Question

Radial symmetry is shown by (a) Ctenophores (b) Coelenterates (c) Adult echinodermates (d) All of these

Short answer

The organisms that display radial symmetry are Ctenophores, Coelenterates, and Adult Echinodermates. Therefore, the correct answer is (d) All of these.

Step-by-step solution

Identifying Radial Symmetry in Ctenophores

Ctenophores, also known as comb jellies, do exhibit radial symmetry. They have a body that can be divided into similar halves not just along one plane, but multiple. Thus, we can say that option (a) is correct.

Identifying Radial Symmetry in Coelenterates

Coelenterates, now mostly referred to as Cnidarians, include organisms like jellyfish and corals. They too exhibit radial symmetry. Thus, we can say that option (b) is also correct.

Identifying Radial Symmetry in Adult Echinodermates

Adult echinodermates, which include organisms like starfish and sea urchins, show radial symmetry especially noticeable in the case of starfish. Thus, we can say that option (c) is correct.

Final Decision

Since Ctenophores, Coelenterates, and Adult Echinodermates all exhibit radial symmetry based on the definitions and descriptions provided, we can confirm that option (d) 'All of these' is the accurate answer to this question.

Key concepts

Ctenophores

Ctenophores, commonly known as comb jellies, are fascinating marine organisms notable for their unique radial symmetry. Radial symmetry in ctenophores is characterized by their body structure, which can be divided into similar halves through multiple planes passing through the central axis. This type of symmetry allows ctenophores to experience their environment from any direction.
- Ctenophores belong to a separate phylum known as Ctenophora. - They are distinguished by the presence of eight rows of ciliary plates that resemble combs, which aid in locomotion. - Unlike other animals with radial symmetry, ctenophores possess a "colloblast" instead of cnidocytes, which are specialized cells for capturing prey.
Radial symmetry in ctenophores is not just a physical attribute but also a lifestyle adaptation. It allows these organisms to efficiently interact with their prey and predators from any angle, making them effective hunters in their watery habitats.

Coelenterates

Coelenterates, also known as Cnidarians, encompass a diverse group of organisms such as jellyfish, corals, and sea anemones. These organisms are well-known for displaying radial symmetry. This form of symmetry means their body plan is organized in a circular manner around a central point, which is ideal for sessile and planktonic life.
- Cnidarians are characterized by their cnidocytes, specialized cells that they use primarily for capturing prey. - Their radial symmetry facilitates their life in aquatic environments, where food can be encountered from any direction. - Cnidarians can exist in two main forms: the medusa and the polyp, both exhibiting radial symmetry.
This symmetry allows cnidarians to efficiently feed and defend themselves since their body structure supports equal growth and development in all directions around their central axis.

Echinodermates

Echinodermates, specifically the adult forms, such as starfish and sea urchins, are classic examples of organisms that exhibit radial symmetry. This symmetry becomes more pronounced as they reach adulthood.
- Unlike their larval stages, which display bilateral symmetry, adult echinodermates have a five-point radial symmetry, known as pentaradial symmetry. - This distinct body plan is advantageous for their benthic lifestyles, allowing for uniform movement and interaction with their environment. - Echinodermates have a unique water vascular system that aids in their locomotion and feeding.
Starfish, a well-known echinoderm, embodies this radial symmetry, allowing it to regenerate lost limbs and ensuring survival in diverse marine environments. Through their radial symmetry, echinodermates maximize their ecological roles and interactions within ocean habitats.