Download Species Richness: The number of species present in a community

Chapter 5
Ecosystems and Living Organisms
Lake Victoria, East Africa
What Happened to Lake Victoria?
Nile Perch
Cichlids
Deforestation
Evolution:
A genetic change in a population of
organism that occurs over time.
Charles Darwin
The Origin of Species by
Means of Natural Selection
(1859)
What Did Darwin Suggest?
• Inherited traits favorable to survival in a given
environment would tend to be preserved and
unfavorable ones would be eliminated.
• Adaptations: Evolutionary modifications that
improves the chances of survival and
reproductive success of the population in a
given environment.
What Doe Natural Selection Involve ?
Those individuals with a combination of genetic
traits better suited to environmental conditions
are most likely to survive and reproduce.
Four components of Natural Selection: (page 82)
1. overproduction
2. variation
3. limits on population growth , or a struggle
for existence
4. differential reproductive success
Interactions among Biological
Communities
• Read the Envirobrief – page 85
• Resource – anything from the environment
that meets a particular species’ needs
• Make a flow chart identifying the chain of
events that occurred in the Northeastern
United States.
What Were the Interactions
• Bumper acorn crops ---- large mouse
populations
• Mice eat gypsy moth pupae
• Gypsy moths cause defoliation of oak leaves
• Abundant acorns attract tick-bearing deer.
Ticks’ offspring feed on mice
• Mice carry Lyme disease – causing bacterium
–which can be transmitted to humans being
bitten by an infected tick/
How do Species Interact?
• Interspecific competition
• Predation
Symbiosis:
* parasitism
* mutualism
* commensalism
How Species Interact
• Interspecific competition – occurs when parts
of the fundamental niches of different species
overlap
Species must….
a. migrate to another area
b. shift its feeding habits or behavior through
natural selection and evolution
c. suffer a sharp population decline
d. become extinct in that area
Species compete in two ways…
Interference competition – one species may
limit another’s access to some resource
Defend territory – release chemicals, chase away,
stinging
Species compete in two ways…
• Exploitation competition – competing species have
roughly equal access to a specific resource but differ
in how fast or efficiently they exploit it
The faster you eat… the more you get!.
Let’s Practice
1. Some plants displace others by having leaf
and root systems that allow them to absorb
more sunlight and soil nutrients than their
competition.
2. Other plants produce chemicals that inhibit
the growth or germination of seeds of
competing species.
Competitive Exclusion
Two species that require the same resource
cannot coexist indefinitely in an ecosystem in
which there is not enough of that resource to
meet the needs of both species.
How do Species Avoid or
Reduce Competition
Resource Partitioning
Character Displacement
Predator–Prey Relationships
• Ways to get lunch – pursuit, ambush
• How to get away
– Protective mechanisms – run fast, keen eye sight
– Camouflage
– Chemical warfare
– Warning coloration
– Mimicry
– behavioral strategies
– Protection from living in large groups
Symbiotic Species Interactions
Parasitism
Mutualism
Commensalism
Range of Tolerance
Limiting Factors
Species Richness: The number of
species present in a community
What determines species richness?
1. Abundance of ecological niches
2. Greatest at the margins of adjacent communities
ecotone – a transitional zone where two or more
communities meet
edge effect- the change in species composition
produced at ecotones
3. Inverse relationship to the geographical isolation of a
community.
4. Reduced when one or more species is dominant in a
community
5. Inversely related to the stress on a habitat
6. Geological history – (climate changes)
Species Richness: The number of
species present in a community
• Tropical Rainforest and
coral reefs have
extremely high species
richness.
• Isolated islands and
mountain tops have low
species richness
Geographical
Isolation
Ecosystem Stability
• Ecosystems with greater species richness are better
able to supply ecosystem services – environmental
benefits, such as clean air, clean water, and fertile
soil.
• Community stability – the ability of a community to
withstand environmental disturbances, have more
species richness.
Example:
• monocultures and pest vs. blight on a specific trees
in a forest of other species