Test 2 LIFE 220
Dispersion
The spacing of individuals with respect to one another within the geographic range. -Clustered (clumped) -Regular (evenly spaced) - Random
In general, an increasing degree of environmental heterogeneity of a community has a ________ effect on species richness? a) Neutral b) Negative c) Spatially explicit d) Positive
d) Positive
Vegetation patches within a given area that are at different stages of succession are known as: a) autosequences b) ecotypes c) clines d) chronosequences
d) chronosequences
Vegetation communities are often reset in succession by what? a) competition b) parasitism and predation c) disturbance d) invasions
d) disturbance
Which of the following traits are typically characteristic of an r-selected species? a) It lives in a stable environment. b) it competes well against other species. c) It is an ecological specialist d) it is long-lived e) None of the above.
e) None of the above
Trophic Cascades
occur when predators in a food web suppress the abundance of their prey, releasing the next lower trophic level from predation.
Ecotone
A boundary created by sharp changes in environmental conditions over a relatively short distance, accompanied by a major change in the composition of species.
Food Web
A complex and realistic representation of how species feed on each other in a community.
Metapopulation
A group of populations that are separated by space but consist of the same species. These spatially separated populations interact as individual members move from one population to another.
Cohort life table
A life table that follows a group of individuals born at the same time from birth to the death of the last ind. Plants, sessile animals.
Static life table
A life table that quantifies the survival and fecundity of all individuals in a population during a single time interval.
Survivorship:
A measure of survival - the probability of surviving from birth to any later age class. Denoted as l_x. Survivorship in the first age class is always 1 because all ind. in the pop are initially alive.
Geographic range
A measure of the total area covered by a population. All areas that a population's members occupy during their life.
Inhibition
A mechanism of succession in which one species decreases the probability that a second species will become established. -Common causes are competition, predation, and parasitism. (One species inhibits another by out-competing them)
Facilitation
A mechanism of succession in which the presence of one species increases the probability that a second species can become established. -Original species alters environment to make it suitable for another species. -Colonizers enable the invasion of other species by providing needed nutrients or conditions.
Tolerance
A mechanism of succession in which the probability that a species can become established depends on its dispersal ability and its ability to persist under the physical conditions of the environment. -Species that can handle stressful environments become established quickly.
Logistic growth
A model that describes slowing growth of pops at high densities.
Chronosequence
A sequence of communities that exist over time at a given location. Compare different communities with different levels of succession.
Omnivore
A species that feeds at several trophic levels.
Keystone species
A species that substantially affects the structure of communities despite the fact that individuals of that species might not be particularly numerous. Exert very strong control on community composition and function.
Food webs in communities
A system of interlocking and interdependent food chains, a possible path that enery and nutrients take when moving in an ecosystem.
Landscape model
Add types of barriers to migration, locations, and various properties of "good" habitats (e.g. nesting, feeding). Considers both differences in the quality of the suitable patches and the quality of the surrounding matrix.
Example of facilitation
Alder trees fix N2, allowing N-limited spruces to invade on developing soils. Marram grass on sand dunes, stabilize the dunes, produces litter that accumulates and provides nutrients.
Community
Assemblage of species that live and interact in the same place.
Total Fertility Rate
Average # of children a female will have during her entire reproductive life
Plant community structure along an environmental gradient can often be explained by ________: a) differences among species in their competitive ability b) differences among species in their abilities to tolerate environmental stress c) differences among species in their resistance to herbivores d) a tradeoff among species with respect to competitive ability and stress tolerance
Both b) and d)
Source-Sink model
Builds upon the basic metapop model and accounts for the fact that not all patches of suitable habitat are of equal quality. Add pop density in patches as a function of habitat quality and migration of "surplus" offspring.
Population Ecology
The dynamics of species populations and how these populations interact with the environment
Pioneer Species
The earliest species to arrive at a site.
Compare the pop growth models
The exponential model uses continuous data, whereas the geometric model uses discrete data that are calculated at each time point. Both models reveal the same in increase in pop size over time.
Climax community
The final seral stage in the process of succession
Climax community
The final seral stage in the process of succession. - A community will return to a climax com. composition following a disturbance.
Carrying Capacity = K
The maximum pop size that can be supported by the environment.
