Download Evidence for Evolution

1/28/2014
HOW LONG DID ALL THIS TAKE?
EVIDENCE FOR EVOLUTION
1. The Fossil Record
TIMELINE
“THEORY” OF PANGAEA

Key events in evolutionary
history of life on Earth
3.5–4.0 bya:
life originated
 2.7 bya:
free O2 = photosynthetic
bacteria
 2 bya:
first eukaryotes

FIRST EUKARYOTES

~2 bya
Development of internal membranes
 create internal micro-environments
 advantage: specialization = increase efficiency

natural selection
infolding of the
plasma membrane
plasma
membrane
nuclear
endoplasmic envelope
reticulum (ER)
nucleus
1ST ENDOSYMBIOSIS
 Evolution of eukaryotes
 origin of mitochondria (own DNA)
 engulfed aerobic bacteria, but
did not digest them
 mutually beneficial relationship

natural selection
internal membrane
system
aerobic bacterium
mitochondrion
DNA
cell wall
Prokaryotic
cell
Prokaryotic
ancestor of
eukaryotic
cells
plasma
membrane
Endosymbiosis
Eukaryotic
cell
Ancestral
eukaryotic cell
Eukaryotic cell
with mitochondrion
1
1/28/2014
2ND ENDOSYMBIOSIS

Evolution of eukaryotes
 origin of chloroplasts
 engulfed photosynthetic bacteria,
but did not digest them
 mutually beneficial relationship

Eukaryotic
cell with
mitochondrion
THEORY OF ENDOSYMBIOSIS

Evidence


natural selection
photosynthetic
bacterium

chloroplast
Endosymbiosis
structural
 mitochondria & chloroplasts
resemble bacterial structure
genetic
 mitochondria & chloroplasts
have their own circular DNA, like bacteria
functional
 mitochondria & chloroplasts
move freely within the cell
 mitochondria & chloroplasts
reproduce independently
from the cell
Lynn Margulis
mitochondrion
Eukaryotic cell with
chloroplast & mitochondrion
CAMBRIAN EXPLOSION

When you think “fossil,” what comes to mind?
Oh,I know…
 Fossil – any part or trace of a once-living organism

Diversification of Animals
 within 10–20 million years most of the major phyla
of animals appear in fossil record


Many types…
543 mya
Trace fossils include burrows,
tracks, even fossilized poop!
Amber
•
Amber is fossilized tree sap. It often traps
pollen, insects and other small animals.
Insects
trapped in
amber.
Fossil burrows
Dinosaur tracks
Dinosaur & Fish Poop
2
1/28/2014
Petrified Wood
•
Molds/Castings
When wood is buried in ash or sandy sediments,
silica can form within the wood structure, eventually
replacing the organic material.
Molds and castings form when the hard shell or exoskeleton of
an organism is buried in sediment.
• The sediment hardens around the body, then the body dissolves
or decomposes, leaving a void or mold.
• The mold can fill with minerals to form a cast in the shape of
the mold.
•
Casting of a
fossil trilobite
These petrified logs are
found at Petrified Forest
National Park in Arizona.
Imprint Fossils
Frozen Organisms
In some places, animals and plants get trapped in
snow and are preserved for thousands of years.
This obviously happens only in cold mountainous
and polar areas.
•
•
•
When plants and animals fall in fine sediments, their
bodies can sometimes leave an imprint that shows up
when the resulting rock layers are split apart.
Above - Otzi, the famous “Ice Man”
found frozen in the Italian Alps
Clockwise from left - The
imprints of feathers can be
seen in the Archaeopteryx
fossil. A dragonfly imprint in
the same fine sediment bed.
The delicate imprint of an
extinct fern’s frond.
Left - Dima, a baby mammoth
found preserved in the Siberian
permafrost by Russian miners.
Fossil Bones
•
•
Bones and teeth of vertebrates are resistant enough to
remain intact when the rest of the body has decayed.
Dinosaur skeletons are among the most spectacular
fossils ever found.
A 12,000 year old mammoth
skeleton
INDEX FOSSILS
Sue, the largest, most complete T. rex
fossil ever found. It resides at the
Field Museum in Chicago.
3
1/28/2014

DATING FOSSILS

3.
4.

No absolute age; only older/younger
WHAT IT TELLS US…
2.

Relative Dating –compare fossil placement with
fossils in other layers of rock

1.
Radioactive Dating – measuring the amount of
remaining radioactive isotopes in a sample
Absolute age
Half-Life – length of time required for HALF the
radioactive atoms to decay

Ex. Carbon-14 begins to decay when an organism dies (HL = 5730
yrs). The remaining amt is compared to the amt of Carbon-12 to
determine the age.
HALF-LIFE OF A PENNY LAB
Plants and animals
change
Environments change
Immense time span
Extinction is the fate of
a species
WHAT IS AN ADAPTATION?

