Darwin and natural_selectionPresentation Transcript
studied medicine at Edinburgh University (1825-1827) where the sight of blood and surgery without anesthetics repulsed him studied to become a clergyman at Cambridge University (1827-1831) born in Shrewsbury, England, in 1809 Charles Darwin
After Cambridge, Charles was recommended for a surveying trip on the HMS Beagle . Darwin sailed around the world on the Beagle for 5 years, working as a naturalist.
Darwin made many observations and collected evidence on his voyage that led to his theory about the way life changes.
At the time Darwin made his trip, the majority of people believed the Earth and all of its forms of life had been created only a few thousand years in the past.
People also believed in fixity of species ; in other words, species never changed . After careful observation and study of new scientific discoveries, Darwin began to think otherwise. People also believed that the Earth had not changed during those few thousand years . The first dinosaur to be described scientifically was Megalosaurus by William Buckland in 1824.
Darwin was influenced by geologist James Hutton’s writings that described geologic forces he thought had changed and were still changing the earth. Hutton proposed that the Earth had to be much more than a few thousand years old. The Father of Geology
Darwin was also influenced by geologist Charles Lyell who wrote Principia Geologica . Lyell’s book proposed that tremendous geologic processes had shaped the Earth such as seen in volcanoes active in the present.
On the voyage, Darwin noticed that everywhere he went, the animals and plants differed vastly. Patterns in the species suggested that the species had changed over time and had given rise to new and different species.
The Galapagos Islands lie 500 miles west of Ecuador in the Pacific Ocean, directly on the equator. Many of Darwin’s conclusions were based on observations of wildlife in the Galapagos Islands. “ Galapagos” means turtle.
What it must have been like to be Darwin… Darwin noticed on these islands, there were several types of finches. Galapagos finches
In particular, Darwin observed something odd about the finches: they all looked like a bird he had seen on the South American continent. Galapagos finches
Darwin wondered if the birds and other animals had been created to match their environment, why didn’t these birds look like the birds of the African continent, since the environments of both the Galapagos and Africa were similar.
Darwin guessed that some of the birds from South America migrated to the Galapagos. Once on the islands, the birds must have changed over the years.
This would explain the numerous species of birds present. woodpecker finch cactus finch large ground finch
Darwin called this… or evolution (change in species over time) Darwin concluded: Each species has descended, with changes, from other species over time. Descent With Modifications
Malthus was a British social scientist who proposed theories on factors controlling population growth: Darwin based his theory on his own observations and the writings of Thomas Malthus. People have more children than are able to survive. There are built-in population checks: disease, famine, and war.
Darwin extended these principles to biology, which helped him form his theory of… Natural Selection … or Survival of the Fittest.
Natural selection was the mechanism by which Darwin proposed that evolution took place. On the Origin of Species Darwin published his theory in the book
Five basic components of Natural Selection
1. All species have genetic variation. Every species is different, even within itself. Variation is caused by mutations and meiosis.
2. Organisms produce more offspring than can survive . Many that survive do not produce offspring. The female green sea turtle lays a clutch of about 110 eggs. She may lay several clutches. It is likely that less than 1% of the hatchlings will ever reach sexual maturity.
3. Since more organisms are produced than can survive, there is competition (struggle for existence) . Competition exists WITHIN and AMONG species. Within and Among Species for And Within a Species for food water mates shelter space
The constant struggle for survival is affected by short-term natural disasters. (drought, fires, floods, snowstorms, hurricanes, and tornadoes) The constant struggle for survival is also affected by long-term changes in the environment. (ice ages, biome shifts, etc)
4. Survival of the fittest Some organisms are more suited to their environment as a result of variations in the species. Individuals that are fit to their environment survive and leave more offspring than those who aren’t. Fitness: the ability of an individual to survive and reproduce in its specific environment. Fitness is a result of adaptations. He who spreads the most genes wins! 1st
5. Descent with modification : Living species today are descended with modifications from common ancestral species that lived in the past. Characteristics of fit individuals increase in a population over time. Over time, genes for less favored characteristics will be eliminated from the gene pool. Example: giraffes and their increasingly longer necks.
Natural Selection: Survival of the Fittest An adaptation is any inherited characteristic (a genetic variation) that can increase an organism’s chance of survival. An organism does not change because of need or desire to survive. The organism either already has the variation that enables it to survive or it dies. the variation exists first. the environment changes. a variation may give an advantage to survive environmental change.
As the environment changes, organisms must have variations that allow them to survive (adapt) to those changes or die Extinction If an entire population of a species cannot adapt, that species becomes extinct.
There have been at least 5 MASS extinctions during Earth’s history where a huge % of the living species were destroyed Mass Extinction At least one of these has been attributed to meteor impact and it’s consequences.
It is estimated that 1/5 or more of the world’s species will become extinct if the rainforests are destroyed. Many scientists say that the earth is currently experiencing a mass extinction crisis.
What do you think biodiversity is?
ANSWER: the variation of life forms in an ecosystem
How do you think biodiversity would be affected by mass extinction?
ANSWER: biodiversity would decrease significantly
Biodiversity Life Variation
If we are in a period of mass extinction . . . What animals will your grandchildren be able to see in the wild? Visit the World Wildlife Fund website for more information on endangered species. Photos by MartinHarvey World Wildlife Fund International
Works Cited Davis, Donald E. “Meteor Impact”. (Also public domain from NASA.) No date. Online image with permission. Dinosaurs and Their Extinction. June 10, 2004. <http://www.donaldedavis.com/PARTS/DDDINOS.html> “ Snow Alaska”. No date. Online image. Public Domain. Mineral Management Service. June 10, 2004. GeekPhilospher.com <http://geekphilosopher.com/bkg/snowAlaskaIce.htm> “ Clearcut in Cameroon Rainforest”. No date. Online image. June 11, 2004. Earth Crash Earth Spirit. <http://www.eces.org/archive/gallery/forestsgfx/forests39.shtml> Harvey, Martin. No date. Online image. World Wildlife Fund. June 11, 2004. <http://www.panda.org> “ Allosaur”. No date. Online image. Public Domain. Dinosaur National Monument. National Park Service. June 10, 2004. http://www.nps.gov/dino/index.htm