Classificati
Animalia
on
Chordata
Vertebrata
Tetrapoda
Amphibia
Anur
a
Ran Buf
a o
tigrin buf
a o
Generalized
Characters
1. Amphibia-
both on
Frogs can live
land and in
freshwater and belong to
class
2. Poikilotherms- They do not
have constant body
temperature
3. Camouflage/ Mimicry- They
have the ability to change the
color to hide them from their
enemies
4. Aestivation- summer sleep
5. Hibernation - winter sleep
Morphology
1. Skin - smooth and slippery
due to the presence of
mucus.
2. The skin is always moist.
3. Color- dorsal surface- olive
green with dark irregular
spots.
4. Ventral side- uniformly pale
yellow.
5. Never drinks water but
absorb it through the skin.
Morpholo
1. Body-head and gy
trunk.(neck and tail are
absent.)
2. Above the mouth, a pair of nostrils is present.
3. Eyes- bulged and covered by nictitating
membrane.
4. Tympanum- Either side of eyes/ receives
sound signals.
5. Forelimbs- four digits and hind limbs
help in swimming, walking, leaping and
burrowing.
6. Hind limbs- five digits/ larger and
muscular
Sexual dimorphism
Male frogs-
1. sound producing
vocal sacs.
2. Non functional
in female frogs
3. copulatory pad on
the first digit of the
fore limbs.
4. Which are absent
in female frogs.
Digestive
system
(1)Short alimentary canal
Mouth - buccal cavity -
pharynx - oesophagus –
stomach – intestine – rectum -
cloaca.
(2)Digestive glands
(a) Liver - secretes bile
that is stored in the gall
bladder. (b)Pancreas –
produces pancreatic juice
containing digestive
enzymes.
Digestio
1.Food is captured by the bilobed tongue.
2. n of HCl and gastric juices secreted
Digestion by the action
3. from the walls of the stomach.
4. Partially digested food called chyme is passed from
stomach to the first part of the small intestine, the
duodenum.
5. The duodenum receives bile from gall bladder and
pancreatic juices from the pancreas through a
common bile duct.
6. Bile emulsifies fat and pancreatic juices digest
carbohydrates and proteins. Final digestion takes place in
the intestine.
7. Digested food is absorbed by the numerous finger-like
Respiratio
n
In water - cutaneous
respiration Dissolved oxygen
in the water is exchanged
through the ? by diffusion.
On land-
Pulmonary respiration - Air
enters through the nostrils
into the buccal cavity and
then to lungs.
Cutaneous respiration -
During aestivation and
hibernation
Vascular
Frogs have closedsystem
type vascular
system
(a) Blood vascular system
1. Heart
2. Blood vessels
3. Blood.
(b)Lymphatic system
1. Lymph (lacks few proteins and
RBCs)
2. Lymph channels
3. Lymph nodes.
Hear
1. Myogenic t
2. Upper part of the body cavity.
3. Three chambers - 2 atria and 1
ventricle
4. Covered by pericardium.
5. A triangular structure called sinus
venosus joins the right atrium.
6. It receives blood through the
major veins called vena cava.
7. The ventricle opens into a sac
like conus arteriosus on the
ventral side of the heart.
Blood vessels
1. Arterial system –The blood from the heart is
carried to all parts of the body by the arteries
2. Venous system –The veins collect blood from
different
parts of body to the heart.
3. Hepatic portal system – Special venous
connection between liver and intestine
4. Renal portal system - Special venous
connection between kidney and lower parts
of the body
Bloo
The blood is composed d
of plasma and cells.
Blood cells -
1. Nucleated RBC (red blood cells) or
erythrocytes
2. WBC (white blood cells) or leucocytes
3. Platelets.
The blood carries nutrients, gases and water
to the respective sites during the circulation.
Excretory
system
A pair of kidneys -
1. Compact, dark red and
bean like, situated a little
posteriorly in the body
cavity on both sides of
vertebral column.
2. Each kidney is
composed of several
structural and functional
units called uriniferous
tubules or nephrons.
Ureters –
Two ureters emerge from the kidneys in the male
frogs.
Cloaca –
The ureters act as urinogenital duct which opens
into the cloaca.
In females the ureters and oviduct open
separately in the cloaca.
Urinary bladder –
The thin-walled urinary bladder is present
ventral to the rectum which also opens in the
cloaca.
The frog excretes ? and thus is a ? animal.
Endocrine glands
The prominent endocrine glands found
in frog
1. Pituitary
2. Thyroid
3. Parathyroid
4. Thymus
5. Pineal body
6. Pancreatic islets
7. Adrenals
8. Gonads.
Nervous system
Central nervous system
Brain-
1. Enclosed in cranium.
2. Fore brain - olfactory lobes, paired
cerebral hemispheres and unpaired
diencephalon.
3. Midbrain - a pair of optic lobes.
4. Hind-brain - cerebellum and medulla
oblongata.
5. The medulla oblongata continues into
spinal cord, which is enclosed in the
vertebral column.
Peripheral nervous system
1. Cranial nerves
2. Spinal nerves
Autonomic nervous system
3. Sympathetic nerves
4. Parasympathetic nerves
There are ? pairs of cranial nerves arising from
the brain
Sense
organsCellular aggregations
Well organised organs
Eyes – around nerve endings
A pair of spherical
structures Situated in the Sensory papillae - touch
orbit in skull. These are
simple eyes Monocular Taste buds - taste
vision
Nasal epithelium -smell
Ears-
External ear is
absent Tympanum
present Stato-
Male reproductive
1. A pair of organs
yellowish ovoid
testes adhered to the upper
part of kidneys by
peritoneum ( mesorchium).
2. Vasa efferentia-10-12 in
number that arise from
testes.
3. They enter the kidneys on their
side and open into Bidder's
canal.
4. Finally it communicates with
the urinogenital duct that
comes out of the kidneys and
Female reproductive
organs
1. The include a pair of
ovaries.
2. The ovaries are situated
near kidneys and there is
no functional connection
with kidneys.
3. A pair of oviduct arising
from the ovaries opens
into the cloaca
separately.
Fertilisation,
Development
1. A mature female can
lay 2500 to 3000 ova
at a time (oviparous) .
2. Fertilisation is external
and
takes place in water.
3. Development involves a
larval stage called
tadpole.
4. Tadpole undergoes
metamorphosis to form
the adult.
Economic importance
1. Frogs are beneficial for mankind because they eat
insects and protect the crop.
2. Frogs maintain ecological balance because these
serve as an important link of food chain and food
web in the ecosystem.
3. In some countries the muscular legs of frog are
used as food by man.
