11/22 quiz Flashcards
biogeography
study of the spatial distribution of species
wants to explain why species are found where they are
what can studying islands allow us to do?
learn a lot about the processes that determine species composition and diversity across the globe
who is the “father of biogeography”? what did he discover?
alfred wallace
discovered the fauna of the philippines was more similar to that of africa than of new guinea
what are wallace’s six biogeographic regions?
neartic, neotropical, ethiopian, paleartic, oriental, and australasian
what did wallace’s regions coincide with?
tectonic plates
what did continental drift do?
change locations of continents and oceans
how does a community get its species? (global perspective)
migration - depends on dispersal ability
establishing self upon arrival - depends on a/biotic factors
time - new species from speciation (vicariance, local adaptations, etc.)
how many species should an area have?
can predict based on speciation and extinction events in an area (ignoring migration)
larger geographic area increases…
probability of speciation
speciation often occurs when populations can become isolated (get rid of gene flow)
large areas increase the chance of population…
isolation and divergence
larger geographic area decreases…
the probability of extinction
larger areas can support larger populations -> less chance of extinction by chance events
larger areas increase the geographic range of species, which in turn…
allows species to spread out and decrease extinction risk
smaller populations have a larger probability of…
becoming extinct
smaller geographic areas increase the probability of…
extinction
what is the species-area relationship?
the positive relationship between species richness and area
occurs over a variety of scales
what is the formula for the species-area effect?
S = cA^z
to find number of species
what do the variables mean in the species-area effect?
S = number of species
A = area
z = slope of the line
c = constant
how can we plot species-area effect?
logS = logc +z*logA
logS on y-axis and logA on x-axis
c = intercept of log-log curve
z = slope log-log curve
where have most species-area relationships been studied?
islands, even if not literal islands
lakes, mountain tops (“sky islands”), habitat fragments
what predictions can we make based on the species-area relationship?
more species on large islands
fewer species on small islands
more isolated islands -> more speciation due to less gene and immigration
what are other contributing factors to the number of species on an island?
area of the island
number of species already there (extinction and immigration rates)
habitat heterogeneity
proximity to other islands
who determined the equilibrium theory of island biogeography?
MacArthur and Wilson
what is the equilibrium theory of island biogeography?
island communities reach an equilibrium number of species
what is the equilibrium number of species on an island dependent on?
the immigration and extinction rates of the island
which are both affected by the size of the island and its distance from the mainland
species number doesn’t change, but species ___ does
composition
what is “turnover”?
replacement species in island equilibrium theory
the number of species on an island is a balance between…
immigration (from the mainland)
extinction (of resident species)
how can we find the equilibrium number of species on a graph of number of species on an island and rate of immigration or extinction?
where the curves for immigration and extinction intersection
with more species on an island, you can expect…
less immigration of new species and more extinction
how can we use the theory of island biogeography practically?
when designing protected areas
like forest fragments or nature preserves, isolated patches connected by migration
which island will recover from defaunation the fastest? a close one or a far one?
the close one
how can we generally describe islands when considering equilibrium theory of island biogeography?
isolated patched connected by migration
ex: forest fragments and nature preserves
how can we apply the EToIB?
when designing protected areas
what is the Biological Dynamics of Forest Fragments Project?
one of the largest and longest-running ecological experiments to date
researching the role of size, isolation, shape, and configuration of forest fragments on species diversity maintenance
what were the treatment groups in the BDFFP?
4 different plots (1, 10, 100, and 1000 ha)
plots surrounded by forest (control) or deforested land (fragments)
what was the primary findings of the BDFFP?
diversity declines with isolation
edge effects cause positive feedback loops (exacerbating circumstances)
what were the regenerative findings of the BDFFP?
if the area around the fragment is allowed to regenerate after deforestation, fragments would have to be at least 1000 ha to preserve most of the bird species
if land is not allowed to regenerate (which is usually the case w/ agricultural land), we’d need at least 10000 ha fragments
how can lack of regeneration and forest fragmentation affect animal/insect species
most birds/insects/arboreal mammals will avoid entering clearings as little as 100 m wide
species become isolated and dispersal is prevented
what was the metatron?
structure of enclosed communities
able to remove/add connects with doors and alter climates and temperatures
how did MacArthur and Elton propose that species richness and community stability are related?
more diverse communities are more stable
what is stability?
the tendency of a community to remain the same in structure and function
more stable = more resistant to disturbances
the higher the species richness of a plot before a drought…
the less plant biomass is lost during the drought
up to a threshold of 10-12 species bc the species richness vs drought resistance plot begins to level off
species diversity is related to community stability and what other community functions?
