Transcript Ichthyology Fall 2000

Reading Assignment:
• Chapter 12--Systematics, genetics,
and speciation
basking shark
end
Freshwater vs. Saltwater
• 58 % of fishes are marine
• 41 % freshwater
• Earth’s waters:
– 97% saltwater; 70% of surface of Earth
– 0.0093 % freshwater; 1% of Earth surface
end
Diversity of Life Styles:
• nekton (self mobile)
• plankton (drifters)
• bottom dwellers
(benthic)
• open water (pelagic)
• surface oriented
(epipelagic)
•
•
•
•
•
•
carnivorous
omnivorous
herbivorous
filter feeders
parasites
diadromous
end
Fish Diversity
Phylum
Subphylum
Superclass
Class
other verts?
Chordata
Craniatata (cranium)
Gnathostomata (jaws)
Myxini Cephalaspidomorphi Chondrichthyes Actinopterygii
hagfish
lampreys
cartilaginous fishes ray-finned fishes
sharks, skates, rays
end
Why do we recognize fish?
• Constraints & Characteristics of water
– density (800 x denser than air)
– support (lighter skeleton, diminished limbs)
– viscosity (streamlined shapes)
• Evolutionary convergence
• Absence of divergence
end
Thoughts on the Evolution of Fishes
• What are general characteristics of fishes
and vertebrates? (consider their protist and
invertebrate ancestors)
• size
• locomotion
• bilateral symmetry
end
Advantages of size:
• Survivability:
predator avoidance
prey availability
environmental selection and
avoidance
end
Requirements for size:
• support (skeletal system)
• mechanisms of locomotion
• systems
end
Simplest form of locomotion in cordates
Notochord--flexible, incompress.
Direction of locomotion
sinusoidal movement
end
Vertebral column:
vertebrae
discs
Flexible
incompressible
end
Dorsal fin--spines
Dorsal fin--rays
Caudal fin
Caudal peduncle
Pectoral fins
Pelvic fins
Anal fin
end
end
Physical Aspects of Aquatic
Environments
-O
Water:
H
104.5
+
covalent bond
H
polar molecule
end
Water is a polar molecule
• dissolves polar substances--salts, etc
• doesn’t dissolve non-polar substances--fats,
oils, waxes
end
Soap molecule:
polar
oil
non-polar
end
Ionization of water:
+
O +
2H2O
H3
hydronium ion
H+
OH
hydroxide ion
H+ . H2O
end
How much does water ionize?
Hint: pH = -log H+
log
10
-7
10
g-ions/l
0.0000001 g-ions/l
Note: inverse log scale
end
Many other substances ionize in water:
Salts:
NaCl
Acids: H2CO3
carbonic acid
Bases: NH3 + H2O
ammonia
Na+
+
Cl-
H+
+
HCO3bicarbonate
NH4+
+
OH-
ammonium
end
O
Density of water
O
H
Ice:
H
voids
O
H
H
O
H
voids
H voids H
H
O
H
H
Covalent bond-share electrons Hydrogen bond-electrostatic
end
As temp of ice increases:
Density
g/ml
TEMP.
•
•
•
•
•
Ice - 0.917
Molecules vibrate more rapidly
0 °C
water - 0.9999
hydrogen bonds begin to break
free molecules fill voids
1.000
3.94 °C
water becomes densest
vibrations increase in amplitude;
intermolecular distances increase
100 °C
0.996
Significance with respect to life?
end
Density of water increases
slightly with salinity
salinity
end
Stratification:
epilimnion
less dense
hypolimnion
more dense
thermocline
end
end
Semester Projects
• 100 point project
• usually library research leading to a written
paper
• do some preliminary research to define
topic
• have topics approved by September 30
• Project due at end of semester
end
Thought experiment:
Engineer a new species:
• Given a certain biomass to work with, how
big would you make them? Why?
– Considerations related to size
• extremes
• survivability versus cost of losing an individual
• What other characteristics would you
choose? Why?
– locomotion?, symmetry?, survivability?
end
Evolutionary race among
predators and prey:
size
guidance
locomotion
bilateral symmetry
end