Chapter 23.1 Page 670-672 Chapter 23.2 Page 673-678 Animal Diversity  Chapter 23.1 Page 670-672 Chapter 23.2 Page 673-678 

Animal Characteristics 23.1 Animals are diverse but share common characteristics.   Animals are the most physically diverse kingdom of organisms. All animals share a set of characteristics.

Making Connection We are animals. So are jellyfish, squid, cockroaches, tapeworms, sea stars, and the family dog. Animals live in nearly every environment on Earth, from high in the atmosphere to the deepest sea trench. While they come in a huge variety of shapes and sizes, they all share a common ancestry and a set of common physical and genetic characteristics.

Animals are the most physically diverse kingdom of organisms. Animals differ in size,  shape, body composition.  Some have specialized tissues and organs; others do not.

All animals share a set of characteristics. All Animals Are Multicellular Heterotrophs Animal Cells Are Supported by Collagen. Animals Are Diploid and Usually Reproduce Sexually Most Animals Have Hox Genes

Collagen  is a three stranded protein unique to animals. Animal body parts that contain collagen include skin, bone, ligaments, fingernails, and hair. 

Homeotic are a class of genes that control early development.

Homeobox  a DNA sequence within a homeotic gene that regulates development in animals

Animal Diversity 23.2 More than 95 percent of all animal species are invertebrates. Each animal phylum has a unique body plan. Animals are grouped using a variety of criteria. A comparison of structure and genetics reveals the evolutionary history of animals.

Making Connections When you think of an animal, something familiar such as a dog or a snake probably comes to mind. Both of these animals are vertebrates, a group that represents one small subset of animals. However, most animals are invertebrates and look nothing like your mental picture. To understand the vast diversity of animal life, biologists look for unique characteristics that help them sort animals into distinct groups and arrange those groups into a family tree.

Each animal phylum has a unique body plan.

Vertebrate  is an animal with an internal segmented backbone

Invertebrate  are animals without backbones. 

Phylum  Groups of animals that are divided based on shared characters  such as, structural and functioncharacteristics different from every other animal group. 

Animals are grouped using 3 criteria.

Bilateral Symmetry Organism's body can be divided equally along only one plane, which splits an animal into mirror-image sides. 

Radial Symmetry Organism's body parts arranged in a circle around a central axis

Protostome the mouth is formed first, and the anus second.

Deuterosome the first opening forms the anus, and the mouth is formed second.