Aquatic Animals:
* External fertilization: Eggs are released into the water and fertilized externally by sperm.
* Advantages:
* No need for direct contact between male and female.
* Can result in a large number of offspring.
* Challenges:
* Eggs are vulnerable to predation and environmental factors like currents.
* Requires a high concentration of sperm to ensure fertilization.
Terrestrial Animals:
* Internal fertilization: Sperm is deposited inside the female's body where fertilization takes place.
* Advantages:
* Greater protection for the eggs and developing embryos.
* Increased chance of fertilization due to direct contact.
* Challenges:
* Requires more complex mating rituals and behaviors.
* Can lead to fewer offspring than external fertilization.
Why the difference?
* Water's support: In aquatic environments, water provides buoyancy and support for eggs, which can be easily released and fertilized externally.
* Terrestrial environment: On land, eggs are more vulnerable to desiccation, predation, and environmental fluctuations. Internal fertilization provides a safer environment for the developing embryo.
Exceptions:
* Some aquatic animals (e.g., sharks, rays, and some amphibians) use internal fertilization, adapting to their environment or other factors.
* Some terrestrial animals (e.g., amphibians) still use external fertilization, but their eggs are typically laid in moist environments to prevent them from drying out.
In summary: The difference in fertilization strategies between aquatic and terrestrial animals is a result of the different environmental challenges they face. Aquatic animals benefit from external fertilization in the water's supportive environment, while terrestrial animals rely on internal fertilization to protect their eggs from the harsh conditions on land.