Biology · Lesson 26

Practical 3: fish, toad, lizard, birds, skeleton, girdles and dentition

WAECNECO

What the syllabus asks

WAEC: vertebrate specimens (tilapia, toad, agama lizard, domestic fowl and feathers), mammalian skeleton (vertebrae, girdles, limb bones), teeth and dental formulae; identification, observable features, adaptations, comparisons and drawing.

NECO: vertebrate specimens (tilapia, toad, agama lizard, domestic fowl and feathers), mammalian skeleton (vertebrae, girdles, limb bones), teeth and dental formulae; identification, observable features, adaptations, comparisons and drawing.

What you will learn

Classify vertebrate specimens from observable features.
Describe and explain adaptations of tilapia, toad, agama and fowl.
Identify feather types and parts.
Identify vertebrae, girdles and limb bones and state functions.
Describe tooth structure and work out dental formulae.
Relate teeth to diet.
Draw vertebrate specimens and bones correctly.

Key points

Vertebrate classes are told apart by skin covering, limbs and ears.
Tilapia: fins, scales, operculum, lateral line; catfish has barbels and no scales.
Toad: warty, parotoids, webbed toes, no claws; agama: scales, claws, tail.
Feathers: quill, contour, down, filoplume; barbules interlock.
Vertebrae: atlas, axis, cervical, thoracic, lumbar, sacral, caudal by their features.
Girdles: scapula with glenoid; pelvis with acetabulum; limb bones and joints.
Teeth: incisor, canine, premolar, molar; total = 2 × (upper + lower).

Start here: Vertebrate specimens on the practical paper

Vertebrates appear on the practical paper as whole preserved or fresh animals (tilapia, catfish, toad, agama lizard, domestic fowl, rat), as parts (feathers, a fowl’s leg, eggs), and as bones and teeth of a mammal, usually the rabbit, rat, dog, goat or human. All vertebrates belong to Phylum Chordata and have a backbone (vertebral column), a skull enclosing the brain, and usually two pairs of limbs or fins.

Vertebrate classes: observable features
Class	Skin covering	Limbs	Example specimens
Pisces (Osteichthyes)	scales; slimy mucus	paired fins	tilapia, catfish, mudskipper
Amphibia	moist or warty skin without scales	4 limbs, no claws	toad, frog
Reptilia	dry horny scales	4 clawed limbs (none in snakes)	agama lizard, gecko, snake, tortoise
Aves	feathers; scales on legs	wings and legs; beak, no teeth	domestic fowl, pigeon
Mammalia	hair or fur	4 limbs; external ear (pinna)	rat, rabbit, bat

What the questions ask

Typical tasks: name the class; state observable features that adapt the animal to its habitat; give two differences between two specimens (such as a toad and a lizard, or tilapia and toad); state the mode of fertilisation; draw the specimen or a bone; identify a vertebra from its features; write a dental formula and relate the teeth to diet. In 2023 WAEC asked candidates to classify catfish eggs, a fowl’s egg and a picture of a uterus with a foetus into Pisces, Aves and Mammalia, and to give modes of reproduction.

Reproduction table you should know

Modes of reproduction
Class	Fertilisation	Eggs / young
Fish (tilapia)	external	many small eggs without shells; tilapia broods eggs in its mouth
Amphibia	external, in water	jelly-coated eggs; tadpole larva
Reptilia	internal	leathery-shelled eggs laid on land
Aves	internal	hard calcareous-shelled eggs; incubated
Mammalia	internal	young develop in the uterus (placenta) and are suckled

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Practice questions

1. Tilapia breathes using

gills
lungs
skin only
tracheae

Show answer

A: gills
Covered by the operculum.

2. The lateral line in fish detects

light
chemicals
temperature
vibrations and pressure changes

Show answer

D: vibrations and pressure changes
Sense organ.

3. The toad belongs to the class

Pisces
Mammalia
Amphibia
Reptilia

Show answer

C: Amphibia
Moist skin, metamorphosis.

4. The agama lizard has

fur
dry scaly skin
moist naked skin
feathers

Show answer

B: dry scaly skin
Class Reptilia.

5. Feathers are found only in

birds
reptiles
mammals
amphibians

Show answer

A: birds
Class Aves.

Key words

Operculum: Bony gill cover of a bony fish.
Lateral line: Sense organ along the side of a fish detecting vibrations.
Parotoid gland: Poison gland behind the eye of a toad.
Calamus: Hollow base (quill) of a feather.
Rachis: Shaft of a feather bearing the vane.
Centrum: Solid body of a vertebra.
Odontoid process: Peg on the axis around which the atlas rotates.
Acetabulum: Socket of the pelvic girdle for the femur.
Glenoid cavity: Socket of the scapula for the humerus.
Diastema: Gap between front teeth and cheek teeth in herbivores.
Dental formula: Numbers of each tooth type in one half of upper and lower jaws.

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