Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Chapter 25
The History of Life on Earth
25
...
I
...
B
...
Haldane hypothesized that the early atmosphere was a
reducing environment
• In 1953, Stanley Miller and Harold Urey conducted lab experiments that showed that the
abiotic synthesis of organic molecules in a reducing atmosphere is possible
• Instead of forming in the atmosphere, the first organic compounds may have been
synthesized near volcanoes or deep-sea vents
• Abiotic Synthesis of Macromolecules
• RNA monomers have been produced spontaneously from simple molecules
• Small organic molecules polymerize when they are concentrated on hot sand, clay, or rock
• Protocells
• Replication and metabolism are key properties of life and may have appeared together
• Protocells may have been fluid-filled vesicles with a membrane-like structure
• In water, lipids and other organic molecules can spontaneously form vesicles with a lipid
bilayer
• Self-Replicating RNA and the Dawn of Natural Selection
• The first genetic material may have been short pieces of RNA capable of guiding polypeptide
synthesis and self-replication
• Early protocells containing such RNA would have been more effective at using resources and
would have increased in number through natural selection
25
...
3 Key events in life’s history includes the origins of single-celled and multi celled
organisms and the colonization of land
• The geologic record is divided into the Archaean, the Proterozoic, and the Phanerozoic eons
• The Phanerozoic encompasses multicellular eukaryotic life and is divided into 3 eras:
Paleozoic, Mesozoic, Cenozoic
• The First Single-Celled Organisms
• The oldest known fossils are stromatolites, rocks formed by the accumulation of
sedimentary layers on bacterial mats
• Prokaryotes were Earth’s sole inhabitants from 3
...
1 billion years ago
• Oxygen revolution: 2
...
3 billion years ago; caused extinction of many prokaryotic
groups
• The oldest fossils of eukaryotic cells date back 2
...
5
billion years ago
• The “snowball Earth” hypothesis suggests that periods of extreme glaciation confined life to
the equatorial region or deep-sea vents from 750 to 580 million years ago
• The Cambrian explosion refers to the sudden appearance of fossils resembling modern
animal phyla in the Cambrian period (535 to 525 million years ago)
• DNA analyses suggest that many animal phyla diverged before the Cambrian explosion,
perhaps as early as 700 million to 1 billion years ago
• The Colonization of Land
• Fungi, plants, and animals began to colonize land about 500 million years ago
• Vascular tissue in plants transports materials internally and appeared by about 420 million
years ago
• Plants and fungi today form mutually beneficial associations and likely colonized land
together

25
...
5 Major changes in body form can result from changes in the sequences and regulation
of developmental genes
• Genes that program development control the rate, timing, and spatial pattern of changes in an
organism’s form as it develops into an adult
• Heterochrony is an evolutionary change in the rate or timing of developmental events
• The Evolution of Development
• The evolution of new morphological forms can be caused by changes in the nucleotide
sequences or regulation of developmental genes
• New morphological forms likely come from gene duplication events that produce new
developmental genes
• Changes in morphology likely result from changes in the regulation of developmental genes
rather than changes in the sequence of developmental genes
25

---