Question

When the body of an animal can be divided into equal left and right halves by one plane symmetry. It is known as (a) Bilateral (b) Radial (c) Biradial (d) Asymmetric

Short answer

The correct answer to this question is (a) Bilateral.

Step-by-step solution

Understand the question

In this exercise, you are asked to determine the type of symmetry which divides an animal into two equal left and right halves. We know from basic biological terms referring to symmetry that there are different types of symmetries.

Interpret the options

Bilateral symmetry means the body of an organism can be divided into roughly equal and similar parts around a central axis. This typically applies when there is one plane that could divide the body into two symmetrical halves, such as in humans. Radial symmetry means an organism can be divided into similar halves by multiple planes, like in starfishes or jellyfishes. Biradial symmetry is a combination of radial and bilateral symmetry, which is not common. Asymmetric means that an organism cannot be divided into any two similar halves.

Selection of the right option

Given the condition - a body that can be split into equal left and right halves through one plane - the most suitable match is bilateral symmetry. The description matches the definition of bilateral symmetry more than the others.

Key concepts

Bilateral Symmetry

One of the distinctive features in the animal kingdom is bilateral symmetry, prevalent in many species including humans, where it plays a role in how organisms interact with their environment. Imagine drawing a line down the center of an animal's body; if the left and right halves appear as mirror images, then the organism exhibits bilateral symmetry. This type of symmetry is not only about appearance; it influences an organism's mobility and behavior, with a distinct head and tail (anterior-posterior axis), and a back and belly (dorsal-ventral axis).

Bilateral symmetry is advantageous for directional movement and is commonly observed in animals that move actively in their environments, such as mammals, birds, fish, and reptiles. It also helps establish a foundation for complex organ development, as it allows for specialization of body parts to perform various functions.

Radial Symmetry

In contrast to the bilateral arrangement, radial symmetry refers to organisms that can be sliced into mirror-image halves along multiple planes, all going through a central axis. Creatures like starfish, sea anemones, and jellyfish are examples of radially symmetrical animals. This type of symmetry is often found in organisms that are sessile (immobile) or that move very little, and in those whose surroundings are more or less uniform in all directions.

Importance in Nature

In radially symmetrical animals, body parts radiate from the center, allowing them to interact with the environment in all directions simultaneously. This is particularly beneficial for predation or defense, as they can reach out in any direction without needing to reorient their bodies. For students of NEET biology, understanding radial symmetry is critical as it provides insight into the evolutionary adaptations of different species within their ecological niches.

Asymmetry

Asymmetry in biological terms means the absence of any plane of symmetry, resulting in an organism's body that cannot be divided into two mirror-image halves. It is a rare occurrence in the animal kingdom but is most commonly associated with species like sponges. These organisms have a random organization of cells and structural components which reflects their simple level of organization and sedentary lifestyle.

The study of asymmetrical organisms adds a fascinating dimension to evolutionary biology, showing that life can thrive without the need for symmetrical body plans. NEET biology aspirants should understand that asymmetry represents a fundamental category of biological organization, exemplifying a significant aspect of diversity in form and function within living organisms.

NEET Biology

NEET, or the National Eligibility cum Entrance Test, is a highly competitive exam for students who wish to pursue medical and dental undergraduate courses in India. Biology is a crucial part of NEET, comprising about 50% of the questions in the exam, solidifying its position as a make-or-break subject for aspiring medical students.

Emphasis on Concepts

Concepts such as types of symmetry are imperative for students to master as they form the basis for a broad range of topics in the NEET biology syllabus, including taxonomy, anatomy, and physiology. A deep understanding of symmetry aids in grasping the complexities of evolutionary patterns and ecological adaptations. Therefore, it's essential for students to comprehend these foundational concepts thoroughly to secure a good score and pave their way for a successful career in the medical field.