What are the characteristics of the Metazoa? 2. What are the Porifera and why aren’t they in the Eumetazoa? Animals in the eumetazoa are divided into different groups based on many different physical characteristics that you need to learn about using standard vocabulary. 3. What is body symmetry? What is the difference between radial and bilaterally symmetry? 4. Give some examples, because the first “branch” in the eumetazoan phylogeny in Figure 18.1 is based on the type of symmetry in a group. This 2:33 video can help you understand symmetry. Radial Symmetry Examples Bilateral Symmetry Examples 5. Animals develop from different embryonic tissue layers. Some only have two layers and more advanced ones have three embryonic tissue layers. What are these layers and what types of tissues develop from these embryonic tissues
The Correct Answer and Explanation is:
- Characteristics of Metazoa:
Metazoa, or animals, are multicellular, eukaryotic organisms that are heterotrophic, meaning they consume other organisms for energy. Their cells lack cell walls, unlike plants or fungi. Most have specialized tissues, and their development involves a blastula stage. They reproduce sexually (though some also reproduce asexually), and most are capable of movement at some stage in their life cycle. - What are Porifera, and why aren’t they Eumetazoa?
Porifera, or sponges, are simple aquatic animals that lack true tissues and organs. They have porous bodies and filter water to feed. Because they do not have true tissues or organized body structures like a nervous or digestive system, they are not included in the Eumetazoa. Eumetazoa includes animals with true tissues, including muscles and nerves, and more complex body organization. - What is body symmetry? What is the difference between radial and bilateral symmetry?
Body symmetry refers to how an animal’s body can be divided into parts that are mirror images.
- Radial symmetry means the body can be divided into similar halves by multiple planes through the central axis, like a pie.
- Bilateral symmetry means the body has only one plane that divides it into mirror-image halves, with a distinct front, back, left, and right side.
- Examples of symmetry:
- Radial symmetry examples: jellyfish, sea anemones, and starfish (as adults).
- Bilateral symmetry examples: humans, dogs, insects, and fish.
The first branch in the eumetazoan phylogeny separates animals with radial symmetry from those with bilateral symmetry.
- Embryonic tissue layers and their roles:
Animals develop from two or three embryonic layers:
- Ectoderm: forms the skin and nervous system.
- Endoderm: forms the lining of the digestive tract and associated organs.
- Mesoderm (in triploblastic animals): forms muscles, bones, and the circulatory system.
Animals with only ectoderm and endoderm are called diploblastic (e.g., cnidarians), while those with all three are triploblastic (e.g., most animals, including humans).
