Community Ecology and Ecosystems

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Transcript Community Ecology and Ecosystems

Chapters 54
Concept 4: Community Ecology – Analyzing the interactions and
relationships within and between species and the effects of
environmental factors on species diversity and composition.
 Community Ecology (Ch 54)
 The difference between a fundamental niche and a
realized niche
 The role of competitive exclusion in interspecific
 The symbiotic relationships of parasitism, mutualism,
and commensalism
 The impact of keystone species on community structure
 The difference between primary and secondary
Review – Define the following!
 Population
 Community
 Ecosystem
 Biome
 Biosphere
 Habitat
 Niche
 Population – a group of individuals all of the same species living
in the same area
Community – a group of populations living in the same area
Ecosystem – describes the interrelationships between the
organisms in a community and their physical environment
Biome – a major ecosystem, classified by the predominant
vegetation and characterization of adaptations of organisms to
that particular environment
Biosphere – composed of all the regions of the earth that
contain living things.
Habitat – type of place where an organism lives
Niche – all biotic and abiotic resources in the environment used
by an organism.
Try This
 What are four factors that may limit the geographic
distribution of a species? Give an example of each of
the factors.
Try This
 What are four factors that may limit the geographic
distribution of a species? Give an example of each of
the factors.
- Dispersal: an area may be beyond the dispersal ability of a
- Behaviour and habitat selection: insect larvae may be able to
feed on more plants, but females oviposit on a single type of
- Biotic factors: the presence of predators or competitors may
restrict a species’ range
- Abiotic factors: climate (sunlight, water, temperature, wind)
may determine whether a species can inhabit an area
Community Ecology
 Community Ecology is concerned with interspecific
interactions (relationships between populations of
different species).
 We will look at three types of community interactions:
1. Interspecific Competition – competition between
different species for resources
2. Predation – partial or complete consumption of a
plant or animal
3. Symbiosis – two species living in close contact
Community Ecology
Interspecific Competition
exclusion principle
(Gause’s principle)
True predator
(niche shift)
Realized niche
Interspecific Competition
How do the following principles relate to each other?
What are some examples?
 Competitive Exclusion
 Resource Partitioning
 Character Displacement
 Fundamental Niche vs Realized Niche
Interspecific Competition
 Competitive exclusion principle (Gause’s principle)
 States that no two species can
occupy the same niche
 In other words, if two species
are competing for exactly the
same resources, one is more
likely to be successful
 Example: Paramecium
Interspecific Competition
 Resource Partitioning
 When some species
coexist in spite of
apparent competition
for the same resources
 These species occupy
slightly different niches!
 Example: five species
of warblers coexist in
spruce trees by feeding on insects in different regions of
the tree and by using different feeding behaviours to
obtain the insects
Interspecific Competition
 Character displacement (niche shift)
 A result of resource partitioning
 Selection for characteristics that
enable individuals to obtain
resources in their partitions
more successfully
 Example: Two similar species of
Finches coexist on the same island
in the Galapagos; both eat seeds.
One has a beak specialized for
small seeds, one has a beak specialised for larger seeds
Interspecific Competition
 Realized Niche
 In absence of interspecific competition,
a species will occupy its fundamental niche
 In presence of interspecific competition,
one or both species may be able to exist
by occupying its realized niche,
taking out any overlap
 Example: barnacle species C
can experimentally live on the
entire intertidal. In the natural environment barnacle
species B outcompetes C at the lower tide levels. C will
survive in its fundamental niche: the higher tide levels.
How do the following principles relate to each other?
What are some examples?
 True Predator
 Herbivory
 Parasite
 Parasitoid
 Adaptations
 Cryptic vs. Warning Colouration
 Mullerian vs Batesian Mimicry
 True Predator
 Kills and eats an animal
 Most predators have adaptations such as acute senses,
speed, agility, claws, teeth, fangs, stingers, or poison
 Prey defenses include hiding, fleeing, forming herds or
schools, self-defense, and alarm calls
 Shark preying on seals (BBC)
 Herbivore
 Animal that eats plants
 Includes granivores (eat seeds), grazers (eat grasses),
borrowers (eat leaves)
 Leads to adaptations as well!
