intro to animal diversity chapter 32. what is an animal?
TRANSCRIPT
Intro to Animal DiversityChapter 32
What Is An Animal?
What Is An Animal?
What Is An Animal?
• Multicellular• Heterotrophic• Eukaryotic• No cell walls – held
together with structural proteins, mainly collagen
Body Plans
• Animal phyla are categorized based on features that are either present or absent.
• Features often included:– Symmetry– Tissue layers– Body cavities– Protostomes vs. deuterostomes
Body Symmetry
• Asymmetrical• Radial• Bilateral– Dorsal & ventral– Anterior & posterior
Body Tissues
Body Tissues
• No true tissues (no gastrulation)• Diploblastic– Ectoderm & endoderm
• Triploblastic– Also has mesoderm
Body Cavities
• Acoelomate
• Pseudocoelomate
• Coelomate
Protostomes vs. Deuterostomes
Protostomes vs. Deuterostomes
Animal phylogenetic tree
• Zoologists currently recognize about 35 animal phyla
• The current debate in animal systematics– Has led to the development of two phylogenetic
hypotheses, but others exist as well
• One hypothesis of animal phylogeny based mainly on morphological and developmental comparisons
Animal phylogenetic tree
Porif
era
Cnid
aria
Cten
opho
ra
Phor
onid
a
Ecto
proc
ta
Brac
hiop
oda
Echi
node
rmat
a
Chor
data
Plat
yhel
min
thes
Mol
lusc
a
Anne
lida
Arth
ropo
da
Rotif
era
Nem
erte
a
Nem
atod
a
“Radiata” Deuterostomia Protostomia
Bilateria
Eumetazoa
Metazoa
Ancestral colonialflagellate
Animal phylogenetic tree• One hypothesis of animal phylogeny based
mainly on molecular data
Calc
area
Silic
area
Cten
opho
ra
Cnid
aria
Echi
node
rmat
a
Chor
data
Brac
hiop
oda
Phor
onid
a
Ecto
proc
ta
Plat
yhel
min
thes
Nem
erte
a
Mol
lusc
a
Anne
lida
Rotif
era
Nem
atod
a
Arth
ropo
da
“Radiata”
“Porifera” Deuterostomia Lophotrochozoa Ecdysozoa
Bilateria
Eumetazoa
Metazoa
Ancestral colonialflagellate
Points of Agreement
• All animals share a common ancestor• Sponges are basal animals• Eumetazoa is a clade of animals with true
tissues• Most animal phyla belong to the clade Bilateria• Vertebrates and some other phyla belong to the
clade Deuterostomia
Disagreement over the Bilaterians
• The morphology-based tree– Divides the bilaterians into two clades:
deuterostomes and protostomes• In contrast, several recent molecular studies– Generally assign two sister taxa to the protostomes
rather than one: the ecdysozoans and the lophotrochozoans