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Kingdom Animalia
• Multicellular, heterotrophic eukaryotes• Capable of controlled locomotion• Unique tissue: nervous and muscle• 35 phyla• > 1 million described species• 3 - 30 million estimated number of
species(See Table 32.1 for a more complete list of
common characteristics)
Animal Origins
• Arose from a colonial flagellated protistan– Colonial Theory (Haeckel)
• Coordination and cooperation between cells
• Common features between animals and protists
Proterospongia haeckeli-An extant colonialchoanoflagellate
Note cellular specialization - flagellated cells - amoeboid cells
Supporting Evidence for Colonial Theory
• Flagellated sperm cells throughout Metazoa
• Flagellated body cells among lower Metazoa
• True eggs and sperm in phytoflagellates
• Phytoflagellates and colonial organization
Supporting Evidence
• Flagellated sperm
• Early stages of embryology
• Common themes in animal body plans
• Despite their morphological diversity, animals are monophyletic
Key Features in Animal Diversity
• Level of organization
• Symmetry
• Body plan
• Embryological development
• Understanding differences and patterns evident in animal kingdom = understanding of animal macroevolution
Levels of Organization
• Ancestral form had some specialized cells and some cooperation between cells
• Subkingdom Parazoa, which includes the sponges, lack tissues
• Evolution of tissues was next step in animal evolution
• Compartmentalization into specialized “regions” was the next step
Specialized Cells
Tissues
Organs
Organ Systems
With increasingspecialization, eventuallysee regionalization
Symmetry
How many planes can a body be divided into along its long axis and
still get mirror images?
Animals that move in one direction have bilateral symmetry; can be divided into similar halves on only one plane.
The plane runs from the anterior end to the posterior end (tail).
A plane at right angle to the midline divides animals into dorsal and ventral (belly) surfaces.
Radial symmetry – typically in sessile animals (all or part of their life cycle)
Bilateral symmetry is associated with cephalization
Body Plans
Attributes considered for all animals
• Presence or absence of different tissue types
• Type of symmetry
• Presence or absence of a true body cavity
Body Plans – Bilateral Animals
• All animals based on one of three body plans
• Different body plans provide different adaptive advantages
• Apparent trend - increased potential body size
• Body cavity is area between body wall and internal organs
Body Plans – Bilateral Animals
• Embryological development of tissues
– Ectoderm
– Mesoderm
– Endoderm
Acoelomate - cavity filled with tissue
Pseudocoelomate - cavity filled with liquid
Coelomate - cavity filled with fluid and organs supported by membranes
Protostomes (“mouth first”): the blastopore develops into the mouth.
Deuterostomes (“mouth second”): the blastopore develops into the anus; the mouth develops later.
Embryological Development
• Protostomes• spiral cleavage• determinate cleavage
• mesoderm develops by cell sloughing
• Deuterostomes• radial cleavage• indeterminate
cleavage• mesoderm develops
from tissue folds
Cambrian Explosion
• All animal phyla except one appeared in a geological instant 545 mya
• Some groups disappeared?
• Why such diversity is so short a period of time (20 million years)?
Molecular View of Animal Phylogeny
• Genomes and Proteomes – Hox genes and patterning of body axis in vertebrates
• Feature Investigation – Taxonomic relationship of arthropods