module 4 Flashcards
what is trophic ecology?
the study of feeding relationships between organisms.
equation for efficiency in food webs
(Yt)^n
Yt - trophic yield (function of growth and metabolism)
n - number of trophic levels
what does it mean when a food web is size structured
body size is related to the position of the organism in the food web.
what are marine food webs dominated by?
why is this the case
small organisms
higher rates of reproduction, takes less time to grow, consume less than larger organisms.
bait balls
gather schools of fish or plankton in one area and feed on it.
ram-feeding
swimming through water column with mouth open
lunge-feeding
swim with mouth open and filter it through.
bubble-net feeding
Whales release bubbles through blowholes to trap schools of fish in one area.
chemosynthesis
uses energy released by inorganic chemical reactions to make sugars.
common in places where primary producers cannot receive sunlight for photosynthesis.
5 main chemosynthetic habitats in the oceans
- contiental slope sediments
2.hydrothermal vents
- whale and food falls
- cold seeps
- shallow-water sediments
trophic cascades
non-linear ecological interaction whereby a change in upper (lower) trophic levels induces dramatic shifts in lower (upper) trophic levels.
trophic cascade in otters and kelp
otter numbers decrease
(don’t feed on sea urchins)
sea urchins increase
(feed on kelp)
kelp decreases
trophic compensation
change in upper trophic level does not propagate down the food web.
the potential for compensation depends on the potential for the individuals to respond to predation and on the trophic diversity and complexity of food webs.
mesoconsumer release
when collapses in top predator populations are associated with dramatic increases in abundance of smaller predators.
marine biodiversity
the variety of life in the oceans comprising ecological, organismal and genetic components.
ecological diversity
the variety of biomes, ecosystems and habitats in the ocean.
species diversity
alpha, beta and gamma, taxonomic diversity, shannon’s diversity, evenness across different species
functional diversity
same metrics as species diversity but measured across different functional traits.
genetic diversity
same metrics as species diversity but also phylogenetic differences, measured across populations, individuals and genes.
where is there a higher diversity of reef fish species found?
in the tropics
where is there higher functional diversity of fish?
Galapagos islands and on the south west coast of Africa
biodiversity hotspots
regions or habitats with disproportionately high biodiversity value.
measured as the number of rare, endemic or endangered components
coral triangle
example of a biodiversity hotspot.
- habitat diversity leads to increase in niches
- genera are young, either evolving here or surviving here while going extinct elsewhere
- minimal disturbance from sea level rise
bathymetric gradient
why is this so?
depth gradient
higher species richness and diversity in shallow water.
- don’t have as much data about the deep sea as we do about shallower depths
abyssal plains
flat muddy plains in the deep sea.
deep-sea biodiversity hotspots
cold water coral reefs
seamounts
shipwrecks and other structures.
what are the 7 reasons why diversity reduces with increasing latitude
- time-stability hypothesis
- rapports rule
- Species-area hypothesis
- Differences in geological history
- Gradients in solar energy input/levels of productivity
- Mid-domain effect
- Differences in rates of evolutionary processes
time stability hypothesis
tropics are more stable over
evolutionary time than poles
Rapoport’s rule
small geographic ranges in the tropics permit
species co-existence, broader geographic ranges in higher latitudes
result in lower diversity
Species-area hypothesis
the tropics cover a larger area so can
support more species
Differences in geological history
higher latitudes are younger
Gradients in solar energy input/levels of productivity
low latitudes more productive
Mid-domain effect
denser species packing around geographic
midpoints of distribution
Differences in rates of evolutionary processes
speciation and
extinction rates differ in the tropics and poles.
why is there a higher biodiversity in the southern ocean?
- older ocean - arctic is still being colonised by new species
- larger area
- higher structural heterogeneity (leads to higher number of species’ niches)
intermediate disturbance hypothesis
we always find highest biodiversity in areas with intermediate disturbances.
Infrequent disturbance lets
slower-growing but competitively superior species (k-selected
species) dominate and exclude other species, while frequent disturbance favours only species that are fast-growing good colonisers (r-selected species).
marine biogeography
explores how groupings (clusters) of species form geographically distinct ecosystems and causal mechanisms of these groupings.
biogeographic realm
very large regions of coastal, benthic or pelagic ocean across which biotas are internally coherent at higher taxonomic levels due to shared and unique evolutionary history.
biogeographic provinces
nested in realms
large areas defined by the presence of distinct biotas that have at least some cohesion over evolutionary time frames.
biogeographic ecoregion
smaller units. areas of relatively homogenous species composition, clearly distinct from adjacent systems.
how many marine realms are there?
30
which organisms contribute to differences in boundaries?
endemic species contribute most to the creation of boundaries because of lack of mobility, inputs of freshwater, continental drift, geographical/bathymetric ranges of the animals.
what 6 environmental conditions contribute to creation of boundaries?
- temperature
- salinity
- dissolved oxygen
- nitrate
- phosphate
- silicate
