How many eggs do you think were released by the ovary of a female dog which gave birth to 6 puppies?
The ovary of the female dog released 6 eggs.
Each puppy develops from a single fertilized egg (zygote). As shown in the context, when a sperm fertilizes an ovum, it forms one diploid zygote which develops into one offspring.
Since 6 puppies were born, 6 separate eggs must have been released by the ovary, fertilized by sperms, and each developed into an individual zygote and eventually a puppy. Dogs are polyovulatory animals, meaning they naturally release multiple eggs during each reproductive cycle, unlike humans who typically release only one egg per month.
Explanation
This question tests the student's understanding that one egg (ovum) when fertilized by one sperm produces one zygote, which develops into one offspring. The context clearly explains the fertilization process - 'the haploid nucleus of the sperms and that of the ovum fuse together to form a diploid zygote.' Since each puppy originates from one zygote, 6 puppies require 6 eggs to be released and fertilized. This is similar to the logic applied in Question 20 of the textbook regarding fraternal twins (where 2 eggs are released for 2 babies). Dogs naturally release multiple eggs per cycle, making this biologically possible.
Solution Steps
Step 1: Understand that one fertilized egg (zygote) develops into one offspring
Step 2: Apply this principle - 6 puppies means 6 separate zygotes were formed
Step 3: Conclude that 6 eggs must have been released and fertilized by the female dog