Amphibians Honor

Nature Study

Requirements

What are the characteristics of amphibians?
Answer: Amphibians are ectothermic (cold-blooded) vertebrates, with permeable and moist skin without scales/hair, mixed respiration (cutaneous, branchial in the young, and pulmonary in the adults), reproduction generally in water with external fertilization, eggs without a rigid shell, and development with metamorphosis (aquatic tadpole to terrestrial/amphibious adult). They have a 3-chambered heart. — The term 'amphibian' means 'two lives' (aquatic and terrestrial). The permeable skin allows gas exchange, but makes them sensitive to pollutants - they are environmental bioindicators. Metamorphosis is one of the most striking characteristics, transforming herbivorous tadpoles into carnivorous adults. They inhabit humid environments to avoid desiccation. Their presence indicates a healthy ecosystem.
Give the name of the 3 orders belonging to the class Amphibia and state the main differences between them.
Answer: 1) Anura (toads, frogs, and tree frogs): adults without a tail, long hind legs for jumping, reproduction in water with tadpoles. 2) Urodela or Caudata (salamanders and newts): they keep the tail in the adult phase, an elongated body, four similar legs. 3) Apoda or Gymnophiona (caecilians or blind snakes): without legs, a worm-like body, they live buried in moist soil. — Anura is the largest order (~6,500 species) and the most diverse. Urodela includes salamanders known for their ability to regenerate limbs. Apoda is less known, with caecilians resembling small snakes. Each order evolved distinct adaptations: jumping to escape (Anura), regeneration and camouflage (Urodela), underground life (Apoda). Brazil has great diversity in all three orders.
Popularly, the names toads, tree frogs, and frogs are used to distinguish among anurans. How can we distinguish among these 3 types of anurans? Use images.
Answer: Toads: thick, dry, and warty skin; a robust body; short legs, they walk or take short hops; a predominantly terrestrial habit; they have parotoid glands (behind the eyes) that secrete poison. Frogs: smooth, thin, and moist skin; a slim and aerodynamic body; long and strong hind legs; toes with interdigital membranes (webbing) for swimming; an aquatic or semi-aquatic habit, they live near water. Tree frogs: smooth and moist skin; a generally smaller and slender body; they have adhesive disks (suction pads) on the tips of their toes that allow them to climb and stick to trees, leaves, and smooth surfaces; an arboreal habit (they live in vegetation, away from the ground). — The division is popular, not strictly taxonomic. Toads of the genus Rhinella (formerly Bufo) are the most common in Brazil. Frogs include species of the genera Leptodactylus and Lithobates. Tree frogs belong mainly to the family Hylidae, with characteristic toe disks. Identifying them requires observing the skin, body, toes, and habitat. Comparative images help learning a great deal.
How do amphibians protect themselves?
Answer: Camouflage (mimetic colors matching the environment), aposematism (bright colors warning of toxicity as in the Atlantic Forest tree frogs), secretion of toxins by the cutaneous glands (toads have bufotenin in the parotoid glands), a quick jump to escape, a defensive posture inflating the body, playing dead (thanatosis), and hiding in holes, logs, or foliage. — Amphibians are vulnerable due to their permeable skin and slow movements on land. For this reason they developed chemical (toxins), visual (colors), and behavioral (hiding, jumping) defenses. The toxins of Brazilian toads of the genus Rhinella can be dangerous to dogs. Amazonian tree frogs (Phyllobates) are so toxic that indigenous peoples used them to poison darts.
Make a collection through photos or images taken from a book or the internet of 10 different species of amphibians found in your State or Country.
Answer: Select photos from the field, reliable books, or databases such as Wikiaves and iNaturalist. — Scientific documentation strengthens learning. Each photo should have: the species, the scientific name, the photographer/source, the location, and the date. Brazil has more than 1,000 described species, being the country with the greatest diversity in the world. Varying among toads, frogs, tree frogs, salamanders, and caecilians enriches the collection. Apps such as iNaturalist help with identification and contribute to citizen science, developing responsibility.
Describe or diagram the life cycle of an anuran.
