Community Structure and Biodiversity Chapter 46, part 1
Bell Ringer, 9/9 • Come in and sit down QUIETLY. You can keep your desks in groups as long as you can do so quietly. • What is one question that you wish had been on the test? Write the question and then answer it. • What are some ways that organisms interact in the environment? (‘I don’t know’ is not an acceptable answer. Brainstorm some ideas!)
Levels of Organization • Biosphere: The earth’s surface; where all life exists • Ecosystem: The interactions of all living and non-living things in an area • Community: The interactions of all living things in an area • Population: The members of a species in an area interacting with one another • Organism: One individual living thing
Levels of Organization • Organ System: Group of organs that interact with each other • Organ: Group of tissues interacting with one another • Tissue: Group of specialized cells interacting • Cell: The basic unit of life
Biosphere Ecosystem Community Population Organism Organ System Tissues Cell
Biosphere Ecosystem Community You are here Population Organism Organ System Organ Tissues Cell
Factors that Shape Community Structure • Habitat: The type of place where a species lives • Communities have dynamic structures based on: • Climate and topography • Types and amounts of food and other resources • Species’ adaptations • Species’ interactions • Timing and history of disturbances
Bell Ringer, 9/10 • Come in and find your seat quietly • Get out your notes • Answer the following question on your bell ringer: • Pick ONE factor that shapes community structure and explain how it affects the community.
Factors that Shape Community Structure • All members of a community have the same “address” but different “professions” • Niche: A species’ ecological role; includes conditions, resources, and interactions necessary for survival and reproduction • Fundamental niche: The niche that an organism can have • Realized niche: The niche that an organism ACTUALLY has
Factors that Shape Community Structure • Example: Barnacles
Factors that Shape Community Structure • Ex. Finches
Factors that Shape Community Structure • Coevolution: When two species in close interaction with one another evolve in response to one another • Hummingbirds and flowers • Garter snake and rough skinned newt
Factors that Shape Community Structure • Categories of Species Interactions: • Commensalism: Benefits one species and does not affect the other (bacteria in your gut; barnacles on a whale) • Mutualism: Benefits both species (ants & acacia tree) • Interspecific competition: Harmful to both species • Predation: Free-living organism kills and eats another (lion and gazelle) • Parasitism: Live in or on host and usually don’t kill it (fleas, ticks, mistle toe, tape worms)
Exit Slip, 9/9 • When will your rewritten notes be checked? • Compare and contrast predation and parasitism. Give an example of each.
Bell Ringer, 9/10 • Get your Exit Slips (on 2nd lab table) • Get your pink paper (on 2nd lab table) • On your bell ringer paper, answer the following question: • Explain the difference between a fundamental niche and a realized niche. Give an example of each. • Pick ONE factor that shapes community structure and explain how it affects the community.
Bell Ringer, 9/11 • Get your FRAYER MODELS from the back and put them behind your Ch. 47 notes in your binder • Answer the following questions on your bell ringer: • A unicorn can survive in warm or cool temperatures. Their main competition, the magical fairy, thrives in warm temperatures. Based on this information, what is the unicorn’s fundamental niche? Realized niche?
Factors that Shape Community Structure • Symbiosis: Species that spend most or all of their life cycles in close association • Symbiont: A symbiotic species • Endosymbiont: A species that lives inside its partner • Parasitism, mutualism, and commensalism can all be types of symbiosis • http://www.brainpop.com/science/ecologyandbehavior/symbiosis/
Commensalism • Relationship in which one species benefits and the other is not affected • Cattle egrets and livestock • Army ants and birds • Stomach bacteria?
Mutualism • Interaction in which both species benefit • In some mutualisms, neither species can complete its life cycle without the other • Yucca plants and moths
Mutualism • Most mutualistic interactions are not life or death • Plants have more than one pollinator • Nitrogen-fixing bacteria • Lichens • There is often some conflict between partners • Lichens: Algae and fungal symbionts
Mutualism • Some mutualists defend one another • Clown fish and sea anenomies • Ants and the acica tree
Mutualism • The Theory of Endosymbiosis • Mitochondria and chloroplasts were once independent bacteria engulfed by a bigger cell • Host relied on ATP produced; symbiont relied on raw materials from the host • Eventually, they became incapable of living independently
Mutualism • Evidence for the Theory of Endosymbiosis • Amoeba experiment by KwangJeon (1966) • Resemblance to bacteria in size and structure • Replicates independently of the main cell • Internal membranes resemble those of bacteria See Ch. 20.4 for more information!
