AP Biology

History and Origins of Life on Earth

Reading Guide – Chapters 1.1, 18 and Additional Readings

Chapters 1.1, 18 and Attached Readings

The Origin and History of Life

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OBJECTIVES

  • Conditions of ancient Earth.
  • Importance of a reducing environment (absence of oxygen).
  • Concept of chemical evolution.
  • Haldane’s hypothesis.
  • Miller-Urey experiment.
  • ‘Metabolism-first’ versus ‘RNA-first’ hypothesis.
  • Protobionts and evolution of the protocell.
  • Evolution of self-replication.
  • Heterotroph hypothesis – why did photosynthesis evolve later and significance.
  • Why life first evolved in water.
  • Evidence for endosymbiosis and evolution of the eukaryote.
  • Advent of multicellularity.
  • Timeline for the history of life – know approximate dates of major evolutionary advances.

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In addition to the material in the chapters list above, you will be responsible for understanding the material in the supplemental readings. I recommend you read Chapter 1.1 first, then Chap 18 and the articles. Some of the questions below actually come directly from the supplemental readings.

For chapter 18, focus more on the how Earth’s environment influenced biodiversity of life. Notice how environmental conditions shaped life on Earth, which in turn, influenced the environment on Earth. Do not place effort into learning the radiometric dating techniques, plate tectonics, continental drift, etc. Just read over these sections.

  1. Construct a timeline of the history of earth. (Use Table 25.1 and Figure 1.1 as your guide)

Include the following geologic time divisions:

  • Cambrian vs Precambrian
  • Jurassic
  • Triassic
  • Permian
  • Carboniferous
  • Devonian

And the following events:

  • Total age of Earth
  • Oldest known fossils (prokaryotes)
  • First photosynthetic organisms (thus O2 accumulation in atmosphere)
  • Great Oxidation Event
  • Oldest know eukaryotic fossils
  • First plants appear on land
  • First multicellular organisms
  • Flowering plants appear
  • First land animals appear
  • Mammals appear
  • First hominids appear
  • Modern humans appear
  1. Why is it believed life emerged on Earth only once (i.e. one common ancestor)?
  1. List the environmental conditions of ancient Earth.
  1. Describe the chemical evolution (prebiotic synthesis) theory for the origin of life on Earth.
  1. Describe the Miller-Urey experiment and its significance.
  1. Early Earth did not contain free oxygen in the atmosphere. What is the significance of a reducing (oxidizing means oxygen present, reducing means in absence of oxygen) environment?
  1. Compare the metabolism-first and RNA-first hypotheses.
  1. What are protobionts (protocells)? Relate the spontaneous formation of liposomes with the membrane-first hypothesis regarding the evolution of the cell.
  1. Why are the first organisms believed to be single-celled heterotrophs?
  1. Why do some people suggest RNA was the first genetic material? What is their evidence?
  1. What was the Great Oxidation Event? What organisms were believed to be responsible for this?
  1. What is the advantage of an oxidizing atmosphere?
  1. Describe the endosymbiotic hypothesis regarding the evolution of eukaryotic cells and list the evidence.
  1. Why did evolution to land have to wait until the evolution of photosynthetic organisms?
  1. Why are plants believed to be the first organisms to adapt to land?
  1. What were the first animals to appear on land?
  1. Two events are believed to have led to the diversification of mammals on land – the evolution of angiosperms (flowering plants) and the mass extinction of the dinosaurs. Explain the significance.
  1. What does it mean to say the Archaea are more closely related to eukaryotes?
  1. List some specific characteristics that categorize Archaea as prokaryotic, similar to eukaryotes, and deserving of their own domain.
  1. Given the relationship between molecular changes and the molecular clock, explain why rRNA is generally used for distant evolutionary relationships, while mtDNA comparisons are preferred for recently diverged species.
  1. What is significant about the observation that photosynthetic lineages adorn only the upper branches of the bacterial limb?

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