Title: Evidence of Evolution
1Evidence of Evolution
- Fossils
- Vestigial Structures
- Embryonic Development
- DNA sequences
2Fossils
- 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.
3Fossil Formation
We can only date igneous rock using radioactive
isotopes Sedimentary rock is dated using layers
of igneous rock above and below it.
4Radioactive Isotopes Are Used to Date Fossils /
Geological Layers of the Earth
5Geology - 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).
6Plate Tectonicsaffects biogeography (how species
are distributed in geographical areas)
7Fossil Record Human Evolution
8Some 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
9Some 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 ?
10Living Fossils
- Species that are relatively unchanged from their
distant ancestors
Horseshoe crab a living fossil arthropod
Coelacanth a living fossil fish
11Embryonic 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.
12Human Embryonic Development
13Vestigial StructuresInherited, No Longer
Functional
14Atavistic 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)
15Homologous StructuresSimilar Structure from
Common Ancestry
16Lizard Human Cow Bird
Bat Whale
17(No Transcript)
18Analogous StructuresSimilar Function, NOT Common
Ancestry
19Artificial Selection / Selective Breeding
Domestication and selective breeding by people
have generated many breeds/varieties of animals
and plants.
20Artificial Selection of Crop Plants
21Selective Breeding of Cattle
(Videos at pbs.org 5-6 min.)