BHAVAN'S GANDHI VIDYASHRAM

KODAIKANAL

INVESTIGATORY PROJECT
STRUCTURAL ORGANISATION IN ANIMALS
( FROG )

CLASS : XI
NAME : T.NIKITHA
 CERTIFICATE

This is to certify T.Nikitha of Class XI has completed the Project titled

“Structural organisation in animals” under my guidance. This project can
be considered as a part of the Practical Examination AISSCE conducted by
CBSE.

INTERNAL GUIDE PRINCIPAL

 ACKNOWLEDGEMENT

I would like to convey my sincere gratitude to Almighty God.

I would like to express my sincere gratitude to Mrs. V. Gowri, who

directed me to complete this project successfully.

I wish to acknowledge my heart full thanks to our honourable

Principal Dr. Meera Rajkumar for continuous encouragement and
support.

I thank my Parents for their valuable support, motivation and

encouragement.

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 CONTENT

S.NO TOPIC PG.NO

1. INTRODUCTION 5
2. MORPHOLOGY 6
3. ANATOMY 8
4. DIGESTIVE SYSTEM 10
5. RESPIRATORY SYSTEM 12
6. CIRCULATORY SYSTEM 14
7. EXCRETORY SYSTEM 16
8. NERVOUS SYSTEM 18
9. REPRODUCTIVE SYSTEM 20
10. CONCLUSION 22
11. BIBLIOGRAPHY 23
 1. INTRODUCTION

Frogs can live both on land and in freshwater and belong to class Amphibia of
phylum Chordata. The most common species of frog found in India is Rana
tigrina.

They do not have constant body temperature i.e., their body temperature varies
with the temperature of the environment. Such animals are called cold blooded
or poikilotherms. You might have also noticed changes in the colour of the frogs
while they are in grasses and on dry land. They have the ability to change the
colour to hide them from their enemies (camouflage). This protective coloration
is called mimicry. You may also know that frogs are not seen during peak
summer and winter. During this period they take shelter in deep burrows to
protect them from extreme heat and cold. This is known as summer sleep
(aestivation) and winter sleep (hibernation) respectively.
 2. MORPHOLOGY

The skin is smooth and slippery due to the presence of mucus. The skin is
always maintained in a moist condition. The colour of dorsal side of body is
generally olive green with dark irregular spots. On the ventral side the skin is
uniformly pale yellow. The frog never drinks water but absorb it through the
skin.

 Body of a frog is divisible into head and trunk. A neck and tail are absent.
Above the mouth, a pair of nostrils is present.

 Eyes are bulged and covered by a nictitating membrane that protects them
while in water.

 Feet On either side of eyes a membranous tympanum (ear) receives sound

signals. The forelimbs and hind limbs help in swimming, walking,
leaping and burrowing.
 The hind limbs end in five digits and they are larger and muscular than
fore limbs that end in four digitshave webbed digits that help in
swimming.

 Frogs exhibit sexual dimorphism.

 Male frogs can be distinguished by the presence of sound producing

vocal sacs and also a copulatory pad on the first digit of the fore limbs
which are absent in female frogs.

 The body is bilaterally symmetrical and dorsoventrally flattened.

 The skin of frog is moist and slippery due to the presence of mucus.

 The body of a frog is divisible into head and trunk.

 A pair of nostrils is present above the mouth.

 Size varies from 18 to 20 CM in length and 5 to 8 CM in width .

 The frog never drinks water but absorbs through the skin.

CLASSIFICATION :

KINGDOM ANIMALIA
PHYLUM CHORDATA
SUB PHYLUM VERTEBRATA
SECTION GNATHOSTOMATA
SUPER CLASS TETRAPODA
CLASS AMPHIBIA
ORDER ANURA
FAMILY RANIDAE
GENUS RANA
SPECIES TIGRINA
 3. ANATOMY

The body cavity of frogs accommodate different organ systems such as

digestive, circulatory, respiratory, nervous, excretory and reproductive systems
with well developed structures and functions.

The anatomy or body composition of the frog is somewhat identical to the

anatomy of humans. Both the frogs and humans possess similar kinds of organs
and systems. The body of a frog may be distinguished into a head, trunk, and a
short neck. The flat head comprises the mouth, brain, nose, ears, and eyes.
Anatomy is classified into :
 DIGESTIVE SYSTEM
 RESPIRATORY SYSTEM
 CIRCULATORY SYSTEM
 EXCRETORY SYSTEM
 NERVOUS SYSTEM
 REPRODUCTIVE SYSTEM

Frogs have two forelimbs in the front, or anterior end, and two powerful hind
limbs in the rear, or posterior, for swimming. Each forelimb has four toes, but
the hind limbs have five toes with webbing in between. The webbing creates
resistance in the water, allowing frogs to be agile swimmers.

