BSC2011 Summer 2013 Final Exam Study Guide !1 UNIT IV: Ecology 1. Define ecology. How does a population differ from a community? How does a community differ from an ecosystem? Please provide a specific example that exists in nature of: a population, a community, and an ecosystem. Ecology: The study of the interactions between organisms and their environment Population Community A group of organisms of the same species living in a particular area One species All the organisms living in a particular area Not just one species, all species Community Ecosystem All the organisms living in a particular environment (all species) Organisms make up the biotic factors of an ecosystem The biotic & abiotic components of a particular environment Biotic: Living components (all of the organisms in a particular environment) Abiotic: Nonliving physical & chemical factors • Population: A group of organisms of the same species living in a particular area o Ex) A group of blue-footed boobies inhabiting the same region of the Galapagos islands • Community: All the organisms living in a particular area (all species) o Ex) All the snakes, birds, sloths, etc. that live in the Amazon rainforest • Ecosystem: The biotic & abiotic components of a particular environment o Biotic: Living components (organisms) Predation & parasitism Competition Density Disease o Abiotic: Nonliving physical & chemical factors Temperature Light Topography/physical structure 2. Define demography and list the types of vital statistics demographers use to study populations. What is meant by the age structure of a population? • Demography: The study of populations o Vital statistics & the factors that influence these • Vital Statistics o Population Size – absolute number of individuals o Population Density – number of individuals per area/volume o Population Dispersion – how individuals are distributed in a population Clumped, uniform, random?!BSC2011 Summer 2013 Final Exam Study Guide !2 o Sex Ratio – What percentage male/female? o Age Structure – the distribution of different age classes in a population Function of birth rate & death rate and how these vary with age\ 3. Explain what is meant by an energy “trade-off” and give an example. • Energy – An organism has a limited amount of energy to allocate to enhance its fitness (enhance survival & reproduction) o Energy spent on survival is taken away from reproduction o A trade-off exists between energy spent on survival versus reproduction o Ex) Albatross puts more energy into surviving than annual reproduction By living longer, they can produce enough offspring to maintain the speciesBSC2011 Summer 2013 Final Exam Study Guide !3 Life-History Reproductive Patterns • Semelparity: Reproduce once & die o Many offspring o Low rate of survival o Adaptation to less stable environment o Ex) Salmon, dandelions • Iteroparity: Repeated reproduction throughout life o Usually fewer offspring o Higher survival o Adaptation to more stable environment o Ex) Most mammals 4. What is a survivorship curve? Survivorship Curve: Shows how survival varies with age 5. What are the 4 types of 2-species interactions and how do they compare? • Mutualism (+/+): Both parties benefitBSC2011 Summer 2013 Final Exam Study Guide !4 o Ex) Plants & their pollinators Plants get pollinated Pollinators get food (nectar) • Commensalism (+/0): One species benefits, other species is unaffected o Ex) Cows & cattle egrets Egret eats insects stirred up by the cow while grazing Cow is unaffected • Predation (+/-): One species preys on another o Herbivory – Animals eat plants o Parasitism – One organism lives on or in a host (usually without killing the host) o Parasitoidism – Organism lays eggs in or on the host o Pathogens – Disease-causing organisms (bacteria) • Competition (-/-): When organisms attempt to utilize the same resources o Intraspecific Competition: Between members of the same species Ex) Male white tailed deer competing for mates o Interspecific Competition: Between different species Ex) Cheetahs and lions live in close proximity & feed on the same prey 6. What is competition and how does it affect population growth rates? What is resource partitioning, provide an example, and what role does it play in a community? What is character displacement and provide an example? • Competition (-/-): When organisms attempt to utilize the same resources o A species that is out-competed by a similar species will experience a decline in population growth rate • Resource Partitioning: Where resources in an environment are limited, different species have evolved to "share" the specific resource o Ex) Zebra and wildebeest, both large herbivores & grazers living together in the African grasslands, feed on different parts of the grass plants • Character (Trait) Displacement: When similar species evolve phenotypic differences where they co-occur o Ex) Beak size trait in two species of bird living on the same island will get displaced upward & downward to reduce competition & increase fitness 7. What does Gause's work illustrate about the effects of competition on population growth rates? Gause’s work postulates that in order for two competing species to exist in a stable environment, the two species must differ in their respective ecological niche. Otherwise, one species will eliminate or exclude the other through competition. That species’ population growth rates will be adversely affected as result, and likely decline.BSC2011 Summer 2013 Final Exam Study Guide !5 8. What is the niche concept and how is it useful in the study of competition? How and why is a species’ fundamental niche different from its realized niche? • Niche: All that a species needs to survive in its habitat o Closely related species evolve in a way to occupy different niches in order to reduce competition Fundamental Niche Realized Niche Complete potential niche space an organism could occupy The fundamental niche is where a species CAN live, negating the effects of predation, resource limitation, etc. The actual niche space an organism occupies in a particular environment The realized niche is where the species DOES live, because certain factors have forced it to retreat from parts of the fundamental niche 9. What did Connell's study, in which he
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