Problem 2 - Biology: Life on Earth with Physiology

Question

How does the respiratory system of a frog change when it undergoes metamorphosis? Why are these changes necessary?

Step-by-Step Solution

Answer

During metamorphosis, a frog's respiratory system undergoes significant changes to adapt to its transition from aquatic to terrestrial life. The gills, used by tadpoles to extract oxygen from water, disappear, and functional lungs develop, allowing adult frogs to breathe air. Additionally, the frog's skin becomes more vascularized and moist, enhancing its capacity to absorb oxygen directly from the air. These changes are crucial as they support the frog's increased oxygen demands due to its growth and increased muscular activity, allowing it to thrive in various environments.

Step 1: Understand the life cycle of a frog and its respiratory system during each stage

A frog undergoes metamorphosis in three main stages: egg, tadpole, and adult frog. During each stage, the respiratory system evolves to adapt to the frog's changing environment and needs. 1. As an egg, the developing embryo receives oxygen through diffusion from the surrounding water. 2. When the frog is in its tadpole stage, it has gills for respiration, extracting oxygen from the water. 3. Finally, as an adult frog, it possesses lungs to breathe air and also absorbs oxygen through its moist skin.

Step 2: Describe the changes in the respiratory system during metamorphosis

As the tadpole transforms into an adult frog, several crucial changes occur to its respiratory system: 1. Loss of gills: The gills, which allowed the tadpole to extract oxygen from the water, disappear as the tadpole grows into a frog. 2. Development of lungs: The lungs develop and function for the first time during metamorphosis, allowing the frog to breathe air. 3. Strengthening of the skin's respiratory capacity: The skin of the adult frog becomes more vascularized and moist, enhancing its ability to absorb oxygen from the air directly.

Step 3: Explain why these changes are necessary

The changes in the respiratory system are essential for the following reasons: 1. Transition from aquatic to terrestrial life: The transformation from a tadpole to an adult frog marks the shift from aquatic to terrestrial life. This transition requires the frog to adapt its respiratory system to extract oxygen from the air, rather than water. 2. Increased oxygen demand: As the frog grows, its size and muscular activity increase, leading to a higher demand for oxygen. The lungs provide a more efficient means of oxygen uptake to support the frog's energy requirements. 3. Adaptation to the environment: Adult frogs often live in environments where the water quality may not be suitable for respiration through gills. Therefore, they rely on their lungs and skin to absorb oxygen from the air, allowing them to survive in various habitats. In summary, the changes to a frog's respiratory system during metamorphosis are essential for its transition from aquatic to terrestrial life and to support its increased oxygen demands. The development of lungs and the adaptations in the skin play a crucial role in ensuring the frog can successfully thrive in its new environment as an adult.

Key Concepts

Respiratory System

The respiratory system of a frog undergoes fascinating transformations during its life cycle. It allows the frog to adapt to different environments as it grows. A frog's respiratory system is essential for moving oxygen into its body and removing carbon dioxide. This system changes significantly from the tadpole stage to adulthood. For tadpoles, the primary mode of breathing is through gills, which are effective in water. However, as they grow and become frogs, they need to survive on land. This is where lungs become necessary. These organs help frogs breathe air and support their new lifestyle outside the water. Additionally, adult frogs breathe through their skin, which stays moist and helps in gas exchange. This combination of lungs and skin respiration helps them to thrive in varied environments.

Tadpole

Tadpoles are the larval stage in a frog's life cycle. They look quite different from adults, resembling fish more than frogs. Initially, tadpoles are built to live completely in aquatic environments.
Tadpoles are equipped with specialized organs called gills.
These gills allow them to extract oxygen from the water to survive.

• Tadpoles have feathery gills, which increase the surface area for better oxygen absorption.
• They live almost entirely underwater, requiring an efficient way to breathe in that environment.
• Their bodies are structured to support this aquatic lifestyle, including a tail for swimming.

As they mature, tadpoles undergo metamorphosis, losing their gills and developing lungs to prepare for life on land.

Lungs

Lungs are vital organs that become functional as the tadpole transforms into an adult frog. Frogs develop lungs during metamorphosis, which is crucial for their survival on land.
Adult frogs use these lungs to breathe atmospheric air.

• Lungs fill with air, allowing oxygen to diffuse into the blood and carbon dioxide to be expelled.
• They are more efficient at delivering oxygen compared to gills.
• Lungs enable frogs to inhabit terrestrial ecosystems, where they cannot rely on water-based respiration.

Like us, frogs must regularly surface to breathe, but they are also adept at absorbing some oxygen through their wet skin. This dual respiratory ability offers them flexibility in different environments.

Gills

In the early stages of a frog's life as a tadpole, gills are the primary respiratory organ. They are specifically designed to work in water.
These gills are essential for breathing when the tadpole resides underwater.

• The gills extract dissolved oxygen from the water efficiently.
• They are located on the sides of a tadpole's head, resembling tiny, delicate frills.
• As the tadpole grows, these gills will eventually disappear as they are replaced by lungs and skin respiration.

This transition is necessary as the surrounding water may not always have enough oxygen, especially as tadpoles develop into frogs and move to terrestrial habitats. Losing the gills and gaining lungs helps frogs adapt to their changing environment and oxygen needs.