Difference Between Metagenesis and Metamorphosis

Key Difference – Metagenesis vs Metamorphosis
 

Metagenesis and metamorphosis are two terms related to growth and life cycle of organisms. Metagenesis is defined as the alternation of sexual and asexual generations of an organism within the life cycle. Metamorphosis is defined as the process in which organism shows distinct structural forms or different structural stages from adult organisms during the normal development. This is the key difference between metagenesis and metamorphosis. There are two alternate sexual and asexual generations in the life cycle of the organisms which show metagenesis whereas there are four distinct structural forms in the life cycle of organisms which show metamorphosis.

CONTENTS
1. Overview and Key Difference
2. What is Metagenesis
3. What is Metamorphosis
4. Side by Side Comparison – Metagenesis vs Metamorphosis
5. Summary

What is Metagenesis?

In some plants and animals, there are two generations in the life cycle as sexual and asexual. Sexual reproduction and asexual reproduction alternatively occur in the life cycle. This alternation of sexual and asexual generations in the life cycle is known as metagenesis. In one generation, these plants and animals reproduce asexually and in the next generation, they reproduce sexually. Hence, the sexual and asexual structures are alternatively developed in generations. The special feature of the metagenesis is that two types of diploid individuals can be identified in their reproductive cycle since one is asexually reproduced and the other is sexually reproduced.

For example, metagenesis shown by cnidarian Obelia has two alternate generations (hydroid and medusoid phases) where the polyp produces medusa asexually and medusa produces polyp sexually. Metagenesis occurs in some plants (bryophytes) as well. In mosses and ferns, two alternate sexual and asexual generations are present. They are known as gametophyte generation and sporophyte generation.

Figure 01: Metagenesis of a Moss

What is Metamorphosis?

Metamorphosis is a process seen in some animals. During the life cycle of an organism, if it is able to identify different forms which are distinct from the adult form, it is known as metamorphosis. Several different structural forms can be distinctively identified in the life cycle after the embryonic stage during the normal development. These distinct forms undergo changes in their body structures and internal organs to develop into matured form. For example, butterfly shows metamorphosis, and the transformation is clearly visible during its life cycle. There are four distinct structural forms named eggs, larvae, pupa and adult (mature form) in the butterfly life cycle.

Metamorphosis can be either perfect (complete) or imperfect (incomplete). Complete metamorphosis includes four forms: egg, larva, pupa, and adult, as shown by butterfly. Incomplete metamorphosis has forms which resemble the mature form during the normal development. Their life cycles have three forms named eggs, nymphs, and adult; for example, these three forms can be identified in the life cycle a grasshopper. Eggs hatch into nymphs which resemble mature individuals without wings and the life cycle does not include the pupa stage. Nymphs show the same food habits similar to the adult organism.

Figure 02: Complete and incomplete metamorphosis

What is the difference between Metagenesis and Metamorphosis?

Summary – Metagenesis vs Metamorphosis

The terms metagenesis and metamorphosis relate to the characteristics of the life cycle of an organism. Metagenesis is the alternation of a sexual phase and an asexual phase in the life cycle of an organism. Sexual and asexual generations alternatively appear in the life cycle. Metamorphosis is a phenomenon which shows several distinct structural forms during the development of the adult. This is the difference between metagenesis and metamorphosis. The forms in metamorphosis differ from structure and habit. It can happen in either perfect or imperfect manner. In perfect metamorphosis, four forms named egg, larvae, pupa and adult can be identified. In imperfect metamorphosis, three forms named egg, nymph, and adult can be identified.

Reference:
1. “Metagenesis.” A Dictionary of Ecology. Encyclopedia.com, n.d. Web. 24 May 2017. http://www.encyclopedia.com/earth-and-environment/ecology-and-environmentalism/environmental-studies/metagenesis
2. “Arthropod Morphology.” Metamorphosis. N.p., n.d. Web. 24 May 2017. <https://www.amnh.org/learn/biodiversity_counts/ident_help/Parts_Arthropods/metamorphosis.htm>

Image Courtesy:
1. “Moss life Cycle” (Public Domain) via Commons Wikimedia
2. “Holometabolous vs. Hemimetabolous.” By Username1927 – Own work (CC BY-SA 4.0) via Commons Wikimedia

ncG1vNJzZmivp6x7pbXFn5yrnZ6YsqOx07CcnqZemLyue8OinZ%2Bdopq7pLGMm5ytr5Wau265xK2YoJ2emsCqv4yapZ1lpqh6rrHTmqSoqqCdvLS10mg%3D