primary productivity
soil fertility (resources in soil)
water quality (purification) and availability
O2 and CO2 exchange
resilience (rate)
evidence shows that species diversity have a positive effect on primary productivity, meaning…
plots with more species produce higher biomass (grew more)
how is the finding that species div. has a positive effect on primary productivity relevant to human behavior?
we typically plant crops with only one species of plant (monocultures), such as corn, meaning this is less efficient for their growth
however, this would also complicate our ability to produce biofuels bc would need microbe that can break down multiple plant species
how are biofuels obtained?
fermentation of plants, such as corn or soybeans
Tilman’s experiment showed that “prairie ethanol” generates ___ energy than biofuel made from monocultures
more
what is another benefit of prairie ethanol production for the environment?
much lower environmental effects that traditional biofuels
- less fertilizer and pesticides
- less greenhouse emissions
what is landscape ecology?
the study of the causes and consequences of spatial variation across a range of scales
what is a landscape?
an area where at least one element is spatially heterogeneous
mosaic of environments/patches
what does heterogeneous mean in terms of landscapes?
varies from one place to another
what is a patch?
relatively homogeneous area that differs from its surroundings
what is a matrix?
element in landscape that is spatially most continuous
background for patch mosaic
landscape dynamics are influenced by patch…
size
shape
composition
number
position (isolation)
species dispersal around a landscape (and migration between patches) if impacted by…
- spatial configuration of patches
- permeability of the matrix
what is meant by matrix permeability?
how likely species are to cross it, often species-specific (some species are more likely to cross the matrix)
what’s an example of matrix impermeability?
is salt water is between two areas and the organism is unable to swim or survive in that salinity
what are GIS?
geographic information systems
what do GIS do?
allow us to analyze and display data about a specific area
can include rainfall, vegetation, aerial photos, satellite imagery, and field studies
there are ___ 1 kilometer forest fragments in the US
no
we have logging roads in forest preserves
what are edge effects?
abiotic and biotic changes at patch boundaries
how can edge effects influence species dispersal?
barrier to inner-forest species’ ability to disperse
if there’s no trees, monkeys won’t leave the fragment bc they aren’t used to it and don’t want to
facilitate dispersal of invasive species
loss of humidity and soil moisture can promote invasive plant and beetle growth
how can edge effects change species abundance?
promote edge specialists, like deer
how far can edge effects extend?
up to 1 km from edge, which is larger than immediately apparent
relevant to US forest fragment sizes
what is SLOSS?
the consideration of whether nature preserves should be single large regions or several small ones
also what the best shape would be, consider amount of edge
what motivated SLOSS?
“we’re gonna lose stuff either way, but what’s the best way to do it?”
in terms of structuring nature preserves
what are other edge effects?
nest predation and parasitism in birds
interactions with domestic animals (cats, dogs, cattle)
legal and illegal hunting
edges can often be called…
“biological traps”
bc of potential for adverse effects
what are habitat corridors?
continuous connection for movement between patches (amphibians, mammals, etc.)
what are habitat stepping stones?
checkpoints allowing for shorter stretches of unsuitable habitat to be crosses (birds, flying insects)
why is facilitating movement (like with corridors and stepping stones) important?
increases gene flow and genetic diversity within populations
allows recolonization of locally extinct populations
what are the negative effects of facilitating movement between patches?
movement of predators, competitors, and pathogens
this is important to considering conservation options for some species
how can we decide the best way to facilitate species movement between patches?
work with local communities to identify goals of self and community to hit as many as possible
unfortunately, many protected areas in the US and elsewhere were designed to…
protect scenic places and not species
what’s the best for reserve size?
larger
what’s the best for reserve number?
one large instead of a few small ones of the same area
what’s the best for reserve proximity?
several close together better than far apart
what’s the best for reserve connectivity?
connection by corridors is better than unconnected
what’s the best for reserve shape?
compact shapes to minimize boundary/edge length
what’s the best for reserve buffer zones?
preferred to have a buffer than not have one
most reserves in the US are … directionally
N -> S with little elevation
most things will have to move outside their preserve to cope with ___
climate change
need to connect isolated reserves/provide corridors
photosynthesis is the ___ of most food chains
basis
plants only use a ___ of the visual light spectrum
subset; photosynthetic pigments
what is photosynthesis?
mechanism of converting sunlight into energy
other organisms can use energy produced (glucose)
what is the basic chemical reactions of photosynthesis?
light + H2O -> light-dependent reactions
+ CO2 -> calvin cycle
-> glucose and O2
how do plants take in CO2?
stomata
also used to release water
what is the trade-off between CO2 acquisition and H2O preservation?
open stomata allows plant to obtain CO2, but also forces H2O loss
closed stomata allows for preservation of H2O but deficiency of CO2
what are the photosynthetic pathways?
