Vertebrate Zoology

BIO254

Spring 2004

Dr. Chester

The Vertebrates

•      What Are Vertebrates?

–   50,000 extant species

–   They range in size form 2 grams to 100,000 kilograms

–   Live in virtually all habitats

•   From deep sea to aerial

–   Complex body forms and diverse behaviors

•   E.g. carnivores (from search for prey, “sit and wait”, high speed attackers or suction feeders

Subphylum Vertebrata

•      Contains the fishes, amphibians, reptiles, birds and mammals

•      Posses the same four chordate characteristics, plus:

–   Cranium (brain case)

–   Vertebral column

Functional Morphology

•      Study of how structures relate to their function

Function Versus Role

•      Function in an organism

•      Biological role

Organic Evolution

•      “Theory of mutability of species”

•      Organisms on Earth have been changing over time

•      Organisms present today are descendants of those that were present earlier

Preadaptation

•      Protoadaptation or Exaptation

•      Structure or behavior possesses the necessary form and function before the role arises that it will eventually serve

•      Function does not evolve in anticipation of the biological role

•      Traits serve the roles of the moment

Renovation not New Construction

•      Evolutionary change involves renovation

•      Existing structures are altered

•      New structure is an old part altered for a new role

•      As a result, descendant organisms bear traces of ancestral structures

Phylogeny

•      Traces the course of evolutionary change

•      Dendrograms = graphical representation of phylogenies

Phylogenetic Systematics

•      Willi Hennig (1966)

•      Cladistics

•      Clade

–   Group of organisms that belong to one lineage plus the common ancestor

–   Evolutionary lineage

•      Organisms are placed together that belong to the same clade

•      Based on geneology and not within group variation

Apomorphy

•      Derived character

•      Derived - different from the ancestral condition

•      Symapomorphy - shared derived characteristic

Plesiomorphy

•      Characteristic inherited unchanged from an ancestor

•      Symplesiomorphy

–   Shared ancestral characteristics

•      “Only shared derived characteristics (synapomorphies) are useful in cladistics”

Cladogram

•      Dendrogram depicting geneology, or how clades are arranged.

•      Represents an hypothesis about lineages and their evolutionary relationships

•      Primitive condition

–    ancestral state of a character

•      Derived condition

–    Descendant state after transformation

Cladistic Concepts

•      Monophyletic

•      Polyphyletic

•      Paraphyletic

Homology

•      Homologous

–   Traits that are inherited from a common ancestor

Analogy

•      Structures that perform a similar function but may or may not share a common ancestor

•      For example: bird wings and insect wings.  Both used for flight

Convergence

•      Morphological, embryological and paleotological studies have utilized phenotypes to observe underlying genetic similarities

•      Convergence = Distantly related organisms resemble each other

•      For example: octopus eye and mammalian eye

•      Analogous but not homologous structures

Homoplasy

•      Features that simply look alike

•      For example: Insects that have wings shaped like leaves

–    Do not function in photosynthesis ¹ analogous

–    Insects and plants share no common ancestor ¹ homologous

Parsimony