[Year/Subject] 2nd Year, Science

From Tadpoles to Frogs

Objectives[Course Name] Various Animals

Increase the pupil’s awareness of the body structure of animals by observing tadpoles and frogs that live nearby.
Ensure that the pupils are aware that the major changes seen in the body structure of tadpoles and frogs is a way that theanimal adapts to its living environment.

Optimum Season
Of all larva at the Sera Yume Kouen, Nature Observation Field, the Japanese brown frog, montane brown frog, common toadand other species that are undergoing metamorphosis relatively latey, and the black-spotted frog, tree frog and other frogs thatare undergoing metamorphosis relatively early, can be observed at the start of July. This period is one in which all species offrog living within the park are most active, and thus the optimum time to observe them.

Items to PrepareSpoon-net: to catch tadpoles or frogs
White plastic tray: to observe tadpoles thathave been caught
Breeding case: To observe frogs, and toobserve and raise tadpoles It is recommended to observe tadpoles thatare developing rear legs as shown in thepictures on the right page.
 The buds (primodia) of a tadpole's rear legsdevelop between the upper areas of theanus and the base of the tail. Have pupils
observe these areas.

Example answers (partially entered)

From Tadpoles to Frogs
Most animals obtain the nutrients required to live through food, and move around theirenvironment accordingly in search of this food. Yet, their behavior differs depending on
the type of animal because the places that they live, the way they eat, move and how theyare aware of their surroundings are different. This is also related to the way their bodies areconstructed.
Amphibians in particular make immense changes to the area they live when they movefrom water to land, and undergo immense changes to their body structure as they
metamorphose from tadpoles to frogs. Let's have a closer look to see what changes there
are, and make comparisons with fish, which live in the same aquatic environment.
 Observation date & time: Observation area:
 Weather: Temperature:

External
nostril (nose)

Eyes Dorsal lineMouth
Eardrum (ear)Toes
Anterior limb
(front leg)

Anus
Lateral line
Posterior limb
(rear leg)

1. Compare the differences in living areas and body structure of tadpoles and frogs
Living area
Method of movement
Parts used to move
TailFinsFront Frogs are vertebrates, so have pupils checkfor the presence of spine (backbone) inboth frogs and tadpoles.
 Discuss the fact that there is a strong
relationship between the area the animals
live in, their method of movement and theirbody structure.
 By noting the differences in food they eat,you can indicate to the pupils that there aredifferences with their inner organs.
 Amphibians such as frogs differ to reptiles,
avian species and mammals in that theycannot completely live away from water.
Ensure that pupils are aware that indeposits and growth of larva requires thepresence of water.

Legs

Rear

Mouth
External nostril (nose)
Eardrum (ear)Body color or patterns
Skin condition
Spine (backbone)

TadpolesIn water
Swim with tail
Tail
Present
Present (dorsal fin, abdominal fin)
Not visible as they are under theskin
Developing externally. Becomesbigger and more complex as thebody grows longer.
Small as they eat algae andmicrobes (plant-based)
Present (1 pair)
Not present
Earth-colored in grey or black withno pattern
FaintPresent

Frogs
Land around water, grass and trees
Jumps with front and rear legs
Front and rear legs
No present
No present
One pair behind its head
Better developed than the frontlegs, thick, longLarge as they eat animals such as
insects
Present (1 pair)
Behind their eyes
Varies with species, green or
brown is most common
Quite thick, moist surface
Present

Major changes in body structure during the optimum period for metamorphosis
Further information on this topic is provided in the reference materials on pages 25 to 28. Please make use of these referencematerials.
 A large number of sample responses havebeen provided here, however thiscorresponds to the many different
observations that pupils could have
2. Observe how each body part changes with metamorphosis
during this exercise.
Catch some wild tadpoles that already show development in their rear legs, and record
Changes to body structure in order to live
what you observe from the day their front legs appear to the day their tail completely
on land also include changes to internal
disappears (the metamorphosis period varies with ambient temperature and roomtemperature).
organs, and accordingly, metamorphosis
State ofObservations
actually refers to the period between themetamorphosis
larva stages where the rear legs are not
1st day
visible, until the tail disappears. The- Front legs start appearing- Jagged mouth remains
fascinating period from after theappearance of front legs until the tail- Mouth edges extending laterally, positioned between the front edge of the nostrils and2nd day
mouth
disappears is referred to as the- Tail has become black, not as transparent- Abdominal fin and dorsal fin becoming shorter“metamorphic climax”.
- The tail has become shorter, however is longer than the rear legs
 The start of metamorphosis is defined as
3rd day- Mouth edges have extended to the center of the eyes
the appearance of the front legs, and ends
- Tail has darkened further, abdominal fin and dorsal fin have disappeared- Tail is shorter than rear legs
when the tail disappears completely.
 The metamorphic climax varies between- Mouth edges extended to the rear edge of the eyes
4th day- Jagged mouth has disappeared completely
frog species and temperature, however- Tail has become even shorter, however some darkness remains- Ear drums have become visible between eyes and front legs
continues for approximately one week.
 The photos show the metamorphosis
5th day- Tail has disappeared completely, now in the form of a baby frog.
process of the Japanese tree frog as away of outlining metamorphosis.
3. Compare tadpoles with fish, which live in the same aquatic environment
 The end of metamorphosis is shown by
the photo taken on day five on the left.
Overall length- Five types of fins: dorsal fin,Head andThe rear tip of the rear legs extends pastTailabdominal fin, pectoral fin, anal fin,trunkEyes
the anus.
Dorsal fin
tail fin
Snout
During the metamorphic climax, theOne
pairofgill
flaps
todischarge
Tail
Abdominal fin heighttadpole’s digestive system is undergoingwater sucked in through the mouth in
Mouthorder to extract oxygen in the water
structural change, and accordingly will
Spiracle
Anus
Tail muscle- Body surface covered with toughnot eat any food.
Body structure of a tadpole
scales
Placing approximately seven sheets ofDorsal fin- Lives its entire life within water
Tailfinkitchen paper into the breeding case
Scalesduring the metamorphic climax will keep
Eyes
Snout
the area moist with water, making it
Anal fineasier to raise and observe the tadpoles.
Mouth Pectoral Abdominal
Gill flap fin
fin AnusBody structure of a fishDiscussion key points
Have pupils compare the body structure of
tadpoles and fish.
Amphibians and fish do have several
similarities, however despite living in the sameaquatic environment, both species display
different characteristics. This is the reason why
these two species are classified as different
vertebrates.

Observation key points
 Sketches and descriptions are used so that pupils can check for a shortening of the tail, fin conditions, changes in tail color,shape of the front portion of the head, structure of the eyes and mouth, position of edges when the mouth spreads open
laterally, the appearance of eardrums, colors of certain species and speckles or patterns in the dorsal skin.
 Species that live amongst leaves, such as the Japanese tree frog or Schlegel's green tree frog, have rounded toes on theirfront and rear legs as suckers developed.
 The larger opening in a frog’s mouth is so that they can catch small animals quickly following their change from an
herbivorous to a carnivorous diet after metamorphosis is complete.

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