Lecture 31 Outline of Last Lecture II. Age structuring and reproductive strategies a. Survivorship Curves III. Community Ecology a. Niches and Definitions Outline of Current Lecture b. Symbioses c. Community structure/trophic webs/ energy transfer i. Trophic Structures Current Lecture Community Ecology II Symbioses 1. Resources are limited (in any ecological community some things will die) 2. There is strong intra- and inter- species competition 3. Species have evolved complex inter-species interactions = symbioses 4. For biologists any close interactions between two or more species that have evolved over time — usually it means that it is an interaction that benefits both species, however in biology it refers to both positive and negative Mutualistic relationship = clownfish living inside a sea anemone -clownfish eat critters and drop waste in anemone who can use that waste, protect anemone from certain predators that would eat it -anemone protects clownfish against other fish (its own predators) 6 different forms of interactions Antagonistic : one gains, one loses -Predation — predator winning, other losing (+/-) -herbivory — one eats plant, plant loses (+/-) -parasitism — parasite is gaining, host is losing (+/-) -competition — for some limited resource, both organisms are losing out (-/- ) Mutualistic: -strict mutualism — both gain (+/+) 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. !-commensalism — one gains, and the other is indifferent (+/0) -ex: barnacles on a whale — the barnacles are gaining, and while the whale may be losing a bit of ability to move through the water, but not really Predators are necessary for the biological community -may be negative for each individual but they can promote diversity in the community -ex: when newts aren’t present (predators) you have fewer tadpole species Video is an example of one of the forms of symbioses. Oxpecker eating ticks off of giraffes, zebras, hippos. Which one is it? -probably a mutualist relationship, but you could make an argument for parasitism No organism can survive without other organisms heterotrophs are all either predators or parasites plants are producers but even they can’t survive on their own (fungi form mutualistic relationships with plants roots to pass nutrients) - fungus sucks up nutrients that the plant cant get itself and gives it to the plant, while the plant give the fungus carbon, which it can’t get alone. What is an organism? ex: most termites can’t digest wood — unable to break it down - they have protists (eukaryotic organism living in their mid-gut) that make enzymes that can digest wood - these protists don’t live anywhere but in termite, and neither can survive without the other - protists can’t move around on their own — there are bacteria around the outside of the protist that help the protist move around to digest the wood - there is another bacteria that digests the glucose from the wood - all of these organisms work together -what is the organism in this situation? none of them can live on their own, they’re all different species and reproduce separately **Clicker Question** Dwarf mistletoes are flowering plants that grow on certain forest trees. Obtain nutrients and water from vascular tissues of the trees. The trees derive no known benefits from the dwarf mistletoes. Which of the follow best describes this interaction? -mistletoes are sucking things out from the tree, taking out nutrients. -parasitism TL;DL Community structure/ trophic webs/energy transfer individual symbioses add up to make the biological community’s structure Example from Bylot Island (less diverse)-in picture, arrows show direct and indirect actions among organisms -grass growth is hurt by lemmings and goose which gain by eating on the grass (+/-) -the lemming populations lowered by owls and foxes, who eat them (+/-) -both snowy owl and arctic foxes prefer to eat lemmings than geese, so geese gain an indirect benefit (+) *allows you to understand what would happen if you got rid of one of these species *allows you to form a Trophic pyramid Bottom of Trophic pyramid -plants fix carbon through photosynthesis — all of the energy comes from here -plants eaten by primary consumers -primary consumers are eaten by secondary or tertiary consumers -all of these are consumed by scavengers (detrivores) — eat dead organisms At each trophic level there is energy loss — 99% of solar energy is either stored as heat or lost -at each step only 10% of energy is transferred — you’re losing the other 90% as respiration or feces/ death **Clicker Question** Which statement is true? -biomass tends to decrease in higher trophic levels -Biomass = not of an individual organism, it is the total of that trophic level (all the organisms) -tertiary consumers tend to be larger in size, not smaller although there is fewer of them -lots of little things, few large things Trophic Structures -usually short — not a long string of interactions because you get so much loss at each level -standard carnivore doesn’t eat carnivores, it eats herbivores -true for energy and biomass -secondary and tertiary consumers tend to be fewer but larger -saprotrophs — many more and higher biomass **Clicker Question** Approx. how many kg of carnivore biomass can be supported by a field plot containing 1,000 kg of plant material? -only 10% of energy moves on the the next level : 10% of 1000 is 100, which is the kg of herbivores. The next level is kg of carnivores = secondary consumers, tertiary level of consumers would be 1 kg but together that would be 11 kg -answer = 10 kg Trophic Web -species have many complicated relationships past predation -we usually don’t know what role a species plays until it is removed2 type of “unusually significant” species Dominant Species -american Chestnut tree : used to extend all up and down the eastern seaboard, enormous trees that don’t really exist anymore -served as homes to all sorts of species of animal (birds, insects) — much more important in environment than just primary producers -Mast = nuts, eaten by deer, bear, turkey, etc. -with the loss of the chestnut tree, all of the animals have less to eat (less mast being produced). Even though there is