Challenges%20of%20Life%20in%20the%20Sea

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• Challenges of Life in the Sea
• Salinity
• Diffusion and Osmosis
• 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
• Water diffuses from region of higher water
  concentration (lower salt concentration) to
  region of lower water concentration
• Possible to move molecules against concentration
  gradient by using energy to power active transport

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Fig. 4.13
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• Challenges of Life in the Sea
• Salinity
• Regulation of Salt and Water Balance
• Osmoconformers
• Energetically inexpensive
• Limits distribution to areas with stable salinity
  (Where?)
• Osmoregulators
• Expend energy to maintain body fluid composition
• Less constrained by salinity in habitat
• Euryhaline vs. Stenohaline

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Fig. 4.14
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Fig. 4.15
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• Challenges of Life in the Sea
• Temperature
• 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
• Polar
• Cold temperate
• Subtropical (warm temperate)
• Tropical
• Eurythermal vs. Stenothermal

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Fig. 4.16
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• Challenges of Life in the Sea
• Temperature
• Ectotherms Body temperature essentially
  determined by temperature of environment
• Often poikilotherms (cold blooded)
• Some species warm certain tissues to improve
  performance (tuna, billfish, some sharks)
• Endotherms Maintain elevated internal body
  temperature
• Usually homeotherms (warm blooded)
• Energetically expensive
• Insulation may help to conserve heat
• Blubber
• Feathers
• Hair

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• Challenges of Life in the Sea
• Surface-to-Volume Ratio
• Organisms exchange heat and substances across
  body wall
• 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

Fig. 4.17
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• Prokaryotes
• Bacteria
• Many shapes - spheres, coils, rods, rings
• Very small cells (usually less than 1 µm across)
• 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
• Most are decomposers (break down organic
  material)
• Important in nutrient recycling
• Important components of organisms diets,
  especially for benthic organisms

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• Prokaryotes
• Bacteria
• Autotrophic Bacteria
• Photosynthetic (Photoautotrophic)
• Obtain energy from sunlight
• Contain chlorophyll or other photosynthetic
  pigments
• Important primary producers in open ocean
• Chemosynthetic (Chemoautotrophic)
• Obtain energy from chemical compounds
• - Hydrogen
• - Hydrogen sulfide
• - Ammonia

Fig. 4.7
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• Prokaryotes
• Bacteria
• Cyanobacteria (Blue-green)
• Photosynthetic
• Contain chlorophyll phycocyanin phycoerythrin
• Some form filaments or mats
• Some similarities to eukaryotic algae
• Contain chlorophyll a
• Produce gaseous O2
• May have been first photosynthetic organisms on
  earth
• Fossil stromatolites from 3 billion years ago
• Calcareous mounds containing sediment and
  cyanobacteria

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http//www.fossilmall.com/Science/About_Stromatoli
te.htm
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http//www.fossilmall.com/Science/About_Stromatoli
te.htm
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• Prokaryotes
• Bacteria
• Cyanobacteria (Blue-green)
• Occur in a variety of habitats
• Polar bear hair
• Endolithic (inside calcareous rocks and coral
  skeletons)
• Rocky shorelines (black crusts)
• Epiphytic (on algae or plants)
• Endophytic (inside algal or plant cells)
• Many carry out nitrogen fixation
• Very important process
• Some forms have lost ability to photosynthesize
• Live as heterotrophs