Animal DiversityKingdom Animalia

What is an Animal?

• Multicellular, heterotrophic, eukaryotic• Store carbohydrates as glycogen (plants store theirs as starch)• Lack cell walls• Nervous and muscular tissue• Sexual reproduction leading to an diploid zygote that undergoes

mitosis

Cambrian Explosion

• Most major animal groups around today originated in the Precambrian and Cambrian era• Explosion of diversity in a relatively short period of time• Many of the Cambrian species are extinct but their body plans remain

in species alive today

Animal Phylogeny• Animal kingdom is probably monophyletic• Evolutionary history is reconstructed using comparative anatomy and

studying embryology• There are 4 key evolutionary branch points in animal evolution

1. Development of true tissues2. Split between radial and bilateral symmetry3. Development of a body cavity4. Developmental differences between protostomes and deuterostomes

True Tissues

• Tissues are a group of cells that work together for a single function• Sponges lack true tissues and are considered a more primitive animal

group• Cnidaria are the first animal group to develop true tissues: muscles

and nervous tissue• Led to the ability to move and therefore interact with their

environment

Symmetry• Asymmetry- no pattern of symmetry around an axis…• No way to divide the org into similar looking halves

• Radial-more than one line of bisection• Bilateral- one line of bisection ie a distinct right and

left side • Also typically have dorsal and ventral surface, anterior and

posterior surface

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Body Cavity

• Also called a coelem: Fluid filled cavity found between body wall and digestive tract• Tube within a tube• Cushions your internal organs• May have been an adaptation in burrowing organisms

• Many different types and ways that a body cavity develops• Acts as a hydrostatic skeleton in some less advanced animals• Some evidence that it allows for a larger animal to evolve.

Embryology- Protostom vs Deuterotome• Protostomes-mouth forms first then the anus during embryological

development• Most invertebrate groups

• Deuterostomes- anus forms first then the mouth• Can split up cells at 4 cell stage and each will continue to develop into a complete viable

organism• Echinoderms and chordates

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Other Notable Trends in Animal Life

• Increased complexity and specialization of structures• Example-development of tissues, organs, segmentation

• Greater dependence on sexual reproduction• Improved sensory systems and increasingly complex brain• cephalization

• Expanding patterns of behavioral patterns

Segmentation• Repeated grouping of parts or compartments• Aids in movement and evolution of appendages• Groups of segments and their appendages have become

specialized for a variety of “jobs” among regions ie a division of labor

Cephalization

• Def-Having a head• Sensory organs, centralized nervous system and feeding parts are all usually

concentrated here• Are there advantages to this arrangement?• Is there a particular kind of symmetry associated with this?

Cephalization Advantage-• Anterior end of a travelling animal will encounter

stimuli-food, danger etc… first• Adaptation for burrowing, crawling, swimming• Radial animals tend to be sessile or planktonic- can

meet environmental symmetry from all sides• Active animals moving in a distinct direction “meet”

the environment from one end and bilateral symmetry fits that lifestyle

Animal Phyla

Vertebrate Animal Phyla

• Chordates: all members have a notochord, hollow dorsal nerve cord, and pharyngeal arches• Urochordata• Caphalochordata• Vertebrata