Transcript Patterns in Communities - Sonoma Valley High School

Patterns in Communities &
Succession
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
Diversity
• Genetic
diversity is the
variety of
genetic
information
• ecosystem
diversity is the
variety of
different
ecosystems in
the world
Insects
54.4%
Protists
4.2%
Other Animals
19.7%
Plants
18%
Fungi
3.4%
Bacteria
0.3%
Diversity of different groups of organisms
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 known as the species- area effect
– Habitat loss = decrease in species richness
Factors that impact species richness
• Species interactions: a
predator can prevent
competitive exclusion
among prey species
• Disturbance: flood, fire,
clear cutting, plowing,
non-native species all
disrupt communities
– Some communities are
more stable, resistant to
disturbance.
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
Ecological services
•
•
•
•
•
Nature does things 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
Succession
• A series of
predictable changes
to an ecosystem, in
response to natural or
human disturbances
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.
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
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.