Transcript Tracing Evolutionary History

Tracing Evolutionary
History
Chapter 15
15.1- 15.9 Earth History &
Macroevolution
1. Macroevolution
The fossil record which is stored in
layers of rock chronicles
evolutionary history
Macroevolution- the major
changes in the history of life on
Earth.
Studying fossils in rock strata allows
biologist to trace macroevolution
2. Geologic Time Scale
Geologic Time Scale- A table that
gives an overview of
macroevolution measured in
millions of years (mya)
Divided into four major groups
called Eras:
1. Precambrian
2. Paleozoic
3. Mesozoic
4. Cenozoic
Each era ends w/ a mass extinction
Mass extinction- many forms of life
disappeared from the fossil record &
were replaced w/ species that
diversified from the survivors
Radiometric Dating- technique used
to measure the actual age of rocks
by measuring the radioactive
isotopes
The isotopes of elements build up
in the organism when they are alive
Ex:
Ex: living organisms have a lot
of Carbon -12 & small amounts
of Carbon- 14; that it absorbs
from the atmosphere. When an
organism dies the Carbon stops
building up & the C14 slowly
decays to a different element.
Radiometric Dating
Half-life- the time it takes an
element that is decaying to
decrease by half
Carbon-14 has a half-life of 5,730
years.
It takes 5,730 years for half of a
sample of C-14 to decay & turn
into another element
The table below shows the reduction
of a quantity in terms of the number
of half-lives elapsed.
Number of
half-lives
elapsed
Fraction
remaining
0
1/
1
100
1
1/
2
50
2
1/
4
25
3
1/
8
12 .5
4
1/
16
6 .25
5
1/
32
3 .125
6
1/
64
1 .563
7
1/
128
0 .781
...
...
...
n
1/(2n)
100/(2n)
Percentage
remaining
3. Continental
Drift
Earth was on large land mass
called Pangaea
Tectonic plates are drifting apart
2cm/yr.
North America & Europe are
moving farther apart.
Lungfish distribution,
a result of continental
drift
4. Mass Extinctions
An artist's rendering of the asteroid impact that took place 65 million
years ago and likely killed off nearly every large vertebrate species on
the planet, including, many think, the dinosaurs. (Credit: Don
Davis/NASA)
99% of all
of the
species on
earth are
now extinct
There have been six
periods of mass
extinction
Key adaptations
allowed some
species to survive
and proliferate &
evolve while others
died out
Exaptation- a
structure that
evolved in one
situation & later
adapted to a
different function.
A pineapple plant, a
bromeliad adapted to arid
(dry) soils. The bottom of the
leaves form a catch-basin to
collect rainwater & the plants
roots absorb water from the
catch basin
6. Phylogeny
A phylogenic tree for Galapagos finches
Phylogeny- the evolutionary history of
an organism
Phylogenic trees- a diagram that
traces evolutionary relationships.
A phylogenic tree for dogs
7. Classification
Classifucat
Classification of the Brown Bear