Intro to Animal Diversity
Chapter 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
Animal phylogenetic tree
“Radiata”
Deuterostomia
Metazoa
Ancestral colonial
flagellate
Nematoda
Nemertea
Rotifera
Arthropoda
Annelida
Protostomia
Bilateria
Eumetazoa
Mollusca
Platyhelminthes
Chordata
Echinodermata
Brachiopoda
Ectoprocta
Phoronida
Ctenophora
Cnidaria
Porifera
• One hypothesis of animal phylogeny based
mainly on morphological and developmental
comparisons
Animal phylogenetic tree
Arthropoda
Nematoda
Rotifera
Annelida
Mollusca
Nemertea
Platyhelminthes
Ectoprocta
Phoronida
Brachiopoda
Chordata
Echinodermata
Cnidaria
Ctenophora
Silicarea
Calcarea
• One hypothesis of animal phylogeny based
mainly on molecular data
“Radiata”
“Porifera”
Deuterostomia
Lophotrochozoa
Bilateria
Eumetazoa
Metazoa
Ancestral colonial
flagellate
Ecdysozoa
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