Evolution1

Evolution

The process in which significant changes in the inheritable traits (the genetic make-up) of

Early Ideas to explain the World

• Myths abound in each culture to explain the existence of the world and life.

• Prevalent explanation in Western society was based on the Bible: natural

surroundings do not change significantly • Life Forms are immutable

• Earth was created fairly recently: Sunday,

Oct. 23rd, 4004 BC (Archbishop Janes

And here he is…..

Food for Thought

• What is science based on? • What is a theory?

Despite the Church’s Teaching,

contrary evidence emerged

• 15th century: Leonardo da Vinci found sea

shells fossils in the Alps • His conclusion:

• _{these sea shell deposits were very}

old they had formed in an ancient sea

Fossils

• Preserved remains of an organism or its activities:

• Bones, shells and teeth • Footsteps

Fossil Formation

• The prospective fossil becomes covered with sediment and eventually are

compressed into strata (layers) and harden into sedimentary rock.

Fossil Formation cont’d…

• The organism just leaves a n impression in hardened material

• Cells may be replaced by minerals = permineralization

• Fossilization is rare – soft tissues

decompose quickly. The most frequent fossils result from hard structures.

Fossil Formation cont’d… 2

• Paleontology: the scientific study of fossil remains

• Baron Georges Cuvier (anatomist), 18th

century:

- many fossils are of extinct species

- the fossils from different sedimentary

Fossil Formation cont’d… 3

- fossils in recent sediments resemble

existing species more than fossils from older sediments

- relative age: an estimate of the age of a

fossil (or rock) depending on the depth of the sediment it was found in: the deeper, the older

- he had no method to determine the

Fossil Formation cont’d… 4

• Cuvier believed that species had only been created once – dilemma????

• His solution: catastrophism

Georges Cuvier

The Age of Earth:

The Age of Earth Cont’d

• 1866: assuming the Earth was cooling down: 400 mya, then 15 – 20 mya

• 1903: Pierre Curie: radioacvtive decay falsifies Earth’s current temperature and the cooling-down effect:

Radiometric Dating

• Radioisotopes: atoms with an unstable nuclear arrangement decay

• Parent isotope → daughter isotope • The rate at which the parent isotope

decays is called the half-life, the time after which 50 % of the parent isotope has

Radiometric Dating Cont’d 1

http://facstaff.gpc.edu/~pgore/myart/radgraph.gif

• 14C → 14 N: 5730

years (100 – 100 000yrs)

• 235U → 207 Pb: 713

mya (10 mya – 4.6 bya)

• 40K → 40 Ar: 1.3 bya

We stand on the shoulders of

giants… and so did Darwin

http://www.planeterde.de/Members/timo_meyer/vortrag_harms/james-hutton/image

• 1795: Hutton

proposed actualism: geological processes that occur in the

present also occurred in the past.

Giants Cont’d 1

http://www.geolsoc.org.uk/webdav/site/GSL/shared/images/geoscientist/Lyellresized.jpg

• Sir Charles Lyell (1830) proposed

uniformitarianism: Earth’s surface has always

changed and continues to change through similar, uniform and very gradual processes.

• → Earth must be very

Giants Cont’d 2

http://upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Georges-Louis_Leclerc,_Comte_de_Buffon.jpg/466px-Georges-Louis_Leclerc,_Comte_de_Buffon.jpg

• Comte Georges Buffon (mid 18th

century) proposed that species can change over time,

Giants Cont’d 3

• Chevalier de Lamarck (student of Buffon, mid 19th cent): recognized the

role of the environment: Species must be able to adapt to a changing

environment. Each species becomes

gradually more complex (during its lifetime) =

acquired traits. New species are created continually by

Charles Darwin

• Went on a world

voyage as a 22-yr old as a naturalist. The voyage lasted 5 years • His role was to

Darwin Cont’d

• He left England believing in the

immutable nature of species.

• His careful analysis of evidence and

observation made him one of the giants of

Darwin’s Observations 1

• Biogeography: the analysis of the

geographic distribution of organisms

• Flying organisms inhabit remote islands • Organisms in adjacent regions resemble

each other, but occupy different niches • Organisms in areas distant from each

Darwin’s Observations 2

http://www.bio.miami.edu/dana/pix/homologous.jpg

• Homologous features: structures that share a common origin but serve different functions in

modern species • Species that share

homologous features are closely related

• Homologies are

Darwin’s Observations 3

http://raptorrehab.files.wordpress.com/2009/04/bird_wing_by_lily.jpg

http://www.microscopy-uk.org.uk/mag/imgjul05/apismap/dw-apis-fore-wing-l.jpg

• Analogous Features: structures similar in function but in origin or anatomical

structure

• Analogous features

Darwin’s Observations 4

http://www.iss.k12.nc.us/schools/shs/jmccartney/vestig.gif

• Vestigial features: rudimentary and nonfunctioning

structures that are homologous to

functioning structures in related species

Darwin’s Observations 5

http://www.nature.com/nrg/journal/v7/n11/images/nrg1918-f2.jpg

• Homologies exist in embryonic

development: the

more closely related species are, the more their embryos

Darwin’s Observations 6

• Anatomical Oddities: anatomical features that ‘don’t make sense”: webbed feet in birds that never swim; babies born with tailbones, and third nipples

Darwin’s Observations 6

http://images.google.ca/imgres?imgurl=http://campus.udayton.edu/~INSS/Dillon230/WebUNIT-III/2ArtificialSelection-cabbage_files/image002.gi

http://images.google.ca/images?gbv=2&hl=en&client=firefox-a&rls=org.mozilla:en-US:official&um=1&ei=b2dnS9bALdThlAfy24CUCg&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=artificial+selection&spell=1&start=0

• Artificial Selection: through selective breeding, humans have been able to change and shape the attributes of

domesticated species (Ex: dogs, cats,

A Missing Link: Malthus’ Essay

• 1798: Essay on the Principle of Population

• _{Plants and animals (including humans)}

produce more offspring than can survive.

• D.’s conclusion: There must be

competition. Favourable variations are preserved, unfavourable ones are

In summary:

1. There is variation within the individuals of a species

2.Some of this variability can be inherited

3. Every generation produces more offspring than can survive

Ergo….

1. Members of the same species compete with each other for survival

2. Individuals with favourable traits are

more likely to survive and reproduce, and hence pass on their favourable traits

3. 3. These individuals contribute more