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

Animal Origins

• Despite their morphological diversity, animals are monophyletic

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

Fig. 32.8

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

Fig. 32.8

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

Fig. 32.4c

Acoelomate

Fig. 32.4b

Pseudocoelomate

Fig. 32.4a

Eucoelomate

Acoelomate - cavity filled with tissue

Pseudocoelomate - cavity filled with liquid

Coelomate - cavity filled with fluid and organs supported by membranes

Fig. 32.8

Embryology and Developmental Biology

All animals gothrough the sameinitial stages of embryonic development

(see Fig. 32.3)

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

Fig. 32.5

Fig. 32.8

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

• See Table 32.2

• Will be helpful for Chapters 33-34

• For second Animal Diversity lab

Fig. 32.8