Dispersal aka Migration
The movement of individuals from one area to another. Individuals leaving their origin, and not usually returning.
Subpopulation
When a larger population is broken up into smaller groups that live in isolated patches.
Ideal free distribution
When ind. distribute themselves among different habitats in a way that allows them to have the same per capita benefit.
David Tilman
Wrote "Resource Competition and Community Structure". -Resource is something that can be consumed and have its amount be reduced. -Consumers use resources for maintenance and growth. -When its availability is reduced, biological processes are affected, reducing population growth.
Late-succession success
Determined by -Height -Ability to grow as a seedling under low-light conditions -Longevity -Seed dispersal -Seed viability
What factors affect the number of individuals in one species in one place?
-Age distribution -Rates of birth and death -Population growth
Population Age Structure
-Age structure diagrams are snapshots of pop at particular moment -Expanding pop - lots of new births -Stable pop - few births -Diminishing pop - natality < replacement
Spatial Population Structure Models:
-Basic Metapopulation model -Source-Sink model -Landscape model
Barriers to movement between sub-pops
-Distance between sub-populations -Nature of the intervening environment (distance, physical qualities) -Mobility of the species -No habitat corridors
Human Population General Trends:
-Fertility rates have declined -Mortality rates have declined -Pop growth continues because fertility rates still higher than replacement rates
Population genetics
-Gene pool of a pop is regulated by equilibrium and non-equilibrium effects -The non-equilibrium effects drive evolution in population
Spatial Population structure in Pop ecology
-Habitats are a mosaic of patches that vary in space and quality -Pops are divided into sub-pops -By definition, organisms are not likely to leave their sub-pop -Collections of sub-pops are "meta-pops" - Studies of spatial distribution of populations is in the sub-discipline of "Landscape ecology"
How do populations grow?
-Number of ind. already present = N -Population's carrying capacity = K -Growth rate = r (life-history strategy)
Environmental conditions restrain perpetual exponential growth:
-Pops given unlimited resources can grow exponentially -The LOGISTIC equation describes changes in pop growth rate with increased pop size
Canopy gaps in secondary succession
-Small disturbances can eliminate one or a few individuals from a late-successional community. -These gaps are pockets where successional stage is pushed back, key to diversity maintenance. -Gaps are a persistent part of the landscape because death is inevitable (e.g. occur before a senescent turnover).
3 types of Pop Structure:
-Spatial -Temporal -Genetic
Periodic fluctuations:
-can result from time delays in response to pop densities -pops can have intrinsic periodicity, like a pendulum -the "momentum" can come from high birth rates at low pop density -cycles driven by predators
Geometric growth
Compares population sizes at regular time intervals. Young ind. added to the pop at regular (e.g. annual) intervals.
Interspecific competition
Competition among different species
Intraspecific competition
Competition among same species
Total Population size =
Density * Area = Total pop size
Regular (Evenly spaced) dispersion
Each individual maintains a uniform distance between itself and the neighbors.
Seral stage
Each stage of community change during the process of succession. Annual plants (ragweed, crabgrass) --> Perennial plants and grasses (asters, goldenrod, broom sedge) --> Woody shrubs (blackberry)--> Fast growing trees (poplar, soft) --> Slow growing trees (oak, hard)
Density-Dependent factors
Factors that affect population size in relation to the pop's density -Competition - result of limited resources -As populations grow, interactions between competitors intensify. -Disease -Starvation
Density-Independent factors
Factors that limit pop size regardless of the population's density
Genetic patterns in populations
Genetic bias for local adaptations
Species-Area Curve
Graphical relationship in which increases in area (A) are associated with increases in the number of species (S). S = C * A^Z where C and Z are constants.
Population
Group of individuals of the same species living in the same place at the same time
Basic Metapopulation model
Habitable patches separated by uninhabitable barrier, occasional migration.
Life History characteristics
Important for understanding population growth potential of a population
Age Structure
In a pop, the proportion of individuals that occurs in different age classes.
Clustered (clumped) dispersion
Ind. are aggregated in discrete groups, a cluster.
Density in pop growth
Ind. per unit area, called crude density: Includes: -Natality (birth rate) -Mortality (death rate) -Age structure
"r" is
Intrinsic growth rate. Births minus deaths.
