Honors Biology Ch. 14

1
HonorsBiologyCh. 14

• The History of Life

2
I. Fossil Evidence of Change

• - The fossil record shows that past organisms
  were very different from those alive today and
  have been affected by several mass extinctions.

3
A. Earths Early History

• - Earth formed about 4.6 billion years ago.
• - Earths early atmosphere was very different and
  contained almost no free oxygen.

4
B. Clues in Rocks

• 1. Fossils
• - any preserved remains of a
  once-living thing
• - examples

5
2. Fossil Formation

• a. An organism dies quickly and is buried under
  sediments.
• b. Sediments build up over the years.
• c. Pressure causes mineralization (organic
  tissues replaced by mineral deposits).

6
3. Dating Fossils

• a. Relative Dating
• - Law of Superposition rocks (and fossils)
  contained in upper layers are younger
  than those found in lower layers

7
b. Radiometric Dating

• - determining the age of rock or fossils by
  measuring the rate of decay radioisotopes such
  as Carbon-14, Uranium-238

8
C. The Geologic Time Scale
9
C. The Geologic Time Scale

• 1. Precambrian (4,600 542 MYA)
• - Life (prokaryotes) probably began 3.5 billion
  years ago.
• - Photosynthesis evolved 3 billion years ago.

10
2. Paleozoic Era (542- 251 MYA)

• - Cambrian explosion marks appearance of most
  phyla of living animals.

11
3. Mesozoic Era (251- 65 MYA)

• - Age of dinosaurs ( conifers)
• - Emergence of coral reefs

12
4. Cenozoic Era (65 MYA- Present)

• - followed the mass extinctions of many
  terrestrial and marine animals

13
4. Cenozoic Era (65 MYA- Present)

• - followed the mass extinctions of many
  terrestrial and marine animals

The Cretaceous mass extinction was probably
caused by a comet or asteroid and led to the
extinction of the dinosaurs.
14

• - Age of mammals, insects flowering plants
  diversified

A Pleistocene Environment
15
II. The Origins of Life

• - Evidence suggests a sequence of chemical events
  lead to the origin of the first cells.
• - Life has continuously evolved since then.

16
A. Early Ideas

• 1. Spontaneous Generation
• - The idea that life could arise from nonliving
  things.

17
A. Early Ideas

• 1. Spontaneous Generation

18
2. Biogenesis

• - Disproved by F. Redi (1668) and Louis Pasteur
  (1859).
• - Living organisms come only from other living
  organisms.

19
2. Biogenesis

• - Disproved by F. Redi (1668) and Louis Pasteur
  (1859).
• - Living organisms come only from other living
  organisms.

20
B. Modern Ideas

• - Miller and Urey (1953) showed that simple
  organic molecules could spontaneously form from
  inorganic compounds.

21
C. Endosymbiotic Theory

• - Mitochondria and chloroplasts probably
  originated as free-living prokaryotic cells.
• - Both organelles has their own DNA and ribosomes
  distinct from eukaryotic host cells.
• - Both reproduce independently from host cells.

22

• The End