Question

Echinoderms in their larval state have ____. a. triangular symmetry b. radial symmetry c. hexagonal symmetry d. bilateral symmetry

Short answer

d. bilateral symmetry

Step-by-step solution

Understand echinoderms and their larval state

Echinoderms are a group of marine animals that include starfish, sea urchins, and sand dollars. They have an internal skeleton and a water vascular system that helps them move and feed. In their larval state, they go through a series of developmental stages before becoming adults.

Review different types of symmetry

There are various types of symmetry in living organisms: a. Triangular symmetry: This refers to objects or living organisms that are symmetric when rotated 120 degrees around their center point. b. Radial symmetry: This type of symmetry is present when multiple lines of symmetry radiate from a central point. Typical examples of radial symmetry include starfish and sea anemones. c. Hexagonal symmetry: This refers to objects or living organisms that are symmetric when rotated 60 degrees around their center point. d. Bilateral symmetry: This type of symmetry is present when an organism can be divided into two equal and mirrored halves along a single plane. Most animals, including humans, have bilateral symmetry.

Identify the symmetry of echinoderms in their larval state

As we know, echinoderms typically exhibit radial symmetry in their adult forms. However, in their larval state, they exhibit a different type of symmetry. They have bilateral symmetry, which means they can be divided into two equal and mirrored halves along a single plane. So, the correct answer is: d. bilateral symmetry

Key concepts

Echinoderm Development

Understanding the intricacies of echinoderm development is essential when diving into marine biology, particularly as it reveals the fascinating transformation these organisms undergo. Echinoderms, such as starfish, sea urchins, and sand dollars, have a unique developmental process. In their early stages, echinoderm larvae are a far cry from the radial symmetry their adult counterparts display.
Instead, they exhibit bilateral symmetry, hinting at their evolutionary ties to other bilaterally symmetrical animals. This bilateral phase is part of their planktonic stage, during which they are freely swimming and developing in the ocean. As they mature, a complex metamorphosis takes place, and they transition to the more familiar radial symmetry, ready to settle onto the sea floor. This developmental shift is not only a testament to the adaptability of echinoderms but also plays a key role in their survival strategy, allowing the larvae to disperse widely before adopting a benthic lifestyle.

Types of Symmetry in Organisms

Symmetry is a fundamental aspect of biological organization, with different organisms showcasing varying patterns that contribute to their structure and function.

Bilateral Symmetry

found in echinoderm larvae, is one of the most common types, with organisms having a single plane of symmetry that divides them into mirrored halves. It is typical in animals, including humans, and is associated with an active lifestyle of locomotion and directed movement.

Radial Symmetry

, on the other hand, is characterized by multiple planes of symmetry that all pass through a central axis, common in adult echinoderms and species like jellyfish or anemones, reflecting a lifestyle more attuned to a fixed position or slow movement.

Triangular and Hexagonal Symmetry

are less common in the animal kingdom but can be found in some microorganisms and crystals. Recognizing these patterns enriches our understanding of organismal design and evolutionary adaptation.

Marine Biology

Marine biology, the study of life in the oceans and other saltwater environments, encompasses a broad range of topics that include the life cycles of marine organisms like echinoderms. The oceans are a vast and complex habitat, where creatures have adapted in extraordinary ways to thrive in their specific niches.
Through the lens of marine biology, we appreciate the incredible biodiversity and interspecies relationships found within marine ecosystems. For instance, the transitional development of echinoderms from a bilaterally symmetrical larval stage to a radially symmetrical adult is just one example of the remarkable strategies marine life employs. Furthermore, understanding the adaptive features of marine organisms, including their symmetry, provides insights important for conservation efforts, ecosystem management, and even biomimicry in technological applications.