Vertebrate Zoology: Chapter 1
The diversity, Classification and
Evolution of vertebrates
Diversity
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Numerous & diverse
More than 50, 000 species
Range in size from small fishes (0.5 g)
to full mature whales (>100 000 kg)
Habitats vary
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Deep oceans to top of the highest
mountains
DIVERSITY
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Feeding Behavior
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Obtain energy from food they eat
Complex and vary extensively
Carnivores eat other animals and catch they prey
in various ways
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Some search for prey
Some wait in hiding for their prey
Some pursue their prey at high speeds
Some swallow prey while it is still alive and struggling to
kill itself
Snakes inject toxins that paralyze the prey
All cats kill prey with a distinctive bite on the neck
DIVERSITY
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Herbivores eat plant materials
Developed some specializations
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Well sculptured teeth
Digestive tracts with special places for
bacteria that digest some of the plant
materials e.g. cellulose
DIVERSITY
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Reproduction: necessary for survival and
continuity
Great diversity WRT mating and courtship
In general males court females
Females care for the young
Male female roles reversed for some animals
Modes of reproduction vary from egg laying
to live births
DIVERSITY
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Parental Care
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Some babies self sufficient: precocial
young (fish and amphibians)
Others require extended periods of
parental care (humans)
DIVERSITY: Types of
Vertebrates
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Hagfishes (Myxinoidea)
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Long and slender & pinkish
produce large quantities of sticky slime
Almost blind
Jawless (Agnatha)
No trace of vertebrae (backbone)
Marine and parasitic, also scavenge
DIVERSITY: Types of
Vertebrates
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Lampreys (Petromyzontoidea):
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Jawless
Both marine and freshwater
Round mouth
Rudimenatry vertebrae
Scaleless fishes
Slimy, no internal hard tissue
Larva is called ammocoetes
Chondrichthyes: Sharks, rays and
ratfishes
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All classified as chondrichthyes (Chondro= cartilage,
ichthyes = fish
All lack true bone, have a cartilage skeleton
Only teeth and vertebrae are sometimes calcified
Jawed fish
Some sharks are small <=15 cm, others are large.
Largest is 10m
Rays live on bottom of water bodies and tend to have
flat bodies
Broad fins used for swimming
Ratfishes are long with slender tails
Osteichthyes
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Bony fishes; very diverse
Bone skeleton
Numerous vertebrae
Dermal scales on skin, skin has mucus
glands
Jaws are present
Divided into major groups
Osteichthyes
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Lobe Finned fishes (fleshy finned)
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Also called sarcopterygians
Only eight species
Ray Finned Fishes
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Fins appear like webs of skin supported by bony
or horny spines
More than 20 000 species, dominant aquatic
vertebrates (from deep seas to freshwater
streams and ponds)
Major source of food for people
Osteichthyes
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2 groups of Actinopterygians:
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The chondrostei
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Bichis, sturgeons, paddlefishes
Sturgeons are the source of carvia
Paddlefish have a paddle-like snout and found in
Mississippi river
Neopterygians
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More modern
Include the teleostei group with more than 20 000
species
Familiar teleosts are trout, bass, salmon, panfish, sole
swordfish, salmon and tuna
AMPHIBIANS: Salamanders, Frogs
and Caecillians
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Aquatic larval form (e.g tadpoles)
Terrestrial adult form
Bare skin, lack scales, hair, or feathers
Three orders
AMPHIBIANS: Salamanders, Frogs
and Caecillians
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Salamanders/Urodela
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Frogs (Anurans): Frogs, toads, treefrogs
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Elongated animals, terrestrial, usually with four
legs; Have tails as adults
Short bodies, no tails as adults; Large heads
Large hind legs (walking, jumping, climbing)
Caecilians
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are an order of legless amphibian.
most have no tail, also called rubber eels
Burrowing animals
Turtles
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Turtles are easily distinguished by the
presence of a shell which encloses the
animal in a bony case.
Turtles inhabit a variety of terrestrial and
aquatic environments, from the open
ocean to the arid deserts.
