Problem 3 - Biology Today and Tomorrow with Physiology

Question

A(n) ______ undergoes gastrulation. a. gastrula b. blastula c. somite d. neural tube

Step-by-Step Solution

Answer

A blastula undergoes gastrulation.

Step 1: Understand Gastrulation

Gastrulation is a phase early in the embryonic development of most animals. During gastrulation, the single-layered blastula is reorganized into a multilayered structure known as the gastrula. Understanding what gastrulation entails helps identify the stage or structure involved in this process.

Step 2: Identify Key Terminology

Let's break down the terms given in the options: \(1\) Gastrula: This is the structure formed after the process of gastrulation. \(2\) Blastula: This is the early stage before gastrulation. \(3\) Somite: This is a division of the body of an embryo in the early stages of development in vertebrates. \(4\) Neural tube: This is the precursor to the central nervous system. Recognizing these terms is essential for answering the question.

Step 3: Choose the Correct Option

From Step 2, we understand that gastrulation is a process happening to the blastula. Therefore, the structure that undergoes gastrulation is the blastula, as it is reorganized into the gastrula. This means the correct choice is option \(b\), blastula.

Key Concepts

Embryonic Development

Embryonic development is a complex process that begins right after fertilization and involves multiple stages leading to the formation of a fully developed organism. It is a highly coordinated sequence of events where the single-cell zygote divides and differentiates into diverse cell types and structures. The core stages of embryonic development include:

• Fertilization: The joining of sperm and egg to form a zygote.
• Cleavage: Rapid cell division without growth, resulting in a cluster of cells called a morula.
• Blastulation: Formation of a hollow ball of cells known as the blastula.
• Gastrulation: Transition of the blastula into a multilayered structure called the gastrula.

Each stage is crucial for ensuring cells are correctly organized to form tissues and organs. Mistakes during embryonic development can lead to congenital anomalies.
Understanding these stages helps in comprehending how complex life forms arise from a single cell.

Blastula

The blastula is a critical early stage during embryonic development. It occurs after the cleavage stage, where the zygote undergoes rapid divisions to form a solid ball of cells called the morula. As the cells continue to divide, the morula transforms into the blastula, which is characterized by a hollow fluid-filled cavity known as the blastocoel.

• The outer layer of cells in the blastula is known as the blastoderm.
• The blastocoel provides necessary space for cell movements during subsequent stages, such as gastrulation.

At this point, cells are not yet specialized but are prepared to undergo significant movements and differentiation. The blastula stage is crucial as it sets the stage for gastrulation, where the groundwork for forming distinct tissue layers in the embryo begins.

Gastrula

The gastrula represents a major milestone in embryonic development, marking the transition from a simple to a complex embryo. During the process of gastrulation, significant changes occur as the single-layered blastula is reorganized into a three-layered structure. These three layers are:

• Endoderm: Forms the inner layer and develops into the digestive tract and other internal organs.
• Mesoderm: Forms the middle layer and gives rise to muscles, bones, and the circulatory system.
• Ectoderm: Develops into the outermost layer, giving rise to the skin and nervous system.

These layers, known as germ layers, are foundational as they determine the fate of the cells, guiding them towards forming various parts of the body. Gastrulation is essential because it sets the stage for organogenesis, where actual organs and tissues begin to develop. Understanding the gastrula phase helps in comprehending how early cell structures can lead to complex multicellular organisms.