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Theory of Evolution & Microevolution
Chapter 13
Evolution
• Darwin and his theory
• Evolution Evidence
Charles Darwin
Natural Theology
• Based on a literal view of the Genesis Story
• Earth 6,000 yrs old
• No new species
• No physical changes (valleys, mountains)
Putting Darwin in the context of his time
Important people
• Linnaeus
• Lamarck
• Malthus
• Lyell
Linnaeus
• Studying biology to reveal a divine plan
• Developed modern taxonomy
• Made Binomials: Homo sapiens
• Based groupings on morphology
• Did not believe in evolution,
• Taxonomy data would later provide some of best evidence
Lamarck
• Got the genetics wrong
• Stressed acquired traits-(wrong)– Giraffes stretched their necks– Babies had longer necks
• But- said species evolved to be better suited to environment – right!
Malthus
• British economist studied Paris after the revolution
• Limited resources
• Excess population growth
• Struggle to survive,
• competion among individuals
• Survival of the richest
Malthus
• Darwin was influenced by Thomas Malthus’s Essay on the Principle of Population (1798)– Populations
increase geometrically, while food supply increases only arithmetically
Fig. 2.6
Lyell
• British geologist.
• Following Hutton’s work
• Earth is old
• Valleys formed by erosion
• Mountains by uplifting
• Slow processes over LONG periods of time
Fig. 2.13
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
North America
Marquesas
SocietyIslands
GalápagosIslands
Valparaiso
Straits of Magellan
Cape Horn
North AtlanticOcean
SouthAmerica
Bahia
Cape VerdeIslands
Tierra del Fuego
FalklandIslands
Port Desire
Buenos AiresMontevideo
Rio de Janeiro
Ascension
St Helena
WesternIsles
CanaryIslands
South AtlanticOcean
Cape ofGood Hope
Africa
Europe
IndianOcean
Madagascar
MauritiusBourbon Island
British Isles
KeelingIslands
King George’sSound
AsiaNorth PacificOcean
PhilippineIslands
Equator
FriendlyIslands
Hobart NewZealand
Sydney
Australia
5 year voyage of the Beagle
Evidence that Made Darwin think..
• The variation among organisms in a population• Biogeography – where species are found around
the globe• Fossil record• Comparative morphology – Linnaeus's
classification• Artificial Selection • Geology and the age of the earth• Malthus and economic theory• Lamarck’s theory and adaptations
Evolution- Just a Theory?
• Theory vs. Law vs. Dogma
Terms:
• Theory – explain a process
• Law- describes a phenomenon, a formula
• Dogma is not testable – beliefs
• Science is limited to things we can measure, test.
• Hypothesis – is an “educated” guess to explain a problem,
Scientific Method
• Problem, observation
• Background information, literature search
• Hypothesis based on previous work
• Experiment to test hypothesis
• Analyze results
• If hypothesis supported – publish a paper.
Darwin’s Theory
• Populations have inherent variation among individuals.
• These traits are heritable• Resources in the environment are limited• Populations have a greater fertility than
their environment can sustain.• Populations would grow exponentially, but
most remain stable in size.
A population of Liguus fascitus
Variation in shell coloration patterns
Darwin’s Theory continued:
• There is a struggle to survive among the offspring called Natural Selection.
• The survivors are better fit
• Fitness is the ability to have more offspring (frequency of genes in the genepool).
Natural Selection
• “struggle “ or competition does not have to be a fight to death
• May just be as simple as a seed germinating earlier and getting established first. It produces 120 seeds. A later germinating plant makes only 50 seeds.
• “Fitness” is the success rate of the offspring in future generations.
Fig. 2.7
Some Evidence for Evolution
• Microevolution- antibiotic, pesticide resistance– Artificial selection
• Fossil record• Biochemical comparisons
– Protein sequences– DNA, gene comparisons
• Morphological comparisons• Embryology• Biogeography• Genetically modified organisms
Fig. 2.9
Fig. 2.5
Fig. CO 2
Fig. 2.10
Evolution in progress around us:
• Antibiotic resistance
• Herbicide, Pesticide resistances
• New disease threats (AIDS, SARS, Ebola, West Nile Virus)
• Climate change
• Introduced species
• Biotechnology ???
Fig. 2.8
Darwin and Human Evolution
• Published “Descent of Man” in 1871
• Wasn’t first to hypothesis our relation to apes
• caused more popular criticism of his general theory
All made by Artificial Selection from wild mustard
Artificial Selection: human designed breeding of plants and animals for desired traits by selecting which individuals get to reproduce.
backbone
pelvic girdle
coccyx (boneswhere manyother mammalshave a tail)
small boneattached topelvic girdle
thighboneattached topelvic girdle
Missing Links
Galapagos Finches
• Specialization to different feeding sources may have diversified the species.
Sexual Selection
Directional Selection modifies Beak depth during
drought periods
Fig. 2.16
Fig. 2.15
Homologous features
• Derived from a common ancestor
• Often do not have similar functions
• Changes in the timing of genes forming body parts can alter their over-all shape.
proportions in infant
proportions in infant
adult
adult
chimpanzee
human
1
1
1
1
1
1
2
2
2
2
2
2
2
3
3
3
3
3
3
3
4
4
4
4
4
5
5
5
5
early reptile
pterosaur
chicken
bat
porpoise
penguin
human
Analogous Features• Have same functions ( by convergence)
• Do not have a common ancestry
• Are not derived from the same ancestral feature
Butterfly and Bird
• No bones in butterfly, not from common ancestor
• Structures not related
Ecotypes
• Populations that adapted to local environmental conditions.
• Still one species – inter-fertile• Can form clines – serial ecotypes along a
gradient– Common garden experiment (e.g. elevation and
yarrow)
• Need to preserve local adaptations in plants– In Botanical garden they always list source of plant– Restoration Ecology – try to propagate local plants to
use in marsh etc. restoration.
Ecotypes forming a cline Fig. 23.8
Convergent Evolution
• Sometimes unrelated species may superficially look alike
• Both species have adapted to similar habitats.
• Evolution comes up with similar adaptations to the conditions
• Does not mean they are closely related
Convergent Evolution
Ocotillo Allauidia
North America Madagascar
Fig. 13.9b