What is anatomy in detail?

Anatomy (from Ancient Greek ἀνατομή (anatomḗ) 'dissection') is the branch of
biology concerned with the study of the structure of organisms and their parts.
Anatomy is a branch of natural science that deals with the structural
organization of living things.

What is the anatomy of a frog and a human?

Frogs and humans share the same basic organs. Both have lungs, kidneys, a
stomach, a heart, a brain, a liver, a spleen, a small intestine and a large intestine,
a pancreas, a gall bladder, a urinary bladder and a ureter. Males and females of
each species have testes and ovaries respectively.
 4. DIGESTIVE SYSTEM

The digestive system consists of alimentary canal and digestive glands. The
alimentary canal is short because frogs are carnivores and hence the length of
intestine is reduced. The mouth opens into the buccal cavity that leads to the
oesophagus through pharynx. Oesophagus is a short tube that opens into the
stomach which in turn continues as the intestine, rectum and finally opens
outside by the cloaca.

Liver secretes bile that is stored in the gall bladder. Pancreas, a digestive gland
produces pancreatic juice containing digestive enzymes. Food is captured by the
bilobed tongue. Digestion of food takes place by the action of HCl and gastric
juices secreted from the walls of the stomach. Partially digested food called
chyme is passed from stomach to the first part of the small intestine, the
duodenum. The duodenum receives bile from gall bladder and pancreatic juices
from the pancreas through a common bile duct. Bile emulsifies fat and
pancreatic juices digest carbohydrates and proteins. Final digestion takes place
in the intestine. Digested food is absorbed by the numerous finger-like folds in
the inner wall of intestine called villi and microvilli. The undigested solid waste
moves into the rectum and passes out through cloaca.
Pathway of digestive system :
Mouth → Buccal cavity → Oesophagus → Stomach → Intestine → Rectum →
Cloaca → Cloacal aperture.

Frogs are carnivorous they have short intestine. Liver is the largest organ in
digestive system. Stomach of frog comprises a large broader anterior part called
cardiac stomach and a short narrower posterior part called pyloric stomach.
Liver - The largest structure of the the body cavity. This brown colored organ is
composed of three parts, or lobes. The right lobe, the left anterior lobe, and the
left posterior lobe. The liver is not primarily an organ of digestion; it does,
however, secrete a digestive juice called bile.

How is a frog's digestive system similar to humans?

We both have a mouth, esophagus, stomach, pancreas, liver, gall bladder, small
intestine, and large intestine. Humans & amphibians have lots of similarities!

What are the digestive enzymes in frogs?

The activity of some digestive enzymes has been investigated in a crude
pancreas homogenate of frog Rana esculenta. The levels of amylase, trypsin and
chymotrypsin depend on nutritional status being lower in fasted animals;
ribonuclease and lipase levels do not seem to be affected by fasting.

What does the frogs digestive system tell you about what it eats?
Frogs eat live prey, which travels to the stomach via the esophagus and dies by
drowning in stomach acid or suffocating. The food then follows the small
intestine, where it is broken down and absorbed, after which it enters the large
intestine and is excreted through the external cloaca.
 5. RESPIRATORY SYSTEM

Frogs respire on land and in the water by two different methods. In water, skin
acts as aquatic respiratory organ (cutaneous respiration). Dissolved oxygen in
the water is exchanged through the skin by diffusion. On land, the buccal cavity,
skin and lungs act as the respiratory organs. The respiration by lungs is called
pulmonary respiration. The lungs are a pair of elongated, pink coloured sac-like
structures present in the upper part of the trunk region (thorax). Air enters
through the nostrils into the buccal cavity and then to lungs. During aestivation
and hibernation gaseous exchange takes place through skin.

The frog has three respiratory surfaces on its body that it uses to exchange gas
with the surroundings: the skin, in the lungs and on the lining of the mouth.
While completely submerged all of the frog's repiration takes place through the
skin.

A frog may also breathe much like a human, by taking air in through their
nostrils and down into their lungs. The mechanism of taking air into the lungs is
however sligthly different than in humans. Frogs do not have ribs nor a
diaphragm, which in humans helps serve in expand the chest and thereby
decreasing the pressure in the lungs allowing outside air to flow in.

In order to draw air into its mouth the frog lowers the floor of its mouth, which
causes the throat to expand. Then the nostrils open allowing air to enter the
enlarged mouth. The nostrils then close and the air in the mouth is forced into
the lungs by contraction of the floor of the mouth. To elimate the carbon
dioxide in the lungs the floor of the mouth moves down, drawing the air out of
the lungs and into the mouth. Finally the nostrils are opened and the floor of the
mouth moved up pushing the air out of the nostrils.