Answer: 1) Adults mate in water with external fertilization; 2) The female deposits gelatinous eggs; 3) Aquatic tadpoles with gills and a tail hatch within a few days; 4) The tadpoles grow feeding on algae; 5) The hind legs appear, then the front ones; 6) The gills are replaced by lungs. — The cycle lasts weeks to months depending on the species and the climate. Metamorphosis involves anatomical changes (loss of the tail, exchange of gills for lungs), physiological ones (a change in diet from herbivorous to carnivorous), and behavioral ones (a transition from aquatic to amphibious). It is a process controlled by the thyroid hormone. Droughts can delay the cycle and climate change affects reproduction globally.
Explain the economic value of amphibians.
Answer: Amphibians have economic value in the biological control of pests (they consume vector insects such as mosquitoes), biomedical research (toxins have become analgesic and antibiotic drugs), commercial breeding (frogs in frog farming for food), environmental bioindication (the health of ecosystems), scientific education (a model in laboratories), and ecological tourism in regions with abundant fauna. — Toads and frogs eat thousands of insects per night, controlling agricultural pests and disease-transmitting mosquitoes. Amphibian toxins have produced medicines such as ABT-594 (an analgesic stronger than morphine). Frog farming produces frog legs for gastronomy. The presence of amphibians indicates clean water - their extinction warns about pollution. They generate jobs in research, breeding, and ecotourism.
Where do toads spend the winter or the dry season?
Answer: Toads enter estivation (the dry season) or hibernation (the cold winter), burying themselves in moist soil, hiding under rocks, fallen logs, crevices, dead leaves, mud at the bottom of ponds, or burrows. They reduce their metabolism, breathe through their skin, and can remain still for months until conditions improve with rain or warming, resuming normal activity afterward. — As water-dependent ectotherms, amphibians cannot withstand prolonged extreme climates. Estivation in humid places preserves the permeability of the skin. The metabolism drops drastically and they can absorb atmospheric water through their skin. In temperate regions they hibernate at the bottom of lakes under the layer of ice. This behavior shows fine adaptation to the climate and is studied in ecology.
Which part of the body is used to amplify the sound that anurans produce? Are both males and females able to croak? What do anurans use their croaks for?
Answer: Anurans amplify the sound through the vocal sac, an elastic membrane in the throat (in some genera there are also lateral sacs). Only the males croak, the females generally being mute or with discreet vocalization. The croaks serve to attract females (the reproductive call), demarcate territory against other males, express danger or stress, and identify the species acoustically. — The vocal sac works as a resonance chamber amplifying the sound produced in the vocal cords. Each species has a characteristic croak - bioacousticians identify species by their song. Females choose males by their croak (sexual selection). In some species the collective croaking creates impressive choruses on humid nights. Common toads such as the cane toad croak especially after rains in Brazil.
Observe an amphibian in its natural habitat or in captivity for about 15 minutes and write a report on what you observed.
Answer: Scientific observation develops attention, patience, and respect for life. Amphibians are timid; sudden movements scare them off. Recording behaviors chronologically reveals patterns. Ideal locations: puddles, marshes, humid gardens, ponds at dusk. Captivity allows prolonged observation but the natural setting teaches more about the habitat. The report trains scientific writing and strengthens the connection with the nature created by God.
What and how do most anurans feed?
Answer: Most adult anurans are carnivorous insectivores, feeding on insects (flies, mosquitoes, grasshoppers, beetles, ants), spiders, earthworms, slugs, and small vertebrates. They capture prey with their extensible and sticky tongue, projected rapidly in a fraction of a second. — The dietary change between tadpole (herbivore) and adult (carnivore) is one of the most striking transitions of metamorphosis. The anuran's tongue is fixed at the front and shoots backward, trapping the prey with sticky saliva. They swallow the prey whole, with the eyes sinking down to help push it. Larger anurans such as the bullfrog can eat small snakes, fish, and even other anurans. They are excellent biological controllers.