Question

Which of the following does not grow? (a) Amoeba (b) Yeast (c) Dead body (d) Planaria

Short answer

The answer is (c) Dead body, as it is non-living and therefore does not have the biological capacity to grow.

Step-by-step solution

Identify each option

The first step is to identify every option given in the question. We have four options here: (a) Amoeba, (b) Yeast, (c) Dead body, and (d) Planaria.

Classify each option

Classify each option into their biological categories. (a) Amoeba and (d) Planaria are both types of organisms belonging to the Kingdom Protista and Kingdom Platyhelminthes respectively. (b) Yeast is a type of fungi. (c) A Dead body is not a living organism.

Determine if it can grow

(a) Amoeba, (b) Yeast, and (d) Planaria are all living organisms and have the capacity to grow. They all reproduce and increase in size, which are indications of growth. (c) A Dead body no longer has biological functions and therefore can't grow.

Key concepts

Amoeba

Amoebas are remarkable single-celled organisms known for their distinctive shape-shifting abilities. Classified under the Kingdom Protista, amoebas thrive in various environments, including freshwater, saltwater, and even moist soils. These tiny organisms are fascinating due to their incredible adaptability and growth capabilities.

Amoebas grow by a process called binary fission. During this process, an amoeba duplicates its nucleus and cytoplasm before splitting into two separate amoebas. This method of asexual reproduction allows amoebas to multiply rapidly when conditions are favorable.

Some key points about amoebas include:

• They move and feed using pseudopodia, which are temporary extensions of their cell body.
• Amoebas can encapsulate themselves when environmental conditions become harsh, reactivating once favorable conditions return.
• These organisms are a fundamental part of the ecosystem as they help decompose organic matter.

Understanding amoebas sheds light on how primitive organisms can adapt and thrive in diverse environments.

Yeast

Yeast, a type of fungi, plays a vital role in both natural ecosystems and human industries. Known scientifically as Saccharomyces cerevisiae, yeast is a single-celled organism that thrives almost everywhere, from plant surfaces to animal bodies. It is widely recognized for its role in fermentation, a process crucial in food production, particularly in baking and alcohol production.

Unlike multicellular fungi, yeast reproduces primarily through a process called budding. In this process, a new cell forms and separates from the parent cell, leading to a new individual. This method allows yeast to grow and proliferate incredibly quickly under suitable conditions.

Some important features of yeast include:

• Yeast cells have a high rate of growth and reproduction in environments rich in sugar, such as dough or fruit juices.
• They produce carbon dioxide and alcohol as byproducts of fermentation, which are key in bread making and brewing industries.
• Beyond being indispensable in cuisine, yeasts are also used in scientific research due to their simple eukaryotic structure.

Understanding yeast helps appreciate its dual role as both a critical biological catalyst and a practical asset in various industries.

Planaria

Planaria are extraordinary flatworms belonging to the class Turbellaria within the Kingdom Platyhelminthes. Noted for their simple body structure and incredible regenerative abilities, planarians are commonly found in freshwater environments, such as ponds and streams.

Planaria grow not only by cell division but also exhibit remarkable capabilities for regeneration. A unique feature of planaria is their ability to regenerate entire body parts. This means if a planaria is cut into pieces, each piece has the potential to grow into a complete organism. This capability is due to specialized cells called neoblasts.

Key aspects of planaria include:

• Planaria have a simple nervous system yet can exhibit complex behaviors like learning and memory.
• Their regenerative abilities make them a focus of scientific research, particularly in studying stem cells and healing.
• Planarians feed on small organisms and organic matter, contributing to the ecosystem's nutrient cycle.

Studying planaria provides insight into the complexities of regeneration and potential applications in biological sciences.