1. Interaction in Ecosystems
Biotic Interactions
Symbiotic Relationships
The costs, benefits and consequences of interactions

2. Interactions between species
Type of Interaction
Effect on population density
Parasitism
Commensalism
Mutualism
Predation
Competition
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3. Maintaining symbiotic relationships
Symbiotic relationships are affected by both
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. ….

4. Managing symbiotic relationships
Humans can manage their symbiotic relationships with other species
E.g.
Humans can manage symbiotic relationships between other species
Very important to discuss the use of drugs, pesticides and herbicides here – mentioned in the curriculum!

5. Interactions with the environment
Organisms respond to changes in the environment in 2 main ways
Conformation
Regulation
Note that there has been a major change in the structure of the curriculum here. DART and the monograph have organised their notes according to the now outdated curriculum although the information is still there if a search is carried out.

6. Conformation
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
This usually involves physiological changes
E.g. Changes in the production rate of glomerular filtrate
Tends to be a temporary adaptation
Explore what tolerance and resistance mean

7. 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
E.g.
growth of winter coat (morphological)
Active only at night (behavioural)

8. Conformation cont…
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

9. Conformation cont… Example 1 – osmoconformers
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
Have a body temperature that fluctuates with the environment (cold-blooded organisms or ectotherms)
Reptiles

10. Dormancy
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
Predictive dormancy – occurs in advance of the adverse conditions (therefore is genetically programmed)
Consequential – occurs in response to conditions
When might predictive and consequential dormancy occur

11. Dormancy cont… Forms of dormancy Resting spores Diapause
Examples – bacterial spores, fungal spores, seeds
Brought on by drought or temperature extremes
Diapause
Most common in insects or earthworms
Stage in the life cycle where metabolism is suspended
Brought on by drought or low temperature

12. Dormancy cont… Hibernation Aestivation Inactivity in mammals
Lowered metabolic rate to conserve energy
Brought on by periods of food shortage (usually in association with cold temperatures)
Aestivation
Common in lungfish and amphibians
Lowering of metabolic rate (said to induce a state of torpor)
Brought on by hot, dry conditions

13. Regulation
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

14. Regulation cont…. Example 1 – osmoregulation Example 2 – homeotherms
The ability of an organism to maintain a constant internal water and salt concentration
Example 2 – homeotherms
Maintain a constant body temperature
AKA – warm-blooded organisms or endotherms