Transcript The Toolbox of Science

A quick look at Evolution.
Charles Robert Darwin
 Charles Robert Darwin (1809 –1882) was
an English naturalist who proposed and
provided scientific evidence that all species
of life have evolved over time from
common ancestors.
Darwin
 His 1859 book On the Origin of Species
established evolution by common descent as
the dominant scientific explanation of
diversification in nature.
 Evolution: the gradual change in a species
over time.
Darwin
 Darwin figured that a species gradually
adapted and changed through the process he
called natural selection.
 Natural Selection: favorable traits
(Adaptations) become more common in
younger generations of a species, and
unfavorable traits become less common.
Natural Selection
 Darwin identified a few major factors that
contribute to Natural Selection:



Overproduction.
Competition.
Variation.
• What do you think these all mean? CD
Natural Selection
 Overproduction:

Almost every species produces more offspring
than can possibly survive.
•
•
•
•
Frog Eggs
Sea Turtles
Minnows
Insects
– Why? CD
Overproduction.
Natural Selection
 Variation: Minor differences appear
between offspring.




Faster swimmer
Longer necks
Longer noses
Sharper beaks
Variation
Variation
Variation
Natural Selection
 Competition: Since food and resources are
limited, offspring must compete with each
other.




Faster ones catch faster prey
Stronger shells better defense
Heavier shells make you slow…
Slower might make it easier to catch…hmmm
Natural Selection
Tough Grass vs Tender
Natural Selection
Natural Selection
Fast vs Slower
Natural Selection
Natural Selection
Jumpy vs Clever and Still
Natural Selection
Jumpy vs Clever and Still
Natural Selection
Resistant to a new disease
Natural Selection
Natural Selection
Warmer coat in a long cold winter
Natural Selection
Natural Selection
The Survivors
Video
 Evolution and Natural Selection
Filler
 Making observations today about evolution
makes sense. We can see differences
between animals right now in our own
neighborhoods. Check out the black
squirrels in Princeton…..Why are they
black? Any ideas?
More Filler...
 Here's why some scientists believe the black
squirrels were multiplying: In winter, their
dark coats allowed them to retain heat from
sunlight, leaving them less desperate for
warmth than their lighter-colored cousins.
 "If you can do it with solar heat, you don't
need quite as much metabolic heat," and,
therefore, need less food,
Still More
 In some cases, this advantage seems to have
outweighed the potential downside of a
black coat -- being more conspicuous to
hawks and other predators. Scientists
believes that black squirrels were slightly
more likely to survive and reproduce, and
their genes were passed on to succeeding
generations.
Enough about today….
 Can we find evidence of past changes….
 Sure!
Fossils
 Fossil: The preserved remains or traces of
an organism that lived in the past.
Types of Fossils
 Petrified fossils: Minerals replace buried
remains changing them into rock.

Petrified wood example
Types of Fossils
 Molds and Casts: organisms dissolve
leaving a hollowed space that fills with
minerals.

Ohio stone examples
Types of Fossils
 Preserved Remains: Preserved in substances
other than sediment.



Amber
Tar pits
Ice
Video
 Becoming a fossil
Dating a fossil
 Relative dating.

Estimates the order of events by observing
where fossil organisms lay in the geological
record.
 Absolute dating

Using radioactive decay rates.
• Carbon-14
• Potassium-40
5730 years
1.3 billion years
Time Lines
You
Life
5,000,000,000 Years Ago
1,000,000,000 Years Ago
100,000,000 Years Ago
1,000,000 Years Ago
10,000 Years Ago
100 Years Ago
Today