating:
How does life arise? Experimental group Spontaneous generation (abiogenesis): life from nonliving things Francesco Redi: disproved theory by showing that flies must come from other flies Control group
How does life Arise? Spontaneous generation: Louis Pasteur: concluded that microorganisms must come from other microorganisms used S-shaped flasks that let in only air = no organisms
Biogenesis: life only from other living things Miller & Urey: showed that organic molecules could have formed the beginning of life
Early Cells Protocell-- Large complex structure that carries out some life functions Anaerobic prokaryotes– no oxygen in original atmosphere; autotrophs released oxygen as they performed photosynthesis to make food Aerobic organisms—(heterotrophs)respiration with O2 in atmosphere Complex eukaryotic cells--evolved from prokaryotic cells as conditions for life improved
The origin of cells: Prokaryotes: cells without a nucleus or organelles Eukaryotes: cells with a nucleus and organelles cells grew in complexity once conditions for life improved
Early Cells Endosymbiont theory--Present day eukaryotic cells evolved from symbiotic relationships between early prokaryotes