Shoulders and hips are inside the ribs
Unique animals
Tuatara, Lizards, Snakes
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Skins is covered with scales
Tuatara
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Small nearly extinct order of very unusual lizardlike reptiles know as the beaked reptiles. Have
unique features such as a third eyelid.
All living species found in New Zealand
Lizards: > 4000 species
Snakes: > 2700 species
Alligators and Crocodiles
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Semi aquatic predators, same lineage
as dinosaurs
Long snouts with numerous teeth
Skins contains bones (osteoderms)
beneath the scales
Care for their young
BIRDS: AVES
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Lineage of dinosaurs
Characterized by flight, and feathered
wings.
> 9000 species
Very active during the day, great
vocals!!
Mammals
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>4500 species
Mostly eutherians (placental animals): show
placentation and long gestation
Marsupials, placentation to a small extend, very short
gestation. Give birth to very immature young that
would then grow in the external pouch (kangaroo)
Marsupials are mostly in Australia( Kangaroos,
Koalas, and wombarts)
Some marsupials hatch young from eggs instead: the
platypus and the echidnas from australia
Vertebrate Classification:
terms
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Books classifies vertebrate from an
evolutionary standpoint
Phylogenetics: used to classify
vertebrates
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This is a field of biology that deals with
relationships between organisms. It
includes the discovery of these
relationships and the study of the causes
behind this pattern
Phylogeny
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The evolutionary relationships among
organisms, patterns of lineage
branching produced by the true
evolutionary history of the organisms
being considered
Cladistics
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Phylogenies are proposed thru a process
called cladistics or phylogenetic systematics
It attempts to produce a hypothesis about
the evolutionary sequences of events that led
to a group of organisms
Each group of organisms is called a clade
Its makes use of shared derived characters
Clade
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Phylogenetic lineage originating from a
common ancestor
It is a group of organisms which include
the most recent common ancestor of all
its organisms and all the descendents of
that common and recent ancestor
Comes from the Greek word Clado
meaning twig or branch
Derived Character
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Modified version of the primitive condition of
that character. Thus the character has
changed from its ancestral condition
Presence of hair is a primitive character state
of all mammals, whereas the hairlessness of
whales is a derived state for one subclade
within mammals
Also called apomorphy (apo = away from,
morph = form)
Shared Derived Character
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A character derived from the ancestral
conditions and is shared among several taxa
that all descended from a common ancestor
that first exhibited the derived character.
E.g. foot bones(tarsals, carpals, digits) of
terrestrial vertebrates: Bones not seen in
ancestral pattern seen in lobe finned fishes.
Also called synapomorphy (syn = together)
Apomorphy: means derived character
Primitive Character
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All called Plesiomorphy
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Inherited characters seen in ancestors of a
clade. Not derived
Original condition of that character within
the clade under consideration
Presence of hair is a primitive character
Hairlessness is a derived state for one
subclade of mammals -whales
Shared Primitive Character
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A character that is the same as the
ancestral condition and is shared
among several taxa
These carry no information WRT
phylogeny of the organisms under study
All called sympleisomorphy
Cladograms
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Hypothesised phylogenies from cladistics:
Cladograms are diagrams showing animal
branches during evolution
It’s a hypothesis about a group of
animals
Subject to change as more data is available
or re-evaluated
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Cladograms are not truths
Cladograms
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Evlutionary relationship between humans and
great apes
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Some cladograms show humans as the sister
taxon to the chimpanzees
Others show show gorilla as the sister taxon
Thus a cladogram is a hypothesis that like
any other hypothesis or theory in science is
subject to change as more data are
accumulated
See figure 1.2: study the cladogram and
understand the data.
Other cladistics terminology
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Taxa: Groups of organisms of same species
or different species
Clades: groups of organisms in a cladogram
Monophyletic groups. Groups of organisms
which contain the common ancestor plus all
descendents (e.g. mammalia is a
monophyletic group (clade) as it contains all
living and extinct mammals plus the ancestor
of all mammals
Other cladistics terminology
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Paraphyletic
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Groups that do not contain the common
ancestor