Which of these are effects of environmental change on individual organisms? Check all that apply. 1. death 2. loss of habitat 3. change in competition 4. impacts on growth and development 5. extinction 6. a decrease in resources

In order to function adequately, the immune system is dependent on numerous regulatory interactions between organs, in a complex set of hormone and neuropeptide connections involving the nervous and endocrine systems. When an organism is faced with a stressor-broadly defined as ‘any aversive condition, be it a predator or an aggressive conspecific, disturbance to established social hierarchies, overcrowding, an infective parasite or foreign peptide or thermal extremes’ (Husband & Bryden 1996) that would affect fitness if not avoided or successfully tolerated (Martin 2009) - various body systems act together to activate and coordinate responses. This cascade of events involves synergistic, agonistic or antagonistic interactions between the sympathetic adrenomedullary system, the hypothalamic-pituitary-adrenocortical axis and the hypothalamic-pituitary-gonadal axis (Lawrence & Kim 2000). Although such stress responses are essential to survival, inadequate, excessive or unremitting adrenocortical and autonomic function is detrimental for reproduction and survival and can have dramatic effects on immunocompetence (Leonard 2006), thereby increasing susceptibility and vulnerability to disease (Friedman & Lawrence 2002).