Transcript 4 The Chemical and Physical Environment

4 The Chemical and Physical
Environment
Notes for Marine Biology:
Function, Biodiversity, Ecology
By Jeffrey S. Levinton
Measures of Physiological Performance
• Consider an organism that is faced with
an environmental change
• First, it must have receptors to sense the
change
• Information must be transferred to the
systems that generate an adaptive
response - response that improves fitness
Measures of Physiological Performance 2
• Types of adaptive response:
 Behavioral
 Physiological (cellular changes at large
systemic level)
 Biochemical (changes of concentrations of
enzymes, ions within specific cell types)
Acclimation, Regulation, and Conformance
• Acclimation: Following an environmental
change, organism responds, perhaps
strongly, at first, but then internal state
changes and organism reaches a new
equilbrium - process is acclimation
Acclimation, Regulation, and Conformance 2
• Regulation: The organism maintains a
constant state within the body, despite
variation in the external environment
Acclimation, Regulation, and Conformance 3
• Conformance: Environmental change in
the external environment might be
followed by the internal state of an
organism matching the environmental
change
Acclimation, Regulation, and Conformance 4
Scope for Growth 1
• Physiological condition will be reflected in
resources available for growth
• Greater the cost for metabolism (reactions in
cells that cost energy), the less available to
invest in growth and reproduction
• Scope for growth are the resources available
beyond the maintenance metabolism (= a
positive energy balance)
Scope for Growth 2
A mussel has less scope for growth with less food and higher temperature
Mortality differences show physiological
differences
Neomysis
americana
Rhithropanopeus
harisii
50 %
mortality line
Test temperature °C
Mortality test: R. harisii is more temperature tolerant than N. americana
Temperature 1
• Temperature variation is common in
marine environment:
Latitudinal temperature gradient can be
very pronounced
Seasonal temperature change common
Short term changes (e.g. weather changes,
tidal changes)
Temperature 2
• Temperature regulation:
Homeotherms - regulate body
temperature, usually higher than ambient
Poikilotherms - do not regulate body
temperature
Temperature 3
• Temperature regulation:
Homeotherms - advantage of constancy of
cellular chemical reactions, disadvantage
of heat loss
Poikilotherms - advantage of no cost of
keeping temperature constant and high,
but at the price of metabolic efficiency
Temperature 4
• Heat gain - problem for poikilotherms in
intertidal zone at low tide or tidal pools
on a hot day
Circulation of body fluids - brings heat to
surface of body so it can be dissipated
Evaporation - also allows heat loss to
avoid overheating
Temperature 5
• Heat loss - problem for homeotherms
who maintain high body temperatures
Insulation - used by many vertebrates
(blubber in whales, feathers in birds)
Countercurrent heat exchange circulating venous and arterial blood in
opposite directions while vessels are in
contact to reduce heat loss
Temperature 6
Countercurrent heat exchange -
Heating
Chamber
37°C
28 °C 30 °C 32 °C 34 °C 36 °C
27°C
29 °C 31 °C 33 °C 35 °C 37 °C
Example of countercurrent heat retention
Temperature 7
Countercurrent heat exchange in dolphin
limb - artery is surrounded by veinlets,
which return heat
Temperature 8
Metabolic rate
Poikilotherms - can compensate for
temperatures by means of acclimation;
can stabilize metabolic rate over a wide
range of intermediate temperature
Stabilization of metabolism
over wide range of temperature
Temperature
Temperature 9
Seasonal acclimation of poikilotherms shift from winter to summer relation of
metabolic rate to temperature
Metabolic rate
Winter-acclimated
Summer-acclimated
Temperature
Temperature 10
• Evolution of temperature tolerance:
Species evolve differences in temperature
tolerance, e.g., Antarctic species may not
be able to survive waters warmer than 10
C
Populations living along a latitudinal
gradient might evolve local physiological
races, with different temperature
responses
Temperature 11
• Freezing - a problem in winter in
some habitats and in high latitudes
where sea ice forms, can destroy cells
as cell cytosol freezes
Some fish have glycoproteins, which
function as antifreeze
Temperature 12
• Heat Shock - has effects on
physiological integration of
biochemical reactions in cells, can
denature proteins that cannot
function at high temperature
(unfolding of three-dimensional
structure, which destroys binding
with substrates)
Temperature 13
• Heat Shock 2 heat shock proteins - are formed during
heat stress, which forestall unfolding of
protein 3D structure
ubiquitin - low molecular weight protein
that binds to degraded proteins, which
are then degraded by intracellular
proteolytic enzymes
Temperature 14
• Heat Shock 3 Disruption of membranes - heat shock
disrupts packing of structural
phospholipids in cell membranes, which
disrupts transport of ions, other cell
functions
Temperature 15
• Seasonal extremes of temperature affect
both activity and reproduction
• Effects are different at northern and
southern limits of geographic range
Temperature 16
• Survival and reproductive effects at ends
of a latitudinal range of a species
Winter
Survival limiting
Reproduction limiting
Summer
High latitude
Low latitude
Salinity 1
• Salinity change affects organisms because
of the processes of diffusion and osmosis
Salinity 2
• Osmosis - movement of pure water across
a membrane permeable to water, owing
to difference in total dissolved material
on either side of membrane
solute
Salinity 3
• Osmosis - movement of pure water across
a membrane permeable to water, owing
to difference in total dissolved material
on either side of membrane
• If salt content differs on either side of a
membrane, osmotic pressure is created,
water moves across in direction of higher
salt content
Salinity 4
• Example of osmosis problem - animal
with a certain cellular salt content is
placed in water with lower salinity: water
will enter animal if it is permeable - cell
volume will increase, creating stress
Salinity 5
% Body volume change
• Experiment - Place sipunculid Golfingia
gouldii in diluted seawater. At first
volume increases, but then worm excretes
salts through nephridiopores, regulating
5
volume back
0
1
2
Time (hours)
Salinity 6
• Diffusion - random movement of
dissolved substances across a permeable
membrane; tends to equalize
concentrations
Salinity 7
• Diffusion - random movement of
dissolved substances across a permeable
membrane; tends to equalize
concentrations
• Problem - diffusion makes it difficult to
regulate concentration of physiologically
important ions such as calcium, sodium,
potassium
Salinity 8
• Most marine organisms have ionic
concentrations of cell constituents similar
to seawater
Salinity 9
• Organismal responses to changing
salinity:
Organic osmolytes (e.g., free amino acids
used by invertebrates) used to counteract
osmotic problems. Used to avoid using
inorganic ions (e.g., Na) which are
physiologically active.
