10A: Characteristics of Animals

What is an Animal?

• Zoologist: A scientist who studies animals.

• All animals have certain characteristics.

  • Animals are made of many eukaryotic cells.

  • Animals are consumers.

  • Most animals have specialized cells that are organized into tissues, organs and systems.

  • Most animals can move during at least part of their lives.

  • Most animals eat their food rather than merely absorb it.

  • Animals reproduce sexually (though some can reproduce asexually).

Characteristics

• Symmetry: can be divided by one or more imaginary lines into mirror-image halves.

  • Bilateral symmetry.

    • Midline

  • Radial symmetry

  • Asymmetry

• Heads

  • Cephalization: The sense organs and brain are clustered at one end of the body.

• Guts and body Cavities

  • Not all animals have a digestive tract.

  • Animals can be classified on the basis of the presence of absence of a body cavity.

  • Complete guts: digestive tract has two openings.

  • Incomplete guts: Digestive tract has one opening

• Presence of a Backbone

  • Chordates: animals that have a notochord.

    • In most chordates, the notochord develops into a backbone.

    • Vertebrates: Animals with a vertebrae that protects the animal's spinal cord.

    • Invertebrates: Animals that never have a notochord.

  • Temperature Control

    • Endotherms: animals that can regulate their inner temperatures.

    • Ectotherms: Animals that cannot regulate their inner temperatures.

Classifying Animals

• Our modern classification system has its roots in the work of Carolus Linnaeus.

  • His work reflected biblical beliefs.

• Evolutionists have made many changes to the way in which organisms are classified.

• Creationists are trying to determine biblical kinds.