Question

In animals that have a gastrovascular cavity, digestion is ________. a. intracellular b. extracellular

Short answer

In animals with a gastrovascular cavity, digestion is extracellular.

Step-by-step solution

Understanding the Gastrovascular Cavity

The gastrovascular cavity is a body cavity that functions in both digestion and the distribution of nutrients. It is found in simple animals such as cnidarians (e.g. jellyfish) and flatworms. This cavity allows these animals to digest food outside of their cells.

Defining Intracellular Digestion

Intracellular digestion takes place inside the cells, where food particles are engulfed through phagocytosis and broken down with enzymes within lysosomes.

Defining Extracellular Digestion

Extracellular digestion occurs outside the cells. It involves the breakdown of food substances in a cavity or organ where enzymes are secreted, breaking down the food into absorbable components that can then be absorbed into the cells.

Analyzing the Gastrovascular Function

In the gastrovascular cavity, extracellular digestion is the primary type, as enzymes are secreted into the cavity and food is broken down outside of the cells.

Answer Selection

Since the question asks about the type of digestion in organisms with a gastrovascular cavity, and we've identified that digestion in the gastrovascular cavity is extracellular, the correct choice is 'extracellular'.

Key concepts

Gastrovascular Cavity

A gastrovascular cavity is a fascinating structure that serves as a dual-purpose system for digestion and nutrient distribution in certain organisms. This cavity is essentially a simple pouch with a single opening that acts as both mouth and anus. In living beings like cnidarians, such as jellyfish, and flatworms, the gastrovascular cavity allows for the external breakdown of food.

Within this cavity, digestion takes place outside the cells. Digestive enzymes are secreted directly into the cavity where food is broken down before being absorbed by the surrounding cells. This method of digestion is quite efficient for the simple body structures of cnidarians and similar organisms.

Cnidarians

Cnidarians are among the most primitive multicellular organisms, commonly known for their intriguing body structures, like jellyfish, corals, sea anemones, and hydras. These creatures are equipped with a gastrovascular cavity, which is central to their digestive and nutritional systems.

Cnidarians have a simple body plan that supports extracellular digestion. The single opening of their gastrovascular cavity serves as both an entry and exit point, which simplifies their digestive process significantly. Despite their simplicity, cnidarians are equipped with specialized cells for various functions, including ones that line their digestive cavity for efficient enzyme secretion and nutrient absorption.

Nutrient Distribution

Nutrient distribution in organisms with a gastrovascular cavity is straightforward yet effective given their anatomical simplicity. After food is broken down by enzymes in the cavity, the nutrients can be absorbed directly by cells lining the cavity.

This absorption occurs through diffusion or active transport, ensuring that every cell receives necessary nutrients. The single-cavity-and-opening system employed by these organisms is both economical and efficient for their metabolic needs. This structure allows nutrients to be quickly distributed throughout the organism, aiding in growth and energy production.

Digestive Enzymes

Digestive enzymes play a crucial role in the process of extracellular digestion within the gastrovascular cavity. These enzymes are proteins that break down complex food substances into simpler, absorbable molecules.

In the gastrovascular cavity, enzymes are secreted to act on food substances outside the cells. This extracellular digestion enables organisms to utilize larger food particles that would otherwise be difficult to digest if confined within individual cells. By breaking down these complex molecules, digestive enzymes ensure that nutrients are made available for absorption, supporting the organism's survival and energy requirements.