Parasitism • Parasites spend all or part of their life living in or on other organisms • Steal nutrients from the host • Have big impacts on host populations: Disease, weaken host so it is vulnerable to predation or unattractive to potential mates, cause sterility, shift sex ratios of host species, and many more!
Parasitism • Parasites usually don’t kill the host right away • Ideally, a host will live long enough to give the parasite time to reproduce • The longer the host survives, the more offspring are produced • Host usually only dies from the parasite (not secondary effects) when: • It is overwhelmed with parasites or • A parasite invades a novel host with no defenses against it
Parasitism • Parasites often lead to secondary effects on the host • Gradual drain of nutrients leads to the inability to fight off secondary infections
Parasitism Mistletoe Roundworms Ophiocordycepsunilateralis Flea Tapeworm Lymphatic Filariasis
Bell Ringer, 9/12 • What evidence have scientists found for the Theory of Endosymbiosis? • Why is it beneficial to parasites to keep the host alive as long as possible? • Why do some scientists believe that commensalism does not really exist in nature?
Videos • http://www.youtube.com/watch?v=zTGcS7vJqbs • Mutualism • http://www.youtube.com/watch?v=Xm2qdxVVRm4 • Ants: • http://www.youtube.com/watch?v=UozWJTuhbMQ • http://www.youtube.com/watch?v=R3Mt2E1M6dU • Parasites: • http://www.youtube.com/watch?v=i80DvTmLPeE • http://www.youtube.com/watch?v=uvdiYg6ZN-U • http://www.youtube.com/watch?v=xDMzubAvzgg
Bell Ringer, 9/13 • Put your homework in the tray • On your bell ringer… • Choose a parasite that you learned about yesterday and explain its interaction with its host. • List the levels of organization.
Virtual Lab • http://www.biologycorner.com/worksheets/virtual_lab_population.html#.UjJ2odJQEud
Bell Ringer, 9/14 • In Friday’s virtual lab, what happened when the two paramecium were grown together? Why?
Competitive Interactions • Competition among members of the same species is very intense; leads to evolution by natural selection • Natural selection: Process of evolution in which individuals of a population vary in the details of a heritable trait and reproduce with varying amounts of success • Evolution: Change in a line of descent
Competitive Interactions • Interspecific competition is not usually as intense • Interference competition: One species actively prevents another from accessing from a resource • Exploitative competition: Species don’t interact directly; they reduce the amounts of resources available for the other by using it
Competitive Interactions • Any two species differ in their resource requirements • Competition is the most fierce when the supply of a shared resource is the main limiting factor for both
Competitive Interactions • G. Gause (1930) conducted an experiment involving two species of ciliated protists • Both compete for the same prey (bacteria) • Separately, their growth curves are almost the same • When grown together, one grew slightly faster and outpaced the other, driving it to extinction
Competitive Interactions P. aurelia P. caudatum Population density Population density 20 4 8 12 16 24 20 4 8 12 16 24 Time (Days) Time (Days) Time (Days)
P. caudatumand P. aurelia Population density 4 8 12 16 20 24 Time (Days)
Competitive Interactions • This experiment is the basis of the competitive exclusion principal • Whenever two species require the same limited resource to survive or reproduce, the better competitor will drive the less competitive to extinction in that habitat • Competitors can only coexist if their resource needs are not exactly the same • Example: Gause’s second protist experiment
Think About It… • Can you think of any examples of times this has occurred in nature? • If yes, describe the situation. • If no, make up a hypothetical situation and explain it.
Competitive Interactions • When two competitor species coexist they suppress each other’s population growth • Concept shown in experiment by Nelson Hairston • Hairston studied two species of salamanders • In two plots, he removed one of each type of salamander. In the control plot he left the populations the same • In plots with one salamander, populations soared • On control plot, populations stayed in check
Competitive Interactions • When two species in an ecosystem are similar, they must find a way to coexist or one will be driven to extinction • They do this in two main ways: • Resource partitioning • Character displacement
Competitive Interactions • Resource partitioning • Subdividing an essential resource • Reduces the competitions among species that require it • Ex. Plant roots
Competitive Interactions • Character displacement • Over generations a trait of one species diverges to lower the competition with other species • Natural selection favors individuals that differ most from the other species • These are the individuals that get to survive and reproduce (the goal of nature) • These are the traits that are passed on to future generations