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

Interactions between species Type of Interaction Effect on population density Parasitism Commensalism Mutualism Predation Competition + / - + / 0 + / + + / - - / -

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. ….

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!

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 DART and the monograph have organised their notes according to the now outdated curriculum although the information is still there if a search is carried out.

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

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)

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

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

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

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

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

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

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