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The Diversity of Fishes:
An Introduction
Lecture 2 – August 26

Muddiest Point

WHAT ISN’T EVOLUTION?
Evolution doesn’t work in a straight line, it lacks direction

Muddiest Point

Muddiest Point

Phylogenetic definition
All chordates are fish; however, for this class, we will limit the scope of “fish” to occupy a
phylogenetic position from cephalochordates (lancelets) up to amphibians.

Fish Trees

Fish Trees

Fish Trees

Fish Trees
Craniata

Fish Evolution
•
Fishes have been around for nearly
500 million years (predating man
by almost this entire period and all
other vertebrates by nearly 100
million years)

The vertebrate bauplan evolved from our aquatic fish
ancestors
◦
Body arrangement/jaws/limbs
◦
Vertebrate eye/vision
◦
Internal fertilization/intrauterine nourishment
◦
Viviparity
◦
Big brains


The vertebrate bauplan evolved from our aquatic fish
ancestors
◦
Body arrangement/jaws/limbs
◦
Vertebrate eye/vision
◦
Internal fertilization/intrauterine nourishment/placenta
◦
Viviparity
◦
Big brains
◦
Respiration – How do fish breath?
Embrace your inner fish

The Diversity of Fishes
•
32,000 valid living species
•
515 families
•
62 orders
–
108 jawless fish spp. (70 hagfish, 38 lamprey)
–
970 cartilaginous fish spp. (403 sharks, 534 skates, 33
chimeras)
–
30,000 + bony fishes

Habitat of Fishes
•
70% of the Earth’s surface is covered in water
•
Fishes are found in all aquatic habitats
–
Thermal hypersaline springs 104° F (40° C)
•
Soda Lake Cichlid – Tilapia spp.
–
Antarctic Waters <0° F
–
Caves/ground water
–
Anoxic swamps
–
Mud
–
Hydrothermal vents
–
High elevation (5km above sea level)
–
Deepest ocean (8km – 5 miles down)
•
Abyssobrotula galatheae found in the Puerto Rican Trench

Habitat of Fishes
•