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%
Insects and microorganisms have efficiencies of ____ or more
40%
____ is the percentage of production transferred from one trophic level to the next
Trophic efficiency
how much energy is transferred from one trophic level to the next
10%
The rate of decomposition is controlled by what
temperature, moisture, and nutrient availability.
____ results in relatively low levels of nutrients in the soil
Rapid decomposition
where are most of the nutrients in rainforests
in the trees and other living organisms
____ and ____ ecosystems store large amounts of undecomposed organic matter, as decomposition rates are low
cold and wet
why is decomposition hard in wet ecosystems
Decomposition is slow in anaerobic conditions
Nutrient cycles are called ____ because they involve both biotic and abiotic components
biogeochemical cycles
what are the two characteristics that define the main reservoirs of elements
-whether they contain organic or inorganic materials
-whether these materials are directly available for use by organisms
what are four major factors to consider in the cycling of water, carbon, nitrogen, and phosphorus
- Each chemical’s biological importance
- Forms in which each chemical is available or used by organisms
- Major reservoirs for each chemical
- Key processes driving movement of each chemical through its cycle
Water moves by the processes of ____, ____, ____, _____, and movement through surface and groundwater
-evaporation
-transpiration
-condensation
-precipitation
know the water cycle
-
Carbon-based organic molecules are essential to ____ organisms
all
Carbon reservoirs include
fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, the atmosphere, and sedimentary rocks
CO2 is ____ through photosynthesis
taken up
know the carbon cycle
-
The main reservoir of nitrogen is the ____
atmosphere
what must nitrogen be converted to be taken up by plants
NH4+ (ammonium) or NO3– (nitrate)
what converts nitrogen to usable elements for plants
bacteria
Nitrogen is a component of ____, ____, and ____
amino acids, proteins, and nucleic acids
Organic nitrogen is converted to NH4+ by ____
ammonification
NH4+ is converted to NO3– by ____
nitrification
____ converts NO3– back to N2
Denitrification
Phosphorus is a major constituent of ____, ____, and ____
nucleic acids, phospholipids, and ATP
____ is the most important inorganic form of phosphorus
Phosphate (PO43–)
The largest reservoirs of phosphorus are ____, ____, ____, and ____
sedimentary rocks of marine origin, soil, the oceans, and organisms
____ of rocks releases phosphate into the soil, and it reaches aquatic systems through ____
weathering and leaching
Nutrient loss is much ____ in the deforested site compared with the undisturbed site
greater
nutrient loss in a forest ecosystem is controlled mainly by____
plants
what are the two key strategies for restoring biological communities
bioremediation and biological augmentation
____ is the use of organisms to detoxify ecosystems
Bioremediation
what organisms are used in bioremediation
prokaryotes, fungi, or plants
____ uses organisms to add essential materials to a degraded ecosystem
Biological augmentation
what organisms are used in biological augmentation
-nitrogen-fixing plants
-mycorrhizal fungi
Populations are dynamic; they change in size through ____, ____, ____, and ____
births, deaths, immigration, and emigration
Organisms transfer energy and matter in ecosystems through ____
trophic interactions
How many species (plant/animal) have been named and described on earth?
