Download Species - a group of individuals that is able to breed with each other

Species - a group of individuals that is able
to breed with each other
Population - any group of organisms of the
same species in a particular space
Community - a group of organisms living
in a given area, an assemblage of
populations of different species living
close enough for potential interactions
Characterizing and describing communities
requires us to focus on the distribution and
abundance of different species that exist as
recognizable ecological units.
• “Community” as a spatial concept
- depends a lot on researcher’s perception of
environmental variability
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Factors that influence community
development:
• physical habitat - light, temperature, moisture
• chemical environment - pH, nutrients
• biotic interactions - either with other
individuals of the same species
or with other species
Types of biotic interactions:
Intraspecific
interactions between members of the same
population (= population dynamics)
Interspecific
interaction between populations of different
species living together (= community dynamics)
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Interaction type
Description
Neutralism
Predation
(includes herbivory)
Neither population affects the other.
One organism uses another for a food source.
Predator (pop. 1) usually larger than prey (pop. 2)
Parasatism
Competition
Population 1
Population 2
0
+
0
-
One species benefits while the other is harmed
(though usually not killed). Parasite (pop. 1)
usually smaller body size than the host (pop. 2).
+
-
Occurs within or between species that share a
limiting resource. Negative affect on both
populations.
-
-
Amensalism
Commensalism
One species is harmed or inhibited by the other.
Benefitial to population 1 (the commensal) but
neutral or of no benefit to population 2.
+
0 or +
0
Protocooperation
Both species benefit,
not required for existence.
+
+
Mutalism
Both species benefit,
obligatory relationship.
+
+
orange text = antagonistic interactions
green text = beneficial interactions
Parasitism:
a relationship between two species in which one
benefits (parasite) at the expense of the other
(host).
a parasite draws nourishment from the live body
of another species
e.g.
fleas, ticks, tapeworms, aphids, mistletoe,
most fungal and bacterial infections/diseases
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Predation:
also relationship between two species in which
one benefits (predator) at the expense of the
other (prey).
a predator draws nourishment from the
dead/killed body of another species.
e.g.
herbivory,
lion attacking a deer,
hawk feeding on a sparrow
Big Problem with Introduced and Invasive Species
Normally, host & parasite and prey & predator have co-evolved …
• host/prey has some measure of defense against the parasite/predator
• parasite/predator not as virulent and lethal so as to either not kill off the host
or to not so drastically reduce the numbers of prey that they disappear
altogether (much more so for specialist, less so for generalists).
But introduced and invasive species are especially virulent and destructive
because they usually co-evolved elsewhere with a different set of defenses and
attacks with similar related host/prey species, but the “new” hosts/prey never
evolved those defenses and get “taken out” much more effectively, sometimes
to the point of extinction.
• Chestnut blight and Hemlock wooly adelgid (from Asia to E. USA)
• Brown tree snake (from Solomon Islands, New Guinea, N. & E. Australia,
E. Indonesia to Guam and other Pacific Islands)
• Cane Toads (from Cuba and Caribbean to Brisbane and Florida)
• Gypsy Moths (Asia & Europe to US)
• Rabbits (and Myxomatosis via mossies and intro’d fleas) in Australia
• Kudzu
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Model of the vegetation-herbivore-predator
cycle involving the snowshoe hare and lynx.
Competition:
any interaction that is mutually detrimental to both
participants, within or between species that share
limited resources
e.g.
• Lions and hyenas competing for zebra carcasses
• Animals competing for foraging territories and
breeding and nesting/denning sites
* Fast growing trees intercept light and shade out
plants beneath their canopy
** Bigger trees with larger root systems taking up
relatively more water than smaller understory
trees with smaller root systems
* Asymmetrical competition
** Symmetrical competition
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Competition can be:
intraspecific -
between members of the same
species / population
interspecific -
between different populations
of different species
competition occurs when 2 or more groups use the same
limiting resource (e.g. food, water, space, light)
Competition is density dependent when more organisms desire a limited resource,
competition for it is more intense.
the more similar the requirements of the two
groups (the more similar their niches), the more
intense the competition.
This can lead to the mutual exclusion of competing
species, instead of coexistence.
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The ecological niche:
fundamental role an organism plays in a community
what does an organism do?
what does an organism require to survive?
what is its relationship to food and enemies, etc. ?
“Niche” describes the way an organism interacts
with all the biotic and abiotic factors in the
environment.
“functional niche” – what it does in the ecosystem
“resource niche” – what it requires
Niche overlap:
what happens if two or more species use a portion
of the same resource (e.g. food) simultaneously?
= more intense competition
Competitive exclusion principle:
“Complete” overlap cannot occur
two species with identical needs for the same limiting
resources cannot coexist in the same place
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Outcome of competitive exclusion:
1. Extinction
2. Habitat restriction /
Resource partitioning
3. Character displacement
— phenological changes in the morphology of
individuals in the population depending on
whether or not the competitors are typically
present or not.
1. Extinction
Two species of paramecium in direct competition both do not persist.
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P. aurelia (alone)
P. aurelia (mixed)
80
P. caidatum (alone)
60
40
20
0
P. caidatum (mixed)
0
2
4
6
8
10
12
14
16
18
Time (days)
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2. Habitat restriction/ Resource partitioning:
Feeding zones in a spruce tree of 5 species of warbles.
Cape may
warbler
Yellow rumped
warbler
Black throated
warbler
Bay breasted
warbler
Blackburnian
warbler
Partitioning of the soil resource by a group of desert
plants, different root systems develop to minimize
competition for water.
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Spatial zonation based on environmental tolerances and competitive ability
3. Character
displacement:
Beak sizes of
ground finch,
different beak
morphologies
allow the two
populations to
consume different
foods.
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Commensalism:
a relationship between two
species that is beneficial to
one, but neutral or of no
benefit to the other.
e.g. epiphytes (plants that
grow on the branches of trees)
- they depend on the tree for
support only, their roots draw
nutrients from the humid air.
Protocooperation:
a relationship between two populations where both
benefit
association is not required for either to survive
e.g.
sea anemones sometimes take up residence on the
back of a hermit crab’s shell
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Mutualism:
a relationship between two species where both
benefit. continued association is required for
either to survive.
e.g.
termites and bacteria (in termite guts)
lichens (blue-green algae and fungi)
Diversity or Biodiversity
describes complexity of interactions in a community
composed of:
richness - number of species in a community
evenness - compares the relative abundance
of different community members
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Community 1:
25 A
25 B
25 C
25 D
Community 2:
97 A
1B
1C
1D
equal richness (same number of members)
different relative abundances (evenness)
Stability
absence of fluctuation in a system
Resistance and Resiliency
ability of a system to resist change or to recover
rapidly after a disturbance
Some ecosystems may be very stable due to lack of disturbance or
because it takes a relatively big strong disturbance to push the m out
of equilibrium and to have any significant effect (= hi resistance),
BUT once sufficiently disturbed they may have very little ability to
quickly recover (if at all) back to the original state (= lo resiliency).
Other ecosystems may be less resistant but more resilient.
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