Ex) plants may produce toxic chemicals
- Tannins, nicotine, morphine, the flavours of cinnamon,
cloves, peppermint
 Parasite
 Spends most or all of its life living on another organism
(the host), obtaining nourishment by feeding on its
 Endoparasite: live within their host
Ex) tapeworms, malarial protist
 Ectoparasite: feed on the external surface of their host
Ex) mosquitoes, aphids
 Parasitoid
 Special kind of parasite (insects) that lay eggs in or on
living hosts. Eggs hatch and larvae feed on body of
living host… eventually killing it.
 Ex) some small wasps
Video: National Geographic
(2 min)
 Fungus Video!:
Predation - Adaptations
 Cryptic colouration, or camouflage, makes predator
or prey difficult to spot
 Ex) fur of snowhare is white in winter,
brown in summer
 Ex) canyon tree frog
 Warning colouration, or aposematic
colouration, warns predators
 Ex) Black and Yellow bees = DANGER!
 Ex) Poison dart frog
Predation - Adaptations
 Mullerian mimicry
 Several animals, all with the
same defense mechanism,
share the same colouration
Ex) bees, yellow jackets, wasps
 Batesian mimicry
 An animal without any special
defense mechanism mimics the
colouration of one that does
Ex) defenseless fly
“pretending to be a bee”!
Ex) larvae mimicking a
poisonous snake
How do the following principles relate to each other?
What are some examples?
 Mutualism
 Commensalism
 Parasitism
 Mutualism
 Relationship in which both species benefit (+,+)
Ex) lichens: fungi and algae!
Ex) clownfish and sea anemones
Ex) Ocean sunfish and birds
 Many have evolved from predator-prey or parasite-host
Ex) flowering plants attracting animals to pollinate or
disperse seeds
 Commensalism
 Relationship in which one species benefits, while the
seond species in neither helped nor harmed (+,0)
 Ex) birds building nests in
 Ex) egrets gathering around
 Examples difficult to find
in nature
 Parasitism
 Relationship where the parasite benefits, while the host
is harmed (+,-)
 Note: Some Biologists prefer to use the term symbiosis
for mutualism or commensualism only.
 The evolution of one species in response to new
adaptations that appear in another species
 Ex) specific pollinators of specific plants
 In reality, very hard to find evidence in nature for
TRUE coevolution!
 Why? – Most adaptations are in response to a category
of organisms, rather than coupled interaction between
just two species.
 ie) lions have depth perception as an adaptation to
hunting many species, not just another!
 ie) warning colour of tree frogs to alert many predators
 Although true examples or coevolution is difficult to
find, most biologists agree that interspecific
interactions lead to evolutionary adaptations through
natural selection…
 Predation and Competition are the key processes
in driving community dynamics.
 Summary of adaptations:
 Secondary compounds in plants (poisons), camouflage
(cryptic colouration), aposematic colouration (warning
colouration), Mullerian mimicry, Batesian mimicry,
coevolution of pollinators and plants
Try This
 What kind of mimicry do the following represent?
 Harmless species resembles a poisonous or distasteful
 Mutual imitation by two or more distasteful species
Try This
 What kind of mimicry do the following represent?
 Harmless species resembles a poisonous or distasteful
Batesian mimicry
 Mutual imitation by two or more distasteful species
Mullerian mimicry
Try This
 Two species, A and B, occupy adjoining environmental
patches that differ in several abiotic factors. When
species A is experimentally removed from a portion of
its patch, species B colonizes the vacated area and
thrives. When species B is experimentally removed
from a portion of its patch, species A does not
successfully colonize the area. What might you
conclude from the results?
Try This
 What might you conclude from the results?
 Species A is limited to its range by abiotic factors, and
species B is limited to its range because it cannot
compete with species A.
 Species A is living in its fundamental niche, while
species B is living in its realized niche.
 Species A’s fundamental niche and realized niche are the