Patterns in Communities

1
Patterns in Communities Succession
2
Species Richness

• Species richness number of species in a
  community
• Species evenness relative abundance of species
• Biodiversity the variety of life forms in an
  area

3
Diversity

• Genetic diversity is the variety of genetic
  information
• ecosystem diversity is the variety of different
  ecosystems in the world

Diversity of different groups of organisms
4
Latitude and habitat size

• Latitude impacts species richness
• The closer to the equator the greater the species
  richness
• Hypothesis Ice age, climate stability, year
  round photosynthesis (see textbook for details)
• The increase in species richness as habitat area
  increases is know as the species- area effect
• Habitat loss decrease in species richness

5
Factors that impact species richness

• Species interactions a predator can prevent
  completive exclusion among prey species
• Disturbance flood, fire, clear cutting, plowing,
  non-native species all disrupt communities
• Some communities are more stable, resistant to
  disturbance.

6
Why biodiversity is important

• Food
• There are 80,000 edible wild plant species that
  could be use by humans
• Medical
• Over 50 of all medicines contain natural
  products

7
Ecological services

• Nature does thing that would cost trillions of
  dollars for humans to do
• provide clean water
• maintain healthy soils prevent erosion
• control pests disease-carrying organisms
• Buffer against storms
• Pollinate crops

8
Succession

• A series of predictable changes to an ecosystem,
  in response to natural or human disturbances

9
Primary succession

• begins where no soil exists, change is slow
• Pioneer species such as lichen and moss create
  soil
• Later grasses and other annual plants move in
  along with insects and the animals that eat them.

10
Secondary succession

• change after a disturbance like fire or farming
• Soil still exists
• Shrubs replace grasslands
• Trees replace shrubs
• Climax community is the last stage (forest
  community)
• Until the habitat is disturbed again

11
Summary review

1. What is the difference between species richness
   and species evenness?
2. What factors influence biodiversity?
3. Name the ecological services nature provides.
4. What is the difference between primary and
   secondary succession? Describe the types of
   communities at each stage of succession.
5. Reflect on the importance of natural disturbance
   and why human disturbance is different.