Radioactivity Integrated Science Chapter 25 Notes Chapter 25 Notes.
Chapter 25 (Class)
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The History of Life on Earth AP Chapter 25
Transcript of Chapter 25 (Class)
The History of Life on Earth
AP Chapter 25
Figure 26.0 A painting of early Earth showing volcanic activity and photosynthetic prokaryotes in dense mats
Overview: Lost Worlds
• Past organisms were very different from those now alive
• The fossil record shows macroevolutionary changes over large time scales including– The emergence of terrestrial vertebrates – The origin of photosynthesis– Long-term impacts of mass extinctions
Fig. 25-1
Fig 25-UN1
Cryolophosaurus
The Age of the Earth
4.6 billion years
Figure 26.2 Clock analogy for some key events in evolutionary history
3.9 billion years ago
• Earth cooled, oceans formed, atmosphere contained nitrogen, CO2, methane CH4, ammonia NH3, and water vapor
• 1920’s Oparin and Haldane hypothesized that under those conditions, organic molecules could be formed
• 1953 Miller and Urey performed an experiment and produced organic molecules
Other ideas
• Submerged volcanoes, deep-sea vents • Carbonaeceous chondrites found in
meteorites contain C compounds• Amino acid polymers from dripping organic
monomers onto hot sand or clay
All of these point to the possibility of an abiotic
synthesis of life.
• Life requires:
accurate replication and metabolism• Protobionts – collections of abiotically
produced organic molecules surrounded by a membrane
• Liposomes – evidence of this possibililty
Fig. 25-3
(a) Simple reproduction by liposomes (b) Simple metabolism
Phosphate
Maltose
Phosphatase
Maltose
Amylase
Starch
Glucose-phosphate
Glucose-phosphate
20 µm
First replicating molecule…
• RNA• Why – capable of copying itself
using ribozymes – enzyme-like RNA catalysts
• DNA would have replaced RNA as a better storage molecule
Figure 26.11 Abiotic replication of RNA
How is the age of fossils and rocks determined?
• Radiometric dating – using half-lives of radioactive isotopes
• Carbon-14 5,730 years• Also patterns of magnetic reversal of
the earth is used
3.5 billion yearsFirst Single-Celled Organism
• Oldest known fossils are stromatolites, rocklike layers of prokaryotes and sediment.
Figure 26.3 Early (left) and modern (right) prokaryotes
2.7 billion years agoOxygen
Evidence of oxygen accumulation from cyanobacteria in banded iron formations
2.1 billion years agoeukaryotic cells
• Fossils of eukaryotic cells• Mitochondria and chloroplasts may have
originated as prokaryotes engulfed by other prokaryotes in endosymbiosis.
• In serial endosymbiosis, mitochondria probably evolved first
1.5 billion years agoMulticellular organisms
• Oldest known fossils are algae• Severe ice ages (Snowball Earth)
prevented diversity of eukaryotes for awhile
535 – 525 Cambrian Explosion
• Great diversity of all types of eukaryotes
500 myaMovement onto Land
• Evolved adaptations to live on land and prevent dehydration
• Plants and fungi colonized land together
250 myaFormation of Pangaea
• Destroyed and altered habitats, changed climates, created geographic isolation
Mass Extinctions
• There have at least 5 mass extinctions.• Permian – 250 mya, over 90% of marine and
terrestrial species disappeared; maybe due to volcanoes, Pangeae, glaciation
• Cretaceous – 65 mya; ½ marine and many terrestrial forms, including dinosaurs; due to environmental changes or asteroids hitting the earth
• Mass extinctions provide many habitats and available niches to organisms that survive which leads to adaptive radiation.
• For ex, mammals did not change much until the after 65 mya and the extinction of the dinosaurs.
Evolution is not goal-oriented!
• Often very complex organs have evolved gradually from simpler structures, such as eyes.
• Evolutionary novelties may arise by modification of existing structures.
