Model, Life History of Frog

Quick Answer: The model, life history of frog, sets out the stages by which a frog develops from eggs laid in water into an air-breathing adult. With a frog life history model, students follow amphibian metamorphosis from spawn and tadpole to froglet and adult.

From Spawn to Frog

Frogs lay their eggs in water, and fertilisation is external: the male releases sperm over the eggs as they are laid. Each egg is surrounded by jelly that swells in water, protecting the embryo and forming the familiar clumps of spawn. The embryo develops into a tadpole that hatches with feathery external gills, a tail for swimming and a mouth adapted for scraping algae.

As the tadpole grows, a fold of skin, the operculum, covers the external gills and internal gills take over. Hind limbs appear first, then the forelimbs break through. In the final change the lungs develop, the gut shortens as the diet shifts to animal food, and the tail is absorbed. The small froglet leaves the water and grows into the adult. Thyroxine, a hormone from the thyroid gland, drives these changes.

The title does not state how many stages are modelled, which species is followed or whether the stages are mounted together; these details can be confirmed with LabEquip.

Care & Handling

• Handle the frog life history model by its base or board so the small tadpole stages are not knocked off.
• Dust it gently and do not wet the painted surfaces.
• Store it flat or upright as designed, away from sunlight.

Specifications

Teaching Uses

• Amphibian life cycles and the meaning of metamorphosis
• Showing the change from gill breathing to lung breathing
• The role of thyroxine in development, in senior biology
• Linking amphibian decline to pond and wetland conservation topics

Why Choose LabEquip

Frog life history models are a fixture in zoology labs because they show in one place changes that take weeks to watch in a pond. LabEquip offers it in its biology lab products, with a separate frog model for adult anatomy. Contact LabEquip through the contact page for quantities.

Frequently Asked Questions

How long does a frog take to develop from egg to froglet?

It varies with species, temperature and food, typically from a few weeks to a few months. Cold water and poor food slow development, and some large species spend the winter as tadpoles.

What controls metamorphosis in frogs?

The hormone thyroxine from the thyroid gland. Rising thyroxine levels trigger limb growth, tail resorption and the switch from gills to lungs; tadpoles that lack iodine, which is needed to make thyroxine, fail to metamorphose.

Why do tadpoles have gills?

Tadpoles live entirely in water, so they absorb dissolved oxygen through gills, first external and then internal under the operculum. Lungs develop later, near the end of metamorphosis, as the froglet prepares to leave the water.

Is fertilisation in frogs internal or external?

External. The male clasps the female in amplexus and releases sperm over the eggs as she lays them in water. The jelly coat then swells and protects the fertilised eggs.

What does a tadpole eat?

Young tadpoles mainly scrape algae and plant material with horny jaws and have a long coiled gut for digesting it. Older tadpoles often eat animal matter too, and the gut shortens as they approach the carnivorous adult stage.

Why is the frog life cycle important for ecology lessons?

Frogs need both water and land, and their permeable skin and eggs make them sensitive to pollution and habitat loss. Falling frog numbers are therefore used as a sign of environmental damage in wetlands.

Last Updated: September 2026