SC253: Ecology and Environmental Problems Lecture Notes PDF

SC253: Ecology and Environmental Problems September 16, 2024  Agenda Lecture: Ecology basics Feedback loops In-class activity: Feedback loops  What is ecology? The science by which we study how organisms (animals, plants, an...

SC253: Ecology and Environmental Problems September 16, 2024  Agenda Lecture: Ecology basics Feedback loops In-class activity: Feedback loops  What is ecology? The science by which we study how organisms (animals, plants, and microbes) interact with each other and with their environment. Environment: Everything external to an organism Biotic: living things in the environment Abiotic: non-living things in the environment Biotic? Abiotic? Ecosystem organization Biomes  The main biomes in the world What distinguishes one biome from another? i.e. why are they different?  Landscape mosaics Mini-ecosystems within larger ecosystem  Ecology is a broad and diverse field Direct & indirect interactions between organisms Physical processes and chemical substances are affected by other organisms How might human actions integrate into these interactions?  What are environmental problems? Problems of humans and our relationships with our environment; when an ecological system is disrupted by human activity Resource for sustainable decision making: Millennium Ecosystem Assessment Sustainable = meeting present needs without compromising the ability of future generations to meet their own needs Demands on ecosystem  Feedback loop When the output of a system results in input that affects the system Action Effect A disturbance is a shift from equilibrium Negative feedback loop – Counteracts a disturbance – Returns the system to equilibrium (Balancing) 1.) Upon exposure to a Equilibrium body temperature slightly colder environment, body temperature drops slightly 3.) Temperature returns to normal; shivering stops 2.) Brain triggers physiological responses to reduced Shivering, blood shunted blood temperature away from surface Negative feedback loop Positive feedback loop – Adds to a disturbance – Moves the system farther away from equilibrium (Reinforcing)  Equilibrium body temperature Upon exposure to extremely cold environment, body temperature drops significantly Shivering and changes in circulation do not help Metabolic rate decreases, body temperature Positive feedback loop decreases  Lots of prey Enough food for lots of predators [Negative feedback loop] Not enough food to sustain predators, Predators consume prey, prey predator population decreases population decreases [Positive feedback loop] Healthy, abundant plants Nutrient-rich soil Lots of organic matter Abundant bacteria that decompose organic matter [Positive feedback loop] MORE healthy, abundant plants MORE MORE nutrients in soil organic matter MORE bacteria that decompose organic matter [Positive feedback loop] Healthy Organic Decomposing Nutrient-rich MORE MORE MORE MORE plants→ matter→ bacteria→ soil→ Healthy organic decomposing nutrient-rich plants→ matter→ bacteria→ soil→ …and so on.  Why the differences in the outcomes? Within certain limits, systems can be stressed and will return to equilibrium states via negative feedback loops. When those stress limits are exceeded, positive feedback loops become established, and the system heads towards collapse. https://youtu.be/inVZoI1AkC8 In-class activity: draw two feedback loops. Positive AND negative. Does not need to be factual. Does not need to be ecological. Must illustrate a cause/effect relationships.