AnimalsAnimal Bodies
Body Structure
Morphology is◦the branch of biology dealing with the form and
structure of organisms.
Symmetry is◦the proper proportion of the parts of a body
with respect to one another and with regard to size and form.
Patterns of Symmetry
Radial SymmetryBasic body plan where the organism can
be divided into similar halves by passing a plane at any angle along a central axis.
Characteristic of sessile and bottom-dwelling animals, as the sea anemone and starfish.
Bilateral Symmetry – most animals…
Bilateral SymmetryBasic body plan where the left and right
sides of the organism can be divided into approximate mirror images of each other along the midline.
Dorsal - backVentral - tummyAnterior - headPosterior – rear end
Bilateral Symmetry…
Cephalization◦specialization of the body with sensory and neural organs in an anterior head
Patterns of Symmetry
Germ Layers – layers formed during very early development of most animals
1. ectoderm = outside layer
2. endoderm = inside layer
3. mesoderm = layer in between the above two
Body Cavities…
Most animals have some type of body cavity.
Body Cavity◦Fluid-filled space between the digestive tract
and the outer wall of the body
Examples:FLATWORM: three germ layers; solid
body – lack body cavity.ROUNDWORM: Body cavity aids in
movement◦Provides a firm structure against which muscles
can contract
Body Cavities…
A body cavity also allows more freedom of movement for the animal
The fluid in the cavity is a reservoir for the transport for nutrients and wastes.◦these diffuse in/out of the animal’s body cells.
Animal Diversity…
ANIMAL DIVERSITYAnimal phyla shown on the same branch
of the phylogenetic tree are thought to be more closely related to each other than they are to other animals.
Likewise, animals shown in different parts of the tree are thought to be more distantly related.
Animal Diversity…
Multicellularity and a limited degree of cell specialization – characteristic of sponges
Sponges have no organized body shape and no true tissues.
True tissues in two layers – found in the cnidarians (hydra, jellyfish, etc.) and the ctenophores (exclusively marine, invertebrates)
True tissues in three layers and bilateral symmetry – characterize all of the other animal phyla
phylogenetic categories are based on◦ the absence or presence and type of body cavity◦ fundamental patterns of development
Animal Diversity…
InvertebratesAbsence of a backboneGreatest number of animal speciesMost of the animals alive today
Animal Diversity…
ChordatesRefers to the notochord
◦A firm, flexible rod of tissue located in the dorsal part of the body (the back).
◦At some stage of development, all chordates have a notochord, dorsal nerve cord, pharyngeal pouches, and a post anal tail.
Dorsal nerve cord◦Hollow tube lying just above (dorsal to) the notochord.
Pharyngeal pouches◦Small outpockets of the anterior part of the digestive
tract.Postanal tail
◦Consists of muscle tissue and lies behind the posterior opening of the digestive tract.
Animal Diversity…
In most vertebrates…The dorsal nerve cord develops into the
brain and the spinal cord.Pharyngeal pouches evolved into gills –
used for breathing.In most vertebrates, the notochord is seen
only in the embryonic stage.It is replaced by the backbone early in
development.
Animal Diversity…
Vertebrates…Make up only one subphylum of the
phylogenetic tree of all animals.Humans are vertebrates.Humans interact extensively with many other
vertebrates.◦fishes◦birds◦mammals
All of these are primary food sources for humans.
Top Related