Biology 101- Evidence of Evolution

Pick up DARWINS NATURAL SELECTION journal. Begin

working on this. EVERYONE NEEDS TO BE IN THEIR SEAT WORKING BY THE TIME THE

BELL RINGS!!

Sources of Evidence for Evolution

From studies of embryology

From studies of DNA

Biochemistry

From the fossil record

From Geographic distribution

From observations

From studies of anatomy

Fossil Structure

Fossil- Remains of organismsUsually found in sedimentary rockRelative age- “date” fossil based on where it is in rock strata

Absolute dating: measures decay of radioactive elements into stable forms (Carbon-14 and Uranium-238)Decay rate is steady (half-life)

How is Half-life calculated?How does radioactive dating work?Since decay is steady, you can calculate how old something is by how much of it is left

Ex: Carbon 14 converts to Carbon 12 when it decays

Decay rate is 5,700 years

If you start with 1 gram of Carbon 14, after 5,700 years there would be ½ gram of it left

Archeopteryx

• Archeopteryx shows evidence of the evolution of birds from reptiles

• There is evidence of feathers (from birds)

• There are claws (from reptiles)

Evidence from common structures: Similar skeletal

organization• Are called Homologous structures- body

parts similar in structure but not necessarily in function

• Suggests common ancestor- but each adapted to different environments

Anatomical studies show..

• What are other organisms that have the ability to fly, but have wings very different from those of birds?

• Structures like the wings of birds and wings of insects are called…

Analogous Structures- similar in function, but different structures

Do not have a common ancestor, but have evolved with similar adaptations due to similar environments

Do these organisms, a bird, mammals and a fish, show analogous structures or

homologous structures?

Convergent evolution: results in analogous structures

Different bone structures, but similar functions due to similar environments

Do these organisms show analogous or homologous structures?

Many different species evolving from a recent common ancestor would be an example of divergent evolution, all showing homologous structures

Over 70 lemur species evolved from a species that colonized Madagascar less than 60 million years ago

Why would this bird have wings if it doesn’t fly?

• Structures are so reduced in size that they are vestiges or traces of homologous organs in other species called VESTIGIAL STRUCTURES

Anatomical Studies show…

Why does a whale have a pelvis and femur bone if it has no hind limbs?

Why does a boa have a remnant hind limb?

Why does this salamander have eyes if it never sees the light of day?

Human vestigial structures

Why do these structures occur?

• These structures may be homologous to ones that had a function in the ANCESTORS of these organisms thus suggesting their evolution from this common ancestor.

Today’s activities

• The Molecular Connection

Getting Started: Tues 4/22

EVIDENCE PT 2 NOTES START HERE….

Embryology Studies

• Even though it may not be apparent during the first stage of development, these 5 organisms are very different at later stages of development and at birth

• Why do they look so similar to each other during early development?

Organisms having more similarities during later stages are thought to have a more recent common ancestor

Studies of Biochemistry• Humans and chimpanzees have no differences in this amino acid

sequence suggesting their close evolutionary relationship • They have a more recent common ancestor than any other two

species shown

Human V-H-T-A-T-A-A-S-D-L-A-T-D-K-R-C-H-E-Y-A

Chimp V-H-T-A-T-A-A-S-D-L-A-T-D-K-R-C-H-E-Y-A

Gorilla V-H-T-A-T-A-A-S-D-L-A-T-D-K-K-C-H-E-Y-A

Horse V-Q-S-A-L-A-S-G-E-V-H-A-D-K-R-V-R-D-Y-A

DNA

• The sequence of the nucleotides making up the DNA would also be similar because DNA determines the sequence of amino acids in the proteins

DNA sequences can be used to make “family tree” so that we can see how closely related different species are

Goat

Deer

Human

Chimpanzee

Duck

Chicken

0.05

• What is this diagram showing you? What could be a possible explanation for this?

Penicillin patch

Bacteria colony grows

Penicillin patches were placed in a bacteria culture. One patch showed growth of bacterial colonies while another one did not. What happened?

Evidence from Geographic distribution

• Biodiversity• First suggested evolution to

Darwin• Species tend to be more

closely related to other species from the same area than to species with the same way of life, but living in different areas

• Islands tend to have many endemic species that are closely related to species from the nearest mainland

Flying Squirrel from North AmericaSugar Glider from Australia

Different Geographic regions, different mammalian “brands”

Has and Does Evolution Occur?

• Scientists do not dispute that evolution does occur. Evolution is a fact.

• How evolution occurs is not completely understood.

• Charles Darwin explained how evolution occurred through natural selection. Natural selection is a well documented theory uniting all of biology.

• Modern evolutionary theory uses ideas of genetics, particularly mutations, to help explain how evolution may occur

Today’s Agenda

• Embryological Evidence• Molecular Connection- DNA analysis (front

table)

• Complete any work you have not already finished.