C3, C4, and CAM
what are stomata?
guard cells that open/close based on ion concentration
what is the C3 pathway?
photosynthetic mechanism used by most plants
has simultaneous c-fixation and l-d rxns (transfer of e-)
uses RuBisCO - inefficient at converting CO2 and plant needs lots of it
ancestral condition
what is RuBisCO?
an enzyme that fixes CO2 to a 3C compound
is the most common soluble protein in nature
holds up to 50% of a leaf’s nitrogen content
what is the problem with C3?
photorespiration: with low CO2, RuBisCO binds to O2 and reverses l-d rxn
what do C3 plants need a lot of and a limit of?
need high conc. of CO2
spends lots of time with open stomata -> lots of water loss
if we increase the conc. of CO2, C3 pathways will become…
more efficient
what effect do hotter temps have on C3 pathway plants?
loss of efficiency - bc losing more water
where are C3 plants most likely to be found?
cool and wet areas
what is the C4 pathway?
similar to C3 but uses a different enzyme in the first stage that has a high affinity for CO2
CO2 reaches Calvin cycle in much higher concentrations and stomata doesn’t need to be open as much
derived and independently occurring across various species
what is one down side to C4 pathway?
it takes more energy overall than C3
needs to produce additional enzyme
when is C4 optimal to use?
in hot dry weather
used by monocots and grasses
where are C4 pathway plants mostly found?
subtropical and tropical regions
what is the CAM pathway?
further adaptation to C4 pathway for extremely dry environments
temporal separation of l-d and C fixation stomata opening (night)
derived and independent origin
what is a pro of CAM pathway?
better preserves H2O in extremely dry environments
what are the down sides to CAM?
photosynthetic production rate is slower - slower growing
daytime photosynthesis is restricted by storage of CO2 from the night
where and what plants usually use CAM?
in deserts
tropical epiphytes - up high and not much contact with soil, limited access to water
desert succulents - usually plants with fleshy water-storing leaves/stems
what are other adaptations to control water loss?
trichomes, small leaves, waxy leaves
what are trichomes?
hairs on plants that protect their surface from direct sunlight and trap moisture
what do small leaves do to help control water loss?
lots of edges break down layers of hot air on leaf surface, facilitate heat dissipation
don’t need big leaves because sunlight is not a limiting resource
how do waxy leaves help control water loss?
they’re waterproof and reduce evapotranspiration - harder for water to escape
what do C3 plants need to survive?
moderate temperatures and high humidity
lose 97% of water taken up by roots through transpiration
C4 pathway plants lose about ___ times less water to transpiration than C3 plants
3
under what conditions do C4 plants perform better than C3 plants?
high temperatures, intense sunlight, drought, and low CO2 concentrations
how do we know which photosynthesis strategy is best?
depends on temperature, CO2, and water availability
C3: less efficient in hotter temps
C4: efficient constantly regardless of temp but more energy costly
what does 60% of grasses being a C4 pathway and abundance around the equator demonstrate?
underlying mechanism to increased biodiversity in these regions
based on efficiency of RuBisCO and photosynthesis
how do plants respond to elevated CO2 concentrations?
increased photosynthesis -> increased plant growth -> plants are made up of more carbohydrates and lack other nutrients -> soils do not have enough nitrogen to keep up with fast plant growth
what happens bc soils can’t keep up with increased plant growth as a result of increased CO2 concentrations?
changes in chemical composition of plant tissues occur (more carbs, less protein) -> lower quality food for herbivores -> herbivores eat more food to compensate
what can happen in the soils due to the loss of nitrogen richness after increased plant growth?
legume plants become more abundant bc they can use mutualisms to obtain nitrogen - ultimately change in species composition
what can happen to individual plants when CO2 levels are elevated? (-)
stomata can close sooner and remain closed for longer -> less evapotranspiration -> less water use -> higher soil moisture
plants can drown
not as much water goes to atmosphere -> change weather patterns
how are plants related to increased CO2 emissions?
important role in mitigating the effects of the increase
what are the effects increased atmospheric CO2 has had so far?
