Transcript Why are there so many species?

Why are there so many species?
Interactions between species
1. Competition(-/-)
2. Symbiosis(+/+)
3. predation – Parasitism(+/ -)
1 – 3 a f fe c t s evo l ut i on, p e rs i s te nc e o f s p e c i e s,
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/III
C1Why.shtml
 http://today.msnbc.msn.com/id/46602078/ns/toda
y-today_people/t/doomsday-vault-holds-seedscould-save-world/#.T3KonGDqrbr