Asymmetry
• Animals have different
patterns of symmetry,
the arrangement of body
parts around a central
axis
– Asymmetry – no
general body plan
– Example: Sponges
• Radial symmetry
– body can be
divided into equal
parts around a
central axis
• Example: starfish,
jellyfish
Radial Symmetry
Oral = side containing the mouth
Starfish
Morro Bay, CA
Bilateral Symmetry
• Bilateral symmetry –
body can be divided
along one plane of
symmetry into two
mirror halves
• Example: humans,
crocodiles, crayfish
Symmetrical
Compare the Difference
versus no symmetry
Bilaterally symmetrical
animals can be divided
into the following
Anterior
planes:
• Anterior – front end
• Posterior – back end
• Ventral – underside
(belly)
• Dorsal – back (top side)
Dorsal
Posterior
Ventral
Cephalization
Bilaterally symmetrical
animals also have
cephalization, which is the
concentration of nerve and
sensory tissue at the
anterior end of the organism
CNS – Central
Nervous System
Note the formation of the
embryonic tissue layers:
endoderm, mesoderm,
ectoderm
Note the formation of the
embryonic tissue layers:
endoderm, mesoderm, ectoderm
Animals have different body plans based
on the development of body cavities
Acoelomate
Pseudocoelomate
Eucoelomate
Body Cavities
• Acoelomate – animal that lacks a body
cavity
• Pseudocoelomate – animal that has a
cavity between the mesoderm and
endoderm
(Not a true
body cavity..
thus pseudo)
Body Cavities
• Coelomate / Eucoelomate – animal that
has a cavity that develops within the
mesoderm ( a true coelom/body cavity)
Animalia
• One main distinction between
the phyla is the presence of a
notochord, which can develop
into a vertebral column
(backbone)
• If animals do NOT possess a
backbone, they are
invertebrates, and if they do
possess a backbone, they are
called vertebrates
Vertebrate
Invertebrate
Porifera
Invertebrate Animals
The following phyla will
be discussed in more
detail in class:
Nomura Jellyfish
• Phylum Porifera
• Phylum Cnidaria
• Phylum
Platyhelminthes Platyhelminthes
• Phylum Nematoda
Cnidaria
Nematoda
Invertebrate Animals
•
•
•
•
Phylum Mollusca
Phylum Annelida
Phylum Arthropoda
Phylum
Echinodermata
Mollusca
Arthropoda
Echinodermata
Annelida
Polychete worm
Vertebrate Animals
• Phylum Chordata
– Class Agnatha
– Class Chondrichthyes
– Class Osteichthyes
– Class Amphibia
– Class Reptilia
– Class Aves
– Class Mammalia