Download Evolution and Natural Selection

Evolution
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= change/time
– Change of what?
– Inherited characteristics
• two types
1. Microevolution – refers to change in the
gene pool of a population
2. Macroevolution – refers to speciation
Species Concept
• What is a species?
• Definition = a group of organisms that are
capable of mating with one another in
nature to produce fertile, viable (living),
offspring
POPULATION GENETICS
• Def: study of changes in the genetic composition of
populations
• What is a population?
• Def: organisms of the same species living together in
the same area/environment
NOTE: If organisms live in the same region, they
experience same environmental pressures from
natural selection!
Peppered Moth
Bacteria & Antibiotic Resistance
How does a
species develop?
• Species develop from other species
(ancestor) through variation over time!
• Variation = differences within a species
– Arise due to mutation, errors in DNA
replication, meiosis, etc.
Does variation alone lead to a new
species?
• No  Isolation!
• When groups separate they change from one
another due to different environmental pressures!
– What happens when 2 best friends go away to different
colleges?
Classification
We classify based on a Hierarchical System!
Big, general  Small, specific
King Phillip Came Over For Great Spaghetti
Kingdom Phylum Class Order Family Genus Species
Kingdoms of Life
Until recently scientists recognized 5 kingdoms:
Monera, Protista, Fungi, Plantae, & Animalia
Monera was split into two: archaebacteria and
eubacteria
Now scientists use a six kingdom model:
1. Eubacteria
2. Archaebacteria
3. Protista
4. Fungi
5. Plantae
6. Animalia
Example!
• Human Classification
• Kingdom Phylum Class Order Family Genus Species
• Animalia  Chordata  Mammalia  Primate 
Hominidae  Homo  Sapien
Binomial Nomenclature
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Carolus Linnaeus - Taxonomy
Scientific Name vs. Common Name
Always written in italics
First word is capitalized = genus
Second word is lowercase = species
Example: White Pine
Pinus strobus
Dog
Canus familaris
History of Evolutionary Theory
• Jean Baptiste Lamarck
– Theory of use & disuse
– Individual organisms change in response to
their environment and pass this acquired
trait to their offspring.
History of Evolutionary Theory
• Charles Darwin
– Early to Mid 1800’s
– Age 22 left England aboard the HMS Beagle
– Galapagos Islands, South America, Africa,
and Australia
Darwin’s Theory
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1859 “On Origin of the Species”
Theory of Natural Selection
– survival and reproduction of organisms that are
best suited to their environment
Theory of Natural Selection
Main Points
1. Populations tend to grow & overpopulate
2. Resource competition  resources are limited
3. Inheritable Variation exists among populations that
makes some individuals more “fit” than others.
4. Those individuals with variation that allows them to
survive better will reproduce more often. Their genes &
traits are passed onto offspring, causing these genes &
traits to increase in proportion in the population.
Evidence for Evolution
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Fossil Record
Comparative Anatomy
Molecular Biology
Biogeography
Embryology
Fossil Record
• Remains of plants or animals that were once
living
• Used to:
– reveal the existence of species that came before &
are now extinct (Life has changed over time!)
– Develop relationships
– Rate of Evolutionary Change
• Incomplete
– Why?
Comparative Anatomy
• Study of different structures used to develop
relationships
• Homologous, Analogous, Vestigial
Molecular Biology
• Study differences in DNA & amino acid
sequences
• Those organisms most closely related
have the most similarities.
Biogeography
• Movement of continents  continental drift
• Trace species back to splits in populations
due to continental drift
Embryology
• Study of
similarities
during embryo
development
What can we conclude from all of
this evidence?
• Descent with Modification!
– New life forms appeared to be
modifications of fossil forms found in
similar geographic areas.
– Implies that modern life forms are
descendents of older life forms that
have changed slowly over time.
Q: What made them change?
• Coevolution
– Change or Evolution of 1 species affects the evolution of
another.
– Ex: Predator Prey (arms race)
• Convergent Evolution
– Occurs when environmental pressures act similarly to
unrelated species.
– Example: whale & shark
• Divergent Evolution
– 2 or more related species become increasingly different
– Related species are introduced into different
environments.
Divergent Evolution
• Adaptive Radiation
– Rapid increase in # of species