Salinity 10
• Osmolytes:
Free amino acids used by many
invertebrates, bacteria, hagfishes. Use
amino acids that have little effect on protein
function (e.g., glycine, alanine, taurine)
Urea used by sharks, coelacanths
Glycerol, Mannitol, Sucrose used by
seaweeds, unicellular algae
Salinity 11
• Bony fishes - have overall salt concentrations of
body fluids of 1/3 strength of regular seawater.
Creates continual osmotic problem of water
loss
Fish must drink continuously
Gills actively secrete salts
Sharks employ urea to maintain osmotic balance
Salinity 12
• Bony fishes - osmotic regulation
Oxygen 1
• Most marine organisms require oxygen for
manufacture of necessary reserves of ATP,
energy source in cells
• Some habitats are low on oxygen Low tide for many intertidal animals
Within sediment - often anoxic pore water
Oxygen minimum layers in water column where organic matter accumulates at some
depths
Oxygen 2
• Oxygen consumption increases with
increasing body mass, but weight specific
oxygen consumption rate declines with
increasing total body mass
Oxygen 3
• Oxygen consumption is greater in
animals with greater activity
Oxygen 4
• Nearly all animals are obligate aerobes,
but many animals have a mix of
metabolic pathways with and without use
of oxygen
Oxygen 5
• Many animals use a variety of means of
breaking down carbohydrates without oxygen:
 Vertebrates use glycolysis - breakdown product
is lactic acid, which accumulates in muscle
tissue
 Invertebrates have alanine and succinic acid as
anaerobic breakdown products
Oxygen 6
• Oxygen uptake mechanisms:
Animals only a few millimeters thick rely upon
diffusion for oxygen uptake
Larger animals use feathery gills with high
surface area to absorb oxygen; mammals have
lungs with enormous surface areas to take up
oxygen
Larger animals have circulatory systems that
circulate oxygen to needy tissues. Many have
oxygen-carrying blood pigments
Oxygen 7
• Blood pigments: substances that
greatly increase blood capacity for
transporting oxygen
Oxygen 8
• Blood pigments: substances that greatly
increase blood capacity for transporting
oxygen
Hemocyanin - copper-containing protein, found in molluscs,
arthropods
Hemerythrin - iron-containing protein, always in cells, found in
sipunculids, some polychaetes, prapulids, brachiopods
Chlorocruorin - iron-containing protein, found in some
polychaetes
Hemoglobin - protein unit (globin) and iron-bearing unit
(heme), found in many phyla(chordates, molluscs,
arthorpods, annelids, nematodes, flatworms, protozoa)
Oxygen 9
• Oxygen binding of hemoglobin (Hb):
Hb + O2  HbO2
Oxygen 10
• Oxygen dissociation curve showing
percent of Hb in blood bound to O2
100
50
0
0
50
100
Oxygen tension (mm Hg)
Oxygen 11
• Hb ability to hold oxygen decreases with
decreasing pH - Bohr effect
Oxygen 12
• Hb ability to hold oxygen decreases with
decreasing pH - Bohr effect
• pH is less near capillaries that are starved for
oxygen, owing to presence of CO2 released
from cells - Hb drops oxygen, which diffuses
into cells
• Bohr effect -
Oxygen 13
% pigment
Saturated by O2
100
Bohr
effect
50
0
0
50
100
Oxygen tension (mm Hg)
% pigment
Saturated by O2
Oxygen 14
• Pigment Hb binding varies with
activity
of
species
100
Less
active
forms
50
More
active
forms
0
0
50
100
Oxygen tension (mm Hg)
Oxygen 15
• Other mechanisms:
Reduction of activity and oxygen uptake when
oxygen is not common (e.g., at time of low tide)
Light 1
• Many animals detect light with aid of a simple layer of
sensory cells, but many species have complex eyes with
focusing mechanisms
Allows detection of prey, predators
Aids in navigation
• Eyes of animals:
Pinhole camera
Nautilus
Light 2
Lens
Fish
Curved, reflective
Scallop
Light 3
• Bioluminescence - light manufactures by
organisms - using specialized light organs,
sometimes with the aid of symbiotic
bioluminescent bacteria
Functions to confuse predators
Perhaps other as yet undiscovered functions
The End