- soil (water, N availability, how organisms interact)
- plant chemical composition
- plant community composition
- herbivore populations
- potentially humans
what type of effcts have plant chemical and community composition changes had on food chains?
bottom-up
how do C4 pathways respond to increased CO2 conc.?
relatively unresponsive
how do C3 pathways respond to increased CO2 conc.?
increased growth if nutrients are available
how do legumes respond to increased CO2 conc.?
increased growth when symbiosis w/ N-fixing bacteria
under high nutrient and CO2 conditions, % of C_ plants decreases
4
outcompeted by C3 which benefit from increased CO2
under low nutrient conditions, % of ___ increases
legumes
what are nutrients?
elements required for development, maintenance, and reproduction
what do organisms need other than energy for metabolism and growth?
specific chemical elements - nutrients
chemical elements/nutrients are constantly cycling between…
organisms and their inorganic forms in the environment
what is a nutrient cycle?
use, transformation, transfer and re-use of nutrient in ecosystem
what is an ecological unit?
a food web that is broken down into species, substances, and abiotic portions
what is the tropic dynamic concept?
where components of the system fit in a structure
typically a pyramid, can identify central points
why are food chains usually only 4-5 trophic levels in size?
it becomes energetically inefficient and too disordered at further levels
what are the types of inorganic energy sources?
chemicals (oxidation of electron donors) and sunlight
what are chemoautotrophs?
eubacteria and archaea which derive energy from the oxidation of electron donors in their environment
such as: H2, H2S, or CH4 (methane)
what are photoautotrophs?
organisms that derive energy from sunlight through photosynthesis
why are we able to do energetic accounting for a given ecosystem?
because energy can only be transferred, never created or destroyed
as energy is lost and we move up in trophic levels we become ___ disordered
more
what is assimilation?
transformation of inorganic elements into organic forms
requires energy as input
ex: photosynthesis
what is dissimilation?
the transformation of organic forms into inorganic compounds
releases energy as product
ex: respiration
why do we obtain less energy in higher trophic levels?
bc eating other organisms become less and less efficient
compare to primary producers who take in direct energy from the sun
what is primary production?
the production of organic compounds from CO2
mainly photosynthesis
what is the basis of food webs on the planet?
primary production
what is gross primary production?
the total amount of energy assimilated by producers
what is net primary production?
the total biomass accumulated in the ecosystem
what is available to consumers
what can primary productivity be limited by?
light, temperature, water, and/or nutrients
how does more direct sunlight affect primary production in the tropics?
it is promoted
how is primary production impacted by upwelling or shallow waters?
promotes bc higher nutrients or higher temp, respectively
how does light limit primary production?
increases rate of production until saturation point
what is the saturation point?
when the rate of photosynthesis stops increasing with light intensity bc pigments saturated
what is the compensation point?
when energy gained through photosynthesis is equal to that used by respiration
what causes an organism to be above or below their compensation point?
above: energy balance is positive, exceed energy used
below: energy balance is negative, not enough energy to make up for use
primary production can vary…
across ecosystems
how does temperature limit primary production?
pp increases with temp, roughly with latitude
optimal temperature can varying with typical climate for that region
ex: temperate species -> 16C while tropical -> up to 38C
how does water limit primary production?
increased rainfall increases pp, only up to a point
past this point, there is too much rain and productivity decreases
why does pp decrease with too much water?
waterlogged soil, decreased decomposition, reduced nutrient regeneration
how can pp be limited by nutrients?
varies for different species, typically in regards to N and P
sometimes increase promotes, sometimes it will overload the organism, other times a specific combination is more effective than any singular increase
elevated CO2 can ___ productivity
increase
how can herbivory control productivity?
think of a bell curve: want enough herbivory so that no one species is outcompeting other primary producers but not too much that the plants aren’t able to grow either
how can energy flow through an ecosystem? give a generic cycle
bedrock and soil minerals -> inorganic soil nutrients -> plant biomass -> plant detritus (feces, dead plant matter, etc.) -> inorganic soil nutrients -> repeat to biomass or run off in groundwater or stream
what can assimilated energy do for an organism?
respiration, production of growth or storage, or excretion
food chains can have ___ or ___ controls
top-down or bottom-up
what causes top-down controls?
primary producer affected by consumers
what can cause bottom-up control?
abiotic factors affect primary production
with each step in a trophic pyramid, ___ of energy is lost
80-95%
what is trophic efficiency/food chain efficiency?
the percentage of energy transferred from one trophic level to the next
how can energy loss along a food chain affect hunting?
determine what can be done sustainably
why are efficiency levels so low?
energy is used for:
maintenance, growth, reproduction
excretion of waste
some components are not assimilated (exoskeleton, bone, cellulose)
what are trophic cascades?
consumer-resource interactions that affect species other than those that are directly involved
domino effect
what are food webs?
