Why are there so many species? Interactions between species 1. Competition(-/-) 2. Symbiosis(+/+) 3. predation – Parasitism(+/-) 1 – 3 affects evolution, persistence of species, and overall diversity of life

Competitive Exclusion Principle The American gray Squirrel vs the British red squirrel http://www.britishredsquirrel.org/ Red squirrel – hazelnuts Gray squirrel - acorns

Niches: How Species Coexist Flour beetle(Tribolium) experiments – Fig. 7.10 p.130 Ecological niche and habitat – knowledge is helpful in assessing impact of development or of changes in land use Measuring niches – Hutchinsonian niche – described as the set of all environmental conditions under which a species can persist and carry out its life functions See fig. 7.11 – flatworm’s fundamental temperature niche vs realized temperature niche

Symbiosis Beneficial to both organisms Ex) bacteria in our large intestine, bacteria in rumen of reindeer Obligate symbionts

Predation and Parasitism Predation – one organism feeds on another Parasitism – one organism lives off of another a moderately grazed pasture has more species of plants than an ungrazed one

Environmental Factors That Influence Diversity See Table 7.2 p. 133 – Factors that tend to increase vs factors that tend to decrease diversity Biogeography – the large-scale geographic pattern in the distribution of species

Why Preserve Biodiversity? See list of values on p. 135 How are we protecting our resources? http://evolution.berkeley.edu/evosite/relevance/IIIC1Why.shtml http://today.msnbc.msn.com/id/46602078/ns/today-today_people/t/doomsday-vault-holds-seeds-could-save-world/#.T3KonGDqrbr