Week 5 - Community Ecology Lecture Notes PDF

SC253: Ecology and Environmental Problems September 30, 2024 Prof. Amy L. Frick  Housekeeping 1. The MIDTERM is on 10/14/24. It will consist of multiple choice and short answer questions. I...

SC253: Ecology and Environmental Problems September 30, 2024 Prof. Amy L. Frick  Housekeeping 1. The MIDTERM is on 10/14/24. It will consist of multiple choice and short answer questions. It may cover anything discussed in class from 9/16-10/7, things from reading that were referenced in class, and material from in-class activities/assignments. 2. Your Ecological Footprint Essay deadline has been pushed back to 10/21/24. New details of this assignment are in the (/Content/Case Study of One) folder. 3. See updated (/Course information/schedule) folder for reading assignments for next week’s class. Ecosystem organization Community  Ecological stability A stable system has low variability (i.e., little deviation from its average state) despite shifting environmental conditions. [Maintained by Action negative feedback] Effect  Lots of prey Enough food for lots of predators [Negative feedback loops maintain equilibrium by keeping a system within a finite range of states] Not enough food to sustain predators, Predators consume prey, prey predator population decreases population decreases  Stability domain: the range of system states STABILITY DOMAIN More prey; fewer predators Fewer prey; more predators  Stability domain: the range of system states STABILITY DOMAIN More prey; fewer predators Fewer prey; more predators STRESS: extra cold winter ->less bunny babies survive A resilient system can withstand stress without collapsing to stay in its stability domain.  Stability domains Resilience: the ANPP: ability of an Above-ground net ecosystem to primary productivity maintain balance after stress How Soil Biota Drive Ecosystem Stability Stability domain shift  “Switch” Complex adaptive systems stay relatively stable for long periods…...but given enough stress, they can change suddenly (switch) to alternate stability domains [Stability domain] STRESS (disease that kill predators) [Stability domain] [new stability domain] Example of stability domain switching: sea otters & kelp Maintenance CRISIS Reorganization Dissolution Sea otters, urchins, and kelp forests Supplemental article: Sea urchin/Kelp - Sciencing Sea otters, urchins, and kelp forests Supplemental article: Sea urchin/Kelp - Sciencing Trophic cascade: a powerful indirect interaction affecting an entire food chain Kelp forest Sea otters (with sea otters) removed Trophic cascades can Urchin population be top-down or explodes bottom-up Forest becomes an Urchins destroy urchin barren kelp forest  Stability domain switching Bernal-Ibáñez A, Cacabelos E, Melo R and Gestoso I (2021) The Role of Sea-Urchins in Marine Forests From Azores, Webbnesia, and Cabo Verde: Human Pressures, Climate-Change Effects and Restoration Opportunities. Front. Mar. Sci. 8:649873. Complex adaptive systems… Formed by community assembly Exist within stability domains Too much STRESS –> SWITCH to a new stability domain --------------------------------------------------------------------- Example of community assembly: ecological succession (time)  Ecological succession: A change in species composition over time until the establishment of a climax community Pioneer species Intermediate species Climax community (time)  Ecological succession: A change in species composition over time until the establishment of a climax community Climax community = STABLE What makes a community stable? Species diversity Richness: the number of species within a community Composition: the identity of the species within a community Community assembly What determines the species composition of a given area? Habitat: the place where an organism lives out its life. (Habitat is a physical location) Niche: an organism’s role in the community and how it interacts with the environment. (How it obtains food, mates, gets protection from predators, etc) Ecological niches Autotroph Heterotroph Decomposer Trophic levels  Trophic levels Apex predator Secondary consumer Primary consumer Primary producer Ecosystem = flow of energy Features of complex adaptive systems: Redundancy Resilience Self-organization/community assembly → food web A food web is the path taken by nutrients and energy as they move through different organisms. A food web is A food chain what happens in is linear. reality. A food web contains many food chains. Vocabulary: Trophic cascade  Sea otters: a keystone species Keystone species: An organism that helps define an entire ecosystem. Without its keystone species, the ecosystem would be dramatically different or cease to exist altogether. Keystone species have low redundancy. Supplemental: Photos of keystone species Relationships between species  Relationships between species Competitive Predator-prey Symbiotic mutualism commensalism parasitic Competition (at any trophic level) Competitive exclusion principle Two species cannot co-exist if they occupy the same niche. Competitive exclusion principle Two species cannot co-exist if they occupy the same niche. Invasive species: may outcompete a native species for food, water, habitat Burmese python (Florida) Rats Cane toad (Florida; Caribbean) Flamboyant tree (Caribbean)  U.S. Customs and Border Protection: Canine Calendar BARRO Predator-prey Symbiosis (coadaptation; coevolution) https://sites.google.com/a/bps101.net/symbiosis-website--eamon-s/content-page  Mutualism (+/+) Hummingbird & flower Fungus & algae (= Lichen)  Commensalism (+/null) Commensal: Epiphyte Host: Tree Commensal: Clown fish Host: Sea anemone Commensal: Remora fish Host: Shark  Parasitism (+/-) Parasite: Mosquito Parasite: Beechdrops Host: Mammal Host: Other plant  Group activity Each group will teach one example of an interrelationship between species (1-2 slides per group). Include a diagram that explains how the organisms in question interact, and identify the type of relationship. Each group member will be expected to speak, so plan accordingly. Aphids / ants Oxpeckers / mammals e. coli (in lower GI tract AND if ingested) Toxoplasmosis in rodents Mycorrhizae / vascular plants Allelopathy (in plants) Upload your figure into the shared Google folder so that other students can view it later.  Housekeeping (recap) 1. The MIDTERM is on 10/14/24. It will consist of multiple choice and short answer questions. It may cover anything discussed in class from 9/16-10/7, things from reading that were referenced in class, and material from in-class activities/assignments. 2. Your Ecological Footprint Essay deadline has been pushed back to 10/21/24. New details of this assignment are in the (/Content/Case Study of One) folder. 3. See updated (/Course information/schedule) folder for reading assignments for next week’s class.