the origin of life · life originated through a series of early chemical events. simple organic...
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SB5.Students will evaluate the role of natural selection in the
development of the theory of evolution.SB5a.
Trace the history of the theory
Turn to p. 392 in your Biology textbook. List 10 facts about the “Earth’s Early History” section in your notebook. Be ready to
share in 8 minutes.
Before Life…Land Environments
Earth was molten when it formed about 4.6 billion years ago
After 500 million years, a solid crust formed
Too much heat for life to exist
Before Life…Atmosphere
Gases in atmosphere came from volcanoes
Water vapor, carbon dioxide, methane, ammonia gas, nitrogen, hydrogen, etc.
The early atmosphere was anaerobic (it had little or no free oxygen).
Where did the first living things come from?
ORIGINS: Early IdeasSpontaneous Generation: Life arises from nonlife
Proposed by Aristotle (384-322 BC)
Also called abiogenesis
Ex: Place damp hay and corn in a corner, and mice would be created.
ORIGINS: Early IdeasSpontaneous Generation Experiments
Francisco Redi (1668) showed that flies and maggots did not spontaneously come from rotting meat.
ORIGINS: Early IdeasSpontaneous Generation Experiments
Lazzaro Spallanzani(1765) boiled nutrient solutions in flasks.
Lazzaro Spallanzani’s Experiment
People did not reject the theory until mid-1800s when it was replaced by the Theory of Biogenesis.
ORIGINS: Early IdeasTheory of Biogenesis: Only living organisms can produce other living organisms.
Louis Pasteur-designed an experiment to show that biogenesis occurred in microorganisms
If life can arise only from pre-existing life, then how did the first life form appear?
ORIGINS: Modern Ideas Life originated through a series of early chemical
events.
Simple organic moleculescomplex organic moleculessimple metabolic pathwaysemergenceof life
Stanley Miller & Harold Urey (1953) were the first to show that simple organic compounds (macromolecules) could be made from inorganic compounds.
ORIGINS: Modern IdeasMiller & Urey’s Experiment
Filled apparatus with water and gases from early atmosphere
Electric discharges simulate lightning for energy
Resulting mixture contained organic compounds including amino acids.
ORIGINS: Modern Ideas The first cells were anaerobic prokaryotes.
Eukaryotic cells first appeared about 1.8 billion years ago when oxygen became a part of the Earth’s atmosphere.
Endosymbiosis: a type of symbiosis in which one organism lives inside the other, the two typically behaving as a single organism
The hot springs of Yellowstone National Park, USA, were among the first
places Archaea were discovered. The biologists are immersing microscope slides in the boiling pool
onto which some archaeansmight be captured for
study.
ORIGINS: Modern IdeasThe Endosymbiont Theory
Proposed by Lynn Margulis in 1966
The ancestors of eukaryotic cells lived in association with prokaryotic cells.
Evidence for the Endosymbiont Theory
Mitochondria and chloroplasts:
have their own DNA (circular like prokaryotic DNA)
have ribosomes resembling prokaryotic cells
reproduce by fission, independent of the rest of cell
ORIGINS: Modern IdeasOther Ideas
Organic reactions began in deep sea vents (hot, volcanic)
Meteorites brought the first organic molecules to Earth
Quick Review1. Differentiate
between spontaneous generation and biogenesis.
2. Describe the endosymbionttheory.