Lecture 32 Outline of Last Lecture a. Symbioses b. Community structure/trophic webs/ energy transfer i. Trophic Structures Outline of Current Lecture c. Community structure/ trophic webs/ energy transfer contd. II. Nutrient Transfer a. Global Carbon Cycle b. Global Nitrogen Cycle Current Lecture Community structure / Trophic webs/ energy transfer Wolves of yellowstone national park -41 wolves were transplanted into Yellowstone, which caused the wolf population to grow dramatically (blue is montana, purple is greater yellowstone area) -controversial because many farmers didn’t want wolves reintroduced These data suggest: (pick all that apply) 1. Tree growth increases after wolf reintroduction 2. Wolves probably prey on bison 3. Wolves probably prey on elk 4. wolf reintroduction dramatically alters the biological community 5. Wolves are a dominant species in the ecosystem -1 is true, aspen height increases, number of cottonwoods increase, and the willow area has increased as well -bison numbers go up -elk numbers go down -4 is definitely true -dominant species = something that spreads into very high numbers, like a tree or kelp. The wolves are a keystone species (keystone comes from an arch, and the one stone that holds the arch up) Bio 152 1st Edition These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best !used as a supplement to your own notes, not as a substitute. !Elk populations were very high in yellowstone before the wolves were reintroduced, and they were changing the environment. The small aspens are coming back because of decreased predation (by elk browsing). The elk numbers were so high they were eating lots of vegetation— keeping it very low After the introduction of the wolf there was much more of the low-growing shrubbery because of the decrease in elk -also saw that when the wolves came back, the elk population came down and the elk didn’t hang out by the streams anymore and deplete the vegetation there, and so things like berries came back. Lead to more bears, eagles, birds and plants and a decrease in coyotes and elk. -lots of coyotes (mid-level carnivore) who got chased out by the wolves -ecosystem as a whole was much healthier -shannon diversity index increased quite a bit after wolf reintroduction. Wolves had direct effects on : only coyotes and elk - indirect effects on the rest of the ecosystem Last time: talked about killer whales and otters -killer whales eating otters, causing otter numbers to plummet. Otters aren’t eating as many sea urchins, which then ate all the kelp. -leads to “sea urchin barrens” the other species that killer whales had been eating (some great whales, sea lions) had started to decline —> this lead the orcas to be eating otters - this is why the orcas just started affecting the kelp chain the way it did (weren’t eating the otters the whole time) TL;DL Why are food chains (part of a trophic web) short? Predict the parts of the trophic web that would have the highest biomass Predict how changes in the trophic web would affect the rest of the web What’s the difference between a dominant and a keystone species? Nutrient Transfer Generalizations: -important elements for life = N, P, K, C, O -all of them begin as inorganic materials, some of them are unavailable (minerals), or available for biological use (in atmosphere, water or soil) -total amount of these doesn’t change, it just cycles in and out of these reservoirs -can become available in different ways— usually fixation -carbon can be “fixed” by plants —> using photosynthesis it can be taken from the air and turned into energy inside the plant -nitrogen must be fixed from the air by bacteria**Clicker Question** You are largely made of oxygen, hydrogen and nitrogen. Where does the carbon come from?? Pick all that apply 1. Diamonds 2. CO2 3. Our diet 4. The citric acid cycle (krebs) 5. Carbon rich fossil fuels -from our diet -breathe out CO2, the carbon that makes up the parts of your organism aren’t coming from carbon dioxide but the plants are fixing the carbon dioxide, and you’re eating those plants -the citric acid cycle *take away from this that the carbon in your body is coming from plants which are taking it from the air Global Carbon Cycle **Clicker Question** Which of the following is the largest reservoir of carbon? -Unavailable sedimentary rock -what’s available is in the atmosphere and in the water that can be fixed by plants Where is the largets flux (movement)? -photosynthesis (plants) -respiration is also large but not as large Global Nitrogen Cycle **Clicker Questions** Why do organisms need nitrogen? Pick all that are possible -its part of nucleotides -its part of amino acids What’s the major inorganic reservoir of nitrogen? -both aquatic organisms and terrestrial organisms are organic (carbon based life forms) -where most of the nitrogen is = in the atmosphere (not available to organisms to use), except for a tiny group of organisms -all proteins and DNA have nitrogen in them that has to come from somewhere, and the only common sources of nitrogen fixation are bacteria and cyanobacteria -nitrogen gets into the soil to be used by the plants, but it gets fixed into the soil using bacteriaIn a natural trophic pyramid where does all of the nitrogen in the hawk’s proteins come from? Aka how does it leave the atmosphere? -Bacteria = how nitrogen enters the food chain -plants fix the carbon dioxide, and this is ultimately where the hawk gets the amino acids, but the nitrogen gets into those AA’s from the bacteria that then give it to the plant In many situations the species in a illogical community are limited by one particular nutrient or factor. -nitrogen or water : these two nutrients are the most common that will limit the growth of any organisms in any ecosystem -when nitrogen is introduced in large quantities it can rapidly change an environment. Causes an algal bloom in the water (eutrophication) eutrophication = nitrogen and sometimes phosphorous wash into the water (aren’t there normally at such high levels) and the organisms can take advantage of them. The algae bloom, then they die where they’re eaten by detrivores, which use all of the oxygen the water. This oxygen loss in the water causes a “dead