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 :
1. Characteristics of Metazoa:
Metazoa, or multicellular animals, have several distinguishing features:
- Multicellularity: Metazoans are made up of more than one cell and have complex tissue and organ structures.
- Heterotrophy: They obtain energy by consuming other organisms, unlike plants that are autotrophic.
- Movement: Most metazoans can move at some point in their life cycle, often with specialized structures like muscles or cilia.
- Reproduction: Metazoans typically reproduce sexually, although some can reproduce asexually as well.
- Specialized Cells and Tissues: Metazoans have specialized cells for different functions, such as nerve cells for signaling or muscle cells for movement.
- Development from Embryo: They undergo a developmental process that starts from a fertilized egg (zygote) and proceeds through various stages like blastula and gastrula.
2. Porifera and Eumetazoa:
Porifera, commonly known as sponges, are simple animals that lack true tissues and organs, which is why they are not classified in the Eumetazoa group. Eumetazoa are animals with true tissues, which are groups of cells that perform specific functions and are organized into organs. Sponges, on the other hand, have a loose aggregation of cells and don’t form true tissues or organs, which is why they are placed outside the Eumetazoa clade. The absence of nervous, digestive, and circulatory systems distinguishes Porifera from eumetazoans.
3. Body Symmetry:
Body symmetry refers to the arrangement of body parts around a central axis. The two main types of symmetry in animals are:
- Radial Symmetry: Organisms with radial symmetry have body parts arranged around a central axis, like spokes on a wheel. This symmetry allows the organism to interact with the environment from all directions equally. Examples include jellyfish, sea anemones, and starfish.
- Bilateral Symmetry: Organisms with bilateral symmetry have a single, mirrored left and right side when divided down the middle. This symmetry allows for directional movement and more specialized body parts at the front (anterior) end. Examples include humans, dogs, and insects.
4. Radial vs. Bilateral Symmetry Examples:
- Radial Symmetry Examples:
- Jellyfish (Cnidaria)
- Sea anemones (Cnidaria)
- Starfish (Echinodermata)
- Bilateral Symmetry Examples:
- Humans (Chordata)
- Insects (Arthropoda)
- Dogs (Chordata)
5. Embryonic Tissue Layers:
- Diploblastic Animals: Animals like cnidarians (jellyfish) are diploblastic, meaning they have two embryonic layers:
- Ectoderm: The outer layer that forms the skin and nervous system.
- Endoderm: The inner layer that forms the digestive system.
- Triploblastic Animals: Most other animals are triploblastic, meaning they have three layers:
- Ectoderm: Forms the skin and nervous system.
- Mesoderm: Forms muscles, circulatory system, and other internal structures.
- Endoderm: Forms the digestive system and some other internal organs.
Triploblastic animals are more complex due to the development of the mesoderm layer, enabling more advanced body structures and systems.