Question Video: Recalling the Defining Feature of Vertebrates | Nagwa Question Video: Recalling the Defining Feature of Vertebrates | Nagwa

Question Video: Recalling the Defining Feature of Vertebrates Biology • First Year of Secondary School

Which of the following is a defining feature of an animal belonging to the vertebrate subphylum? [A] The animal develops an external skeleton. [B] The animal develops a backbone or spine. [C] The animal uses the environment to regulate their own temperature. [D] The animal has a segmented body.

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Video Transcript

Which of the following is a defining feature of an animal belonging to the vertebrate subphylum? (A) The animal develops an external skeleton. (B) The animal develops a backbone or spine. (C) The animal uses the environment to regulate their own temperature. Or (D) the animal has a segmented body.

The kingdom Animalia can be divided into two subphyla: vertebrates and invertebrates. What distinguishes these two groups? A key feature of animals belonging to the vertebrate subphylum is the presence of a vertebral column, which is also known as a spine or backbone. Invertebrates, on the other hand, do not have a vertebral column. Instead, many invertebrates, such as crustaceans like lobsters, have external skeletons to support and protect their inner tissues and organs, while other invertebrates, like jellyfish, have no skeleton at all.

As external skeletons are only found in invertebrates and not vertebrates, which is the group that this question concerns, option (A) cannot be the correct answer.

The use of the environment to regulate body temperature is a feature of ectothermic animals. For example, many reptiles, like lizards, bask in the Sun, using the heat it radiates to warm up their bodies. While all invertebrates are ectothermic, only some vertebrates are. Ectothermy is therefore not a defining feature of all vertebrates, as some, like us humans, are endotherms. Endotherms internally regulate their own body temperature through mechanisms like sweating or shivering without utilizing the external environment. This means that answer option (C) can be eliminated as it does not appropriately describe all animals belonging to the vertebrate subphylum.

While vertebrates do have segmentation in their backbones, this feature is not exclusive to this subphylum as some invertebrates, such as lobsters, also have segmented bodies. As a result, we can eliminate answer option (D) too.

This leaves us with answer option (B), which appropriately describes a defining feature of an animal belonging to the vertebrate subphylum. The animal develops a backbone or spine.

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