we the galapagos islands definitions to know scientific theory = a well- supported, testable...
TRANSCRIPT
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
We the Galapagos Islands
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
We the Galapagos Islands
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?
We the Galapagos Islands
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
We the Galapagos Islands
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
We the Galapagos Islands
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.
We the Galapagos Islands
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
We the Galapagos Islands
Darwin’s Finches
FYI, each beak is designed for a
different purpose.
Leaves
Seeds
Insects Grubs
Tool using
Seeds and Fruit
Box 12
We the Galapagos Islands
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
We the Galapagos Islands
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
We the Galapagos Islands
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
We the Galapagos Islands
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.
We the Galapagos Islands
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!
We the Galapagos Islands
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
We the Galapagos Islands
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
We the Galapagos Islands
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
We the Galapagos Islands
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