Segmentation and Notochord: The Architectural Rules of Animalia
Two of the earliest and most consequential decisions embryonic development makes are how the body is partitioned and whether a dorsal supporting rod appears. This quiz tests your command of those two ideas exactly as the standard definitions state them.
- Metameric segmentation — external and internal division into segments with serial repetition of at least some organs.
- Metamerism — the phenomenon itself, classically demonstrated by the earthworm.
- Notochord — a mesodermally derived rod-like structure formed on the dorsal side during embryonic development.
- Chordates vs non-chordates — the cleanest single criterion for sorting the phyla of Animalia.
Work carefully with the wording: the definition demands both halves of each criterion. A merely wrinkled body is not segmented, and a rod that is not mesodermal is not a notochord.
Q1. In animal classification, the body being externally and internally divided into segments with a serial repetition of at least some organs is called:
This is the exact definition of metameric segmentation given in the lesson; the phenomenon itself is called metamerism.
Q2. The phenomenon of having a body divided into serially repeated segments is known as:
The lesson states that the pattern is called metameric segmentation and the phenomenon is known as metamerism.
Q3. Which animal is used in the lesson as the standard example of metameric segmentation?
The lesson states that in the earthworm the body shows the pattern called metameric segmentation.
Q4. For segmentation to qualify as metameric, the division of the body must be:
The definition requires the body to be externally and internally divided into segments, with serial repetition of at least some organs.
Q5. A student observes an animal whose body is only wrinkled and banded on the surface, with no internal repetition of organs. This animal:
The lesson makes clear that an animal which is merely wrinkled or banded does not qualify; the division must also be internal and involve organs.
Q6. The phrase "serial repetition of at least some organs" in the definition of segmentation means that:
The lesson explains that the wording is deliberately permissive: it does not require every organ to be repeated, only that some are.
Q7. The notochord is best defined as:
This is the exact definition of the notochord given in the lesson, specifying both its origin and its position.
Q8. The germ layer from which the notochord is derived is:
The lesson defines the notochord as a mesodermally derived rod-like structure.
Q9. During embryonic development, the notochord is formed on which side of the body?
The lesson states that the notochord is formed on the dorsal side during embryonic development.
Q10. Animals that possess a notochord are called:
The lesson states that animals with a notochord are called chordates.
Q11. According to the lesson, animals which do not form a notochord are called:
The lesson states that animals which do not form this structure are called non-chordates.
Q12. Which of the following ranges of animals is given in the lesson as examples of non-chordates?
The lesson gives non-chordates as porifera to echinoderms.
Q13. Which of the following is a chordate according to the notochord criterion?
The notochord criterion is the presence of a notochord during embryonic development; coelom and segmentation are separate features.
Q14. Which statement about the notochord is correct?
The notochord is a rod-like structure formed on the dorsal side during embryonic development, not a cavity or a series of pouches.
Q15. Which pair of features is used in this lesson to help arrange the phyla of Animalia?
The lesson states that segmentation and the notochord together separate animals that otherwise look quite different and sit at the heart of how zoologists arrange the phyla of Animalia.