Transcript ENVI 21 Life in the Ocean

I.
Challenges of Life in the Sea
A.
Salinity
1.
Diffusion and Osmosis
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Diffusion problematic – leads to loss of important ions
Selectively permeable cell membrane limits movement
of certain molecules (large, electrically charged) but
allow movement of small molecules, e.g. water
Osmosis – Diffusion of water across selectively
permeable membrane
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Water diffuses from region of higher water
concentration (lower salt concentration) to region
of lower water concentration
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Possible to move molecules against concentration
gradient by using energy to power active transport
Fig. 4.13
I.
Challenges of Life in the Sea
A.
Salinity
2.
Regulation of Salt and Water Balance
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Osmoconformers
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Energetically inexpensive
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Limits distribution to areas with stable salinity
(Where?)
Osmoregulators
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Expend energy to maintain body fluid composition
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Less constrained by salinity in habitat
Euryhaline vs. Stenohaline
Fig. 4.14
Fig. 4.15
I.
Challenges of Life in the Sea
B.
Temperature
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Rates of metabolic reactions double for each
10 oC increase in temperature
Most marine organisms adapted to specific
temperature range
Species distributions often based on
temperature of water
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Polar
Cold temperate
Subtropical (warm temperate)
Tropical
Eurythermal vs. Stenothermal
Fig. 4.16
I.
Challenges of Life in the Sea
B.
Temperature
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Ectotherms – Body temperature essentially
determined by temperature of environment
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Often poikilotherms (“cold blooded”)
Some species warm certain tissues to improve
performance (tuna, billfish, some sharks)
Endotherms – Maintain elevated internal body
temperature
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Usually homeotherms (“warm blooded”)
Energetically expensive
Insulation may help to conserve heat
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Blubber
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Feathers
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Hair
I.
Challenges of Life in the Sea
C.
Surface-to-Volume Ratio
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Organisms exchange heat and substances
across body wall
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Fig. 4.17
Nutrients
Gases
Waste products
Rate of exchange depends on S/V ratio
Ratio decreases as organism size increases, if
shape stays the same
Smaller organisms exchange materials by
diffusion
Larger organisms have special systems to
exchange materials
II. Prokaryotes
A.
Bacteria
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Many shapes - spheres, coils, rods, rings
Very small cells (usually less than 1 μm across)
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Little known until second half of 20th century
Exceptions - 570 to 750 μm diameter in sediments
(filamentous) and fish guts
Rigid cell walls
May reach very high densities under favorable
conditions
Heterotrophic Bacteria
1.
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Most are decomposers (break down organic material)
Important in nutrient recycling
Important components of organisms’ diets, especially
for benthic organisms
II. Prokaryotes
A.
Bacteria
2.
Autotrophic Bacteria
a.
Fig. 4.7
Photosynthetic (Photoautotrophic)
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Obtain energy from sunlight
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Contain chlorophyll or other photosynthetic
pigments
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Important primary producers in open ocean
b. Chemosynthetic (Chemoautotrophic)
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Obtain energy from chemical compounds
- Hydrogen
- Hydrogen sulfide
- Ammonia
II. Prokaryotes
A.
Bacteria
3.
Cyanobacteria (Blue-green)
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Photosynthetic
Contain chlorophyll + phycocyanin & phycoerythrin
Some form filaments or mats
Some similarities to eukaryotic algae
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Contain chlorophyll a
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Produce gaseous O2
May have been first photosynthetic organisms on
earth
Fossil stromatolites from 3 billion years ago
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Calcareous mounds containing sediment and
cyanobacteria
http://www.fossilmall.com/Science/About_Stromatolite.htm
http://www.fossilmall.com/Science/About_Stromatolite.htm
II. Prokaryotes
A.
Bacteria
3.
Cyanobacteria (Blue-green)
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Occur in a variety of habitats
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Polar bear hair
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Endolithic (inside calcareous rocks and coral
skeletons)
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Rocky shorelines (black crusts)
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Epiphytic (on algae or plants)
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Endophytic (inside algal or plant cells)
Many carry out nitrogen fixation
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Very important process
Some forms have lost ability to photosynthesize
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Live as heterotrophs