Factors causing community change originate outside the community; usually large-scale environmental factors like climate chagne, large-scale disterbances
Autogenic Succession, Autogenic Factors
Factors causing community change originate within the community, from inter-specific interactions (compeition, predation, mutualism) and the different physiologies of species
A region with a very high number of endemic species
Broad areas of more of less uniform life form of vegetation, with associated animal cmmunities, examples- tundra, taiga, temperate forest, tropical rain forest, savanna, grassland, desert, chaparral (shrublands)
The group of species that co-exist and interact in a particular place and time
Any sudden or abrupt removal or destruction of live biomass. Disturbances can range from small events to very large events
Disturbance return interval or frequency
The average amount of time between disturbance events of a defined size (flood depth and duration)
A combination of the number of species and their relative abundance (evenness)
A simple count of the number of species in an area
Evenness and Dominance
The relative numbners of individuals of each species in total number of indiciuals in a sample. In a community with high evenness, all species are equally represented amount the indiciduals. In a community with low evenness (-high dominance), one or a few species account for most of the indicuals and all other species have only a few indivuals present.
A mathematical formula that incorporates both richness and evenness into a single measure of diversity;l it describes the uncertainty of identifying of identifying any randomly chosen indicual from a community (the high the divevrsity, the higher the uncertainty).
Shannon Diversity Index equation
s = total number of species
pi = fraction of individuals that are in species i
= ni / N
An area over which one community grades into another, with species characteristic of each of the two comunities may be found together, and the physical environment typically has characteristics intermediate between those of the two different communities. An example is the vegetation at the boundary between a forest and a field.
A species that is found only in a single restricted area.
The presence of one species enhances the growth and/or survival of another species.
Discovered 'superorganism' concept of the community.
'individualistic' concepts of the community
R. H. Wittaker
Data collected along gradients supports the individualistic idea (gradient approach)
Asked the big question-why are there so many species?
collaborator in developing island biogeography theory
collaborator in developing island biogeography theory
Experimental test of island biogeography
Change in ecosystem function during sucession
A regualrly changing environmental property (elevation, moisture, temperature)
A group of organisms within a community that all use a suite of resources in the same way (insects whose larvae grow within seeds; bottom feeding fish; ground-nesting birds; annual plants growing in gaps in the forest canopy)
The concept put forward by Henry Gleason to describe the concept of the community as a group of speices that happen to live in the same place because they have similar responses to environmental factors, but are not particularly related to or dependent on each other.
Net Primary productivity
The total amount of new biomass produced by plants during a defined period of time, usually a year or a growing season; usually measured as "grams of biomass per unit area per unit time (grams/hectare/year)
The use of pollen and plant fossils to study communities an climate in the past
A species capable of establishing and growing on bear surface
Sequential change in species composition of communites over time
Sequence of communities that occur on a substrate that never had a biotic commmunity on it
Sequence of communities that occur on a substrate that was previously occupied by a biotic community
A set of intermediate stages in the sequence of communities changing over time
The final stage of a sere; the community that persists for a long period of time (a concept not often used today)
A set of concurrently eisting patches of different successional stages
The concept put foward by Frederic Clements to descrube the concept of the community as a group of tightly connected organisms that all depend on each other, and that respond to environmental factors as coordinated group
Form of competition in which members of the same species vie for the same resource in an ecosystem (e.g. food, light, nutrients, space).
Interspecific competition, in ecology, is a form of competition in which individuals of different species vie for the same resource in an ecosystem (e.g. food or living space).
When species grow together without causeing harm to one another (defeating survival rates)
Consume part of prey individual
Consumes part of one individual
The concept that two species cannot long coexist if they have identical niches
An n-dimensional hypervolume which defines the limits within which a given species can survive and reproduce
Herbivory can change the set of plants that co-exist by reducing fitness of some species but not others.
