Module 2 – Origin of Life

Theories on the Origin of Life
1. Creationism – religious belief that humanity, life, the Earth and the universe are the creation of a supernatural agency
2. Spontaneous generation (abiogenesis) – organic life could and does arise from inorganic matter
- disproved in 1668 by Francisco Redi and in 1859 by Louis Pasteur
3. Gold’s “Deep-Hot Biosphere” Model – 1970 by Thomas Gold
- life first developed not on surface of the Earth but several kilometers below the surface
4. Extraterrestrial formation – Organic material came from space specifically Mars
- supported by Francis Crick of DNA fame
5. Panspermia – is the hypothesis that seeds of life exists already all over the Universe, that life on Earth may have originated through these seeds (comets)

Evolution – change in lines of descent
-    as the process by which populations of organisms change over time
-    theorized by Charles Darwin in 1859 in his book “On the Origin of Species by Natural Selection; or the Preservation of Favoured Races in the Struggle for Life”.

Pre-Darwinian Ideas about Evolution
Aristotle (384-322 BCE)
-    saw much evidence of natural affinities among organisms
-    visualized organisms as being “imperfect but moving toward a more perfect state”
-    did not discuss mechanism

Leonardo da Vinci (1452-1519)
-    correctly interpreted unexpected fossil finds as the remains of animals that had existed in previous ages but had become extinct.

Jean Baptiste de Lamarck (1744-1829)
-    first scientist to propose that organisms undergo change over time as a result of some natural phenomena rather than divine intervention.
-    Shrink and disappear.
-    Theory of use and disuse

Darwin’s book had 2 concepts
1.    Darwin argued convincingly from several lines of evidence that contemporary species arose from a succession of ancestors through a process of “descent with modification”, his phrase for evolution.
2.    Mechanism of evolution is called Natural Selection

Natural Selection – differential survival and reproduction of individuals in a population that differs in the details of their habitable traits.

Process of Natural Selection
1. A natural population tends to increase in size. As it does, the individuals of the populations competes more for food, shelter, and other limited resources.
2. Individuals of a population differ from one another in the details of shared traits. Such traits have a heritable basis.
3. Adaptive forms of traits make their bearers more competitive, so those forms tend to become more common over generations.