Download Interaction in Ecosystems

Interaction in Ecosystems
Biotic Interactions
2.
Symbiotic Relationships
3.
The costs, benefits and
consequences of interactions
1.
Interactions between species
Type of Interaction
Effect on population
density
Parasitism
+/-
Commensalism
+/0
Mutualism
+/+
Predation
+/-
Competition
-/-
Maintaining symbiotic relationships
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Symbiotic relationships are affected by both
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Biotic factors e.g. host health
External factors e.g. environmental conditions
Both must be suitable to maintain the
symbiotic relationship, if one is changed the
balance of the relationship may change
E.g. ….
Managing symbiotic relationships
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Humans can manage their symbiotic
relationships with other species
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E.g.
Humans can manage symbiotic relationships
between other species
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E.g.
Interactions with the environment
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Organisms respond to changes in the
environment in 2 main ways
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Conformation
Regulation
Conformation
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Conformers internal body conditions change with
environmental changes
Conformers may have strategies that lead to tolerance
and resistance to the environmental changes
Tolerance is the ability of an organism to withstand
variations in environmental conditions
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This usually involves physiological changes
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E.g. Changes in the production rate of glomerular filtrate
Tends to be a temporary adaptation
Conformation cont…

Resistance to environmental changes results
from more overt strategies. In addition to
physiological changes, it involves
morphological and behavioural changes, that
may be longer term
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E.g.
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growth of winter coat (morphological)
Active only at night (behavioural)
Conformation cont…
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Conformers are restricted in the habitats that
they are able to survive in
These tend to be habitats where any
environmental changes are small, occur over
long times or are regular
Conformation cont…
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Example 1 – osmoconformers
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These organisms have the same osmotic potential as their
surrounding environment
The concentration of jellyfish body fluids changes with the
salinity of the seawater.
Note salt concentration of seawater does not vary much
over a short period of time
Example 2 – poikilotherms

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Have a body temperature that fluctuates with the
environment (cold-blooded organisms or ectotherms)
Reptiles
Dormancy
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Dormancy is a means of resisting or tolerating
environmental diversity
Dormancy is an inactive period in the life of an
organism during which growth slows or
decreases.
Dormancy can be

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Predictive dormancy – occurs in advance of the
adverse conditions (therefore is genetically
programmed)
Consequential – occurs in response to conditions
Dormancy cont…

Forms of dormancy
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Resting spores
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Examples – bacterial spores, fungal spores, seeds
Brought on by drought or temperature extremes
Diapause
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Most common in insects or earthworms
Stage in the life cycle where metabolism is suspended
Brought on by drought or low temperature
Dormancy cont…
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Hibernation
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Inactivity in mammals
Lowered metabolic rate to conserve energy
Brought on by periods of food shortage (usually in
association with cold temperatures)
Aestivation
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Common in lungfish and amphibians
Lowering of metabolic rate (said to induce a state of
torpor)
Brought on by hot, dry conditions
Regulation
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Regulators internal body conditions remain
constant despite environmental changes
Regulators can occupy a wide range of habitats
Homeostasis (the process of regulating body
conditions) requires energy
Regulation cont….
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Example 1 – osmoregulation
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The ability of an organism to maintain a constant
internal water and salt concentration
Example 2 – homeotherms
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Maintain a constant body temperature
AKA – warm-blooded organisms or endotherms