To determine the correct answer to the question regarding the dental formula i(3/3); c(1/1); pm(4/4); m(2/3) = 42, we need to analyze the dental formula and understand what it represents in terms of the types of teeth and their arrangement in different species.
Step-by-Step Explanation
- Understanding the Dental Formula:
- The dental formula is a shorthand way of describing the number and types of teeth in an animal's mouth.
- The notation i, c, pm, and m stand for:
- i: Incisors
- c: Canines
- pm: Premolars
- m: Molars
-
The numbers in parentheses indicate the number of each type of tooth in one half of the mouth (upper/lower), and the total number of teeth is calculated by multiplying by 2 (for both halves) and adding the total.
-
Calculating the Total Number of Teeth:
- For the given formula:
- Incisors: 3 (upper) + 3 (lower) = 6
- Canines: 1 (upper) + 1 (lower) = 2
- Premolars: 4 (upper) + 4 (lower) = 8
- Molars: 2 (upper) + 3 (lower) = 5
- Total teeth = 6 (i) + 2 (c) + 8 (pm) + 5 (m) = 21
-
Since this is for one half of the mouth, we multiply by 2: 21 x 2 = 42.
-
Identifying the Species:
-
Now, we need to match this dental formula with the known dental formulas of the options provided:
- A. Rabbit: Typically has a dental formula of i(2/1); c(0/0); pm(3/2); m(3/3) = 28 teeth.
- B. Full Grown Man: Usually has a dental formula of i(2/2); c(1/1); pm(2/2); m(3/3) = 32 teeth.
- C. Young Child: Generally has a primary dental formula of i(2/2); c(1/1); pm(2/2); m(2/2) = 20 teeth (deciduous teeth).
- D. Dog: The typical dental formula for a dog is i(3/3); c(1/1); pm(4/4); m(2/3) = 42 teeth.
-
Conclusion:
- The dental formula provided (i(3/3); c(1/1); pm(4/4); m(2/3) = 42) matches the dental formula of a dog, making option D the correct answer.
Why Other Options Are Incorrect:
- A. Rabbit: The dental formula for rabbits is significantly different, with fewer teeth overall (28), and they lack canines.
- B. Full Grown Man: Humans have a total of 32 teeth, which does not match the 42 teeth in the given formula.
- C. Young Child: Children have a primary set of teeth totaling 20, which is far fewer than the 42 teeth indicated in the formula.
Revision Summary:
- The dental formula indicates the number and types of teeth in an animal's mouth.
- The formula i(3/3); c(1/1); pm(4/4); m(2/3) = 42 corresponds to a dog.
- Other options (rabbit, man, child) have different total teeth counts and arrangements.
- Understanding dental formulas is crucial for identifying species based on their dental characteristics.