BIOGEOSPHERE
Bilingual Biology and Geology
I.E.S. "J.S.Elcano (Sanlúcar Bda.)
5. Amphibians
It is estimated that there are about 7,000 species of amphibians.
Amphibians appeared more than 360 million years ago.
It is the oldest group of tetrapods.
They evolved from a group of fish that developed legs and primitive lungs.
a) Habitat
“Amphibians” means “double life”. All amphibians begin life in water,
but adults are terrestrial animals although they have to live in wet places,
near fresh water.
b) Morphological characteristics
- They have four limbs.
- Their body is divided into: head, trunk and tail.
- Their skin is very thin and is not covered by any protective structure.
They have glands that produce mucus and keep the skin moist.
c) Vital functions:
Nutrition:
The digestive system is complete.
They have a mouth without teeth,
a stomach an intestine and an anus.
It opens outside by the cloaca.
Young usually are herbivorous and adults carnivorous.
Young breathe by gills,
and adults breathe by lungs and skin.
Amphibians have double circulation.
Their heart has only three chambers: two upper atriums and a lower ventricle.
They have incomplete circulation.
They have two kidneys.
Interaction
They have a well developed brain and sense organs:
eyes (with eyelids), ears (without auricles), taste, smell and touch.
Many of them have poisonous glands.
They are poikilotherms (cold-blooded).
Reproduction:
Fertilization can be external or internal.
They are oviparous, except salamanders that are ovoviviparous.
They have to lay eggs into water, because they do not have impermeable shell.
Usually, they do not care the eggs or young.
Young have to change to became adult. They undergo metamorphosis.
d) Classification:
- Anurans (E. g. Frogs and toads).
Their body is compact.
They don’t have tail.
Their hind limbs are longer and stronger
than the forelimbs
Adults are mainly terrestrial.
- Urodeles (E.g. Salamanders and newts)
Their body is elongated.
They have tail.
Their hind limbs and forelimbs are similar
Adults are mainly aquatic.
READING ACTIVITIES
After reading the text, copy and answer the following questions into your notebook:
Remember: you must make complete sentences.
5.1. The following sequence of pictures represents the metamorphosis
of a frog.
a. Cut out them and glue on the right order on your notebook.
Do the same with the labels. Relate every phase with its description.
b. Why do they have to lay eggs in water?
c. What phases have gill breathing?
d. What differences are there between tadpole and adult frog feeding?
5.2. Listen and relate each sentence with a characteristic of Amphibians:
a. Metamorphosis
b. Pulmonary and cutaneous respiration
c. Tetrapods
d. Poikilotherms (cold-blooded)
e. Naked skin with mucuous glands
Now,
check
your
answers!
LISTENING ACTIVITIES
Download this worksheet
and complete it,
while you listen this audio.
SPEAKING ACTIVITIES
Now, in turns with your partner,
answer the questions in the worksheet.
(Diccionario Ing-Esp)
(Juegos de vocabulario)
(Visual dictionary)
(Visual dictionary)
(Glosario de C. Naturales)
(Science audio-glossary)
(Science audio-glossary)
(Pronunciación)
(Enciclopedia de C. Naturales)
(Tabla periódica)
Eva Mª
López Rodríguez
Departamento
Biología y Geología
IES " J. S. Elcano"
Sanlúcar de Barrameda