Which phyla have the different types of body symmetry that animals have?
To determine which phyla have the different types of body symmetry that animals exhibit, we can reference a classification system called the Linnaean taxonomy. Animals can be divided into two major groups based on body symmetry: radial symmetry and bilateral symmetry.
1. Radial Symmetry:
Animals with radial symmetry can be divided equally along any plane passing through the center of their body. In other words, they have multiple planes of symmetry. The following phyla often exhibit radial symmetry:
- Cnidaria: Includes jellyfish, sea anemones, and corals. Their bodies are organized around a central axis.
- Echinodermata: Comprises starfish, sea urchins, and sea cucumbers. They generally have a central disk with arms radiating from it.
2. Bilateral Symmetry:
Animals with bilateral symmetry can only be divided into two equal halves along a single plane. This type of symmetry allows for a distinct head, tail, and distinct left and right sides of the body. Various phyla exhibit bilateral symmetry, including:
- Porifera: Also known as sponges, they are primitive animals without specialized tissues or organs.
- Platyhelminthes: Includes flatworms that often have a flat, ribbon-like body.
- Nematoda: Comprises roundworms which are cylindrical with a distinct anterior and posterior end.
- Annelida: Consists of segmented worms, including earthworms and leeches.
- Mollusca: Includes diverse animals like snails, clams, and octopuses, often characterized by a muscular foot.
- Arthropoda: The largest phylum, consisting of insects, crustaceans, spiders, and other joint-legged animals.
- Chordata: This phylum encompasses vertebrates, including mammals, birds, reptiles, amphibians, and fish.
It's important to note that while the representative phyla mentioned above typically exhibit the described types of symmetry, there may be exceptions or variations within each group. The classification of animals is a complex field, and ongoing research can lead to updates and adjustments in the understanding of various groups.