Any variation that increases an organisms
chance of survival in an environment
EVIDENCE FOR EVOLUTION
2. Comparative Anatomy & Embryology
4
1/28/2014
CONTRIVANCE

HOMOLOGOUS STRUCTURES
A structure that is used for something other than
its original use.
Structures in different organisms that have
shared evolutionary history, i.e. have a common
ancestor
 Similar genes

Anatomical evidence
Homologous structures
spines
ANALOGOUS STRUCTURES

Structures that are similar in function, but do
not share evolutionary history

leaves

Parts evolved from different structures
Ex. insect and bat wings
succulent leaves
needles
tendrils
colored leaves
5
1/28/2014
Analogous structures
VESTIGIAL STRUCTURES

A body structure that has no use in a present day
organism, but was probably useful to an ancestor

Ex. Appendix, tail bone, wisdom teeth
Convergent
Don’t
be fooled
by evolution
their looks!
Those
& tails
Does fins
this mean
& sleek
they bodies
have a are
recent
common
ancestor?
analogous
structures
!
Dewclaw
All ball pythons have anal
spurs, the vestigial remains
of hind legs lost during
evolution of lizard to snake
Solving a similar problem with a similar solution
FOSSIL WHALE LEGS
Vestigial organs
Whales are thought to have evolved from 4legged land animals that lived over 50 million
years ago.
 Paleontologists expected to find whale ancestors
that showed reduced and vestigial legs by looking
in sediments that were between 50 and 30
million years old. Sure enough, they did. Some
examples of this transition are shown below.

Ambulocetus
Pakicetus
Basilosaurus
49 million years ago
42 million years ago
40 million years ago
COCCYX IN HUMANS & APES
Humans and other hominiod apes evolved from
primates that had an external tail.
 In our hominoid ancestor, it was reduced to a small
coccyx or tailbone that is not visible on the outside of
the body.

The coccyx or
tailbone is visible in
the chimp pelvis on
the left and the
human pelvis on the
right.
6
1/28/2014
EMBRYOLOGY
Embryo’s of many animals w/backbones look very
similar
 Same groups of embryonic cells develop in the
same order,
and in similar patterns
Cat

Dolphin
Among some species of snakes, early embryos
have hind limb-buds that quickly disappear as
the embryo develops.
 What does this suggest about snakes?

Chicken
Pig
Mouse
Human
COMPARATIVE DNA/PROTEIN
SEQUENCES

Protein comparison looks at the order of amino
acids that make up a protein. The fewer the
differences, the more closely related the animals.
EVIDENCE FOR EVOLUTION
3. Molecular Biology
Human
Macaque
Dog Bird
Frog
Lamprey
The sequence in
DNA
proteins
Why &compare
is a &molecular
DNA
proteins
record
of evolutionary
across
species?
relationships.
Comparative hemoglobin structure
8
0
32 45
67
125
CLADOGRAM
A
cladogram is a branching diagram
that shows evolutionary
relationships among organisms
 Branches in the cladogram show a
new characteristic (a derived
character) appeared that was not
present in older organisms
10 20 30 40 50 60 70 80 90 100 110 120
 compare
Number of amino acid differences
between common genes
hemoglobin (146 aa) of vertebrate species and
that of humans
cytochrome
C (respiration)
 hemoglobin (gas exchange)
7
1/28/2014
Building “family” trees
SIMILARITIES IN DNA

ancestral species
Can be used to help
determine classification and
evolutionary relationships



A gene in an
Similar Genes
Changes in DNA
Species that share a
more distant common
ancestor should have
more genetic
differences
2 mutations
new
new
mutation
mutation mutation
Species
A
EXAMPLES: CLOSE RELATIVES
Gorilla
Human
Species
B
new
Species
C
EXAMPLE: DISTANT RELATIVE
Chimpanzees are humans’ closest living relative
– in other words, we share a more recent ancestor
with them than any other living species. Our
genes are 98.2% identical.
 The humans and chimps last shared an ancestor
with the gorillas at an earlier time. Human and
chimp DNA is 97.7% identical to a gorilla’s.
 Human, chimp, and gorilla genes are 96.3%
identical to orangutan genes.

Orangutan
2 mutations
Chimpanzee
Half of the genes in a yeast are also found in
humans.
 Experiments have shown that mutant yeast can
be fixed by inserting the human version of a gene
to replace their defective gene.
 Both humans and yeast have a gene for the
myosin protein, which in humans enables
muscles to contract and in yeast enables cell
parts to move.

Yeast
Primates
8