Evolution The cumulative change in the heritable
characteristics of a population 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 Species can evolve New species arise from preexisting ones
http://www.johnkyrk.com/evolution.html
Charles Darwin
Father of Evolution The Origin of the Species, 1859 HSM Beagle Studied finches in Galapagos islands
Evidence for Evolution
http://www.brainpop.com/science/ecologyandbehavior/humanevolution/
Evidence for Evolution 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 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)
Vestigial Structures Darwin called them “rudimentary organs”
Reduced structures that serve no function Lost function and are gradually being lost
Appendix in humans Used to be larger sac to digest cellulose
Pelvic bone in baleen whales Support upright weight Walking
Evidence for Evolution Selective Breeding Humans have selected desirable traits in
domesticated animals for centuries Farmer notices a favourable trait, individual
allowed to breed May also influence other characteristics
Farmer notices a negative characteristic, not allowed to breed
Called artificial selection Eg. Cows Jersey - milk Angus - beef
Populations
Populations tend to produce more offspring than the environment can support
Consequence of overproduction of offspring is a struggle to survive Think back factors that limit population growth
Variation Crossing Over (prophase I)
Creates new combinations of alleles on a chromosome Recombination
Random Assortment (metaphase I) How chromosomes line up at the equator ↑ chromosome number = ↑possibilities 2n = 223= 8, 388, 608 possibilities
Random Fertilization Any sperm cell can randomly fertilize the egg cell Faster swimmer!!
Evolution in response to environmental change
Antibiotic Resistance in Bacteria
Environmental change: methycillin antibiotic (drug)
Evolution in response to environmental change
Peppered Moth (Biston betularia) Environmental change: soot from pollution,
industry typica stood out
Predation Population declines
carbonaria camoflauged Little predation Survive to pass on trait and population increases
Reversing because of clean air acts http://www.techapps.net/interactives/pepperM
oths.swf
Evolution in response to environmental change
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:
Food supply
http://www.sepa.duq.edu/finches.htmlhttp://www.brainpop.com/science/ecologyandbehavior/naturalselection/
Natural Selection Variation produces different traits
give an advantage or disadvantage Inherited characteristics affect the likelihood
of an organisms survival and reproduction Traits that give an advantage are passed on to
the next generation adaptations
Over time, the proportion of the population with the advantageous trait will increase (and those with a disadvantage will decrease) “Survival of the fittest”
Opposing Viewpoints Published in The Economist, 2009
Friends: http://www.youtube.com/watch?v=cXr2kF0zEgI
HW: IB Questions Explain evolution of a species by natural
selection in response to evolutionary change (8 min)
Explain two examples of evolution in response to environmental change (9 min)
Optional: Evolution extra credit assignment Read the Survival of the Sneakiest comic on
Edline. Explain it in one paragraph using ecology
vocabulary