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Chapter 17

Chapter 17 bio 1225 notes.docx

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Department
Biology
Course Code
Biology 1225
Professor
Michael Butler

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Chapter 17 Communities and Ecosystems pg. 334 17.2 Factors that shape communities pg. 335 ***community – all populations of all species that live and interact in some area habitat – the type of place in which a species lives - ***niche – of a species is a description of the way that it utilizes its habitat – - ***fundamental niche ***the resources essential for survival and reproduction of a species including food and its own behaviour if it did not have to compete with any other species species diversity – the number of species and their relative abundance What factors shape a community? 1. Each species occupies a certain habitat and has a unique niche – the conditions and resources it requires, and the interactions it takes part in 2. Communities vary in their species diversity as a result of a. biological factors such as differences in incoming sunlight, temperature and soil quality (climate) b. Biological factors such as species requirements for survival and reproduction as well as interactions with other species ***know for exam - In principle, no two different species, no matter how closely related, can occupy exactly the same fundamental niche, since this will result in one species eliminating the other. - The niches can be very similar, but not the same. For example two fundamental niches may differ only in that one species feeds at night, the other during the day - When two species have niches that greatly overlap they will compete intensely with each other 1 17.3 Species Interactions in Communities pg 336 ***coevolution – joint evolution of two closely interacting species; each species is a selective agent that shifts the range of variation in the other Examples: a. hummingbird and flower b. predator and prey c. host and parasite d. insect and flower e. but NOT fish and whale ***commensalism – species interaction that benefits one species and neither helps nor harms the other competitive exclusion – when two species compete for a limiting resource, one drives the other to local extinction interspective compensation – two species compete for a limited resource and both are harmed by the interaction ***mutualism – species interaction that benefits both species example: an insect and the plants it pollinates symbiosis – one species lives on or inside another in a commensal, mutualistic or parasitic relationship camouflage – body shape, pattern, or behaviour that helps a plant or animal blend into its surroundings herbivory – an animal feeds on a plant, which may or may not die as a result mimicry –two or more species come to resemble on another 2 ***parasite – a. a species that withdraws nutrients from another species (its host) usually without killing it , but they MAY injure or kill it b. ***one species benefits and the other is harmed c. they reside externally or internally to the host d. they are specialists and generally a given parasite only lives in a given host ie. A given parasite CANNOT infect a plant as well as an animal ***predation – one species (the predator) captures, kills and feeds on another (its prey) ***Predator and prey exert selective pressures on each other resource partitioning – use of different portions of a limited resource; allows species with similar needs to coexist warning coloration – distinctive color or pattern that makes a well defended prey species easy to recognize brood parasite – an animal that ricks another species into raising its young, for example a cowbird parasitoid – an insect that lays eggs in another insect, and whose young devour their host from the inside ***Know for exam - A community – consists of coexisting populations of different species that occur in the same area - These populations interact with one another by symbiotic interactions, that may be beneficial, harmful of neutral. ***Populations are held in check by a. resource partitioning amongst species b. predation c. parasitism d. competition *** chemicals in plants and animals function as bad taste to discourage predation, repellents, toxins and warning 3 How do species’ interactions affect a community? 1. Species interactions can result in coevolution 2. An association in which species live together is symbiosis 3. In ***commensualism, one species benefits and the other is unaffected or unharmed 4. In ***mutualism, two species exploit one another in a way that benefits both Example: an insect and the plant it pollinates 5. ***Competitive exclusion occurs when species with identical resource share a habitat – competition for resources has a negative effect on both competitors. If both depend on the same limited resource, the stronger competitor may drive the weaker one to local extinction, a process called competitive exclusion. ***the competitive exclusion principle states that no two species can completely occupy the same niche 6. Interspecific competition favours individuals of both species whose resource needs are most unlike those of the competing species. Over time, competition alters traits related to resource use and leads to resource partitioning 7. Resource partitioning allows similar species to coexist (a subdividing of an essential resource, which reduces competition among species that use it. For example two pigeons are among twelve species that feed on fruit in the forests of New Guinea. Although all of the species eat fruit, the birds can coexist because they eat fruits of different sizes and types.) 8. Predators benefit at the expense of their prey, 9. ***parasites benefit at the expense of their hosts. (*** ie one species benefits and the other is harmed.) 10. ***Predation occurs when a free living predator kills and eats its prey. ***Predator and prey exert selective pressure on each other 4 11. In one type of mimicry, well defended prey species have similar warning coloration 12. Less well defended species also mimic well defended ones. 13. Camouflage hides both predators and prey 14. Herbivory may or may not kill a plant 15. Parasites withdraw nutrients from a host, usually without killing it 16. Brood parasites lay eggs in another’s nest 17. Parasitoids are insects whose larvae develop inside and feed on a host, which they eventually kill.
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