1. Evolution occurs through "descent with modification" as organisms adapt to their environment over generations through natural selection. 2. Natural selection leads to populations changing over time as certain inheritable traits leave more offspring than others. 3. Evidence for evolution includes the fossil record, biogeography, comparative anatomy and embryology, and molecular biology.

1. Evolution = “Descent with Modification”
1. Organisms evolved due to being
spread over different habitats
and therefore adapting and
modifying themselves to fit the
habitat.
2. Natural Selection
• A population of organisms
can change over
generations if certain
inheritable traits leave more
offspring than others and
those others get the chance
to reproduce and continue
the lineage.
• Evolutionary Adaptation

2. Descent with modification

3. Evolutionary Adaptation

4. Evidence of Evolution:
Fossil Record
Fossils chronologically
ordered in rock layers

5. Evidence of Evolution:
Biogeography
Geographic distribution of species: Australian marsupials

6. HOMOLOGY
Evidence of
Evolution:
Comparative
Anatomy and
Embryology

7. Evidence of Evolution:
Molecular Biology
Notice that a Chimp is
more genetically
related to a human
than to an Old World
Monkey!

8. Adaptive Evolution
Natural Selection = Editing
The finches of The Galapagos Islands: The original finch developed into 14
different species. What was the cause for the offshoots?

9. Darwinism Meets Genetics
• A population is the smallest unit of evolution.
– Natural selection acts on individuals.
– However the evolutionary impact of natural selection is only apparent
in tracking how a population changes over time.
• Population Genetics emphasizes the extensive genetic variation within
populations and tracks the genetic make-up of populations over time.
– Not all variation in a population is inheritable.
– Only the genetic component of variation is relevant to natural selection.
– Many variable traits in a population result from the combined effect of several
genes.
Polymorphism

10. Microevolution
1. Genetic Drift
Def: A change in the gene pool of a small population due to chance.
The best measure of Darwinian fitness is the number of fertile
offspring an individual leaves.

11. Genetic equilibrium- allele frequencies
remain constant.
To maintain at equilibrium…
1.Random mating
2.Population must be very large
3.No immigration or emigration
4.No mutations
5.No natural selection

12. Microevolution Cont.
2. Gene Flow
Def: The genetic exchange with another population.
3. Mutations
– A change in an organism’s DNA sequence.
– Ultimate source of genetic variability.
4. Natural Selection
– Directional Selection (selecting in favor of an extreme phenotype)
– Disruptive (Diversifying) Selection (leads to a balance between two or more
contrasting phenotypic forms)
– Stabilizing Selection (maintains variation in a narrow range)

13. •Resistant Genes
•Immediate Benefits
•Long term Disaster
•Evolution direct
connection to daily
lives

14. Macroevolution
• Def: Major biological changes evident
in fossil record.
• CONTRAST: MICROEVOLUTION
• Speciation
– Nonbranching evolution
(transform a population enough
for it to be designated a new
species.)
– Branching evolution (splits a
lineage into two or more species)

15. The Origins of Species
• Ernst Mayr
– Studied the diversity of birds in New Guinea (1927)
– Biological species concept
• Species = “groups of interbreeding natural populations that are reproductively
isolated from other such groups.”
• Reproductive isolation blocks exchange of genes between species and keeps
their gene pools separate.
• Reproductive barriers between species
• Zygote: fertilized egg
• Pre-zygotic (factors that impede mating
between species or hinder fertilization of eggs
if mating is attempted)
• Post-zygotic (mechanisms that operate
should interspecies mating actually occur and
form hybrid zygotes)

16. Isolating Mechanisms
Courtship
Sterile

17. Mechanisms of Speciation
• Allopatric Speciation
– A population forms a new
species while
geographically isolated
from its parent population.
• Sympatric Speciation
– A small population
becomes a new species in
the midst of a parent
population

18. •Speciation occurs only with
the evolution of reproductive
barriers between the isolated
population and its parent
population.
•If speciation occurs during
geographic separation, the
new species will not breed
with its ancestral
population, even if the two
populations should come
back into contact.

