Change Over Time

1
Change Over Time

• The History of Life

2
Fossils and Geological Time

• In biological terms a fossil can be defined as
  evidence of an organism that lived some time in
  the past. Fossils are clues to the past. The
  detectives would be the Paleontologists who study
  the past.

3
History of Paleontology

• Paleontology began in the late 17th century when
  English naturalist Robert Hooke examined fossils
  of marine creatures from England.
• Charles Darwin used the fossil record to form his
  explanation of the theory of evolution in the
  1830s.

4
Fossilization Process

• Few organisms become fossils.
• Organisms usually have to be buried in mud, sand
  or clay soon after they die.
• Most fossils are found in sedimentary rock.
• These rocks form at relatively low temperatures
  and pressures that may prevent damage to the
  organism.
• Metamorphic rock and igneous rock undergo very
  physically demanding transformations that can
  incinerate and destroy organisms,
• which is why they do not typically contain
• fossils.

5
Fossils and Geological Time

• Scientists will date the rocks in an attempt to
  determine the age of the fossil. Two ways to do
  this
• Relative dating When you compare the depth of
  the layer of rock the fossil was formed in
  relative to other layers of rock.
• Radiometric dating Uses
  isotopes.

6
Relative Datingaka Law of Superposition

• Relative dating uses layers to determine age by
  order of appearance.
• Relative dating will not give you a specific age
  in years, just relative to the layers above and
  below the fossil.
• Compare rock layers to layers of clothing in your
  laundry hamperOldest on the bottom (unless
  disturbed).

7
Radiometric Dating

• Technique involves using radioactive isotopes,
  which are atoms with unstable nuclei that break
  down (decay) over time, giving off radiation.
• Most fossils cannot be directly radiometrically
  dated.
• Most dates are for volcanic or igneous rocks, or
  metamorphic rocks that are closely associated
  with fossils sedimentary rocks.

8
Fossils and Geological Time

• Geological Time determined by the fossil
  record.
• The best current estimate for the age of the
  earth is 4.6 billion years.
• Lets discuss fossils next then we will go
  back and look atgeological time.

9
Types of Fossils

• Trace Fossils
• Molds
• Amber-preserved or Frozen Fossils
• Petrified / Permineralized Fossils
• Casts

10
Trace Fossils

• Are the markings or evidence of animal
  activities.
• They include footprints, trails, and burrows.

11
Trace Fossil Example

• Laoporus tracks
• Coconinio Sandstone, Arizona
• Paleozoic Era
• Sold for 2,950

12
Molds

• When an organism is buried, it can decay, leaving
  an empty space in the rock that is the exact
  shape of the organism.

13
Mold Fossil Example

• Marine fossils are commonly buried in shale,
  limestone, and sandstone.
• Hard-shelled invertebrates
• Early vertebrates

14
Amber-preserved or Frozen Fossils

• Sometimes an entire, intact organism can be found
  frozen in ice or preserved in fossilized tree
  sap, such as amber.
• These types of fossils are rare, but valuable to
  science because even the most delicate parts of
  the organism are usually preserved.

15
Amber Fossil Example

• Prehistoric Praying Mantis with its dinner an
  ant!
• Left foreleg raised ready to strike
• La Toca Mines, Dominican Republic

16
Petrified or Permineralized Fossils

• The hard parts of organisms are sometimes
  penetrated and replaced by minerals, atom for
  atom.
• When the minerals harden, an exact stone copy of
  the original organism is produced.
• Empty spaces in original organism are filled in
  by minerals.

17
Petrified Fossil Example

• National Historic Landmark in Saratoga Springs
• Petrified Sea Gardens
• Ocean-reef 500 million-years old

18
Casts

• When a mold of an organism is created, it often
  becomes filled by minerals in the surrounding
  rock, producing a replica of the original
  organism.

19
Cast Fossil Example

• Ammonite
• Era Mesozoic
• Epoch Cretaceous
• 135 million years old

20
Check Your Understanding

• What are fossils?
• What does a paleontologist study?
• How are fossils formed?
• Why are fossils formed in sedimentary rocks?
• Discuss conditions necessary for fossilization.
• How are fossils dated?
• Can you name and describe the 5 types of
  fossils?

21

• So how does this relate to Biology?

22
Fossils, Geological Time Biology

• Life began in the Precambrian era.
• Fish and Reptiles developed during the Paleozoic
  era.
• Dinosaurs were seen in the Mesozoic era.
• We currently live in the Cenozoic era.

23
Study!

• Study your timeline! You will need to know all of
  the eras and periods for the unit exam! Do you
  remember the major periods? If so write them on
  your page. If not look them up and write them
  down.

24
Where do living things come from?

• One theory held in the past is referred to as
  Spontaneous generation. This theory held that
  nonliving material can produce life.
• Fancesco Redi disproved this theory with an
  experiment now known as the Redi Experiment. This
  experiment helped to disprove the spontaneous
  generation of large organisms, but not
  microorganisms.

25
Redis (1626-1697) Experiments
Evidence against spontaneous generation 1.
Unsealed maggots on meat 2. Sealed no
maggots on meat 3. Gauze few maggots on gauze,
none on meat
26
The Origin of Life

• Likewise, Louis Pasteur designed an experiment to
  disprove the spontaneous generation of
  microorganisms.

27
Louis Pasteur (1822-1895)
28
Pasteur's Problem

• Hypothesis Microbes come from cells of organisms
  on dust particles in the air not the air itself.
• Pasteur put broth into several special S-shaped
  flasks
• Each flask was boiled and placed at various
  locations

29
Pasteur's Experiment - Step 1

• S-shaped Flask
• Filled with broth
• The special shaped was intended to trap any dust
  particles containing bacteria

30
Pasteur's Experiment - Step 2

• Flasks boiled
• Microbes Killed

31
Pasteur's Experiment - Step 3

• Flask left at various locations
• Did not turn cloudy
• Microbes not found
• Notice the dust that collected in the neck of the
  flask

32
Pasteur's Experimental Results
33

• So what now?

34
The Theory of Biogenesis

• Pasteurs S-shaped flask kept microbes out but
  let air in.
• Proved microbes only come from other microbes
  (life from life) - biogenesis

Figure 1.3
35
The Origin of Life

• Biogenesis All living organisms must come from
  other living organisms.
• Simple Prokaryotic cells were probably the first
  cells and over time the would have evolved into
  Eukaryotic cells. Evidence for this is seen in
  mitochondrial DNA.

36
Check Your Understanding

• What are the major eras and events that occurred
  during each?
• What is spontaneous generation?
• How was spontaneous generation disproved for
  large organisms?
• How was spontaneous generation disproved for
  microorganisms?
• What is biogenesis?
• Describe the evolutionary process of cells and
  please include evidence for this theory.