Metamorphosis - Developmental Biology Dr.M.Jothimuniyandi

Metamorphosis -Dr.M.Jothimuniyandi - Complete Metamorphosis - Holometabolism - Incomplete Metamorphosis -Hemimetabolism- Hormonal Regulation- Metamorphosis in Amphibians - Significance-Difference between Incomplete metamorphosis and Complete metamorphosis

1. Dr.M.Jothimuniyandi Assistant Professor Metamorphosis

2. Metamorphosis is a biological process in which an organism undergoes significant physical changes after birth or hatching. It is commonly seen in amphibians (like frogs) and insects (like butterflies and moths). The process involves a series of developmental stages where the organism transforms from one life stage to another, often involving changes in form, structure, and function. Metamorphosis is a dramatic and complex process that allows an organism to change its body structure and physiology significantly, adapting to different environments or life functions as it matures. Metamorphosis

3. This biological phenomenon occurs primarily in insects and amphibians, and it can be categorized into two major types: Complete Metamorphosis ( Holometabolism ) : This involves four distinct stages – egg, larva, pupa, and adult. Insects like butterflies, beetles, and flies undergo complete metamorphosis. The larval stage looks entirely different from the adult form, and the pupa stage is a transitional phase. Metamorphosis

4. Incomplete Metamorphosis ( Hemimetabolism ) : In this process, there are three stages – egg, nymph, and adult. The nymph resembles a smaller version of the adult but lacks fully developed wings and reproductive organs. Examples include grasshoppers and dragonflies. In amphibians , metamorphosis is marked by the transition from an aquatic larval stage (like tadpoles in frogs) to a terrestrial adult stage. Changes include the development of lungs, legs, and the resorption of the tail. Metamorphosis

5. Stages: Egg → Larva → Pupa → Adult In complete metamorphosis, the organism undergoes four distinct life stages: Egg: The beginning of life, laid by the female. Larva: After hatching, the organism enters the larval stage, where it is focused on feeding and growth. Examples include caterpillars (butterflies), maggots (flies), and grubs (beetles). The larva looks nothing like the adult. 1. Complete Metamorphosis ( Holometabolism )

6. Pupa: The transformation stage, where the larva forms a protective case (chrysalis in butterflies) and undergoes internal reorganization. During this time, most larval tissues break down, and adult structures develop. Adult: The fully formed organism emerges from the pupa, ready for reproduction. The adult often has wings (insects), fully developed reproductive organs, and features distinct from the larva. Examples: Butterflies, moths, beetles, flies, and ants. 1. Complete Metamorphosis ( Holometabolism )

7. Stages: Egg → Nymph → Adult In incomplete metamorphosis, the transition from juvenile to adult is more gradual, and there is no pupal stage. Egg: Laid by the female. Nymph: The nymph looks like a smaller version of the adult but usually lacks certain adult features, such as wings or functional reproductive organs. It grows and molts several times to reach adulthood. 2. Incomplete Metamorphosis ( Hemimetabolism )

8. Adult: The nymph eventually develops into a mature adult capable of reproduction. Examples: Grasshoppers, cockroaches, and dragonflies. 2. Incomplete Metamorphosis ( Hemimetabolism )

9. Metamorphosis Source: https://smartclass4kids.com/types-of-metamorphosis-stages-and-examples/

10. Metamorphosis Source: https://animaldifferences.com/differences-between-complete-and-incomplete-metamorphosis/

11. In amphibians like frogs and toads, metamorphosis involves a shift from a fully aquatic, gill-breathing larval stage to a primarily terrestrial, lung-breathing adult stage. Egg: Amphibians lay eggs in water. Larva (Tadpole): After hatching, tadpoles swim using a tail, breathe with gills, and feed primarily on algae. Over time, tadpoles develop legs, their tail shortens, and they transition to breathing air with lungs. Adult: The adult frog or toad is fully terrestrial, breathing with lungs, feeding on insects, and capable of reproduction. Metamorphosis in Amphibians:

12. In insects, metamorphosis is controlled by two major hormones: Ecdysone : Initiates molting and controls the transformation from larva to pupa to adult. Juvenile hormone: Keeps the larva in a juvenile state; its reduction allows the progression to pupal and adult stages. In amphibians, metamorphosis is regulated by thyroid hormones (primarily thyroxine ). These hormones trigger changes in body structure, such as the development of limbs and the absorption of the tail in frogs. Hormonal Regulation

13. Adaptation: It allows an organism to exploit different ecological niches at different stages of life, reducing competition for resources between juvenile and adult stages. Survival: The distinct stages provide different forms of protection and adaptation. For example, larvae can be excellent at feeding, while adults are specialized for reproduction. Metamorphosis is a remarkable example of biological transformation that ensures survival and adaptation to changing environmental needs during an organism's life cycle. Significance of Metamorphosis

14. Difference between Incomplete metamorphosis and Complete metamorphosis Source: https://smartclass4kids.com/types-of-metamorphosis-stages-and-examples/

15. Questions? Thank You