Download Ch. 32 Intro to Animal Evolution

Introduction to Animal Evolution
Ch. 32
AP Biology
Ms. Haut
What is an Animal?
• Multicellular, heterotrophic eukaryotes
• Animal cells lack cell walls
• 2 tissues unique to animals: nervous and
muscular
• Most reproduce sexually, with diploid stage
dominating life cycle
Animal Development
• Zygote undergoes
cleavage to form
blastula
• During gastrulation
embryonic tissues that
develop into adult
body parts form
Phylogenetic
Tree of
Animals
Parazoans
• Includes Phylum
Porifera (sponges)
• Classified as parazoa
because they lack true
tissues
Eumetazoans
• Include nearly all other animal phyla
• Organisms that contain true tissues
• Radiata and bilateria are the major branches
Radiata
• Radial Symmetry
• Organisms that are sessile (attached to
substratum) or plankton (drifting)
• Equips them to meet the environment
equally from all sides
– Cniderians (jellyfishes, corals, anenomes)
– Ctenophora (comb jellies)
Bilateria
• Bilateral Symmetry
• Cephalization seen—concentration of sensory
equipment (central nervous system)
• Equips them for mobile lifestyle
• 2 branches:
– Organisms without body cavities (Acoelomates)
– Organisms with body cavities (Pseudocoelomates and
Coelomates)
Acoelomates
• Phylum Platyhelminthes
(flatworms)
• Triploblastic (3 germ layers)
animals with
solid bodies
(no cavity
between
digestive tract
and outer body
walls
Pseudocoelomates
• Phylum Rotifera (rotifers)
• Phylum Nematoda
(roundworms)
• Triploblastic (3 germ layers)
animals
• body cavity
between
digestive tract
and outer body
walls
incompletely
lined with
mesoderm
Coelomates
• Body cavity completely lined by mesoderm
• 2 evolutionary lines
– Protostomes
– Deuterostomes
Protostomes
Mollusks
Arthropods
Annelids (segmented worms)
Deuterostomes
Echinoderms
Chordata
• Distinguished by pattern of
development
– Cleavage pattern:
• Spiral, determinate cleavage
(Protostomes)
• Radial, indeterminate cleavage
(Deuterstomes)
– Coelom formation
• Schizocoelous body cavity
(mesoderm splits)
• Enterocoelous body cavity
(mesoderm folds
– Fate of Blastopore
• Mouth develops from
blastopore (Protostomes)
• Anus develops from blastopore
(Deuterostome)
Coelomates