Chapter 15 Darwin and Evolution Darwin a reluctant

Chapter 15 Darwin and Evolution Darwin: a reluctant rebel AP Biology 2006 -2007

Evolution explains the Diversity and Unity of life 1. Diversity – the abundance of different forms of living things on Earth 2. Unity – the biochemical, cellular, genetic, and physiological characteristics/processes common to all living things AP Biology

What is Evolution? v The change in a species over time (i. e. the gene pool changes due to adaptations) 1. The Process: Descent thru Modification new life comes into existence over time all species come from common ancestry all species comes from existing species via modification AP Biology

History of Evolutionary Thought § Carolus Linnaeus (17071778) Taxonomist u Binomial Nomenclature u Agreed with the “fixity of species” theory u However, he performed hybridization experiments which made him think a species might change with time u AP Biology

La. Marck § Organisms adapted to their environments by acquiring traits u change in their life time § Disuse organisms lost parts because they did not use them — like the missing eyes & digestive system of the tapeworm § Perfection with Use & Need the constant use of an organ leads that organ to increase in size — like the muscles of a blacksmith or the large ears of a night-flying bat transmit acquired characteristics to next generation AP Biology u

History of Evolutionary Thought § Alfred Wallace (1823 -1913) § British naturalist § came up with the same theory as Darwin independently u Natural Selection (Survival of the Fittest) § Darwin’s and Wallace’s ideas § were published at the same time But Wallace did not have as much evidence as Darwin AP Biology

Charles Darwin § 1809 -1882 § British naturalist § Proposed the idea of evolution by natural selection: u Organisms that are best fit for the environment, survive and reproduce (“survival of the fittest”) § Collected clear evidence to support his ideas AP Biology

La. Marckian vs. Darwinian view § La. Marck u in reaching higher vegetation giraffes stretch their necks & transmits the acquired longer neck to offspring § Darwin u AP Biology giraffes born with longer necks survive better & leave more offspring who inherit their long necks

Voyage of the HMS Beagle § Invited to travel around the world 1831 -1836 (22 years old!) u makes many observations of nature u § main mission of the Beagle was to chart South American coastline Robert Fitzroy AP Biology

Voyage of the HMS Beagle § Stopped in Galapagos Islands u AP Biology 500 miles off coast of Ecuador

Galapagos Recent volcanic origin most of animal species on the Galápagos live nowhere else in world, but they resemble species living on South American mainland. AP Biology 500 miles west of mainland

Darwin found… birds Collected many different birds on the Galapagos Islands. Finch? Thought he found very different kinds… AP Biology Woodpecker? Sparrow? Warbler?

But Darwin found… a lot of finches Darwin was amazed to find out: All 14 species of birds were finches… But there is only one species of finch on the mainland! Finch? Large Ground Finch? Finch Sparrow? Small Ground Sparrow? Finch How did one species of finches become so many different species now? AP Biology Woodpecker? Warbler Finch Woodpecker? Warbler? Veg. Warbler? Tree Finch

Tree Thinking Descendant species Ancestral species AP Biology Large-seed Large Ground eater? Finch Warbler? Warbler Finch Small-seed Small Ground eater? Finch Leaf-browser? Veg. Tree Finch

Correlation of species to food source Seed eaters Flower eaters AP Biology radiation Adaptive Insect eaters Rapid speciation: new species filling new niches, because they inherited successful adaptations.

Voyage: 1831 -1836 November 24, 1859, Darwin published “On the Origin of Species by Means of Natural Selection” AP Biology

Natural Selection: 4 steps 1. Natural Variation exists in nature 2. Competition - Organisms struggle for 3. 4. survival: more organisms are produced than the environment can support Survival of the fittest: Only the best adapted survives. Adaptations are important Organisms change over time in response to the environment: organisms change but they have a common descent – they have common ancestors AP Biology

Adaptations: inherited characteristics that allow individuals to “do better” in their environment. Adaptations increase their chance of survival and reproduction AP Biology

Types of Natural Selection a. Directional – a shift in the freq. of a trait in a particular direction common in changing env’ts Ex. Horseracing: pick horses that can run fastest AP Biology

b. Stabilizing – selects for avg. pheno. and against extreme pheno. common in stable, unchanging env’t AP Biology

c. Disruptive – selects for extreme pheno. and against avg. pheno. b/c subject to predation AP Biology

AP Biology

Artificial selection This is not just a process of the past… AP Biology It is all around us today

Selective breeding AP Biology

Natural Selection vs. Artificial Selection § Artificial Selection: nature provides variation, and humans select variations that we find useful (domestic animals and crops) § Natural Selection: the environment is the selective force. Only those organisms that are well adapted will AP Biology survive in the wild.

Sexual Selection AP Biology