5.4 Evolution

IB Biology

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 – TOK Link

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)

Pentadactyl limb

(five digits)

Pentadactyl limb

(five digits)

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

Evolution Video

Great Transformations

Comparative Embryology

Homework

Page 184: DBQ Page 189: Thinking about science

(cover the answers on the side)

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 Variation - A marked deviation from the typical

form or function

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)

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 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