Structural Organisation of Animals - Formula Sheet

Dental Formula of Mammals

The dental formula represents the number and types of teeth present in one half of the upper and lower jaws of a mammal:

Dental Formula = (I, C, PM, M) in upper half jaw / (I, C, PM, M) in lower half jaw

• I = Incisors (teeth used for cutting)
• C = Canines (teeth used for tearing, absent in herbivores)
• PM = Premolars (teeth used for grinding)
• M = Molars (teeth used for crushing and grinding)

Dental Formula of Rabbit (Oryctolagus cuniculus)

Formula = 2033 / 1023 (or written as I 2/1, C 0/0, PM 3/2, M 3/3)

Total Tooth Count Calculation = 2 × (Upper Half Count + Lower Half Count) = 2 × ((2 + 0 + 3 + 3) + (1 + 0 + 2 + 3)) = 2 × (8 + 6) = 2 × 14 = 28 teeth.

Metameric Segment Distribution Formula (Leech)

The total segment count (S) of Hirudinaria granulosa is the sum of segments across its 6 body regions:

S_total = S_cephalic + S_preclitellar + S_clitellar + S_middle + S_caudal + S_posteriorsucker = 5 + 3 + 3 + 11 + 4 + 7 = 33 segments

• S_cephalic = Segments 1 to 5 (5 segments)
• S_preclitellar = Segments 6 to 8 (3 segments)
• S_clitellar = Segments 9 to 11 (3 segments)
• S_middle = Segments 12 to 22 (11 segments)
• S_caudal = Segments 23 to 26 (4 segments)
• S_posteriorsucker = Segments 27 to 33 (7 segments)

Peripheral Nervous System Pair Relation (Rabbit)

N_pns = N_cranial + N_spinal = 12 pairs + 37 pairs = 49 pairs

• N_cranial = 12 pairs of cranial nerves originating from the brain
• N_spinal = 37 pairs of spinal nerves originating from the spinal cord