19. Sympatric Speciation
• Does not widely occur among
animals but may account for over
25% of all plant species.

20. Notice how the hybrid
bread wheat has a set of
chromosomes from each of
its ancestors: T.
monococcum (AA),
Triticum (BB), T. turgidum
(AA BB), T. tauschii (DD)
What can you notice about T.
aestivum that might make it a
good hybrid and the most
important wheat species today?

21. Relative Dating:
Fossil Record
Fossils chronologically
ordered in rock layers

22. Radioactive Dating

24. Continental Drift

25. Meteor of this
size would have
lowered the
temperature of
Earth due to the
blocking of the
sun by
atmospheric
dust.
Theory: 65 million years ago a
catastrophic event occurred killing
off the dinosaurs and about ½ of
the species inhabiting the Earth in
a 10 million year time span.

26. The Origin of Life
• Stage 1: Abiotic Synthesis of Organic Monomers
– Amino Acids
• Chains of nucleotides
– Chains of DNA bases
– Chains of RNA bases
• Building blocks of protein
– Sugars
– Lipids
– ATP

27. The Origin of Life
• Stage 2: Abiotic Synthesis of Polymers
– Monomers, such as amino acids, spontaneously
fused together to form proteins.

28. The Origin of Life
• Stage 3: Origin of Self-Replicating Molecules
inheritance
Ribozyme: catalytic RNA used to fuel RNA replication

29. The Origin of Life
• Stage 4: Formation of
Pre-cells
– Molecular packages with
some properties of life.
– The gap between pre-
cells and true cells is
enormous!
• Natural Selection

30. The origin of
eukaryotic cells
Endosymbiotic Theory
– Membrane bound nuclear material
– Organelles
– More complex than prokaryotic cells
– Ancestors to fungi, plants and
animals

31. Concept Map
Section 17-2
Evolution of Life
Early Earth was hot; atmosphere contained poisonous gases.
Earth cooled and oceans condensed.
Simple organic molecules may have formed in the oceans..
Small sequences of RNA may have formed and replicated.
First prokaryotes may have formed when RNA or DNA was enclosed in microspheres.
Later prokaryotes were photosynthetic and produced oxygen.
An oxygenated atmosphere capped by the ozone layer protected Earth.
First eukaryotes may have been communities of prokaryotes.
Multicellular eukaryotes evolved.
Sexual reproduction increased genetic variability, hastening evolution.

32. Convergent Evolution
• Process by which unrelated animals come to
look like each other.
• Dolphin
• Penguin
• Shark

33. Tempo of Evolution
Spurts of
relatively
rapid
Slow
change
adaptations

34. Flowchart
Section 17-4
Species
that are
Unrelated Related
form in under under in in
Similar Intense
Inter- Small Different
environments environmental
relationshiops populations environments
pressure
can undergo can undergo can undergo can undergo can undergo
Coevolution Convergent Punctuated Adaptive
Extinction
evolution equilibrium radiation

35. Classifying the Diversity of Life
• Systematics
– Reconstructing evolutionary history
– Radioactive dating = tool
– The study of biological diversity: past and present
• Taxonomy
– Identification, naming and classification of species
– Pioneer: Carolus Linnaeus (1707-1778)
• Binomial Nomenclature
• Homo sapien

36. Hierarchical
Classification
Which step is more
specific?
Class or Genus?
How is Domain Eukarya
different from Bacteria and
Archaea?

37. Phylogeny
•Evolutionary history
of a species.
•Tree is based on
homologous
structures, NOT
analogous.
•Two species will
have more common
nucleotide sequences
based on how
recently they
branched from their
common ancestor.

38. The Cladistic
Revolution
The Computer Age

39. 6 Kingdoms vs. 3 Domains
Archaea-
Eubacteria bacteria
?