Download Fossils and Darwin

The Fossil Record
Originally, people thought that fossils were
a naturally occurring part of rock.
THEN…
In 1668, Robert Hooke said
that fossils were the remains
of plants and animals.
Scholars think Robert Hooke used this microscope
when he prepared Micrographia, the first book
describing observations made through a microscope.
The middle glass of this three-lens instrument can be
removed to more closely examine a specimen.
Where can fossils be found?
Sedimentary Rock (formed when
sediment, is deposited by wind or
water in many layers.)
Categories of Fossils
Imprints
Tree bark from a palm or a cycad
Categories of Fossils
Molds
Clam
Trilobite
An external mold of the shell of
Stroboceras (Epistroboceras) texanum
Categories of Fossils
Casts
Categories of Fossils
Petrified Fossils
Petrified wood from Madagascar
Petrified National Forest
Categories of Fossils
Intact Fossils
Insect preserved in amber
This is an area on Wilshire Blvd. in the
area known as the "Miracle Mile"
where remains of various prehistoric
animals indigenous to Southern
California embedded in tar.
Distribution of Fossils
Law of Superposition
Proposed by Nicolaus Steno (1638-1686)
 Successive layers of rock or soil are deposited
on top of one another by wind or water.
 Lowest layer (stratum) --> oldest
Top stratum --> youngest
Law of Superposition
• Used to establish the relative age of a fossil
What is used to determine a
fossil’s absolute age?
What is Biogeography?
Study of the geographical distribution of
fossils and of living organisms.
Biogeographic observations show that
organisms tend to arise in areas where
similar forms lived in the past, suggesting
that new organisms are modified versions of
the older organisms.
Armadillos appeared in North and
South America, where
glyptodonts lived in the past.
Modern kangaroos appeared in
Australia where the now extinct
giant kangaroo had lived.
First scientist to propose that organisms change over time.
By selective use or disuse of organs,
organisms acquired or lost certain traits
during their lifetime. These traits could then
be passed on to their offspring. Over time,
this process led to change in a species.
What are Acquired Traits?
NOT determined by genes!
Instead, these traits arise
during an organism’s lifetime
as a result of the organism’s
experience or behavior.
Examples of Lamark’s Ideas
about Acquired Characteristics
1. The male fiddler crab uses its small
front claw to attract mates and ward
off predators.
2. Because the front claw has been used
repeatedly, it becomes larger.
3. The acquired characteristic, a
larger claw, is then passed on to the
crab’s offspring.
Examples of Lamark’s Ideas
about Acquired Characteristics
• Said that the webbed foot of water birds
resulted from repeated stretching of the
membrane between the toes. Over time,
this produced a broad webbed foot – a
trait preserved by reproduction.
Examples of Lamark’s Ideas
about Acquired Characteristics
Lamarck believed that giraffes
stretched their necks to reach
food. Their offspring and later
generations inherited the
resulting long necks.
Using Lamark’s Hypothesis, how could
your children acquire BIG muscles?
Lamark’s Ideas were Attacked!
• However, his work laid the foundation
for further theories of evolution.
•He was the first to state that organisms
change over time and that new types of
organisms are modified descendants of
older ones.
Charles Darwin (1809-1882)
Proposed the hypothesis that species
were modified by Natural Selection
 Organisms best suited to their
environment reproduce more
successfully than other organisms.
Over time – the # of organisms
with favorable traits increases in
a population.
Voyage of the Beagle
For five years, Darwin was the ship’s naturalist,
which required that he collect specimens and
keep careful records of his observations as the
ship sailed around the world!
The Origin of Species
Published in 1859 –
proposed that natural
selection is the
principle driving
force behind
evolution.
Darwin was forced to publish his life’s
work which he had been working on
for 21 years after Alfred Wallace
approached Darwin with his paper
outlining the process of evolution by
natural selection.
Darwin’s Theories
A. Descent with Modification
Newer forms appearing in the fossil record
are actually the modified descendants of
older species. ALL species had descended
from one or a few original types of life.
Darwin thought that all of the different
species of finches on the Galapagos Islands
descended from a common ancestor.
B. Modification by Natural Selection
• States how evolution occurs
•Some organisms have traits that make them
better able to cope with their environment.
•Organisms with a greater number of these
favorable traits tend to leave more offspring
than organisms with fewer beneficial traits.
B. Modification by Natural Selection
• A population of organisms adapt to their
environment as their proportion of genes for
favorable traits increases.
EVOLUTION is the change in the
genetic make-up of a population
over generations.
Influences on Charles Darwin
(Events that affected his Theory)
1. Essay of Population by Thomas Malthus
– stated that the human population increases
faster than the food supply.
Influences on Charles Darwin
(Events that affected his Theory)
2. Principles of Geology by Charles Lyell – stated
that the earth is changing slowly and the forces
that acted on it in the past are still at work.
Uniformitarianism
Geologic changes required many millions
of years  formation of mountain ranges
would slowly change habitats, requiring
organisms that lived there to adapt to these
changes.