Frogs also have a respiratory surface on the lining of their mouth on which gas
exchange takes place readily. While at rest, this process is their predominate
form of breathing, only fills the lungs occasionally. This is because the lungs,
which only adults have, are poorly developed.

How many lungs do frogs have?

Frogs do not have two lungs. They have only one pair of lungs which are absent
when they are born and develop later on in their life. The baby frogs or tadpoles
use gills just like those of fish. Tadpoles take in water and absorb oxygen in the
water through tiny blood vessels in their external gills.

What is the respiratory system of a frog and human?

Due to different habitat there are differences in the respiratory systems.
Firstly the humans breathe exclusively through their lungs, whereas frogs use
their lungs only for a part of their respiratory process. Secondly, humans use
their diaphragm muscle to contract the diaphragm but it is absent in frogs.
 6. CIRCULATORY SYSTEM

Your circulatory system, also called the cardiovascular system or vascular

system. The vascular system of frog is well-developed closed type. Frogs have a
lymphatic system also. The blood vascular system involves heart, blood vessels
and blood. The lymphatic system consists of lymph, lymph channels and lymph
nodes. Heart is a muscular structure situated in the upper part of the body cavity.
It has three chambers, two atria and one ventricle and is covered by a membrane
called pericardium. A triangular structure called sinus venosus joins the right
atrium.

 It receives blood through the major veins called vena cava.

  The ventricle opens into a sac like conus arteriosus on the ventral side of
the heart.
 The blood from the heart is carried to all parts of the body by the arteries
(arterial system).
 The veins collect blood from different parts of body to the heart and form
the venous system.
 Special venous connection between liver and intestine as well as the
kidney and lower parts of the body are present in frogs.
 The former is called hepatic portal system and the latter is called renal
portal system.
 The blood is composed of plasma and cells. The blood cells are RBC (red
blood cells) or erythrocytes, WBC (white blood cells) or leucocytes and
platelets.
 RBC’s are nucleated and contain red coloured pigment namely
haemoglobin. The lymph is different from blood.
 It lacks few proteins and RBCs. The blood carries nutrients, gases and
water to the respective sites during the circulation.
 The circulation of blood is achieved by the pumping action of the
muscular heart.

What is the circulatory system of a frog ?

The amphibian circulatory system is less complex than the human system. The
frog heart consists of three chambers: two atria that receive blood and one
ventricle that pumps blood. At the anterior region of the ventricle, the conus
arteriosus carries blood away from the heart.
 7. EXCRETORY SYSTEM

The elimination of nitrogenous wastes is carried out by a well developed

excretory system. The excretory system consists of a pair of kidneys, ureters,
cloaca and urinary bladder. These are compact, dark red and bean like structures
situated a little posteriorly in the body cavity on both sides of vertebral column.
Each kidney is composed of several structural and functional units called
uriniferous tubules or nephrons. Two ureters emerge from the kidneys in the
male frogs. The ureters act as urinogenital duct which opens into the cloaca.
In females the ureters and oviduct open seperately in the cloaca. The thin-walled
urinary bladder is present ventral to the rectum which also opens in the cloaca.
The frog excretes urea and thus is a ureotelic animal. Excretory wastes are
carried by blood into the kidney where it is separated and excreted.

What is the excretory system of a frog and human?

Both humans and frogs have urinary systems that include kidneys and a bladder.
But frogs are amphibians, and amphibians also have a cloaca. The cloaca
collects both solid and liquid wastes and pushes them out together.

What type of excretory waste is produced in adult frogs?

In terrestrial animals like adult frog, these wastes are excreted in the form of
urea. The frog the nitrogenous waste is excreted in the form of urea.

What is the excretory organ of the tadpole of a frog?

The kidney, which in tadpoles is relatively simple and excretes excess water and
ammonia, becomes more complex to serve its new function of conserving water
and excreting urea. The gonads differentiate at about the time of
metamorphosis.

What are the similarities between frog and human excretory system?
1)They both have a pair of kidneys for removing the wastes and extra
substances from their bodies.
2)They both have a pair of ureters for the passage of the urine.
3) They both have one urinary bladder for the storage of urine.
4)The path of urea and urine is the same in both organisms.
 8. NERVOUS SYSTEM