Trophic levels
Levels of a food chain of an ecosystem. Not all consumers eat the same thing, organisms in food webs grouped into levels. Trophic = related to feeding/nutrition. 1- primary producers 2- primary consumers 3- secondary consumers 4- tertiary consumers
Mark-Recapture method:
Method of population estimation in which researchers capture and mark a subset of individuals from an area, return it to the area, and then capture again after some time has passed. N = total pop size M = marked individuals n = # caught in re-capture effort x = # of recaptures that were marked
Non-renewable vs. Renewable resources
Non-renewable = not regenerated (e.g. space) Renewable = constantly regenerated or replenished.
New Habitats of succession
Often created by disturbance; disturbance restarts the successional clock. Time periods described as "early" or "late". Occurs over a long period of time. Community changes over time as changes in plant communities occur.
Top vs Bottom control
Phytoplankton (primary producers in aquatic, zoo plankton eats phytoplankton). Bottom-up says Phyto is bottom, controls Zoo pops which is top. Top down says Zoo determines Phyto. Both processes are important. Usually bottom-up!
Distribution
Pops are limited to ecologically suitable habitats.
Net Reproductive Rate
R_0 = the total number of female offspring that we expect an average female to produce over the course of her life.
Temporal pattern in populations
Random, periodic
Fundamental niche
Range of abiotic conditions under which species can persist. Includes temperature, humidity, and salinity.
Realized niche
Range of biotic and abiotic conditions under which a species can persist.
High-density pop
Reduces fecundity and increases mortality
Degradative succession
Serial replacements on dead organic matter by microbes and detritivores
Community Ecology
Study of a unit that arises from the interaction of populations of different species.
Competition among plant species rarely involves only a single resource: TRUE or FALSE
TRUE
"HSS Hypothesis"
The Earth is green because carnivores depress herbivores that would otherwise eat all the plants.
Primary succession:
The development of communities in habitats that are initially devoid of plants and organic soil, such as sand dunes, lava flows, and bare rock. -Lichens, mosses on rock -Grasses in sandy soil on sand dunes
Secondary succession
The development of communities in habitats that have been disturbed and contain no plants but still contain organic soil. -plowed fields -uprooted forests by a hurricane`
Population Structure
The non-random pattern in the population. Can provide info about how the population works
Density
The number of individuals per unit area or volume. Need to know the abundance of a population in a given area and the size of the area to calculate density.
Spatial structure
The pattern of density and spacing of individuals.
Exponential growth
The pop increases continuously at an exponential rate. Young individuals are continuously added to the pop. dN/dt =rN means "the change in population size with respect to time"
Random dispersion
The position of each individual is independent of the position of other individuals. Not common.
Succession
The process by which the species composition of a community changes over time. The Directional and continuous pattern of colonization and extinction on a site by species or changes in relative dominance on a site.
ecological niche modeling
The process of determining the suitable habitat conditions for a species.
Abundance
The total number of individuals that exist within a defined area.
Top vs. Bottom
Top-down control: Like HSS idea, that predators exert control on levels below. The abundance of a trophic group is determined by the existence of predators at the top of the food web. Bottom-up control: That the amount of primary production controls the abundance of higher trophic levels. The abundance of trophic groups in nature are determined by the amount of energy available from the producers in a community.
What is the best definition for an ecological community? a) An assemblage of species that live and interact in the same place. b) Individuals of the same species living and interacting in the same place. c) Individuals of a species within a given area d) A population of populations.
a) An assemblage of species that live and interact in the same place.
Which of the following factors controlling the growth of a pop is MOST likely to be density-independent? a) Drought b) Disease c) Starvation d) Parasites
a) Drought
In a metapopulation, the probability of local extinction increases with: a) Increasing patch size and increasing isolation b) increasing patch size and decreasing isolation c) Decreasing patch size and increasing isolation d) Decreasing patch size and decreasing isolation
c) Decreasing patch size and increasing isolation
The total number of species in a community is called? a) Diversity b) Evenness c) Richness d) Relative abundance
c) Richness
Closed community
coevolution and positive/facilitative interactions among members is prominent
Open community
coevolution is uncommon and diffuse, and competitive interactions predominate.
Spatial patterns in populations
metapopulations and extinction