How do marine organisms cope with life in the sea?

Most show a variety of adaptive responses to conditions within the marine environment

Today, consider general adaptations to physical and chemical environmental (abiotic) conditions.

Examples will include: temperature, salinity, oxygen, and light.

Later in the semester, we will consider adaptations by specific groups of organisms to the biotic and abiotic environment.

Types of adaptive responses:

Behavioral (movements or taxa, panting, shivering)

Biochemical (e.g., enzymes, proteins)

Physiological (e.g., changes in membrane transport, increased circulation)

Morphological (thin vs. thick shells, flat vs. erect body forms)

Assessing adaptation by measuring performance: the tradeoffs between growing, reproducing, and staying alive.

Metabolic rates, growth, death, respiration, reproductive output, etc.

Regulators vs. conformers: two adaptive means for coping with environmental change

Acclimation often allows organisms to perform under a broader range of environmental conditions

Consider some specific environmental factors

Temperature

Salinity

Oxygen

Light

Temperature (a relatively constant environmental feature)

Temperature and metabolic rate

Temperature and physiological performance:

to freeze or not to freeze

to bake or not to bake

Temperature and reproduction

Homeotherms (regulators) vs. Poikilotherms (conformers):

the costs and benefits of changing temperature

 

Salinity (an often rapidly changing environmental feature)

Osmosis "the pressure of being different"

Diffusion "going with the flow"

Coping with a body full of less-than-salty fluids in a sea full of salts:

Drinking water and expelling salts can compensate for osmotic differences

Oxygen

Oxygen is needed for respiration but is toxic at high concentrations/pressures

O₂ consumption generally increases with body mass (although the rate of consumption decreases): Size can matter

O₂ consumption generally increases with activity rate: to move or not to move

Getting enough O₂ is a function of surface area to volume ratios: larger animals require gills

Using different O₂ binding pigments can help with life in O₂ poor environments.

Intertidal organisms may face oxygen starvation

Oxygen minimum layers may occur in mid-water near thermoclines

Light

Light is essential for vision (finding prey, avoiding predators, detecting mates, etc.) and photosynthesis

Light levels diminish rapidly with depth and many marine organisms have very simple eyes

Organisms in high light environments can have very good vision

Light, nonetheless, may provide important cues for behavioral adaptation

Bioluminescence: making your own light in the dark

 

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