Ecology Exam 2 (54-56) Flashcards
what is a disturbance
is an event that changes a community, removes organisms from it, and alters resource availability
what does a nonequilibrium model describe
communities as constantly changing after disturbance
what is high level of disturbance a result of
frequent and intense disturbance
what is low level of disturbance a result of
can result from low frequency or low intensity of disturbance
what does the intermediate disturbance hypothesis state
moderate levels of disturbance leads to greater diversity than either high or low levels of disturbance
what effect does high levels of disturbance have on slow-growing species
it excludes them
what effect do low levels of disturbance have on dominant species
allows dominant species to exclude less competitive species
what is ecological succession
is the sequence of changes in community composition following a disturbance
when does primary succession occur
where no soil exists when succession begins
early-arriving species and later-arriving species may be linked in one of what three processes
-facilitate
-inhibit
-tolerate
early arrivals may ____ the appearance of later species by making the environment favorable
facilitate
early-arriving species may ____the establishment of later species
inhibit
early-arriving species may have no affect on the establishment of later species, which ____ conditions created early in succession
tolerate
what are the stages of glacier succession
- pioneer stage
- Dryas stage
- Alder stage
- Spruce stage
succession is the result of changes induced by what (in glaciers)
vegetation itself
on glacial moraines, pioneer plant species ____ later arrivals by increasing soil nitrogen content
facilitate
what is secondary succession
where soil remains after a disturbance
what are two key biogeographic factors that affect the species diversity of biological communities
latitude and area
where is species richness the greatest
in the tropics and generally declines in a gradient toward the poles
why do the tropics have more species richness
there has been more time for speciation to occur
what are two key factors affecting latitudinal gradients of species richness
evolutionary history and climate
why is species richness less in temperate and polar communities
they have “started over” repeatedly following glaciations
what are the two main climatic factors correlated with biodiversity in terrestrial communities
sunlight and precipitation
what is evapotranspiration
the evaporation of water from soil plus transpiration of water from plants
what does potential evapotranspiration measure
potential water loss, assuming water is available
what location geographically is evapotranspiration and potential evapotranspiration higher
in the warm, wet conditions of the tropics
for a region to be considered diverse what two criteria must be met
-It must have at least 1,500 vascular plants as endemics (a high percentage of plant life found nowhere else on the planet).
-It must have 30% or less of its original natural vegetation. In other words, it must be threatened.
what does species richness on islands represent
a balance between immigration of new species and extinction of established species
immigration and extinction are affected by island ____ and ____ from the mainland
size and distance
as the number of species on an island increases, what happens to immigration and extinction
-immigration decreases
-extinction increases
smaller islands have ____ immigration rates and ____ extinction rate
lower and higher
islands closer to the mainland have ____ immigration rates and ____ extinction rates
higher and lower
when is equilibrium in population reached (on islands)
when the rate of immigration is equal to the rate of extinction
community structure is universally affected by ____
pathogens
what are examples of pathogens
disease-causing microorganisms, bacteria, viruses, viroids, and prions
when are pathogens particularly virulent
in a new habitat
pathogens can have ____ effects on communities
dramatic
____ activities are transporting pathogens around the world at unprecedented rates
human
____ pathogens are transferred to humans from other animals
zoonotic
The transfer of pathogens can be direct or through an intermediate species called a ____
vector
Many of today’s emerging human diseases are ____
zoonotic
Regardless of an ecosystem’s size, its dynamics involve two main processes: ____ and ____
energy flow and chemical cycling
____ through ecosystems, while ____ within ecosystems
energy flows and chemicals cycle
Energy enters an ecosystem as ____ , is conserved, and can be lost from organisms as ____
solar radiation and heat
chemical elements are continually ____ within ecosystems
recycled
ecosystem are ____, absorbing energy and mass and releasing heat and waste products
open systems
if a nutrient’s outputs from an ecosystem exceed its inputs, that nutrient will ____
limit production
What is the primary source of energy for almost every ecosystem on the planet?
the sun
What process is used to capture solar energy for use in an ecosystem?
photosynthesis
What descriptive term is used for all the organisms that use photosynthesis to capture solar energy
primary producers
What is the difference between gross primary production and net primary production?
