Evidence of Evolution

1
Evidence of Evolution

• Fossils
• Vestigial Structures
• Embryonic Development
• DNA sequences

2
Fossils

• Preserved remains or imprint of ancient organisms
• Form mostly when sand/silt settle from water over
  dead organism ? sedimentary rock
• Fossil record is incomplete
• Most living things leave no trace
• Fossils vulnerable to weather erosion
• Soft parts do not fossilize well.
• Provide much of what we know about lifes
  history.
• Fossils are dated by a chemical method called
  radioisotope dating.

3
Fossil Formation
We can only date igneous rock using radioactive
isotopes Sedimentary rock is dated using layers
of igneous rock above and below it.
4
Radioactive Isotopes Are Used to Date Fossils /
Geological Layers of the Earth
5
Geology - Law of Superposition(add to notes)
Sedimentary layers are deposited in a time
sequence, with the oldest on the bottom and the
youngest on the top (provided that there is no
overturning).
6
Plate Tectonicsaffects biogeography (how species
are distributed in geographical areas)
7
Fossil Record Human Evolution
8
Some fossils are famous!
Lucy (Australopithecus afarensis ) --
discovered 1974, Ethiopia 3.4 m.y.a. 40
complete Hip structure shows bipedal upright
walk, brain capacity comparable to that of ape ?
Lucy replica
Reconstruction
9
Some fossils are famous!
Ardi (Ardipithecus ramidus ) 4.4 m.y.a.
Eastern Africa fossils found 1990s -
2004 Evolved a few million years after
humanitys evolutionary family diverged from a
lineage that led to chimpanzees, but it is not
clear exactly how this species is related to
other early hominids. Fossils of this ancient
hominid display a mixture of traits suitable for
two-legged walking and tree climbing
An artists interpretation shows how a
4.4-million-year-old female Ardipithecus may have
looked ?
10
Living Fossils

• Species that are relatively unchanged from their
  distant ancestors

Horseshoe crab a living fossil arthropod
Coelacanth a living fossil fish
11
Embryonic Development

• Ex
• Vertebrate embryos share a tail and gill slits at
  early stages of development, revealing the
  presence of genes that are no longer expressed in
  the adult.

12
Human Embryonic Development
13
Vestigial StructuresInherited, No Longer
Functional
14
Atavistic Traits are thought to be caused by the
expression of genes that had been silenced during
evolution. (Atavus grandfather/ancestor ?
expression of an ancestral trait)
X-ray image of an atavistic tail found in a
six-year old girl (from Palomar.edu)
15
Homologous StructuresSimilar Structure from
Common Ancestry
16
Lizard Human Cow Bird
Bat Whale
17
(No Transcript)
18
Analogous StructuresSimilar Function, NOT Common
Ancestry
19
Artificial Selection / Selective Breeding
Domestication and selective breeding by people
have generated many breeds/varieties of animals
and plants.
20
Artificial Selection of Crop Plants
21
Selective Breeding of Cattle
(Videos at pbs.org 5-6 min.)