-AP Biology - What you need to know…. The Origin of Life

Enduring understanding 1.D: The origin of living systems is explained by natural processes. The process of evolution explains the diversity and unity of life. A number of experimental investigations have provided evidence that the conditions early in the Earth’s history provided an environment capable of generating complex organic molecules and simple cell-like structures. Ex. Miller-Urey Experiment

The “organic soup” model, the hypothesized primitive atmosphere contained inorganic precursors from which organic molecules could have been synthesized through natural chemical reactions catalyzed by the input of energy. In turn, these molecules served as monomers (building blocks) for the formation of more complex molecules, including amino acids and nucleotides.

Some models suggest that primitive life developed on biogenic surfaces, such as clay, that served as templates and catalysts for assembly of macromolecules. Under laboratory conditions, complex polymers and self- replicating molecules can spontaneously assemble. It remains an open question whether the first genetic and self-replicating material was DNA or RNA.

The RNA World hypothesis proposes that RNA could have been the earliest genetic material. Source: ml ml

Quick Review of the Steps that Would Give Rise to the First Cell 1. Monomers 2. Macromolecules 3. Plasma membrane 4. Self Replication (DNA or RNA)

Earth formed about 4.6 billion years ago (bya) and was too hostile for life First evidence of life at 3.5 bya **The earth is very old!** The Age of the Earth

The fossil record provides a timeline for the appearance of organisms on the planet.

Sample Question (AP Test) Fossils of lobe-finned fishes, which are ancestors of amphibians, are found in rocks that are at least 380 million years old. Fossils of the oldest amphibian-like vertebrate animals with true legs and lungs are found in rocks that are approximately 363 million years old. Three samples of rocks are available that might contain fossils of a transitional species between lobe-finned fishes and amphibians: one rock sample that is 350 million years old, one that is 370 million years old, and one that is 390 million years old. (a) Select the most appropriate sample of rocks in which to search for a transitional species between lobe-finned fishes and amphibians. Justify your selection. (b) Describe TWO pieces of evidence provided by fossils of a transitional species that would support a hypothesis that amphibians evolved from lobe-finned fishes.

Discuss how each of the following influenced the origin of living organisms. a) primordial atmosphere b) photosynthesis c) endosymbiosis theory d) RNA world hypothesis