General Zoology Unit Five
Eukaryotic, eumetazoans, deuterostomes
Triploblastic, eucoelomates
Bilaterally symmetrical (cephalization)
Worm like body divided into three segments
Complete digestive system
Closed circulatory system with dorsal heart
Respiration through gill slits
Sexual reproduction – dioecious, external fertilizers with
metamorphosis
Chordate Taxonomy
Kingdom - Animalia
Phylum - Chordata
Subphylum - Urochordata (tunicates)
Subphylum - Cephalochordata (lancelets)
Ex. Branchiostoma
Subphylum - Vertebrata
Superclass - Agnatha
Class - Myxini (hagfish)
Class - Cephalaspidomorphi (lampreys)
Chordate Taxonomy
Kingdom - Animalia
Phylum - Chordata
Subphylum - Vertebrata
Superclass - Gnathostomata
Class - Chondrichthyes (sharks, skates, rays)
Class - Actinopterygii (ray finned bony fish)
Class - Sarcopterygii (lobe finned bony fish)
Class - Amphibia
Class - Reptilia
Class - Aves
Class - Mammalia
Garstang’s Hypothesis of Vertebrate Evolution
Developmental Definitions
Paedomorphosis - the retention of larval traits in
the adult body
Neotony - a process in which the growth rate is
slowed to the extent that sexual maturity is reached
before the ancestral adult form is obtained
Developmental Definitions
Progenesis - the precocious maturation of the
gonads in a juvenile body that stops growing and
never attains the adult body form
Post-displacement - a delay of the onset of a
developmental process relative to sexual maturity, so
that the ancestral adult form is not attained before
reproductive maturity
Garstang’s Hypothesis of Vertebrate Evolution
Vertebrate Ancestry
Fish Taxonomy
Kingdom - Animalia
Phylum - Chordata
Subphylum - Vertebrata
Superclass - Agnatha
Class - Myxini (hagfish)
Ex. Myxine
Class - Cephalaspidomorphi (lampreys)
Ex. Petromyzon
Fish Taxonomy
Kingdom - Animalia
Phylum - Chordata
Subphylum - Vertebrata
Superclass - Gnathostomata
Class - Chondrichthyes (sharks, skates, rays)
Subclass - Elasmobranchii (sharks, skates,
rays)
Ex. Squalus, Raja
Subclass - Holocephali (chimeras or
ratfish)
Ex. Chimera
Fish Taxonomy
Kingdom - Animalia
Phylum - Chordata
Subphylum - Vertebrata
Superclass - Gnathostomata
Class - Actinopterygii (ray finned bony fish)
Ex. Perca, Amia, Polyodon
Class - Sarcopterygii (lobe finned bony
fish
Ex. Latimeria
All five chordate hallmark characteristics
Endoskeleton of cartilage or bone
Complete digestive tract
Closed circulatory system with a ventral heart
Complex nervous system with a brain, dorsal nerve cord and
advanced sense organs
Excretion carried out by paired kidneys
Most have two pairs of appendages
All members have the vertebrate characteristics
All are jawless
All are elongated and eel shaped
None have paired appendages
Scales are absent
Complete digestive system without a stomach
The notochord is persistent into adulthood
All members have the vertebrate characteristics
All members have a jaw
All have or have had paired appendages
All have an endoskeleton of cartilage or bone
Osmoregulation in Fish
Respiration in Fish
Respiration in Fish
Respiration in Fish
Vertebrate Thermoregulation
Ectothermic – obtaining body heat from
the environment
Poikilothermic – non-regulatory, the body
temperature is the same as the ambient
environment
Regulatory ectotherms – maintain a
consistent body temperature through
physiological and behavioral means
Vertebrate Thermoregulation
Endothermic – body heat is produced
internally (homeothermic)
Fish are poikilothermic because water is
a heat sink
Buoyancy in Fish
Squalene (liver oil)
Buoyancy in Fish
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Physostomous
bladder
Buoyancy in Fish
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Physoclistous bladder
Fish Feeding Strategies
Most fish are carnivores
Most ocean species are suspension
feeders
Some are scavengers
A few species are parasites
A few species are herbivores
A few species are omnivores
Fish Reproductive Adaptations
Oviparous - egg laying
Ovoviviparous - retention of eggs
Viviparous – live birth
All three methods are found in
cartilaginous and bony fishes
Cartilaginous fish are internal fertilizers
while most bony fish are external
fertilizers
Fish Reproductive Adaptations
Diadromous - fish that make “two runs”
in their life to live and reproduce
Anadromous - fish that “run up” - salmon
Catadromous - fish that “run down” - eels
Parthenogenesis - no males required,
females produce diploid eggs - Amazon
molly
Amphibian Taxonomy
Kingdom - Animalia
Phylum - Chordata
Subphylum - Vertebrata
Superclass - Gnathostomata
Class - Amphibia
Order - Gymnophiona (caecilians)
Order - Caudata (salamanders)
Ex. Ambystoma, Necturus
Order - Anura (frogs)
Ex. Rana, Bufo
All five chordate hallmark characteristics
Endoskeleton of bone
Thin, gland rich skin with no scales or claws
Large mouth - all members carnivores
Closed double looped circulatory system with a ventral three
chambered heart
Respiration - lungs, gills or cutaneous
Regulatory ectotherms
Excretion through opisthonephric kidneys and urea as the
primary nitrogenous waste
Nervous system with a brain and dorsal nerve cord - well
developed sight and hearing
Reproduction – dioecious, some internal, others external
fertilizers, some metamorphosis
Most are tetrapods
Caecilians
Legless, elongated worm-like bodies
Fossorial, tropical & subtropical organisms
Most are blind, with smell and touch being the best senses
Eggs are laid in moist soil
Some species are viviparous
Salamanders, newts, amphiumas, sirens
Most have four legs & all have a tail
Some aquatic, some terrestrial
Respiration by gills, skin and lungs
Internal fertilization
Metamorphosis and direct development
Paedomorphosis common
Frogs
All have four legs and no tail (one exception)
Some aquatic, some terrestrial
Respiration by skin and lungs
Good vision and nictitating membranes
External fertilization
Metamorphosis and direct development
Amphibian Evolutionary Pressures
Respiration
Thermoregulation
Support
Ecological diversity
Amphibian Respiratory Strategies
Cutaneous
Pulmonary
Buccopharyngeal
Amphibian Respiratory Strategies
Gills
Amphibian Circulation
Amphibian
Circulation
Amphibian Thermoregulation
Many amphibians are regulatory
ectotherms, using physiological and
behavioral means
Aquatic species and salamanders are
poikilothermic, but other terrestrial
species will drop to this level of
thermoregulation during hibernation and
estivation
Amphibian
Metamorphosis
Caudatan Development
Remember!
Neotony - a process in which the growth rate is slowed to
the extent that sexual maturity is reached before the
ancestral adult form is obtained
In caudatans there are two forms of neotony - obligate and
facultative
Obligate
neotony
Facultative
neotony