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 A group of organisms of the same species living in a particular area One species Community All the organisms living in a particular environment all species Organisms make up the biotic factors of an ecosystem Community All the organisms living in a particular area Not just one species all species Ecosystem The biotic abiotic components of a particular environment Biotic Living components all of the organisms in a particular environment Abiotic Nonliving physical chemical 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 Ex All the snakes birds sloths etc that live in the Amazon rainforest Ecosystem The biotic abiotic components of a particular environment o o o Predation parasitism Competition Biotic Living components organisms Density Disease 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 Vital statistics the factors that influence these Population Size absolute number of individuals Vital o Statistics o 1 o o Population Density number of individuals per area volume Population Dispersion how individuals are distributed in a population Clumped uniform random 2 o o Sex Ratio What percentage male female 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 o Energy spent on survival is taken away from reproduction A trade off exists between energy spent on survival versus reproduction 2 o Ex Albatross puts more energy into surviving than annual reproduction By living longer they can produce enough offspring to maintain the species 3 Life History Reproductive Patterns Semelparity Reproduce once die o Many offspring o o o Low rate of survival Adaptation to less stable environment Ex Salmon dandelions Iteroparity Repeated reproduction throughout life o o o o Usually fewer offspring Higher survival Adaptation to more stable environment 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 4 Mutualism Both parties benefit 5 o o o o o o Ex Plants their pollinators Plants get pollinated Pollinators get food nectar Commensalism 0 One species benefits other species is unaffected 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 Parasitoidism Organism lays eggs in or on the host Pathogens Disease causing organisms bacteria Competition When organisms attempt to utilize the same resources Intraspecific Competition Between members of the same species Ex Male white tailed deer competing for mates 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 6 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 7 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 Complete potential niche space an organism could occupy Realized Niche The actual niche space an organism occupies in a particular environment The fundamental niche is where a species CAN predation resource limitation etc live negating the effects of The realized niche is where the species DOES factors have forced it to retreat from parts of the fundamental niche live because certain 9 What did Connell s study in which he separately removed first one and then another of 2 competing species of barnacles demonstrate Remember that he got different results for the two species Results When the lower zone grey species was removed the upper zone species expanded its niche downward The stronger lower zone grey species was able to occupy its fundamental niche and it competitively excluded the upper zone brown species The weaker upper zone brown species was forced to live in a realized 8 niche that was smaller than its preferred fundamental niche 10 What is predation and what kinds of effect does it have on population 9 dynamics Predation a strong selective agent for the
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