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Transcript
CH4 A couple things in this chapter we already covered We will talk about biomes and evolution on Thursday! The Six Kingdoms Figure 20.20 Euglenozoans Forams Diatoms Red algae Green algae Land plants Domain Eukarya Ciliates Amoebas Fungi Animals Methanogens COMMON ANCESTOR OF ALL LIFE Thermophiles Domain Archaea Nanoarchaeotes Proteobacteria Chlamydias Spirochetes Gram-positive bacteria Cyanobacteria (Chloroplasts)* Domain Bacteria (Mitochondria)* Ecology is the study of • the interactions between species and their physical (abiotic) environment (Examples?) • the interactions between and within species (Examples?) What do these things mean? We will focus on the second one….between and within species. Many ecologists like to categorize the different kinds of interactions between organisms by their effect on both members of the interacting pair… Is the interaction positive in terms of survival and reproduction or negative? What kind of an interaction might be bad for both members of the interaction (have a negative affect on survival and reproduction)? Competition We need to distinguish whether competition is … Intraspecific Interspecific And whether it is …. Interference.. when actually interact Exploitation.. use common resources that are in short supply-”get there first” Do plants and phytoplankton compete? How? What is an example of an interaction where one member of the pair gains in terms of survival and reproduction and the other loses? Predation An organisms that feeds on another organism. If a parasite feeds on an organism but does not kill it should we still call it a predator? What is an example of an interaction where both members of the pair gain in terms of survival and reproduction? Example? Mutualism! What is it called when one gains while the other neither benefits or gains? Example? Commensalism! Or to both individuals if INTRASPECIFIC! Where would herbivory fit in? Problems…. •Predators do not always eat other animals- we consider squirrels seed predators (eat whole individual seed-baby plant) •Not all predators are animals- plant predators (venus flytrap), protists (amoeba) •Some herbivores kill the plant they feed on! •In some ways herbivores are a little like parasites (consume part of organism but do not kill) just don’t happen to live on… •Some parasites kill their host so should they be predators? •So in reality a continuum of “bewildering” interactions... Which of these kinds of interactions do you think are the most common? The most “important”? Which of these most affects the flow of energy and chemicals through the food web? Are negative interactions (competition, predation) or positive interactions (mutualism) more important? If you mostly spent your days watching animal planet, discover channel or youtube video clips which would you think was most important? A closer look at mutualisms! (some positive interactions) Tight and coevolved mutualisms • leaf cutter ants and their fungus they farm Loose, facultative mutualisms • plants that have seed dispersal by vertebrates •plants that nurse other plants by making suitable conditions underneath them •you and your surface bacteria •kelp that provides home for inverts/fish How tell the difference between these? Ask… Would partners persist in absence of one another? Are there specific evolved traits? Lets go over some tightly coevolved mutualisms… 1. Mycorrhizae (fungi) and plants •Surround roots or penetrate root cells •Most all plants have (90%) •First plants to live on land seemed to have had this relationship •Plants get water, minerals/ fungi gets sugars 2. Lichen Algae shares photosynthetic materials, fungi contributes minerals + place to live 3. Corals house different algal species • algae receive nutrients (nitrogen+phosphorous) from their coral animal partner •coral receives organic compounds synthesized by algae during photosynthesis •corals can feed on zooplankton in night and get photosynthetic products by day! “Nature” of relationship unclear…. •corals induce the algal cells to release organic compounds •corals also seem to control rate of population growth •These algae can live on their own in the water and are happy there……Is this farming? 4. Legumes and bacteria Bacteria fix nitrogen and obtain photosynthetic products supplied by the plants. Each legume is associated with a different bacterial species. Swellings are called nodules. “Nature” of relationship is unclear here too…. •Bacteria are common in soil (bacteria not dependent) •Plant may control reproduction of colony by releasing a specific chem •Farming? 5. Cellulose digesting mutualists gut bacteria and protists play critical role in digestion of plant material Ruminants have 4 chambered stomachs-basically big fermentation chambers (Microorganisms make up about a quarter of volume) Termites and wood cockroaches are similar..have protists that also have their own internal bacterial community Now what do you think? Is the world dominated by negative or positive relationships? Negative-predation, competition Positive-mutualisms Connects to a historical debate! Frans Snijders (1579-1657) Peter Paul Rubens, Tiger and Lion Hunt, c. 1617–1618. Alfred Lord Tennyson's In Memoriam A. H. H., 1850. Who trusted God was love indeed And love Creation's final law Tho' Nature, red in tooth and claw With ravine, shriek'd against his creed Arthur Henry Hallam Hereupon, the beasts, enraged at the humbug, fell upon him tooth and claw. They were highlighting “the apparent conflict between love as the basis of the Christian religion and what they saw as the callousness of nature.” http://www.phrases.org.uk/meanings/red-in-tooth-and-claw.html How do these interactions play out at the next level up?? Communities The “nature” of communities…p93 4.4 Historical and current Debates concerning Communities Two views of Communities Clements vs Gleason • Clements believed communities are like organisms or “superorganisms” with different species or populations paralleling different organs in a body • Gleason believed they are “chance assemblages” of species each of which is just responding to certain physical requirements (moisture levels, sunlight) If communities are like superorganisms then what might you expect the relationships between organisms within a community to be..loose or tight? What might happen in the community if a species was lost to extinction? If a prairie was one community and the forest another what would the boundary between the two look like? Well defined or unidentifiable as you walked from one to another? Contrast with Gleason If organisms are chance assemblages then …… •casual interactions between species •removing a single species may not have an effect on community properties, structure •communities intergrade continuously (no real boundary between one community and another) Gleason INDIVIDUALISTIC HYPOTHESIS If communities are like superorganisms then there will be •strong, tight interactions between species •removing a single species may have a big effect on community properties, structure •real boundaries when move from one community to the next Clement =INTERACTIVE HYPOTHESIS Fig 53.1 Cambpell Which of these graphs represents what you might find if communties were the way Clements sees them? Which one represents communities the way Gleason sees them?
