Extracellular digestion

Definition

Extracellular digestion is the process by which organisms break down food outside their cells, allowing nutrients to be absorbed after the digestion occurs. This method is significant because it enables larger food particles to be processed, unlike intracellular digestion, which occurs within cells. In some animals, such as sponges and cnidarians, this process plays a crucial role in their feeding mechanisms, utilizing specialized structures and secretions to aid in breaking down complex food substances.

5 Must Know Facts For Your Next Test

1. Sponges utilize specialized cells called choanocytes to create water currents that help bring food particles into their bodies for extracellular digestion.
2. Cnidarians have a gastrovascular cavity where extracellular digestion occurs; they use stinging cells called nematocysts to capture prey before digesting it.
3. The secretion of digestive enzymes into the surrounding environment is key for breaking down food during extracellular digestion, allowing for nutrient absorption.
4. Extracellular digestion allows organisms to feed on larger prey compared to intracellular digestion, expanding their dietary options.
5. The ability to digest food extracellularly is an evolutionary advantage that facilitates the growth and energy acquisition of multicellular organisms.

Review Questions

• How do sponges utilize extracellular digestion in their feeding process, and what role do choanocytes play?
  • Sponges utilize extracellular digestion by drawing water through their bodies using specialized cells called choanocytes. These cells create a current that brings in food particles suspended in the water. The sponges then release digestive enzymes into the surrounding water to break down these particles outside their cells. Once digested, the nutrients can be absorbed through the sponge's cell walls, making it an efficient feeding strategy.
• Compare and contrast extracellular digestion in sponges and cnidarians, focusing on their feeding structures and processes.
  • Both sponges and cnidarians perform extracellular digestion, but they have different structures and methods. Sponges primarily rely on choanocytes to filter feed from water, breaking down food particles outside their cells. In contrast, cnidarians have a gastrovascular cavity that serves both as a site for extracellular digestion and nutrient distribution. They capture prey using nematocysts and then digest it within their gastrovascular cavity before distributing nutrients throughout their body.
• Evaluate the significance of extracellular digestion in multicellular organisms like sponges and cnidarians in relation to evolutionary adaptations.
  • Extracellular digestion has significant evolutionary implications for multicellular organisms like sponges and cnidarians. By allowing these organisms to digest larger food particles outside their cells, it enhances their ability to exploit various food sources effectively. This process not only increases nutrient absorption efficiency but also supports greater complexity in body structure and function. As a result, it plays a crucial role in the evolution of diverse feeding strategies among multicellular life forms.

Related terms

Filter Feeding: A method used by some aquatic animals, including sponges, where they draw in water to capture and consume tiny food particles.

Gastrovascular Cavity: A central cavity in cnidarians that serves both digestive and circulatory functions, allowing for the distribution of nutrients after extracellular digestion.

Enzymes: Biological catalysts that facilitate the breakdown of complex food substances into simpler molecules during the extracellular digestion process.