models that help us define energy flows and predator-prey relationships in an ecosystem
patterns in food web can chance among …
life stages
food webs affect community …
structure
removal of one species can cause overgrowth of another -> breaks up equilibrium
what are the biogeochemical cycles?
nitrogen, phosphorus, decomposition, effects of pollution on ecosystems
what is a reservoir for most of earth’s nitrogen?
the atmosphere (78%)
mostly inaccessible
how can nitrogen enter its cycle?
microorganisms or lightning
how do microorganisms bring nitrogen into a system?
free-living bacteria, cyanobacteria, and symbionts (ex: legumes) perform biological fixation
N2 -> NH3
how does lightning bring nitrogen into a system?
atmospheric fixation by dissolving N into water and forming nitrates (5-8% of total fixation)
N2 -> NO
biological processes happen at a ___ rate
fast
ex: animals, microbes, detritus, bacteria
geological processes occur at a ___ rate
slow
ex: inaccessible organic compounds (coal, oil)
___% of biological nitrogen fixation comes from free-living bacteria
30
use energy from decomposition of detritus
N2 -> ammonia -> nitrite and nitrate by soil bacteria
___% of biological nitrogen fixation is done by symbiotic bacteria
70%
bacteria living in symbiotic relationships with plants, occur in nodules in roots
bacterial nitrogen fixation makes up for ___% of nitrogen assimilated by terrestrial plants
12
where does bacterial nitrogen fixation comes from other than assimilation by terrestrial plants? how?
decomposition
when bacteria die, they release ammonia into the soil
how can we lose nitrate in a system?
bc nitrate does not bond to clay particles, so it can be picked up in water or blown away
often lost to aquatic systems due to run off if plants don’t use it
what can the loss of nitrogen in a system lead to for aquatic systems?
euthophication
what is nitrification?
a dissimilation reaction
in the presence of O2, specialized bacteria: ammonia -> nitrite -> nitrate
what is denitrification?
a dissimilation reaction
when does denitrification happen?
soils with low O2 (anaerobic)
result in specialized bacteria that obtain energy by reducing nitrate to nitric oxide or nitrogen gas, which return to the atmosphere
true or false: nitrification and nitrogen fixation are the same process
false!
fixation takes nitrogen from the atmosphere
ammonia is a ___ ___ for most organisms
waste product
how have humans impacted nitrogen fixation?
increased the pool of fixed nitrogen
started in the twentieth century, we have now exceeded N fixation by nonhuman processes
what are examples of non-human processes that perform nitrogen fixation?
terrestrial, marine, and lightning
what are examples of human processes that cause nitrogen fixation?
crops, industrial, fossil fuels
what is eutrophication?
the increase of nutrients in water
what does eutrophication cause?
dead zones due to hypoxic areas in aquatic systems
what is the series of events that causes dead zones after eutrophication?
explosive algal blooms due to increase nutrient availability (seemingly infinite resources) -> population growth crashes, especially bc algal are short lived organisms -> lots of decay, which uses oxygen -> hypoxic environment at the bottom of aquatic regions -> other things die
how has human activity changed systems’ abilities to manage eutrophication?
used to be able to naturally manage but human contributions have exceeded systems’ abilities
what can algal blooms result in?
O2 depletion, dead zones, large-scale changes, and neurotoxins
what can low nitrogen do to a community?
increase biodiversity by promoting competition
best competitors survive and when something dies, decomposition allows small organisms to still access nitrogen
what does excessive nitrogen do to a community?
reduce biodiversity bc whatever population can grow the fastest persists
phenomenon is used by grass fertilizers
what can too much nitrogen result in an ecosystem?
changes to species composition
some plants increase in primary production, others might even be depleted
what effects does nitrogen loading have on terrestrial ecosystems?
increase plant production but decrease diversity
shift composition to weedy species
decrease consumer species richness and increase consumer abundance
affect nitrogen and carbon cycling
what is a natural solution to our agricultural pest problem? what is interfering with our ability to do it?
having predators in the system would help
monocultures interfere with maintenance of that predator
this is why we should have multi-culture crops
where do we get phosphorus from in the environment?
weathering of rocks bring it into terrestrial systems
how can plants uptake phosphate?
ions in the soil
how do decomposers interact with phosphorus?
they break down organic phosphorus
why can’t most aquatic systems use phosphorus biologically?
it is bound to soil particles which are stuck in the bottom of the system and don’t recycle
why is phosphorus needed?
for cell membrane and DNA/nucleic acids
how do fungi play a role in nutrient cycles?
help uptake nutrients, like phosphorus
how can nitrogen-fixing plants play a role in primary succession?
increase N inputs to the ecosystem and facilitate colonization of other, sometimes invasive, species
