Transcript Darwin
Connect! • Who was Gregor Mendel? • What contributions did Mendel make to the science of biology? • Give 5 facts about Charles Darwin. B. THEORIES OF EVOLUTION • Theories of evolution attempt to explain the diversity among species. • A major part of these theories are adaptations. Adaptations are features (structure, function, or behavior) which make a species better suited to live and reproduce in its environment. Darwin’s Theory • is based on variation and natural selection • developed after he observed variations in species. • According to Darwin, evolution occurs because of natural selection; organisms better adapted to the environment survive and reproduce while others do not. Chunk! • What does the Theory of Evolution attempt to explain? • Define adaptation, and give an example. • What did Darwin base his theory on? • Explain evolution in terms of variations, adaptations, and natural selection. Ideas in Darwin’s Theory: 1. Overproduction – Within a population, more offspirng are born than can possibly survive. 2. Competition – Because of overproduction, there is a competition of a “struggle for existence” between organisms for space, food, water, or other limited resources. Competition limits population size. 3. Variation – Members of a population show variations or differences in traits that make certain individuals better adapted to survive (usually a structure, function, or behavior) 4. Natural Selection – Since some variations are more beneficial than others, there is natural selection against organisms that cannot adapt and they die off. “Survival of the fittest” applies to the individuals who have variations that enable them to survive. 5. Transmission of Variations – Organisms with helpful variations are more likely to survive and reproduce, passing on these variations to their offspring. 6. Speciation – Over long periods of time, variations accumulate in a population. Eventually, the variations are so numerous that the population is different from the original, and represents a new species. Chunk! • Name the 6 parts to Darwin’s Theory. • Give an example of each. Darwin’s Finches • How did all these species of finch come to exist on the tiny Galapagos Islands? Adaptive Radiation in Galapagos Finches • THINK…why do you think this is called “adaptive radiation”? Learn how to read this chart… • • • • • Name two species that do not have to compete for their food. Which species does the warbler finch have to compete with? Why doesn’t the small ground finch compete with the small tree finch? What species does the large ground finch have to compete with? Why? What do the woodpecker finch, warbler finch and cactus finch have in common? • Although variations were a major part of Darwin’s Theory, he did NOT understand the basis for variations. Some variations help in survival, and are passed on to offspring! Inherited factors can make offspring different! • Explain the science behind this cartoon. DYGI? (Do Ya Get IT?!) Image Sources • • • • • • • • • • • • • Darwin - selfexpressions.net/.../CharlesDarwin.jpg Bird adaptations - animals.howstuffworks.com/.../printable Baby snakes - fohn.net/.../baby-corn-snakes.jpg Two snakes, winning snake - static.flickr.com/67/188076925_0c695850e3.jpg Color variations - aqualandpetsplus.com/Snake94.jpg Albino - grandpacliff.com/.../albino-snake-pine-b.jpg Snake species - www.scielo.br/.../jvatitd/v15n4/a06fig02.jpg Photos of Darwin’s finches - www.galapagoscruises.be/darwins-finches.jpg Adaptive radiation - media-2.web.britannica.com/eb-media/11/54911-. Chart - www.pbs.org/.../01/6/images/l_016_02_l.gif Darwin clip art (modified from) - evolution.berkeley.edu/.../darwin_cartoon.gif Mendel redwood cartoon - members.pioneer.net/~mchumor/00images/1818_fo. Mendel clipart - www.larrygonick.com/images/sch/mendel.gif