Chapter 16Chapter 16

Darwin’s Theory of Darwin’s Theory of

EvolutionEvolution

What is evolution??What is evolution??

It simply means……It simply means……

• A change in an organisms genes, over A change in an organisms genes, over periods of time (usually long ones!!) periods of time (usually long ones!!) However this is changing with MRSA and However this is changing with MRSA and viruses HIV and Influenza each year.viruses HIV and Influenza each year.

• Why is it a “theory”???Why is it a “theory”???– A theory is a well-supported explanation of A theory is a well-supported explanation of

things that have happened in the natural things that have happened in the natural world.world.

How did this theory start???How did this theory start???

• By Charles Darwin (2/12/1809) – same day as Abe By Charles Darwin (2/12/1809) – same day as Abe L.L.

• He sailed on the HMS Beagle, (5 years) and He sailed on the HMS Beagle, (5 years) and brought back new animals, plants, bones, fossils brought back new animals, plants, bones, fossils etc..etc..

His observations…Diversity His observations…Diversity - -

• Why do similar ecosystems on Why do similar ecosystems on different continents contain different different continents contain different animals???animals???

• Ex: no rabbits in Australia, no Ex: no rabbits in Australia, no kangaroos in England?kangaroos in England?

Fossils -Fossils -

• Some look similar to modern speciesSome look similar to modern species

• Some look so different they must no Some look so different they must no longer exist todaylonger exist today

The Galapagos Islands-The Galapagos Islands-

• 1000 km. off the coast of Ecuador1000 km. off the coast of Ecuador

• Islands are close, but have different Islands are close, but have different climates. Therefore they have climates. Therefore they have similar species but with similar species but with unique unique differences.differences.

Look at the beaks: what are they adapted Look at the beaks: what are they adapted for? Did they all start out the same and then for? Did they all start out the same and then

change?change?

Tortoises -Tortoises -• The tortoises on each island have The tortoises on each island have

different shells.different shells.

• On Hood Island, vegetation is sparse On Hood Island, vegetation is sparse and higher up. The tortoise shell is and higher up. The tortoise shell is notched, not so on islands with low notched, not so on islands with low lying vegetation.lying vegetation.

Galapagos cont’:Galapagos cont’:

• Marine iguanas are found here but no Marine iguanas are found here but no where else on Earth – why?where else on Earth – why?

16 – 2 Darwin’s ideas16 – 2 Darwin’s ideas

• Earth is not only a few thousand years oldEarth is not only a few thousand years old

• HuttonHutton and and LyellLyell proved this by geological proved this by geological layers and processes. (Continental drift)layers and processes. (Continental drift)

Population Growth:Population Growth:

• MalthusMalthus – – if the population grows unchecked, if the population grows unchecked, there won’t be enough space and food for there won’t be enough space and food for everyone. Life must be a struggle to survive -Are everyone. Life must be a struggle to survive -Are we seeing this today?we seeing this today?

• In animals and plants – only a few young In animals and plants – only a few young

survive…. WHY?? Is this true of humanssurvive…. WHY?? Is this true of humans??

LaMarckLaMarck – Use and disuse – Use and disuse

• If an organism uses something a lot – If an organism uses something a lot – it will pass that trait on to its’ it will pass that trait on to its’ offspring:offspring:

Origin of Species - 1859Origin of Species - 1859• Book published by Darwin. Caused Book published by Darwin. Caused

an uproar because people thought it an uproar because people thought it went against the church, in that went against the church, in that species were created from previous species were created from previous species – not specially created from species – not specially created from God.God.

Artificial Artificial Selection:Selection:• Nature provides variation, while Nature provides variation, while

humans humans select the traits they want.select the traits they want.• Pig farmers will breed the largest pigs, Pig farmers will breed the largest pigs,

cows that milk best etc…. Look at all the cows that milk best etc…. Look at all the dog species!dog species!

Survival of the Fittest: The Survival of the Fittest: The best adapted live and best adapted live and reproduce.reproduce.• Organisms inherit characteristics Organisms inherit characteristics

that increase their chances of that increase their chances of survival. Ex: a lizard that sheds its survival. Ex: a lizard that sheds its tail will survive to reproduce instead tail will survive to reproduce instead of dying out.of dying out.

Descent with modification:Descent with modification:

• Species today look different than Species today look different than their ancestors – because they have their ancestors – because they have descended and changed over time. descended and changed over time. Some still look remarkably the same Some still look remarkably the same though….crocodiles?though….crocodiles?

Evidence of Evolution:Evidence of Evolution:• Fossil record, changes in Earth have Fossil record, changes in Earth have

been seen (continental drift, been seen (continental drift, volcanoes, earthquakes, uplifting of volcanoes, earthquakes, uplifting of mountains) mountains)

• Geographical distribution of living Geographical distribution of living speciesspecies

• Homologous structuresHomologous structures

• Similarities in early developmentSimilarities in early development

Fossil Record:Fossil Record:

• Show ancestors and their gradual changes Show ancestors and their gradual changes into current species.into current species.

• Fossils show differencesFossils show differences

in horse size, feet,in horse size, feet,

skulls etc..skulls etc..

Several species are wellSeveral species are well

mapped! (dinosaurs, elephants,mapped! (dinosaurs, elephants,

Horses etc..)Horses etc..)

Geographical distribution:Geographical distribution:

• Animals share a common ancestor, but Animals share a common ancestor, but were isolated and evolved different traits were isolated and evolved different traits specific to that environment (blubber, fins, specific to that environment (blubber, fins, beaks, fur)beaks, fur)

• Isolated islands typically have their own Isolated islands typically have their own species (Australia). No snakes on Guam species (Australia). No snakes on Guam etc..etc..

Early Development: Early Development: EmbryologyEmbryology

• Look at how similarly organisms look Look at how similarly organisms look as they develop from a fertilized egg. as they develop from a fertilized egg. Human embryos have gills slits and Human embryos have gills slits and tails…tails…

Similar Body Structures: Similar Body Structures: Homologous structuresHomologous structures

• Resemblance in all front limbs of Resemblance in all front limbs of very different animals:very different animals:

Vestigial Organs:Vestigial Organs:

• Serve no purpose now, but at one Serve no purpose now, but at one time probably did.time probably did.

Similar Chemical Similar Chemical Compounds:Compounds:

• All living things use All living things use ATP for energyATP for energy..

• All living things reproduce by All living things reproduce by DNADNA (same nucleotide bases)(same nucleotide bases)

Humans and apes??Humans and apes??

• DNA in apes and man is 97% the DNA in apes and man is 97% the same. Humans have 46 same. Humans have 46 chromosomes, apes 48. They look chromosomes, apes 48. They look the same except that #2 is fused in the same except that #2 is fused in humans and separate in apes:humans and separate in apes:

Fossil Record Problems -Fossil Record Problems -

• Incomplete – getting stronger Incomplete – getting stronger everyday. everyday.

Finding “missing links”.Finding “missing links”.

• Many living things don’t Many living things don’t

turn in to fossils.turn in to fossils.

• Quality of fossils vary.Quality of fossils vary.

• Dating can be difficult.Dating can be difficult.http://www.youtube.com/watch?v=yDdaStk5SEM