Differentiate between internal fertilization and external fertilization.
Hint: The most advanced method of reproduction involves the union of the male gamete, i.e., the sperm, with the female gamete, i.e., the ovum or egg cell. A portion of the sperm penetrates the egg membrane, ultimately leading to fertilization of the ovum.
Complete answer:
Internal fertilization refers to the process where the fusion (syngamy) of the male and female gametes occurs within the female’s body after insemination through copulation. In contrast, external fertilization happens when the fusion of gametes occurs outside the female body, typically in an external environment like water.
The differences between external and internal fertilization are outlined in the table below:
| EXTERNAL FERTILIZATION | INTERNAL FERTILIZATION |
| Occurs outside the female’s body. | Occurs within the female’s body. |
| A large quantity of gametes is typically released into the surrounding environment (e.g., water). | Male gametes are deposited inside the female body through a copulatory organ. |
| Organisms that reproduce via external fertilization must live in or return to aquatic environments for reproduction. | Animals with internal fertilization are fully adapted to life on land. |
| Due to lower chances of fertilization in water, a higher number of gametes are released. | The number of gametes produced is smaller compared to external fertilization. |
| Examples: Fish, amphibians, most algae, etc. | Examples: Reptiles, birds, mammals, bryophytes, and tracheophytes. |
Note: The process of fertilization aids in restoring the total number of chromosomes found in any organism, thereby helping to maintain the stability of the genetic composition across generations.