Download Animal Characteristics

Animals = invertebrates and vertebrates
(95% of all animals are invertebrates)
Animal Characteristics
• The bodies of animals are multicellular.
It is responsible for the enormous variety
of animals.
• All animals are heterotrophs.
• Most animals reproduce sexually, and
some can also reproduce asexually.
• In all but the simplest
animals, there is a
division of labor among
cells called cell
specialization. (This
aids internal body
organization.)
• Most animals can move about their
environment.
One or Two Houses
• Monoecious – (“One House”)
hermaphroditic animals – both male and
female sex organs
• Dioecious – (“Two Houses”) separate
sexes
Body Symmetry:
• None – Sponge
(asymmetrical)
• Radial –similar parts branch in all
directions. -Hydra, Jellyfish,
Pentaradial
• Bilateral, two similar halves in either side
of a central plane of symmetry moth,
primates etc. Bilaterally symmetrical
Animals tend to exhibit cephalization.
• Cephalization: – concentration of sensory and
brain structures in the anterior end (a cephalized
animal has a head). The more complex an
animal the more pronounced the degree of
cephalization.
• It is an advantage because a more complex
animal can respond to an environment more
quickly.
Germ Layers:- (p 683 – 684)
• As a result of gastrulation, three primary layers
form: (Fundamental tissue types found in
embryos of all animals except sponges which
have no true tissues)
• Endoderm – inner layer
• Mesoderm – middle layer
• Ectoderm – outer layer
• endoderm inner layer - The archenteron,
surrounded by endoderm forms the throat
passage, gills, lungs and gut and associated
organs such as pancreas, and liver. (lines
digestive tract & much of respiratory system.)
• ectoderm – outer layer – forms skin, hair,
nails, and nervous system
• mesoderm which forms between the other
layers, forms skeleton, muscles, inner layer of
skin, circulatory system, and lining of the body
cavity (also reproductive system & excretory
system).
Deuterostomes & Protostomes:
Deuterostomes – “second mouth” radial
cleavage of developing embryo, blastopore
(indentation of the blastula) becomes the anus,
second opening becomes the mouth.
(examples - echinoderms – such as star fish,
chordates and vertebrates as well)
• Protostomes – “first mouth” spiral cleavage of
developing embryo, blastopore becomes the
mouth, second opening becomes the anus
(occurs in most animal phyla).
Animals & Body Cavities: (pg 686)
• acoelomate – no body cavity example:
flatworms
• pseudocoelomate – “false body cavity”
mesoderm lines an endodermic gut suspended
in a fluid filled coelom cavity.
• coelomate – true body cavity - An endodermic gut
– is surrounded & supported by a body cavity of
mesoderm. The mesoderm forms tissues or
attachments for organs located in the true body
cavity, such as the liver, lungs, etc.
Mollusks, arthropods,
chordates, & echinoderms
are coelomate animals.
coelom
a) a true hollow, fluid-filled cavity completely
surrounded by mesoderm.
b) The muscles of the body wall are separated from
those of the gut.
c) The body walls can contract without hindering t
movement of food in the gut (digestive tract).