1.8 million species
How many species (plant/animal) are estimated to live on earth
5-100 million species
Tropical forests contain some of the greatest ____ of species
concentrations
what is conservation biology
seeks to conserve biological diversity at all levels, integrates several fields
what fields exist in conversation biology
-Ecology
-Physiology
-Molecular biology
-Genetics
-Evolutionary biology
is extinction a natural phenomenon
yes
the current high rate of extinction is causing a ____
biodiversity crisis
what are the three levels of biodiversity
-Genetic diversity
-Species diversity
-Ecosystem diversity
Genetic diversity comprises genetic variation ____ a population and ____ populations
within and between
The extinction of a population reduces the genetic diversity required for microevolution within a ____
species
Species diversity is the variety of species in an ____ or throughout the ____
ecosystem and biosphere
what is an endangered species
is one that is in danger of extinction throughout all or much of its range
what is a threatened species
is likely to become endangered in the foreseeable future
Globally, ____ of birds and ____ of mammals are threatened
12% and 21%
Extinction may occur at the ____ level, or species may be lost at a ____ scale
local population and global
human activity is ____ ecosystem diversity
reducing
The local extinction of one species can have a ____ impact on other species in an ecosystem
negative
The loss of species also means the loss of ____ and genetic diversity
unique genes
what are ecosystem services
encompass all the processes through which natural ecosystems and their species help sustain human life
what are examples of ecosystem services
-Purification of air and water
-Detoxification and decomposition of wastes
-Crop pollination
-pest control
-soil preservation
-Moderation of weather extremes
The ____ of biodiversity reduces the capacity of ecosystems to perform processes critical to our survival
reduction
Most species loss can be traced to what four major threats
-Habitat loss
-Introduced species
-Overharvesting
-Global change
Human ____ is the greatest threat to biodiversity throughout the biosphere
alteration of habitat
why does habitat fragmentation lead to species loss
because the smaller populations in habitat fragments are more vulnerable to extinction
is habitat loss a major threat to marine and freshwater aquatic biodiversity
yes
what are introduced species
are those that humans move from native locations to new geographic regions, either intentionally or by accident
why can introduced species spread rapidly
they don’t have native predators, parasites, and pathogens
how do introduced species disrupt a community
by preying on or outcompeting native organisms for resources
what is overharvesting
is human harvesting of organisms at rates exceeding the ability of their populations to rebound
what types of species are especially vulnerable to overharvesting
Species with restricted habitats and large organisms with low reproductive rates
Global change includes alterations in ____, ____ chemistry, and broad ____ systems that reduce the capacity of Earth to support life
climate, atmospheric, ecological
what was the first types of global change that caused concern
acid rain
what does acid rain contain
sulfuric acid and nitric acid
what causes acid rain
air pollution from burning wood and fossil fuels
how does acid rain affect freshwater animals
it kills fish and other lake-dwelling organisms
what are the two main approaches that biologists focus on conservation at the population and species levels
-The small-population approach
-The declining-population approach
The small-population approach studies processes that cause extinctions once population sizes have been greatly ____
reduced
A small population is prone to ____ and ____, which draw it down an extinction vortex
inbreeding and genetic drift
The key factor driving the extinction vortex is the loss of the ____ necessary to enable evolutionary responses to environmental change
genetic variation
do small populations and low genetic diversity always lead to extinction
no
what is minimum viable population (MVP)
is the minimum population size at which a species can survive
A meaningful estimate of MVP requires determining the ____, which is based on the population’s breeding potential
effective population size
The declining-population approach focuses on ____ and ____ populations that show a downward trend, regardless of population size
threatened and endangered
The ____ is studied and used to develop and test hypotheses of possible causes of decline
natural history of the species
what is the emphasis of conservation efforts on
the emphasis is on sustaining the biodiversity of entire communities, ecosystems, and landscapes
why do conservation efforts focus on sustaining the biodiversity of entire communities, ecosystems, and landscapes
-The physical features, or structure, of a landscape can strongly influence biodiversity
-Many species use more than one kind of ecosystem or live on the borders between ecosystems
The boundaries, or edges, between ecosystems, are ____ of landscapes
defining features
Some species take advantage of ____ to access resources from both adjacent areas
edge communities
An ____ has its own set of physical conditions, which differ from those on either side of it
edge
be able to explain the case study of the decline of the Red-Cockaded Woodpecker
-Red-cockaded woodpeckers require living trees in mature pine forests with little undergrowth
-What causes a decline?
Logging, agriculture, and fire suppression have reduced suitable habitat
-A combination of habitat maintenance and excavation of breeding cavities enabled this endangered species to rebound
Species adapted to ____ show the greatest decline in small habitat patches
forest interiors
Landscapes dominated by ____ are likely to support fewer species
small fragments
A ____ is a narrow strip or series of small clumps of habitat connecting otherwise isolated patches
movement corridor
Movement corridors promote ____ and reduce ____; and can facilitate natural migration routes
dispersal and reduce inbreeding
what is a biodiversity hot spot
is a relatively small area with numerous endemic species (found nowhere else in the world) and many endangered and threatened species
Biodiversity hot spots are good choices for nature reserves, but this approach has challenges. What are the challenges?
