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Species Interactions &
Community Ecology
Environmental biology
Case Study
 Mussels & the Great Lakes
Border of US and Canada
5 giant lakes & a number of small ones
These were formed by the last Ice Age
More polluted in the past
Took ‘Big Government’ intervention to clean up Clean Water act, 1970
Arrived by ship from Europe

Case Study cont…
 Within 2 years the mussels had established
themselves in all the Great Lakes
 Then spread even further to the great
Mississippi River Watershed - 40% of US
land mass.
 Their main limiters were absent here
Predators
Competitors
Parasites
Case Study cont…….
 IMPACT
 = Economic mostly
 = industrial interference
 = infrastructure damage
 = Ecological
 = Overeat the native phytoplankton
 = Kill local molluscs
 = Alter local ecology towards bottom dwellers
 Permit more light penetration
 Deposit organic matter on bottom
Case Study cont…….
 However, recently they are being
replaced by another species
 Quagga mussel is moving in
 It is reducing the zebra mussels
 What impact this new one shall have?
We will have to wait and see….
INVASION!!!!!
 Look up and see. They are coming…
 ___________
What is ecology?
 The study of how organisms interact
with each other and their physical
environment.
Species Interactions
 Species interact with each other
 Many ways have been studied and
documented
 Some are beneficial to both species
 Other to one or the other
 And some to neither….
Species interaction types
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Competition
 Intraspecific - within a species
Example = _______________????
 Interspecific - between species
Example = _______________????
 Solution is resource partitioning =
basically sharing by adapting
 There is a total negative effect on both!
Predation
 One species kills the other to live
 Predator is the killer
 Prey is the victim
Example = _______________????
 Drives evolution - Natural selection
 These interaction are direct and do
generally cycle…
Figure 5.2
Parasites
 No immediate death involved
Example = _______________????
 Parasite depends on the host for food
and shelter
 The host is harmed to some degree!
 The parasite benefits entirely
 Co-evolution also works here
Herbivory
 Animals feed on plants
 Insects on plants
Example = _______________????
 Plant does not die (at least not initially)
 Plants defend themselves too
Example = _______________????
 Evolutionary Arms Race!
Mutualists
 Both are good for each other
 Provide other with something it needs
Example = _______________????
 Symbiotic
Example = _______________????
 Pollination
Example = _______________????
Ecological Communities
 Each has its;
 Producers - make food
 Consumers  Primary - grasshoppers
 Secondary - frogs
 Tertiary - birds
 Decomposers - Nonliving organic consumers
 recyclers
Food chains & Energy
 As one feeds on another, in a community,
there is a relationship built - this is known
as the food web.
 As one moves further away from
produces then amount of energy available
is reduced (by 90% per level)
 Energy Pyramid
Keystone Species
 If you were to eliminate a single
species from a community and see the
effects of that action, one would notice:
 Most have little impact
 One will devastate the ecosystem
This one species is the keystone species
Example = _______________????
Ecological Succession
 A new volcanic island will be populated
by life in a predictable way;
Primary succession - No life at beginning
Primary species = first
Example = _______________????
Secondary succession - Some form of life
or organic matter remains - and it starts
with that.
WATCH ME!
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Biomes
 What are they?
 Just regions of the planet with certain
similar communities of life.
 The Earth has 12 such regions
 http://www.youtube.com/watch?v=ag5A
TGEplbU
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Biomes…
 In general, there is no sharp
demarcation between biomes.
 Life on Earth is a continuum based on
moisture and heat…
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Other Biomes…
 Also, there are aquatic biomes too…
 These are considered later in the
course