In 1740, Abraham Trembley, a tutor at a count's house in Geneva, was teaching children. Near the count's home, there was a small ditch with clear water and covered with moss. Trembley was very interested in this place and would collect aquatic plants to observe after each class. One day, he discovered a tiny, strange creature. Its body was slender and looked like a small tube, standing on a rock with many branches extending from the top, swaying constantly with the water current. At first, Trembley thought it was a plant and brought it home to keep in a glass tank to see what it would look like when it grew up. However, after observing it for a while, he found that this "plant" could actually move and even prey on small insects in the water! It turned out to be an animal called a hydra, and those "branches" were actually its tentacles.
Later, Trembley also discovered that sometimes hydra could grow many "shoots" like plants from its body. When the "shoots" grew up, they would detach from the mother and become many identical little hydra. The method of reproduction in which hydra directly bud off small hydra from the mother's body is called asexual reproduction. In fact, hydra can also reproduce sexually like most animals, that is, two hydra stick together, one of which produces sperm and the other produces eggs, and the sperm and eggs combine to form a fertilized egg, eventually developing into a new hydra individual.
Since hydra can reproduce offspring in two ways, what are the differences between them? Simply put, the offspring produced by asexual reproduction are only female and inherit all the genes from the mother; while the offspring produced by sexual reproduction are both female and male, with their genes coming from both parents. Just like us humans, your nose might look like your father's, but your mouth might look like your mother's.
Which of these two methods of reproduction is better? Scientists have found that hydra mainly engage in asexual reproduction when there is sufficient nutrition, while in adverse conditions, such as during spring and autumn when the temperature difference is large and food is scarce, they engage in sexual reproduction. This shows that sexual reproduction can make the offspring more adaptable to the environment. Because during sexual reproduction, the genes from the father and mother need to be recombined, which can produce more variants, enabling the offspring to adapt to a variety of adverse environments, which is known as "surpassing one's predecessors in excellence" and is very meaningful for improving the survival competitiveness of organisms. In nature, most organisms that can engage in asexual reproduction are simple lower organisms, such as bacteria, paramecia, and hydra. Higher animals, including humans, use sexual reproduction to reproduce offspring.