Change Through Time

1
Change Through Time

• Chapter 14

2
How Did Life Begin?

• Divine Being
• Many human cultures
• Did not arise spontaneously
• Divine force produced life
• Meteorites
• Contain organic matter
• Organic matter entered the oceans

• Primordial Soup
• Nitrogen, Methane, Ammonia, little oxygen
• Sun, volcanoes, lightning
• Amino Acids, proteins, lipids
• Bubbles
• Of lipid molecules, site of chemical reactions
• Replicating Molecules
• RNA before DNA

3
No human was there to observe how or when life
began!
4
Scientists Look for Clues

• Similarities
• Patterns
• Fossils/Remnants
• Try to explain the how not the why

5
The Early Earth

• The age of Earth is estimated to be more than 4
  billion years
• Use radioactive dating
• Isotopes
• Radioactive
• Half-life
• Ex C-14 5,730 years
• K-40 1,300,000,000 years
• U-238 4,500,000,000 years

6
Early Atmosphere

• Water vapor, little oxygen, carbon dioxide,
• Nitrogen, and ammonia
• Very hot, volcanoes
• 3.9 billion years ago cooled for water to
  condense
• Rainstorms, lightning for millions of years
• 3.9-35 billion years ago first organisms appeared
• No Direct Evidence!

7
Why do Scientists believe this?

• Earths processes
• Destroy reform rock
• Fossils
• Evidence of an organism that lived long ago
• Show diversity of life
• Buried in mud, sand or clay
• Compressed and harden forming Sedimentary
  rockthis happens today lake stream bottoms

8
Geologic Time

• Era
• Period
• Distinguished by the organisms that lived during
  that time
• Several Mass Extinctions entire groups of
  organisms disappear almost at once

9
Precambrian Era

• Life Evolves
• bacteria
• 3.5 billion ya
• Prokaryotes
• Photosynthetic bacteria
• 3 billion ya
• Eukaryotes
• 1.8 billion ya
• 544 million ya

10
Paleozoic Era

• Cambrian
• Invertebrates
• Ordovician
• First Vertebrates
• Silurian
• First Jawed Fish
• First Land Plants

• Devonian
• First Amphibians
• Carboniferous
• First seed plants
• First reptiles
• Permian
• Conifers Dominant
• Largest mass extinction

11
Mesozoic

• Cretaceous
• Flowering plants dominant
• Mass Extinction of the Dinosaurs
• Continental Drift

• Triassic
• First Dinosaurs
• First Mammals
• Jurassic
• First flowering plants
• First Birds

12
Cenozoic

• Tertiary
• First placental mammals

• Quaternary
• Humans evolve

13
The Origin of Life

• Early Ideas
• Spontaneous Generation nonliving produced life
• 1668, Francesco Redi
• mid-1800s, Louis Pasteur Biogenesis living
  organisms come only from other living organisms

14
Redis Experiment
15
Pasteurs Experiment
16
The Origin of Life

• Modern Ideas
• 1930s, Alexander Oparin Primordial Soup
• 1953, Stanley Miller and Harold Urey produced
  amino acids, sugars and other small organic
  molecules
• 1950s proteins, ATP, nucleic acids
• Sidney Fox Protocell formed from AA, large
  ordered structure enclosed by membrane, carries
  out some life activities-growth division

17
Miller and Ureys Experiment
18
Protocells
19
Evolution of Cells

• Prokaryotes evolved from Protocells
• Anaerobic, heterotrophs
• Autotrophs similar to todays Archaebacteria
  live in harsh environments
• Photosynthesizing prokaryotes 2.8 billion ya
  fossils show large increase in diversity

20
Evolution of Cells

• Endosymbiotic Theory
• 1960s, Lynn Margulis
• Chloroplasts and Mitochondria contain DNA that is
  very similar to DNA in prokaryotes and very
  unlike DNA in eukaryotes
• Have their own ribosomes
• Reproduce independently of the cells that contain
  them

21
Endosymbiosis