-An area that is a hot spot for one taxonomic group may not be for another
-Designation of hot spots is often biased toward saving vertebrates and plants
-Focus on hot spots puts a lot of emphasis on protecting a small fraction of the Earth’s surface
-The environmental conditions that favor a particular hot spot community may change over time
Large reserves can support ____, ____ animals with ____ populations or species that are ____ to habitat edges
large, far-ranging, low-density, sensitive
Small, unconnected reserves may ____ the spread of ____ between populations
slow, disease
what are zoned reserves
include relatively undisturbed areas surrounded by areas where human activities are unlikely to harm the protected area
The modified areas surrounding the protected areas serve as ____
buffer zones
what does the field of urban ecology examine
organisms and their environment in urban settings
what are human-caused changes in the environment
-Nutrient enrichment
-Accumulation of toxins
-Climate change
-Ozone depletion
Conservation efforts have historically focused on saving ____
individual species
Human activity often ____ nutrients from one part of the biosphere and ____ them to another
removes and adds
what impact do agricultural crops have on the ecosystem
-depletion of nutrients in the soil
-fertilizers add nitrogen and other nutrients of the ecosystem
what is critical load
is the amount of added nutrient that can be absorbed by plants without damaging ecosystem integrity
Nutrients that exceed the critical load leach into ____ or run off into ____ ecosystems
groundwater, aquatic
Agricultural runoff and sewage lead to what
phytoplankton blooms
what do phytoplankton blooms lead to
eutrophic lakes or runoff regions
what causes dead zones (hypoxic zones) in oceans/lakes
When the phytoplankton die, their decomposition depletes oxygen
where does biological magnification occur
concentrates toxins at higher trophic levels, where biomass is lower
can harmful substances persist for long periods in an ecosystem
yes
Toxic substances can accumulate in the ____ of organisms and become more ____ in the organisms that eat them
tissues, concentrated
what are examples of substances that cause biomagnification
PCBs (polychlorinated biphenyls) and DDT
what is an example of biomagnification
herring gulls of the Great Lakes lay eggs with PCB levels 5,000 times greater than in phytoplankton
what did DDT affect
the bird population (it was used to kill mosquitoes)
Pharmaceutical drugs enter freshwater ecosystems through ____ and ____
human sewage and agricultural runoff
Toxins ____ by microorganisms ____ in the environment for years
that cannot be degraded, persist
Toxins ____ by microorganisms ____ in the environment for years
that cannot be degraded, persist
what is the most common type of marine waste
plastics
what are microplastics
they are particles of plastics that are formed from the breakdown of larger pieces
The release of gaseous waste products into the atmosphere through human activities is driving ____
climate change
what is causing the increase in the concentration of atmospheric CO2
burning of fossil fuels and other human activities
why is the greenhouse effect important for Earth
it keeps the surface at a habitable temperature
what has the increase of greenhouse gases caused
an increase of average global temperature
what is the greenhouse effect
CO2, water vapor, methane, and other greenhouse gases reflect infrared radiation back toward Earth
what has been the impact of climate change
-reduced geographic ranges
-caused population declines
what types of organisms are less likely to survive rapid climate change
Organisms that cannot disperse rapidly or find suitable habitat
what ecosystems show the strongest effect of global warming
Northern coniferous forests and tundra
why has the tree death in coniferous forests of western North America increased
-higher temps
-decreased snowfall
-longer dry periods
what effect has climate change had on cells
affects rates of enzymatic reactions and impairs cellular defense responses
global warming has increased the risk of overheating in some species which leads to what issues for those species
to reduced food intake and reproductive failure
climate change has caused what changes to populations
-size
-timing of growth, reproduction, and migration
Species migration in response to climate change has caused ____ in ecological communities
dramatic changes
Global warming can be slowed by ____ energy use and ____ sources of energy
reducing, converting to revewable
what effect would reduced deforestation have on greenhouse gas emissions
it would decrease emissions
what protects life on Earth from UV radiation
layer of ozone in the atmosphere
what has caused the destruction of atmospheric ozone
chlorofluorocarbons (CFCs) produced by human activity
what does ozone depletion cause to happen in plants and phytoplankton cells
DNA damage
how does ozone depletion affect humans
increases skin cancer and cataracts