Gross primary production is the total amount of solar energy that is captured and converted into chemical bond energy. Net primary production is the gross amount minus the amount of energy that the organism must use to maintain its life at any moment in time.
why is solar energy a part of the ecosystem but not a part of the community
An ecosystem is the community of organisms and all the abiotic factors that affect their specified area. A community is just the living organisms
all food chains begin with ____ energy that is captured by a ____ organism
abiotic and biotic
how is energy passed between organisms
by eating each other
are energy conversions completely efficient
no
what is energy lost as
heat
____ build molecules themselves using photosynthesis or chemosynthesis as an energy source
autotrophs
____ depend on the biosynthetic output of other organisms
heterotrophs
energy and nutrients pass from ____ to ____ to ____ to ____
primary producers to primary consumers to secondary consumers to tertiary consumers
what is a primary producer
autotrophs
what is a primary consumer
herbivores
what are secondary consumers
carnivores
what are tertiary consumers
carnivores that feed on other carnivores
what are detritivores (decomposers)
are heterotrophs that derive their energy from detritus, nonliving organic matter
what are the main detritivores
Prokaryotes and fungi
____ connects all trophic levels
decomposition
In most ecosystems, ____ is the amount of light energy converted to chemical energy by autotrophs during a given time period
primary production
In some ecosystems, ____ are the primary producers
chemoautotrophs
The extent of photosynthetic production sets the ____ for an ecosystem’s energy budget
spending limit
The amount of solar radiation reaching Earth’s surface limits the ____of ecosystems
photosynthetic output
Total primary production is known as the ecosystem’s ____
gross primary production (GPP)
GPP is measured as what
the conversion of energy from light (or chemicals) to the chemical energy of organic molecules per unit time
what is net primary production (NPP)
is GPP minus energy used by autotrophs for respiration (Ra)
NPP is the amount of ____ biomass added in a given time period, not the ____ biomass of autotrophs
new, total
Only NPP is available to ____
consumers
what are the most productive ecosystem per unit area
Tropical rain forests, estuaries, and coral reefs
why do marine ecosystems contribute much to global net primary production even though they are relatively unproductive
because of their size
what limits primary production in aquatic ecosystems
-light limitations
-nutrient limitations
A ____ is the element that must be added for production to increase in an area
limiting nutrient
More than light, nutrients limit ____ in most oceans and lakes
primary production
____ and ____ are the nutrients that most often limit marine production
Nitrogen and phosphorous
What impacts primary production in terrestrial ecosystems?
-temperature
-moisture
____ is the most common limiting nutrient in terrestrial ecosystems
nitrogen
____ can also be a limiting nutrient, especially in older soils
Phosphorus
Various adaptations help plants access limiting nutrients from soil
-Some plants form ____ with nitrogen-fixing bacteria
-Many plants form mutualisms with ____; these fungi supply plants with phosphorus and other limiting elements
-Roots have ____ that increase surface area
-Many plants release ____ that increase the availability of limiting nutrients
-mutualisms
-mycorrhizal fungi
-root hairs
- enzymes
If NEP > 0, then an ecosystem stores carbon and acts as a ____
carbon sink
if NEP < 0, then the ecosystem releases CO2 and becomes a ____
carbon source
____ of an ecosystem is the amount of chemical energy in food converted to new biomass during a given period of time
Secondary production
An organism’s ____ is the fraction of energy stored in food that is not used for respiration
production efficiency
Birds and mammals can have efficiencies in the range of ____ because of the high cost of endothermy
1–3%
Fishes have production efficiencies of around ____
10%
