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Lecture 21

BIO SCI 94 Lecture Notes - Lecture 21: Species Richness, Primary Succession, Keystone Species


Department
Biological Sciences
Course Code
BIO SCI 94
Professor
Robin Bush
Lecture
21

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Bio 94 Lec 21
~A biological community consists of the species that interact with one another within a
particular area.
~ Community ecologists study the nature and consequences of the interactions among species
in a community.
~~We will look at four general types of interactions among species.
~These interactions affect the distribution and abundances of the species. Species thus act as
agents of natural selection on other species.
~These relationships are dynamic, that is, they may change over time and space.
1. Commensalism
2. Competition
3. Consumption
4. Mutualism
~Commensalism occurs when one species benefits but the other species is unaffected (+/0)
~ Competition occurs when individuals use the same resources resulting in lower fitness for
both (-/-).
~Competition occurs when individuals use the same resources resulting in lower fitness for
both (-/-).
~Niche: The range of resources that the species can use and the range of conditions it can
tolerate. More broadly, the role that species plays in its ecosystem.
~ There is a iportat distitio etee a speies’ fundamental nichethe resources it
uses or conditions it tolerates in the absence of competitorsand its realized nichethe
resources it uses or conditions it tolerates when competition occurs.
For any given species, the realized niche
A. is determined solely by abiotic factors in the environment
B. is not part of the fundamental niche
C. may be more restricted than the fundamental niche due to competition with other species
D. is generally less restricted than the fundamental niche
~The niche of a barnacle consists of rocks and other solid materials that are submerged at least
most of the time in the ocean, the ocean itself, and all the nutrients that the ocean provides.
~ Consumption occurs when one organism eats or absorbs nutrients from another, increasing
the osuer’s fitess ut dereasig the iti’s fitess (+/-). Our book includes herbivory,
predation and parasitism in this category.
Constitutive defenses are defenses that are always present. This can be expensive in terms of
energy or producing structures.
Inducible defenses are defenses that are NOT always present they are produced when
needed.
~Co-evolutionary arms race: A series of adaptations and counter- adaptations observed in
species that interact closely over time and affect each other's fitness.
find more resources at oneclass.com
find more resources at oneclass.com
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