The system for control and coordination is highly evolved in the frog. It
includes both neural system and endocrine glands. The chemical coordination of
various organs of the body is achieved by hormones which are secreted by the
endocrine glands. The prominent endocrine glands found in frog are pituitary,
thyroid, parathyroid, thymus, pineal body, pancreatic islets, adrenals and
gonads. The nervous system is organised into a central nervous system (brain
and spinal cord), a peripheral nervous system (cranial and spinal nerves) and an
autonomic nervous system (sympathetic and parasympathetic). There are ten
pairs of cranial nerves arising from the brain.
 Brain is enclosed in a bony structure called brain box (cranium). The brain is
divided into fore-brain, mid-brain and hind-brain. Forebrain includes olfactory
lobes, paired cerebral hemispheres and unpaired diencephalon. The midbrain is
characterised by a pair of optic lobes. Hind-brain consists of cerebellum and
medulla oblongata. The medulla oblongata passes out through the foramen
magnum and continues into spinal cord, which is enclosed in the vertebral
column.
Frog has different types of sense organs, namely organs of touch (sensory
papillae), taste (taste buds), smell (nasal epithelium), vision (eyes) and hearing
(tympanum with internal ears). Out of these, eyes and internal ears are well-
organised structures and the rest are cellular aggregations around nerve endings.
Eyes in a frog are a pair of spherical structures situated in the orbit in skull.
These are simple eyes (possessing only one unit). External ear is absent in frogs
and only tympanum can be seen externally. The ear is an organ of hearing as
well as balancing (equilibrium).

How many nerves does a frog have?

Frogs have ten pairs (20 numbers) of cranial nerves as compared to human,
which have 12 pairs. They arise from the brain and innervate to the different
parts of the body. They may be sensory or motor in nature.

What are the 10 cranial nerves of a frog?

In contrast to humans, frogs have ten pairs (20 numbers) of cranial nerves .
They grow from the brain and innervate into the various parts of the body. In
fact, they may be sensory, or motor. They are – Olfactory, Optic, Oculomotor,
Trochlear, Trigeminal, Abducens, Facial, Auditory, Glossopharyngeal, and
Vagus.

Which nerve is absent in frog?

The phrenic nerve originates in the neck (C3 - C5) and passes down between the
lung and heart to reach the diaphragm. It is important for breathing, as it passes
motor information to the diaphragm and receives sensory information from it. It
is present in humans, and absent in frog.

Can frogs feel pain?

Frogs possess pain receptors and pathways that support processing and
perception of noxious stimuli however the level of organization is less well
structured compared to mammals. It was long believed that the experience of
pain was limited to 'higher' phylums of the animal kingdom.
 9. REPRODUCTIVE SYSTEM

Frogs have well organised male and female reproductive systems. Male
reproductive organs consist of a pair of yellowish ovoid testes ,which are found
adhered to the upper part of kidneys by a double fold of peritoneum called
mesorchium. Vasa efferentia are 10-12 in number that arise from testes. They
enter the kidneys on their side and open into Bidder’s canal.
Finally it communicates with the urinogenital duct that comes out of the kidneys
and opens into the cloaca. The cloaca is a small, median chamber that is used to
pass faecal matter, urine and sperms to the exterior. The female reproductive
organs include a pair of ovaries . The ovaries are situated near kidneys and there
is no functional connection with kidneys. A pair of oviduct arising from the
ovaries opens into the cloaca separately. A mature female can lay 2500 to 3000
ova at a time. Fertilisation is external and takes place in water. Development
involves a larval stage called tadpole. Tadpole undergoes metamorphosis to
form the adult.

Which organ system is different in the male and female frogs?

Apart from that internally also, the reproductive system is different in male and
female frogs. The male frogs have a pair of testes and the female frogs have a
pair of ovaries.

What is the process of reproduction in a frog?

All frogs reproduce sexually, and all hatch from eggs.In almost all frogs, egg
fertilization happens outside the female's body instead of inside. The female
releases her eggs and the male releases his sperm at the same time. Most frogs
need to lay their eggs in water.

What is the life cycle of a frog reproductive system?

A female frog lays hundreds of eggs, after which the male fertilizes them. Some
of these eggs get destroyed on exposure to wind and rainfall. Therefore, out of
hundreds of eggs, only a few get fertilized. A layer of jelly holds the eggs
together and provides protection to the eggs

What does frog sperm look like?

Sperm can be very simple like in Cape river frogs where the sperm head is cigar
shaped and a very simple tail compared to the great complexity of the foam nest
frog (tree frog) with a highly coiled head that can unfold like a spring during
fertilization .
 10. CONCLUSION

Frogs are beneficial for mankind because they eat insects and protect the crop.
Frogs maintain ecological balance because these serve as an important link of
food chain and food web in the ecosystem. In some countries the muscular legs
of frog are used as food by man.

Significance of frogs

Frogs are beneficial in following ways :

 Bioindicators - They are sensitive to environmental changes both in

aquatic and terrestrial habitats. Thus they are bioindicators.
 Components of the food chain - They are an important part of the food
chains and food web.
 Biocontrol - They feed on mosquitoes thus reducing the spread of
diseases which are borne by mosquitoes
 11. BIBLIOGRAPHY

 CLASS 11 NCERT TEXT BOOK

 www.toppr.com
 http://byjus.com
 www.brown.edu.com