Population Responses to Environmental Stress Ecosystems Population Responses to Environmental Stress

Ecosystems Response to Environmental Stress Homeostasis - the maintenance of favorable internal conditions in a system despite flucutations in external conditions

Ecosystems Response to Environmental Stress Feedback Loop - a circuit of sensing, evaluating, and reacting to changes in environmental conditions as a result of information fed back into a system

Ecosystems Response to Environmental Stress Feedback Loop Positive Feedback - a runaway cycle in which a change in a certain direction provides information that causes a system to change further in the same direction

Ecosystems Response to Environmental Stress Feedback Loop Negative Feedback - a cycle in which a change in a certain direction leads to a lessening of that change

Ecosystems Response to Environmental Stress Ecosystem Disturbance Natural Changes Catastrophic Changes Drought Flood Earthquake Disease

Ecosystems Response to Environmental Stress Ecosystem Disturbance Natural Changes Gradual Changes Climate change Immigration Evolution

Ecosystems Response to Environmental Stress Ecosystem Disturbance Human-Caused Changes Catastrophic Deforestation Plowing Pesticides Fires

Ecosystems Response to Environmental Stress Ecosystem Disturbance Human-Caused Changes Gradual Salinization Soil compaction Depletion of groundwater Tourism

Ecosystems Response to Environmental Stress Ecosystem Stability Inertia Constancy Resilience

Ecosystems Response to Environmental Stress Ecosystem Stability Inertia - ability of a living system to resist being disturbed or altered Constancy - ability of a living system to maintain a certain size Resilience - ability of a living system to rebound from an external disturbance

Ecosystems Response to Environmental Stress Ecosystem Stability Do ecosystems have to have high inertia and high resilience to be considered “stable”? Most ecosystems lack high inertia and resilience

Ecosystems Response to Environmental Stress Signs of Ecosystem Illness Drop in NPP Increased loss of nutrients Decline in indicator species Increased populations of pest species Decline in species diversity Presence of toxic chemicals

Ecosystems Response to Environmental Stress Homeostasis and Time Delays Time delays between input of a stimulus and the corresponding response Ozone depletion Global warming CO2 scrubbing

Ecosystems Response to Environmental Stress Homeostasis and Synergy Synergistic Reaction - a reaction that occurs when two or more processes interact so that the combined effect is greater than the sum of their separate effects

Ecosystems Response to Environmental Stress Homeostasis and Synergy Synergistic Reactions Beneficial [CO2 and photosynthesis] Harmful [ozone depletion + global warming]

Ecosystems Response to Environmental Stress Species Diversity and Ecosystem Stability Ecosystems with higher species diversity have higher NPP and are more resilient Biodiversity provides “insurance” against catastrophe

Ecosystems Response to Environmental Stress Species Diversity and Ecosystem Stability Ecosystems with higher species diversity have higher NPP and are more resilient Biodiversity provides “insurance” against catastrophe

Ecosystems Response to Environmental Stress Species Diversity and Ecosystem Stability Tropical Rain Forests High species diversity High inertia Low resilience Most nutrients stored in vegetation

Ecosystems Response to Environmental Stress Species Diversity and Ecosystem Stability Grasslands Low species diversity Low inertia Burn very easily High resilience Most biomass is underground

Ecosystems Response to Environmental Stress Population Responses to Stress Population Dynamics - the major abiotic and biotic factors that tend to increase or decrease the population size and the age and sex composition of a species

Ecosystems Response to Environmental Stress Population Responses to Stress Population Dynamics Size Density - number of individuals per area) Dispersion - spatial distribution of species in their habitat

Ecosystems Response to Environmental Stress Population Responses to Stress Population Dynamics Biotic Potential - the maximum rate at which a population could grow if it had unlimited resources Environmental Resistance - all factors that act to limit the growth a population

Ecosystems Response to Environmental Stress Population Responses to Stress Population Dynamics Carrying Capacity - the number of individuals of a given species that can be sustained indefinitely in a given area

Ecosystems Response to Environmental Stress Population Responses to Stress Population Dynamics Factors influencing carrying capacity Interspecific and intraspecific competetion Immigration Emigration Catastrophic events Food and water supply Habitat

Ecosystems Response to Environmental Stress Population Density and Population Growth Density-Dependent Population Controls Increase in significance as population size increases Competition for resources Predation Parasitism

Ecosystems Response to Environmental Stress Population Density and Population Growth Characteristics of dense populations: Low birth rates Slow growth rates High death rates

Ecosystems Response to Environmental Stress Population Density and Population Growth Density-Independent Population Controls Affect a population’s size regardless of size Natural disasters Deforestation Spraying of pesticides

Ecosystems Response to Environmental Stress Population Density and Population Growth Reproductive Strategies for Survival r-strategists K-strategists

Ecosystems Response to Environmental Stress Population Density and Population Growth Survivorship Curves Show number of survivors of each age group for a particular species Late Loss Constant Loss Early Loss