Lecture 5 Exam 1 Flashcards
1
Q
What is the hydrologic cycle?
A
- heat, evaporation, clouds, precipitation
- distribution of water is not static, powered by solar energy
2
Q
What is turnover time
A
the time required for the entire volume of a reservoir to be renewed
atmosphere: 9 days
rivers: 12-20 days
oceans 3,100 years
3
Q
Describe oceans
A
- circulation driven by winds under coriolis effect
-moderate earth’s climate
gyres: clockwise currents in northern hemisphere and counter-clockwise in southern hemisphere
4
Q
Describe ocean structure
A
- divided into horizontal and vertical zones
- each zone supports distinctive assemblage of life
pelagic: off the bottom
benthic: on the bottom
5
Q
ocean light
A
- 80% absorbed in first 10m
- leaves ~ 3,400 of deep black water, only bioluminescence
6
Q
ocean temperature
A
- sunlight increases velocity of water which decreases density - warm water floats on top of cooler water
-creates thermal stratification
-thermocline: layer where temp changes rapidly with depth
-upwelling: winds blow surface water offshore, cold water rises to surface, brings up nutrients
7
Q
ocean salinity and oxygen
A
-oxygen concentration low compared to air, varies with depth
8
Q
Where is salinity higher, equator or subtropic oceans?
A
subtropic because in equator: precipitation > evaporation
so in subtropic evaporation > precipitation
9
Q
The littoral zone
A
- also called intertidal zone
- extends between highest and lowest tidal levels
- periodically exposed to air: life adapted accordingly
-exposed to wide variation in light intensity
– one of the most dynamic environments in biosphere - waves and tides affect distribution and abundance of organisms
- oxygen not limiting due to mixing caused by waves
- differential tolerances to periodicity of air exposure leads to zonation of species
10
Q
the neritic zone
A
- between the lowest tide level and edge of continental shelf
- high productivity: sunlight and nutrients in sediment
- where you find kelp forests (brown algae) and coral reefs
11
Q
kelp forest and coral gardens
A
-shallow waters around land
- high diversity and productivity
-corals confined to 30 N and S limited by temperature
- kelp in temperate water - like a forest
12
Q
oceanic zone
A
- beyond the continental shelf, seafloor drops rapidly to great depths
- production strictly limited: low availability of nutrients
- divided into several depth zones
13
Q
Describe the biology of oceans. Where does certain life live?
A
- photosynthetic organisms (phytoplankton and zooplankton) are limited to upper epipelagic zone (photic zone)
-due to size, oceans contribute 1/4 of total photosynthesis in the biosphere - though mean rate per square meter similar to a desert - life exists at all depths
- chemosynthesis occurs near undersea hot spring
14
Q
estuaries, salt marshes, and mangrove forests
A
- estuaries are found where rivers meet the sea
- salt marshes and mangrove forests are concentrated along low-lying coasts
- all driven by ocean tides and river flow
- physically dynamic systems leads to chemical variability (salinity and oxygen)
- transport organisms (abundant but may not be species rich), nutrients, oxygen, and remove waste
15
Q
rivers and streams
A
- length: pools, runs, riffles, rapids
- width: wetted/active channels
-vertical: water surface, column - riparian zone is a transition area between the aquatic and upland terrestrial environments
- river currents erode land, carry food, renew oxygen - all affect type of life
- upstream: few minerals, lots of oxygen, fast, moving water
- downstream: lots of minerals, less oxygen, slow moving water
16
Q
Lakes
A
- most of the world’s freshwater resides in a few large lakes. Great lakes of north America contain 20% of freshwater in the world
- littoral zone: shallow near shore, rooted plants
- limnetic zone: open lake
- lakes thermally stratified like oceans. Spring and fall get lot of mixing. In tropics at low elevation little mixing
- salinity varies among lakes
- spring and fall get lot of mixing, renews oxygen and nutrients
17
Q
What is primary production
A
- primary production: fixation of energy (production of new organic matter) by autotrophs in an ecosystem
18
Q
photosynthesis
A
- ultimate source of energy for most heterotrophs
19
Q
trophic level
A
- position in a food web determined by the number of energy transfers from primary producers to current level
20
Q
terrestrial primary production
A
- terrestrial primary production: generally limited by temperature and moisture. high rates generally occur under warm moist conditions. However soil fertility can also explain differences in terrestrial primary productivity
21
Q
Control of primary production via trophic cascades
A
- bottom-up control: primary production affected by physical and chemical factors like temperature and nutrients
-top-down control: primary production affected by consumers
22
Q
energy flow through trophic levels
A
- energy losses limit the number of trophic levels in ecosystems
- as energy is transferred from one trophic level to another (trophic dynamics) energy is degraded
- limited assimilation and consumption
- consumer respiration
- heat production - ecological efficiency: the % of energy transferred from one trophic level to the one above it
- energy quality decreases with each successive trophic level
- pyramid shaped energy distribution
23
Q
oceans: polar caps glaciers: freshwater
A
97-2-1
24
Q
Describe how seasonality affects lakes
A
- spring and fall get a lot of mixing, renews oxygen and nutrients
- this is due to vertical mixing of water column
25
Q
Oligotrophic vs Eutrophic Lake
A
- oligotrophic: well-mixed lakes, lot of oxygen, cool temperatures, low biological productivity, steep bottom
-eutrophic: high productivity, low oxygen, warmer temperatures, shallow bottom
26
Q
What is an autotroph?
A
- autotroph: organism that can synthesize organic molecules using inorganic molecules (CO2) and energy (light or inorganic molecules)
27
Q
what is gross primary production?
A
- gross primary production: total amount of energy fixed by autotrophs
28
Q
What is net primary production?
A
- net primary production: amount of energy leftover after autotrophs have met their metabolic needs, amount available to consumers
29
Q
What is a heterotroph?
A
-heterotroph: organism that uses organic molecules both as source of carbon and energy
30
Q
Aquatic primary production
A
- aquatic primary production: generally limited by nutrient availability. In marine systems, highest rates by marine phytoplankton are generally concentrated in areas with higher levels of nutrient availability
- open ocean tends to be nutrient poor
- vertical mixing main nutrient source but not so much in tropical oceans
31
Q
How does energy flow through the trophic levels?
A
- energy losses limit the number of trophic levels in ecosystems
- as energy is transferred from one trophic level to another energy is degraded
- limited assimilation and consumption
- consumer respiration
- heat production
- ecological efficiency is the percentage of energy transferred from one trophic level to the one above it
- energy quality decreases with each successive trophic level
- pyramid shaped energy distribution
32
Q
Describe energy flow in a forest
A
- 99% of solar energy unavailable for use by second trophic level
- of the net primary production eaten by consumers - 96% lost as consumer respiration (not much left for 3rd trophic level
- as energy losses between trophic levels accumulate, eventually there is insufficient energy left to support a viable population at a high trophic level
- ecosystems store some energy in the form of dead organic matter and biomass but most energy flows through
