The Pace of Evolution The standard view since

The Pace of Evolution • The standard view since Darwin was that evolutionary change occurred extremely slowly – Gradualism -- Imperceptible changes accumulate such that, over thousands or millions of years, major changes could occur • In 1972, Niles Eldredge and Stephen Jay Gould proposed the Punctuated Equilibrium hypothesis – Evolutionary change occurs in bursts separated by long periods of little or no evolutionary change (termed stasis)

Biodiversity • Speciation is responsible for the vast number of species that we have on earth today • Biodiversity: the variety of all forms of life, from genes to species, through to the broad scale of ecosystems

How is Biodiversity Measured? • Look at the different number of “things” present – Number/types of genes in a population – Number/types of forms of a phenotype – Number/types of organisms in a community – Number/types of microclimates in an ecosystem – More?

Biodiversity “Hot Spots” • A biodiversity hot spot – Is a relatively small area with an exceptional concentration of species – Unique geographic/geologic/climactic features – Threatened with degradation/destruction due to direct or indirect human activities – Other characteristics. . . ?

Equator Tropical forest hot spots Chaparral hot spots Figure 20. 17

Why is Biodiversity Important? • Species and Populations rely on Biodiversity to survive in Nature – The more genetically diverse a species (i. e. the greater the variation in DNA characteristics from individual to individual), the more robust it will be in withstanding the environmental changes

Why is Biodiversity Important? • Humans rely on biodiversity for – Food, clothing, shelter – Oxygen, soil fertility, medicinal substances Figure 20. 16

Why is Biodiversity Important? • About 40% of the drugs and other pharmaceuticals on which our modern medicine relies were developed in some way from the genetic resources of wild plants and animals (often from weeds or things that are poisonous to us)

Why is Biodiversity Important? • Some 90% of all our current foodstuffs were domesticated and cross-bred from wild stock found by trial and error by experimenting farmers & we principally use about 30/70, 000 edible species.

Why is Maintaining Biodiversity Important? • The loss of diversity – Limits the potential for new discoveries of food and medicine – Reflects large-scale changes in the biosphere that could have catastrophic consequences