Vertebrate Zoology: Chapter 1

The diversity, Classification and Evolution of vertebrates

Diversity 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 Deep oceans to top of the highest

mountains

DIVERSITY Feeding Behavior

Obtain energy from food they eat Complex and vary extensively Carnivores eat other animals and catch they

prey in various ways 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 Herbivores eat plant materials Developed some specializations

Well sculptured teeth Digestive tracts with special places

for bacteria that digest some of the plant materials e.g. cellulose

DIVERSITY 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 Parental Care

Some babies self sufficient: precocial young (fish and amphibians)

Others require extended periods of parental care (humans)

DIVERSITY: Types of Vertebrates

Hagfishes (Myxinoidea) 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

Lampreys (Petromyzontoidea): 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 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 Bony fishes; very diverse Bone skeleton Numerous vertebrae Dermal scales on skin, skin has

mucus glands Jaws are present Divided into major groups

Osteichthyes Lobe Finned fishes (fleshy finned)

Also called sarcopterygians Only eight species

Ray Finned Fishes 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 2 groups of Actinopterygians:

The chondrostei Bichis, sturgeons, paddlefishes Sturgeons are the source of carvia Paddlefish have a paddle-like snout and found in

Mississippi river Neopterygians

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 Aquatic larval form (e.g tadpoles) Terrestrial adult form Bare skin, lack scales, hair, or

feathers Three orders

AMPHIBIANS: Salamanders, Frogs and Caecillians Salamanders/Urodela

Elongated animals, terrestrial, usually with four legs; Have tails as adults

Frogs (Anurans): Frogs, toads, treefrogs Short bodies, no tails as adults; Large heads Large hind legs (walking, jumping, climbing)

Caecilians are an order of legless amphibian. most have no tail, also called rubber eels Burrowing animals

Turtles 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 Skins is covered with scales Tuatara

Small nearly extinct order of very unusual lizard-like 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 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 Lineage of dinosaurs Characterized by flight, and

feathered wings. > 9000 species Very active during the day, great

vocals!!

Mammals >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 Books classifies vertebrate from an

evolutionary standpoint Phylogenetics: used to classify

vertebrates 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 The evolutionary relationships

among organisms, patterns of lineage branching produced by the true evolutionary history of the organisms being considered

Cladistics 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 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 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 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 All called Plesiomorphy

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 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 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 Cladograms are not truths

Cladograms Evlutionary relationship between

humans and great apes 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 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 Paraphyletic

Groups that do not contain the common ancestor