Compensation: grazing of older leaves off of some plants (like grasses) stimulates new growth and/or flowering
Seed dispersal by fruit predators (scarification)
Plant Defenses Against Herbivory
Chemical (ferulic acid, scopoletin, morphine)
Structural Defenses (spines and thornes)
Predator Satiation (prey occur at high population densities, reducing the probability of an individual organism being eaten)
Disperse seeds UNEVENLY ACROSS SPACE so that some places have LOTS of seeds and some places have only a few -- counting on attracting and satiating seed predators in only one spot.
Disperse seeds unevenly THROUGH A SEASON so that there are LOTS and LOTS of seeds for only a few days -- counting on attracting and satiating seed predators in a short time.
Disperse seeds UNEVENLY ACROSS YEARS so that there are only seeds available in random years -- counting on predators not keying in on a single spot as a seed source year after year.
Detoxification (metabolize or eat around chemical defenses)
Energy transfer is inefficent which may limit the length of food chains (each degree raised only gets 10% of orginial energy)
a species whose activities have a significant role in determining community structure
A Model of Inter-specific Competition
α = negative competitive impact, per individual, of species 2 on species 1
β = negative competitive impact, per individual, of species 1 on species 2
K: carrying capacity
r: per capita growth rate
N: population size
The four outcomes of the Lotka-Volterra Model
1. Species 1 outcompetes species 2
strong interspecific competition
2. Species 2 outcompetes species 1
strong interspecific competition
3. Unstable equilibrium
4. interspecific competition more important than intraspecific → outcome depends on initial
conditions (Priority Effects)
Stable equilibrium (coexistence)
when intraspecific competition is more important than interspecific
Absence of competitors
Determined by Competitiors
Occurs indirectly between two species which are both preyed upon by the same predator. For example, species A and species B are both preys for predator C
A reciprocal relationship between two species where the survival, growth and reproduction of individuals from each species is enhanced. (+,+)
Types of Mutalism
Obligate Symbiotic (lichens, myciorrhizae)
Opportunistic for at least one species
Benefits of dispersal of seeds
Benefits of Pollination Mutualisms
Male Euglossine bees collect fragrant chemicals from orchids for use in mating
Orchids are pollinated through transfer of pollinia Pollinia of different orchid species attach to different parts of pollinators
Pollinators get nectar (food), and flower gets pollen transfer and (hopefully) reproduction
An intimate relationship between two organisms in which one (the parasite) lives on, off or at the expense of the other (host).
*additionally, parasites have at least one life stage that is dependent upon ONE host for the duration of that stage.
Social parasitism (Brood Parasitism)
host raises young of parasite Co-evolution between breed parasites and hosts (nest abandonment and/or raising parasitic young)
Parasite gains a substantial portion of its food by stealing it from hosts
Types of Parasitism
Cold temperatures, strong winds, and permanently frozen soil (permafrost).
Dominant vegetation types are grasses, mosses, and lichens.
Boreal Forest (taiga)
Forests of pine, spruce, fir, and larch
Grasslands and Savannas
containing many grasses but few trees and having low to moderate rainfall
dominated by grammanoid or herbaceous vegetation, generally greater than 80 percent of the total vegetation
A dry, barren area of land, that is characteristically desolate, waterless, and without vegetation
Tropical Rain Forest
lush vegetation, abundant rainfall, and plentiful sunlight
hot and wet all year
Factors Driving Diversity Among Biomes
Climate and variability
Net primary productivity
Factors driving diversity within biomes
Net primary productivity
Immigration and extinction
Values of Diversity
No prior community (non-soil substrate)
Pioneer species start the process
Soil development is critical
Often 100s of years before climax
Animals can influence strongly
Each seral community changes environment
Examples: volcanos, coastal dunes, mine spoil, glacial moraines, sand mines, libersty state park, Warren Grove Gunnery Range
Prior community (soil substrate)
a process started by an event (e.g. forest fire, harvesting, hurricane) that reduces an already established ecosystem
Autogentic species traits
Seeds and Dispersal
Environmental alteration and tolerances
Autogenic species interactions
Changes the availability of envioronmental resources in an ecosystem
Characterized by frequency and intensity
A type of species interaction that benefit at least one of the participants and causes harm to neither.
