UH GEOL 1376 - Geol Lecture 6 (2 pages)

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9 11 14 Cont of Chapter 3 What did Darwin see many South American animals are endemic to South America only live there Darwin collected fossils of their ancestors in the Cenozoic Patagonian Evolutionary convergence pattern in which dependence of distant relatives grow to resemble each other similar ways of life have experienced similar natural selection Galapagos islands volcanic archipelago 600 miles off coast of Ecuador oceanic on Cocos hot spot never connected to mainland populated by castaways blown or rafted from mainland South America large and small islands diverse habitats separated by straits of varying widths contemporary biographic theory explained why each region has a distinctive set of inhabitants local geologic climatic and environmental conditions influence organisms living there regions with similar rocks and climate ought to have similar organisms But Galapagos though volcanic and arid like Cape Verdes have entirely different inhabitants 550 plant species on Galapagos 250 are endemic known nowhere else Dispersal spread in space Passive dispersal hitchhickers wind blown seeds Dominant trees composite sunflowers daisys marigolds dandelions weeds in highlands cactus in arid coastal region Fauna is dominated by reptiles better at passive dispersal than mammals other lizards feed on cactus Large grazing herbivore galapagos tortoise overgrown cousin of small tortoise descendent of small West Indies tortoise Only terrestrial birds 13 species many confined to one island descended from one ancestral emigrant from South America Many feeding habits reflected in shape of beak Evolutionary divergence descendants of one ancestor developed different adaptations and became less similar Evolutionary convergence Adaptive radiations adapted many different ways of life Endemism encouraging divergence some species can only be on one island Galapagos finches geographic isolation natural selection new species insects and land snails show similar phenomena Darwin married