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They are not absolute, can be changed as new evidence is found
Why do so many different animals have the same structures, the arm bones in a human are the same bones as a flipper in a whale?
Why is the sequence of DNA very similar in some groups of organisms but not in others?
Why do the embryos of animals look very similar at an early stage?
Photo courtesy of Swamibu, Flickr Creative Commons
Charles Darwin developed the THEORY OF EVOLUTION BY NATURAL SELECTION
which explained how organisms changed over time (ADAPTED)
Lamarke's Theory of Acquired Characteristics
Some thought that you would gain or lose features if you overused or didn't use them,
PROVEN TO BE WRONG!
Photo courtesy of ucumari, creative commons, flickr
Darwin was a naturalist (what we today call biologists)
He traveled the world and made observations and sketches of many species
His most famous travels were aboard the H.M.S. Beagle where he traveled to the Galapagos Islands
Marine Iguana, photo courtesy of mtchm, flickr creative commons Blue-footed booby, photo courtesy of stirwise, flickr creative commons
Finch, photo courtesy of stirwise, flickr, creative commons Giant tortoise, photo courtesy of Planetgordon, flickr creative commons
Darwin noted that there existed many finches on the islands, but while they had similarities, each was adapted to eating a particular type of island food
He concluded that the finches all came from one ancestral species and evolved into many new species
Cactus finch, photo courtesy of zrim, flickr creative commons
Darwin published this work to explain the variety of species that exist on the planet
He proposed the “Theory of Evolution by Natural Selection”
1. Variation exists among individuals in a species.2. Individuals will compete for resources (food, mates, and space)3. Competition would lead to the death of some individuals while others would survive4. Individuals that had advantageous variations are more likely to survive and reproduce. This process came to be known as Natural SelectionThe favorable variations are called Adaptations Photo courtesy of digitalART2, flickr creative commons
Say in a species of blob….there exists blobs of all shapes and sizes (variation)
Blobs eat the little purple organisms that live underground and on the surface.
During a particularly hot year, food became less abundant (competition), blobs that had the ability to dig into the soil to get food had a better chance of survival. Many blobs died that year…….
The ones that survived mated and passed their genes to the next generation. (reproduction)
The next generation had move blobs with the pointed noses. That is NATURAL SELECTION. Variation Competition Survival Reproduction
Shows numbers extinct animals
Shows similarities between extinct animals and animals that are alive today
The earth’s layers show a time scale of species and when they appeared on earth (and when they died out)
Dinosaurs have always fascinated us, movies such as Jurassic Park capitalize on that fascination. How do we know what dinosaurs looked like? We create a picture based on the bones we find (fossils) and use modern reptiles to guess at their texture and skin color.
Homologous structures – these are parts of the body that are similar, but have different functions
ex. The flippers of whales, and the wings of birds All forelimbs of vertebrates have the same pattern of bones • Common ancestry
Vestigial Organs – these are organs or parts that seem to have no function
Whales have pelvic bones that do not attach to legs
Biochemistry and DNA
When comparing the DNA of one species to another, more similarities are found in species that are more closely related. Lion photo credit: ucumari Tiger photo credit: digitalART2
Embryological Development Embryos of different species develop in almost identical ways. Human fetus at 8 weeks
Direct observation of species change Bacteria become resistant to antibiotics Wolves were bred over many generations to become dogs (artificial selection) • and then bred further to create a variety of breeds
Creationism, sometimes referred to as “creation science” or “intelligent design” is the belief that organisms were placed on this earth by a divine being (God).
It is NOT a theory because it does not follow scientific principles (theories require evidence, and must be based on NATURAL PHENOMENON)
Finding gaps in our knowledge about evolution is a normal part of the scientific process, the existence of these “gaps” and questions does not qualify as evidence that an alternative theory must be correct
Many religious organizations do not have a problem with evolution, and it is compatible with their faith and beliefs.
Ask your religious leaders what their thoughts are.
Also see the National Center for Science Education for a list of statements from a variety of religious groups.