Question Video: Identifying the Phylum of an Aquatic Organism with Radial Symmetry | Nagwa Question Video: Identifying the Phylum of an Aquatic Organism with Radial Symmetry | Nagwa

Question Video: Identifying the Phylum of an Aquatic Organism with Radial Symmetry Biology • First Year of Secondary School

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A scientist makes the following notes on an aquatic organism: (1) Radial symmetry (2) Oral and aboral surface (3) Tube feet present, Which invertebrate phylum does this organism most likely belong to?

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Video Transcript

A scientist makes the following notes on an aquatic organism. Number (1) radial symmetry, number (2) oral and aboral surface, number (3) tube feet present. Which invertebrate phylum does this organism most likely belong to?

Let’s find an answer to this question by first clarifying some key terms. First, we are told that this organism is an invertebrate. The terms vertebrate and invertebrate are descriptions of animals, which are all classified under kingdom Animalia. A vertebrate has a bony vertebral column or backbone surrounding a spinal cord that is connected to the brain. Invertebrates do not have this vertebral column. In most cases, they do not have a spinal cord at all, but at the very least they do not have a backbone.

Then, we are asked which phylum this invertebrate must belong to. Phylum is the grouping of organisms below the kingdom level. Since we have already determined that an invertebrate is an animal, we will only need to consider the phyla within kingdom Animalia. Within kingdom Animalia, the vertebrates are all classified under phylum Chordata. The major invertebrate phyla are Porifera, Cnidaria, Platyhelminthes, Nematoda, Arthropoda, Mollusca, and Echinodermata.

There are only two of these that show radial symmetry: Cnidaria and Echinodermata. So we can eliminate the rest. Radial symmetry describes a body symmetry, or similarity of sides, around a central point or axis.

The other two characteristics given are also specifically characteristics of organisms in phylum Echinodermata. This phylum includes animals such as sea stars, sea urchins, and sea cucumbers. All echinoderms are aquatic and, in fact, marine, meaning that they live in saltwater. Unlike some other invertebrates, echinoderms do not have a clear front end and back end. And they don’t really have eyes like the ones we’ve drawn on here. Instead, they have an oral surface where their mouth is, and an aboral surface which is located on the other side of the organism. They also develop tube feet, which they use to move.

So, the invertebrate phylum best described by these characteristics is Echinodermata. And therefore, the organism mostly likely belongs to Echinodermata.

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