What is Metamorphism?
Metamorphosis is a process in which animals like mammals, insects or even amphibians undergo rapid and extreme physical transformation sometime after birth. The process of metamorphosis can lead to changes in the entire body or simple changes in certain organs of the body. In addition to physical changes, an animal may undergo changes in their form of eating or breathing too. Common examples of metamorphism are the life cycle of a frog. In the life cycle of a frog, the animal transforms from a small tadpole to a frog. Moreover, the life cycle of a frog also experiences changes in the internal organs and systems.
Explain the Life Cycle of a Frog
The life cycle of a frog also known as frog metamorphosis begins at the egg stage. The females lay their eggs which then hatch into tadpoles. The second step of frog metamorphosis includes the development of gills. The tadpoles develop gills that help them to breathe underwater. It is also during this stage of frog metamorphosis that the tadpoles begin to develop lungs. In the third stage, a young tadpole develops into a small frog. A small frog learns how to swim with its hind legs. The most interesting part of a frog metamorphosis is that as the amphibian grows larger, it’s tail size reduces. When the frog turns into an adult it’s tail will disappear completely, and the animal will start to eat insects instead of greens. The cycle of frog metamorphosis keeps relegating as the adult frog will once again lay eggs and produce tadpoles.
What are the Frog Life Cycle Stages?
The frog life cycle stages begin from that of an egg and gradually develops into an adult frog. The intermediate stages include a tadpole and a young adult version of the amphibian. All the changes are accompanied by the physical and internal transformation.
Examples
1. Life Cycle of an Insect
Answer: In an insect life cycle, metamorphism occurs in every stage. At every stage, the insect looks different from what it did earlier. In some animals, we know that the traits from the previous form may remain. But in case of an insect life cycle, that does not happen. A very common example of complete metamorphism in insects is that of a butterfly. In the very beginning comes the larva. The larva has a massive appetite and can almost eat 10 times its body weight. The larva is basically a soft worm-like structure which hardens into the pupa. The out is a hard shell inside which a fully grown butterfly will be formed. The adult butterfly sheds the hard-shelled pupa and stretches out before flying high up in the sky. A few more examples of insects undergoing metamorphism are beetles, bees, ants and moths.
2. Name the Different Types of Metamorphism in Biology.
Answer: Based on the rate of change, metamorphism is of five types:
A metamorphic metamorphosis: It is the kind of metamorphism where the insects undergo very little change.
Gradual metamorphosis: In this kind of metamorphism that animal or insect develops changes over a gradual period of time.
Incomplete metamorphosis: Same as the previous type, in this kind of metamorphism the change comes gradually.
Complete metamorphosis: Complete metamorphosis includes a rapid change of the animal body.
Hyper metamorphosis: This type includes two to three different types of larva that develop into the insect.
Fun Facts of Frog Life
Frogs, usually, absorb water through their skin. Hence, do not have drinkable water.
In the complete life cycle of a frog, an adult frog can lay as many as 4,000 eggs.
Frogs are popularly known for jumping. Some of the frogs can jump as high as 20 times their own body weight in a single leap.
It is a common misconception that frogs are inky green in colour. There are a few frogs which are brightly coloured but very poisonous in nature.
At birth frogs have a long tail, but as they grow into adults the tail disappears.
Significance of Metamorphosis
One of the important components that contribute to the survival of insects is metamorphosis and hence it can be called a successful strategy. Many insects have juvenile phases with environments that are very distinct from the grownups. As a result, bugs can often make use of abundant food resources despite still being able to spread into other environments as adults. Metamorphosis dramatically increases the possibility for adaptability and development.
A Brief About Growth and Maturity
There is one thing to keep in mind when it comes to metamorphosis. Insects cannot mate or reproduce till they have completed their last moult or have emerged as a winged mature insect from a pupa. Wings aren't visible till the last moult, there are a few exceptions of course. When you observe an insect with wings, it means it has reached adulthood. This means that little flies do not grow larger; they just reach their maximum size.
Hormonal Control in Metamorphosis
Iodothyronine-induced metamorphosis is an ancestral trait of all chordates. Hormones produced by endocrine glands towards the front of the body control insect growth and metamorphosis. The prothoracicotropic hormone (PTTH) secreted by neurosecretory units in an insect's brain stimulates prothoracic glands, which emit another hormone, which is usually ecdysone, which causes ecdysis. The corpora allata, a retrocerebral organ, is also stimulated by PTTH, which produces the juvenile hormone, which blocks the growth of adult features after ecdysis.
