We the Galapagos Islands Definitions to Know Scientific Theory = a well- supported, testable explanation of phenomena that have occurred in the natural

We the Galapagos Islands

Definitions to Know•Scientific Theory = a well-

supported, testable explanation of phenomena that have occurred in the natural world.

•Evolution = change over time, the process by which modern organisms descended from ancient organisms


Charles Darwin (1809-1882)• British naturalist famous for his theories of

evolution and natural selection. • Like several scientists before him, Darwin

believed all the life on earth evolved (developed gradually) over millions of years from a few common ancestors.

• In 1831, Darwin took a trip around the world on the ship, the M.S. Beagle, where he collected evidence that led him to propose his famousTheory of Evolution.

Charles Darwin


Darwin’s Voyage on M.S. Beagle

Starting point: 1831, England

Ending point: 1836, England

Darwin’s observations showed him there were patterns to the diversity of life on Earth. Organisms are adapted to the environment where they live.

Did you know there are no rabbits in Australia? No kangaroos in England? No monkeys in North America? No elephants in Alaska?


Fossils• Darwin didn’t just observe and collect living

animals, he also collected fossils.• Fossils = preserved remains of ancient organisms• This led to questions like….

– “Where did all these organisms go?” “Why aren’t they still here?” “Why do they resemble organisms we have living today?”

Glyptodon = dead Armadillo= alive


The Galapagos Islands• The most important,

influential stop on Darwin’s trip was the Galapagos Islands

• The islands had different climates, and therefore, had different varieties of animals and plants1. Giant Tortoises

2. Iguanas

3. Finches


Galapagos Turtles

Pinta IslandIntermediate shell

Pinta

Isabela IslandDome-shaped shell

Hood IslandSaddle-backed shell

HoodFloreana

Santa Fe

Santa Cruz

James

Marchena

Fernandina

Isabela

Tower

The shape of each turtle’s shell is different and the different shapes depend on the turtle’s habitat.


Darwin’s Finches• Darwin also collected finches, birds,

matching their beak and body shapes with different islands- just like the tortoises.

• Beak shapes in the finches indicated their type of diet, what they ate, and this told him where they lived

Ground finchTree Finch


Darwin’s Finches

FYI, each beak is designed for a

different purpose.

Leaves

Seeds

Insects Grubs

Tool using

Seeds and Fruit

Box 12


What took him so long? 25 years later….• In 1858, Alfred Wallace sent Darwin an essay

with the same ideas about evolution! • They presented their work together at a

conference, but….• This pushed Darwin to publish

his work, before Wallace• The Origin of the Species

– Proposed a mechanism for evolution, called Natural Selection

– Presented evidence that evolution has been happening for millions of years


Artificial Selection and Natural Selection• Variation exists in nature and animal and plant breeders use

this through artificial selection– A farmer may like a see a plant with bigger tomato and

use the seeds of that plant for next year’s crop– Or he may breed the two best milk cows to get a cow

who is an even better producer of milk

• Darwin’s greatest contribution was his concept of natural selection

• In the struggle for survival, the most fit- the fastest prey, the strongest predator, the one with the sharpest claws, wins the game of survival. Survival of the fittest.

• Fitness = the ability to survive and reproduce in a specific environment

Adaptation = any inherited characteristic that increases an organisms chance of survival


Proof for Evolution• Fossil record = Darwin argued

that the fossil record provided evidence that living things have been evolving for millions of years

• Geographic Distribution of living species: Descent with modification, says that similar species in similar environments but in different locations, were products of different evolution paths

• They developed similar characteristics because of their environment.

Beaver

Muskrat

Beaver andMuskrat

Coypu

Capybara

Coypu andCapybara


Homologous Body Structures

• What does Homo mean?– Homo = same, similar

• Remember these? – Homozygous- same allele for a trait, tt, TT– Homologous chromosomes- same

chromosome, one from mom one from dad

Turtle Alligator Bird Mammal

Ancient lobe-finned fish

Homolgous structures all develop from the same

embryo tissues but have different functions in the

adult organism.


Vestigial organs• Why do we need our appendix?• It’s useless now, but it may have served

some function in our past• Vestigial organs = organ with little or no

function, left over from the past, ex. appendix

If you can live without it, with no medical

help, then it’s useless!


Ch. 16, Evolution of Populations• Why are we all so different?• Variation in populations is the raw

material for evolution• 2 main sources of variation:

– Mutations = any change in a sequence of DNA, some are harmful, some are beneficial and some don’t have any effect at all

– Gene shuffling = mixing of genes due to random sexual mating

• 23 pairs of chromosomes can produce 8.4 million different combinations of genes

• Crossing over during Meiosis


Variation and Gene Pools • Genetic variation is studied in

POPULATIONS, not individuals• Members of a population share a Gene Pool• Gene pool = consists of all genes, including

all the different alleles that are present in a population– Why?– They descended from a common ancestor

• Relative frequency of an allele = number of times an allele occurs in a gene pool

• So, evolution is any change in the relative frequency of alleles in a population


Natural Selection and Speciation• Natural Selection= (Dr. Malone’s definition)

when individuals who have what it takes survive and reproduce best; survival of the fittest, it’s a dog eat dog, you got to step on someone else to get where you want to go, world

• Founder Effect = when a population shrinks down to only a few members, then rebounds so all of the future members have the “founder’s” genes

• Speciation = when natural selection and other random effects lead to the creation of a new species– Reproductive Isolation = populations become

reproductively isolated from each other, so it leads to evolution of a new species


Speciation• Behavioral Isolation = when two populations can

interbreed, but their different behaviors, or reproductive strategies, just don’t turn each other on, get it?

• Geographic Isolation = two populations are separated by geographic barriers, like mountains or oceans and they can’t interbreed

Move mountain!

Move mountain!

It’s too far to fly!

•Temporal Isolation = two populations are separated by different reproductive times

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We the Galapagos Islands Definitions to Know Scientific Theory = a well- supported, testable explanation of phenomena that have occurred in the natural