The mode of reproduction that is used by hydra to produce offsprings is asexual whereas the jellyfish is capable of reproducing sexually.
When an organism reproduces asexually then the rate at which the offspring are produced is faster, however, there is a lack of genetic diversity as the offsprings are produced from a single parent.
However, in case of sexual reproduction there is more variation and hence in case of a changing environment such as acidification of a lake by a runoff, there is a better chance of jellyfish to survive as it reproduced by sexual reproduction and thus has the ability to give rise to an offspring which will carry the trait to be more resistant.