Moults between larval instars have a significant amount of juvenile hormone, moults to the pupal phase have a lower degree of juvenile hormone, and the ultimate, or interoceptive, moult has no juvenile hormone at all in holometabolous insects. The amount of nymph instar stages in hemimetabolous insects can be influenced by juvenile hormone, according to experiments on firebugs.
Importance of Note-Making in Biology
Note-making is an important aspect of your preparation for the exams. Note-making helps build concentration and keep you proactive and interested during your study session. comprehending what you're learning and clarifying your thoughts selectively choose key concepts. It also saves time and helps you revise better especially in your end-time preparations.
FAQs on Metamorphism - Life Cycle of Frogs and Insects
1. What is metamorphosis? Explain with an example from the NCERT syllabus.
Metamorphosis is a biological process involving a profound transformation in an animal's body structure from one developmental stage to another, such as a larva to an adult. For example, in the life cycle of a frog, a fully aquatic tadpole, which breathes through gills, undergoes metamorphosis to become a terrestrial adult frog that breathes with lungs.
2. What are the key stages in the life cycle of a frog?
The life cycle of a frog, a key example of metamorphosis in amphibians, involves four main stages:
- Eggs: A female frog lays hundreds of eggs in water, in a cluster known as spawn.
- Tadpole (Larva): The egg hatches into a tadpole, which lives in water, swims with a tail, and breathes through gills.
- Froglet: The tadpole gradually develops hind and front legs, its gills are replaced by lungs, and its tail begins to shrink.
- Adult Frog: The tail is completely absorbed, and it becomes a mature frog capable of living on land and reproducing.
3. What is the difference between complete and incomplete metamorphosis in insects?
The main difference lies in the number and nature of the life stages:
- Complete Metamorphosis involves four distinct stages: egg, larva, pupa, and adult. The larva (e.g., a butterfly's caterpillar) looks entirely different from the adult. The pupa is a non-feeding, transitional stage. Examples include butterflies and moths.
- Incomplete Metamorphosis has three stages: egg, nymph, and adult. The nymph typically resembles a smaller, wingless version of the adult and grows by shedding its skin multiple times. Examples include grasshoppers and cockroaches.
4. How does the life cycle of an insect like a butterfly differ from a frog's?
While both undergo metamorphosis, their life cycles differ significantly. A frog's transformation is a switch from an aquatic larval stage (tadpole with gills) to a semi-aquatic/terrestrial adult stage (frog with lungs). In contrast, a butterfly's entire life cycle (larva, pupa, adult) is typically terrestrial. Furthermore, a butterfly's transformation includes a pupal stage (chrysalis), which is absent in a frog's life cycle.
5. Why is the tadpole stage essential for a frog's life cycle?
The tadpole stage is crucial as it serves as the primary growth phase in a separate, food-rich aquatic environment. This reduces competition for food and habitat between the young and the adults. The tadpole's anatomy is perfectly adapted for aquatic life, allowing it to develop and store energy safely before undergoing the complex and demanding transformation into a land-dwelling adult frog.
6. What key hormones control the process of metamorphosis in frogs and insects?
Hormones are the chemical triggers for metamorphosis. In frogs, the process is primarily controlled by thyroxine, a hormone produced by the thyroid gland. In insects, two key hormones are involved: ecdysone, which triggers moulting, and the juvenile hormone, which dictates the outcome of the moult. A high level of juvenile hormone maintains the larval form, while a decrease allows the transition to the pupa and adult stages.
7. How does metamorphosis provide a survival advantage to an animal?
Metamorphosis offers a significant survival advantage by ensuring that the larval and adult stages of an animal do not compete for the same resources. For instance, a caterpillar eats leaves on a plant, while the adult butterfly feeds on nectar from flowers. This strategy allows the species to exploit different ecological niches, increasing overall resource availability and enhancing its chances of survival and reproduction.
8. Can an animal reproduce during its larval stage, such as when a frog is a tadpole?
No, reproduction is exclusively a function of the final adult stage. Larval forms like a tadpole or a caterpillar are sexually immature. Their primary biological purpose is to eat and grow, accumulating the necessary energy and resources to fuel the transformation into an adult. Only after completing metamorphosis does the organism become sexually mature and capable of reproduction.
