A polymorphic life cycle is one in which an organism undergoes two or more distinct phases, each with its own specialized morphology and function. This is in contrast to the typical life cycle of other animals, which consists of a single phase, the adult phase.
Polymorphic life cycles are found in a wide variety of organisms, including plants, animals, and protists. Some of the most well-known examples of polymorphic life cycles include:
* The life cycle of a butterfly: Butterflies undergo four distinct phases during their life cycle: egg, larva (caterpillar), pupa (chrysalis), and adult. Each phase has its own unique morphology and function. For example, the egg is a protective shell that encloses the developing embryo. The larva is a voracious eater that grows rapidly and molts several times. The pupa is a dormant stage during which the larva undergoes metamorphosis. The adult butterfly is a winged creature that can fly and reproduce.
* The life cycle of a jellyfish: Jellyfish undergo two distinct phases during their life cycle: polyp and medusa. The polyp is a sessile, benthic stage that reproduces asexually by budding. The medusa is a free-swimming, pelagic stage that reproduces sexually.
* The life cycle of a malaria parasite: Malaria parasites undergo a complex life cycle that involves both humans and mosquitoes. The parasite begins its life as a sporozoite, which is injected into the human host by an infected mosquito. The sporozoite travels to the liver, where it multiplies asexually. The resulting merozoites then infect red blood cells, where they multiply asexually again. Eventually, some of the merozoites develop into gametocytes, which are sexual forms of the parasite. Gametocytes are taken up by mosquitoes when they feed on infected humans. Inside the mosquito, the gametocytes fuse to form zygotes, which develop into sporozoites. The sporozoites are then transmitted to new human hosts when the mosquito bites them.
Typical of other animals
The typical life cycle of other animals consists of a single phase, the adult phase. This phase begins when the animal is born and ends when it dies. During the adult phase, the animal grows, reproduces, and interacts with its environment.
Some animals, such as insects, undergo a process of metamorphosis during their life cycle. Metamorphosis is a process of physical change that occurs as the animal grows and develops. During metamorphosis, the animal's body changes shape, size, and color. In some cases, the animal may also develop new structures, such as wings or antennae.
Metamorphosis is a complex process that is controlled by hormones. It is thought to be an adaptation that allows animals to survive in different environments. For example, some insects undergo metamorphosis to survive the winter months, while others undergo metamorphosis to find new sources of food.
Comparison of polymorphic life cycles and typical of other animals
The following table compares the key features of polymorphic life cycles and typical of other animals:
| Feature | Polymorphic life cycle | Typical of other animals |
|---|---|---|
| Number of phases | Two or more | One |
| Morphology and function of each phase | Specialized | Not specialized |
| Examples | Butterflies, jellyfish, malaria parasites | Insects, birds, mammals |
Polymorphic life cycles are a complex and fascinating phenomenon. They allow organisms to adapt to a wide range of environments and survive in different conditions.