Question

Male frogs can be distinguished from female frogs due to the presence of:
A. Bulging eyes
B. Vocal sacs
C. Webbed digits in feet
D. Copulatory pad on first digit of fore limbs
E. Olive green-coloured skin with dark irregular spots
Choose the correct answer from the options given below:

• A. B and D only
• B. B and C only
• C. A and B only
• D. C and E only

Hint:

Logic Tip: In frogs, male-specific features are entirely tied to reproduction: making noise to call the female (vocal sacs) and holding onto her tightly once she arrives (copulatory pads).

Answer 1

The Correct Option is A

Concept:
Sexual dimorphism is the condition where the two sexes of the same species exhibit different morphological characteristics. In frogs, males possess specific evolutionary adaptations to facilitate mating, which are absent in females.
Step 1:
Bulging eyes with a nictitating membrane are a general amphibian adaptation that allows frogs to see while submerged in water. This feature is present in both male and female frogs.
Step 2:
Vocal sacs are loose folds of skin under the mouth. They are used exclusively by male frogs as resonating chambers to amplify their croaking sounds to attract females during the breeding season. Females do not have vocal sacs. Thus, this is a distinguishing feature.
Step 3:
Webbed digits on the hind limbs are a functional adaptation for swimming. Because both sexes inhabit aquatic environments, webbed feet are present in both male and female frogs.
Step 4:
During mating (amplexus), the male frog climbs on the female's back. To maintain a strong grip on the slippery female, male frogs develop a specialized rough swelling called a copulatory pad (or nuptial pad) on the first digit (thumb) of their forelimbs. Females lack this structure. Thus, this is a distinguishing feature.
Step 5:
The typical olive green-colored skin with dark irregular spots acts as camouflage against predators in grassy and aquatic habitats. This protective coloration is shared by both sexes of the species.
Step 6:
Since only Vocal sacs (B) and Copulatory pads (D) are unique to male frogs, the correct combination is B and D.