Introduction to Animals (Chapter 23-1 thru 23-2)
Characteristics of All Animals
1. Animals are _______multicellular_____
2. Animals are _____eukaryotic________
3. Animals are ______heterotrophic___________
4. Animal cells lack cell walls
Evolutionary/Developmental Milestones in Animals
1. Cell
specialization_ and levels of _organization__ (enabled groups of cells to
become specialized to perform specific functions)
2. Development of _body symmetry__ and
segmentation
3. Development of an internal _body cavity___(coelom) and tissue layers
 Levels of Cell Organization from smallest to largest is:
Cells, tissues, organs, systems, organism
 __Symmetry_is the balanced distribution of duplicate body parts or shapes.
 The body plans of most multicellular organisms exhibit some form of symmetry,
either _bilateral_ symmetry or _radial_ symmetry.
A small minority exhibit no symmetry (asymmetrical).
Radial Symmetry
Bilateral Symmetry
Asymmetrical
Ex. Jellyfish
crab, human
coral, sponge
 Segmentation allow for the development of

Cephalization
Tissue Layer
Endoderm
Mesoderm
Ectoderm
specialized limbs
is a head region with sensory organs and a brain.
Develops Into
digestion and respiration structures
muscles, bones, blood, skin, reproductive organs
skin, brain, nervous system
 The significance of having a body cavity, or a coelom, is that it
efficiency of food intake and waste removal.
increases the
Animal Kingdom is divided into two main groups
1. Invertebrates – Animals without __Backbones___
2. Vertebrates – Animals with __Backbones___

Over _95_% of all animal species are invertebrates

There are 8 major phyla of invertebrates from the simplest to the most complex…
Invertebrate Phylum
Example(s)
Porifera
Sponges
Cnidarian
Sea anemone, jellyfish
Platyhelminthes (Flatworms)
Planaira, tapeworm
Nematoda (Round Worms)
Pinworm, hookworm
Annelida
Earthworm, leech
Mollusca
Squid, snails, clams
Arthropoda
Crustaceans, spiders, insects
Echnodermata
Starfish, sea cucumber, sand dollar
 The 4 ways we will study body systems is to categorize them into the following
functions:
1. REGULATION: Excretory & Nervous Systems
2. NUTRIENT ABSORPTION: Respiration, Digestion, & Circulatory Systems
3. DEFENSE: Immune, Integumentary, Lymphatic, Skeletal, & Muscular
Systems
4. REPRODUCTION: Reproductive & Endocrine Systems