PRACTICAL NOTE ON TOAD (Bufo bufo)
PRACTICAL NOTE ON TOAD (Bufo bufo).
Habitat:
- under stones
- logs
- under litter
- pond
- hole
Reasons for habitat:
- Streamlined shape for swimming in water.
- Webbed digits in hind limbs for paddling in water
Mode of Reproduction
- Sexual reproduction with oviparity
Type of Fertilisation:
- External fertilisation
Life Cycle:
- Complete metamorphosis
BIOLOGICAL CLASSIFICATION
Phylum Chordata
Reasons:
- Presence of notochord
- Presence of the Dorsal nerve cord
- Presence of Pharyngeal cleft
Class Amphibia
Reasons:
- No Scale on the skin
- Two pairs of limbs
- Moist, loose skin
- Gills at the larval stage and lungs at the adult stage
Other animals in the same class as
- the Frog,
- salamander,
- newt
Order Anura
Reasons:
- Absence of a distinct neck
- Webbed feet
- Absence of tail
Details in the drawing to score marks
- Eyes positioned above the eardrum and the nostril
- Nostril positioned above the eardrum
- Webbed digits in the hind limb
- Four digits in forelimb, five digits in hind limb
- Streamlined shape
- Wide mouth
Observable features
- Nictitating membrane
- Tympanic membranes
- Two pairs of limbs
- Light ventral surface
- Brown/dark dorsal surface
- Glands in the skin
- Wide mouth
- Sticky tongue
- A pair of large eyes
- A pair of long, muscular hind limbs
- Loose, moist, warty, scaless skin
Adaptive features
- Absence of a tail enables hopping/leaping
- The position of the eye and the nostril is useful when floating in water
- Absence of neck (streamlined shape) for movement in water
- The tympanic membrane detects vibration
- Prominent eyes for vision
- Skin-sensitive to chemicals
- Poisonous glands in the skin for defence against predation
- Skin for camouflage against predation
- Moist vascularised skin for respiration in water
- Vascularised buccal cavity for respiration
- Hind Limbs are muscular and webbed to enable jumping on land and propulsion in water
- Fore limbs are short and stout for landing when leaping on land and also for steering in water
- The lower eyelid has a nictitating membrane to clean and moisten the eye
Description of the skin
- Moist
- Loose
- Warty
- Scaless
Types of movement
- Swimming in water
- Hopping/leaping on land
- Crawling on land
Functions of the skin
- Respiration/gaseous exchange
- Protection against mechanical injury
- Poisonous glands for defence
- Camouflage for defence
Functions of forelimbs
- Landing when leaping
- Steering in water
- Crawling
Functions of the hind limbs
- Lifting when jumping
- Propulsion or swimming (paddle) in water
- Crawling
Differences between the forelimb and the hindlimb
| Fore Limb | Hind Limb |
| Four digits | Five digits |
| Short | Long |
| Not webbed | Webbed digits |
| Less muscular | More muscular |
Sense organs
- Skin: Sensitive to chemicals
- Eyes for light
- Nose detects smell
- Tympanum detects vibration
Excretory organs
- Skin
- Lungs
- Kidneys
Gaseous exchange structures
- Skin
- Lungs
- Buccal cavity
Features for Movement in Water:
- Streamlined shape provides reduced resistance for swimming in water
- Webbed digits in hind limbs for swimming
Features for Movement on Land:
- Large, muscular and powerful hind limbs for lifting the body/hopping/jumping
- Short and stout forelimbs for landing during hopping
Adaptation to life in water
- Streamlined shape/absence of neck
- Position of nostril and eye (protruding eyes and nostrils to allow vision and smell when partially submerged
- Webbed hind limbs for propulsion
- Dark dorsal surface and light ventral surface reduce detection when swimming
- Vascularised skin for gaseous exchange.
- Nictitating membrane protects the eye in water
Adaptation to life on land
- Moist skin to prevent desiccation
- Webbed hind limbs for hopping/leaping
- Absence of a tail for hopping
- Camouflaged skin to prevent predation
- Lungs for respiration, etc.
Adaptation to feeding
- Wide mouth to capture insects
- Long sticky tongue for capturing insects
- Large eyes, when pulled inward, help in swallowing food
- Nostril: for smelling/detecting food
Relationship with other specimens in a food chain
- Feeds on insects
- Fed on by snakes
General Adaptations to Escape Predation
- Poisonous and mucous glands in the skin prevent being preyed upon
- Prominent eyes to see
- Olfactory organs in the nose detect smell
- Tympanum/Ear to detect vibrations
- Dark dorsal surface and light ventral surface (countershading) reduce detection when in water.
- Can change colour on land to blend with the environment
- Large hind limbs to hop (escape)
Economic importance of the frog
- Tadpole decreases the population of algae
- Tadpole is food for fish
- Both the tadpole and its adult feed on mosquito larvae
- Frog is a food
- A toad is a carnivore that reduces (serves the purpose of biological control of) pests of man and crops, such as insects
Similarities between toad/frog and lizard
- Wide mouth
- Nostril above the mouth
- Protruding eyes
- Tympanum present
- Two pairs of limbs
Differences between toad/frog and lizard
| Toad | Lizard |
| Webbed digits | Digits are not webbed |
| Clawless digits | Clawed digits |
| Skin not scaly | Scaly skin |
| No tail | Tail present |
| Nuchal crest absent | Nuchal crest present |
| Gular fold absent | Gular fold present. |
Similarities between the skin of a toad and the lung of a goat
- Highly Vascularized (rich supply of capillary network)
- Wet
- Large surface area
Significance of the similarities
- Highly vascularized for efficient transport of gases
- Wet for efficient diffusion of gases in solution
- Large surface area provides maximum contact with its external environment
Similarities Between the Toad and the Tilapia
- Prominent eyes
- Mouth
- Cloacal opening
- Dark dorsal surface
- Light ventral surface
Differences Between the Toad and the Tilapia
| Toad | Tilapia |
| Scales absent | Scale present |
| Eyes positioned on top of the head | Eyes positioned at the side of the head. |
| Presence of legs | Legs absent |
| Absence of fins | Presence of fins |
| Absence of tail | Presence of tail |
| Absence of operculum | Presence of operculum |
| Absence of lateral line | Presence of lateral line |
| Presence of a poisonous gland | Absence of a poisonous gland |
| Dorsoventrally flattened | Laterally flattened |