Resource ratio hypothesis
A hypothesis that assumes that species can coexist in a community by using resources the same resources but in different proportions.
(light vs nutrients and water)
Biotic Interactions and Invasion
The process of assisting the recoverry of an ecosystem that has been degraded, damaged or destroyed
Two factors of Ecological Restoration
Directing ecological succession
– Community assembly and dynamics
– Successional trajectories
Land management applications
How is restoration implimented?
Attributes of restored systems
Habitat islands experiment
Introduction of an invasive species to see how fast the species will invade
Goals and moving targets of Restoration
Ecological Constraints of restoration
Propagules: A vegetative structure that can become detached from a plant and give rise to a new plant
Interactions - missing and new
Soil quality and biota
Changed disturbance regimes
Genotypes of planting material
Ecological Opportunities of Restoration
Restore natural heritage of the land
Restore ecological functions
Minimize, but not eliminate, management needs and costs
Improve biodiversity in surrounding areas
Add ecological resiliency for the future
A relationship between the area of a habitat, or of part of a habitat, and the number of species found within that area.
Larger areas tend to contain larger numbers of species, and empirically, the relative numbers seem to follow systematic mathematical relationships
These factors include the relative balance between immigration and extinction, rate and magnitude of disturbance on small vs. large areas, predator-prey dynamics, and clustering of individuals of the same species as a result of dispersal limitation or habitat heterogeneity.
Net Primary Production
Net primary production is the rate at which all the plants in an ecosystem produce net useful chemical energy.
It is equal to the difference between the rate at which the plants in an ecosystem produce useful chemical energy (GPP) and the rate at which they use some of that energy during respiration.
Some net primary production goes toward growth and reproduction of primary producers, while some is consumed by herbivores.
Intermediate Disturance Hypothesis
The Intermediate Disturbance Hypothesis (IDH) states that local species diversity is maximized when ecological disturbance is neither too rare nor too frequent.
At low levels of disturbance, more competitive organisms will push subordinate species to extinction and dominate the ecosystem.
At high levels of disturbance, due to frequent forest fires or human impacts like deforestation, all species are at risk of going extinct.
According to IDH theory, at intermediate levels of disturbance, diversity is thus maximized because both competitive K-selected and opportunistic r-selected species can coexist.
Major Events in Earth History
Archean Chronometric Eon (3000 mya): Photosynthetic cyanobacteria; production of molecular O2
Precambrian Eon (2500 mya): Great Oxidation Event
Phanerozoic Eon (580-540 mya): Sufficient atmospheric O2 for formation of O3, Colonization of land
Phanerozoic Eon (570-530 mya): Cambrian Explosion, evolutionary burst of life
Phanerozoic Eon (424 mya): Primitive plants move onto land
50,000 ya: Early colonization of Europe and ASia by modern humans
200 ya: Beginning of Anthropocene
How is the Earth Warming?
A layer of greenhouse gases – mainly H2O vapor and
including much smaller amounts of CO2,CH4 &N2O–act as a thermal blanket for the Earth, absorbing heat and warming the surface to a life-supporting average of 59 °F (15 °C).
Evidence of climate change
Sea level rising (about 17 cm in last centur)
Declining Arctic Sea Ice: both extent and thickness
Extreme Events: extreme high and low temeprtures as well as intese rainfall
Ocean Acidification: Increase in CO2 increases the ocean acidity (30% since 1750).
Each organism has a specific thermal range. When temperatures exceed the thermal range of an organism, it's probability of lethal heat stress increases.
Warming in the tropics, although relatively small in magnitude, is likely to have the most deleterious consequences because tropical insects are relatively sensitive to temperature change and are currently living very close to their optimal temperature.
In contrast, species at higher latitudes have broader thermal tolerance and are living in climates that are currently cooler than their physiological optima, so that warming may even enhance their fitness.