1. Evolution Unit

2. How do genetic variations occur?
What is Evolution?
Change in the genetic makeup of a population over time.
Fitness – those with favorable variations for survival and reproduction.
Populations can evolve, not individuals.
Diverse gene pool good for long-term survival of a species. Genetic variations are important!
How do genetic variations occur?

3. Where does Variation come from?
Mutation
random changes to DNA
errors in mitosis & meiosis
environmental damage
Sexual reproduction
mixing of alleles
genetic recombination
new arrangements of alleles in every offspring
new combinations = new phenotypes

4. Genetic variation in a population

5. Essence of Darwin’s ideas
Natural selection
heritable variation exists in populations
over-production of offspring
more offspring than the environment can support
competition
for food, mates, nesting sites, escape predators
differential survival
successful traits = adaptations
differential reproduction
adaptations become more common in population

6. Lamarckian vs. Darwinian view
in reaching higher vegetation giraffes stretch their necks & transmits the acquired longer neck to offspring
Darwin
giraffes born with longer necks survive better & leave more offspring who inherit their long necks 

7. Evidence Supporting Evolution
2006 Fossil Discovery of Early Tetrapod
“Tiktaalik”
“missing link” from sea to land animals
Evidence Supporting Evolution

8. Evidence for Evolution
Paleontology – fossils show change in a species over time
Biogeography – Similar species are found in similar ecosystems around the world
Morphology – Comparing structures
Homologous structures – body parts with similar structure but possible different function. Shows common ancestry
Analogous structures – similar structure develops in organisms that share a common ecosystem but not a common ancestry
Biochemical or Molecular -
Similarities in gene sequences, proteins, DNA

9. Fossils Preserved remains of living things
Paleontology is the study of the fossil record
Most organisms do not leave a fossil after death
Explains the “missing links”
Sedimentation Fossils
As the organism decomposes the spaces will be filled with the minerals from the silt

10. The Archaeopteryx Fossil
Forelimb has three functional fingers with grasping claws.
Reptilian Features
Lacks the reductions and fusions present in other birds.
Breastbone is small and lacks a keel.
True teeth set in sockets in the jaws.
The hind-limb girdle is typical of dinosaurs, although modified.
Long, bony tail.
Avian Features
Vertebrae are almost flat-faced.
Impressions of feathers attached to the forelimb.
Belly ribs.
Incomplete fusion of the lower leg bones.
Impressions of feathers attached to the tail.
LEFT: Archaeopteryx lithographica
Found in 1877 near Blumenberg, Germany

11. How old is that fossil? Relative Dating Absolute Dating
Age of fossils based according to their location in strata
Absolute Dating
Age of fossils determined by analyzing the content of radioactive isotopes found in the fossil.
Half-life: The length of time required for half of the radioactive elements to change into another stable element.
Unaffected by temperature, light, pressure, etc.
All radioactive isotopes have a dependable half life. Ex: C14 decays into N14

12. Relative Dating

13. Absolute Dating
How radioactive “naturally occurring” elements get inside an organism:
A.K.A – Radiometric dating

14. Homologous Structures
Anatomical evidence
Anatomical evidence
1. These structures are called… homologous
2. These structures are evidence for…. common ancestry
3. similar internal structure = similar development
4. different function = different environment & niche
5. close evolutionary r’ship!

15. Analogous structures Solving a similar problem with a similar solution
Convergent
evolution
Don’t be fooled by their looks!
same function different development & anatomy
Those fins & tails & sleek bodies are analogous structures!
convergent evolution - NOT common ancestor
Those fins & tails
& sleek bodies are analogous structures!
Does this mean they have a recent common ancestor?
Solving a similar problem with a similar solution

16. Comparative hemoglobin structure
Molecular Homology
The sequence in DNA & proteins is a molecular record of evolutionary relationships.
Why compare DNA & proteins across species? 10 20 30 40 50 60 70 80 90
100
110
120
Lamprey
Frog
Bird
Dog
Macaque
Human 32 8 45 67
125
Comparative hemoglobin structure
Molecular Record
What are we comparing here? - comparing DNA (base sequence) & proteins (amino acid sequence)
What assumption do we make about genes and relatedness?  the more closely related, the more DNA bases & amino acids you have in common
have to compare genes for protein the organisms have in common… can’t compare genes for proteins you don’t have
Number of amino acid differences between
hemoglobin (146 aa) of vertebrate species and that of humans

17. These are remnants of structures that were functional in ancestral species
Vestigial organs
Why would whales have pelvis & leg bones if they were always sea creatures?
Remains of ancestral structures = mutations can occur without affecting survival & reproduction
Evolutionary relationship
snakes & whales — remains of pelvis & leg bones of walking ancestors
eyes on blind cave fish
human tail bone

18. Evolution evidence at the cellular level
Domains: Archaea, Bacteria and Eukarya
Elements conserved through all: DNA, RNA and many metabolic pathways.
Eukaryotes – core features:
Cytoskeleton
Nucleus
Membrane-bound organelles
Linear chromosomes
Endomembrane system