5.4 Evolution
IB Biology
Evolution
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The cumulative change in the heritable characteristics of a
population
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Cumulative – small changes over time (many generations)
Heritable – gene-controlled factors/traits
Population – not an individual
Life on Earth is unified by its common origins
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Species can evolve
New species arise from preexisting ones
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http://www.johnkyrk.com/evolution.html
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Charles Darwin
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Father of Evolution
The Origin of the Species, 1859
HSM Beagle
Studied finches in Galapagos islands
Evidence for Evolution – TOK Link
Evidence for Evolution
http://www.brainpop.com/science/ecologyandbehavior/humanevolution/
Evidence for Evolution
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Fossil Record
Remains of extinct species
provide evidence that
species are continuously
evolving
Shows a change in species
over time
http://www.brainpop.com/science/ecologyandbehavior/humanevolution/
Evidence for Evolution
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Homologous Structures
Structures that may look different and perform a different
function, but have a “unity” in structure (eg. bone position)
Common ancestry
Look different because they have adapted to perform
different functions (adaptive radiation)
Pentadactyl
Pentadactyllimb
limb
(five
(fivedigits)
digits)
Vestigial Structures
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Darwin called them “rudimentary organs”
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Appendix in humans
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Reduced structures that serve no function
Lost function and are gradually being lost
Used to be larger sac to digest cellulose
Pelvic bone in baleen whales
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Support upright weight
Walking
Evidence for Evolution
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Selective Breeding
Humans have selected desirable traits in domesticated
animals for centuries
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Farmer notices a favourable trait, individual allowed to breed
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May also influence other characteristics
Farmer notices a negative characteristic, not allowed to breed
Called artificial selection
Eg. Cows
Jersey - milk
Angus - beef
Evolution Video
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Great Transformations
Comparative Embryology
Homework
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Page 184: DBQ
Page 189: Thinking about science
(cover the answers on the side)
Populations
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Populations tend to produce more offspring than the
environment can support
Consequence of overproduction of offspring is a struggle
to survive
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Think back factors that limit population growth
Variation
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Variation - A marked deviation from the typical form or
function
Variation
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Crossing Over (prophase I)
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Random Assortment (metaphase I)
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Creates new combinations of alleles on a chromosome
Recombination
How chromosomes line up at the equator
↑ chromosome number = ↑possibilities
2n = 223= 8, 388, 608 possibilities
Random Fertilization
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Any sperm cell can randomly fertilize the egg cell
Faster swimmer!!
Evolution in response to environmental change
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Antibiotic Resistance in Bacteria
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Environmental change: methycillin antibiotic (drug)
Antibiotic resistance in bacteria
Methycillin
Antibiotic resistance in bacteria
Methycillin resistant
Methycillin susceptible
Antibiotic resistance in bacteria
Take your prescription until the
very end!!!
Evolution in response to environmental change
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Peppered Moth (Biston betularia)
Environmental change: soot from pollution, industry
typica stood out
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carbonaria camoflauged
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Predation
Population declines
Little predation
Survive to pass on trait and population increases
Reversing because of clean air acts
http://www.techapps.net/interactives/pepperMoths.swf
Evolution in response to environmental change
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Galapagos finches
Darwin visited Galapagos islands in 1853
Observed the size and shape of beaks many species of finches
Finches on each island had different selection pressures, and
over the years had adapted to suit own island – own species
Common ancestry
Environmental change:
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Food supply
http://www.sepa.duq.edu/finches.html
http://www.brainpop.com/science/ecologyandbehavior/naturalselection/
Natural Selection
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Variation produces different traits
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Inherited characteristics affect the likelihood of an
organisms survival and reproduction
Traits that give an advantage are passed on to the next
generation
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give an advantage or disadvantage
adaptations
Over time, the proportion of the population with the
advantageous trait will increase (and those with a
disadvantage will decrease)
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“Survival of the fittest”
Opposing
Viewpoints
Published in
The Economist, 2009
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Friends:
http://www.youtube.com/watch?v=cXr2k
F0zEgI
HW: IB Questions
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Explain evolution of a species by natural selection in
response to evolutionary change (8 min)
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Explain two examples of evolution in response to
environmental change (9 min)
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Optional: Evolution extra credit assignment
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Read the Survival of the Sneakiest comic on Edline.
Explain it in one paragraph using ecology vocabulary