Reproduction of Cnidarians Medusae usually reproduce sexually using eggs and sperm. The planula then develops into a polyp that can reproduce either sexually or asexually. One type of asexual reproduction by polyps leads to the formation of new medusae.

All Cnidarians have tentacles with stinging cells in their tips which are used to capture and subdue prey. In fact, the phylum name “Cnidarian” literally means “stinging creature.” The stinging cells are called cnidocytes and contain a structure called a nematocyst. The nematocyst is a coiled thread-like stinger.

Cnidarians carry out extracellular digestion, where enzymes break down the food particles and cells lining the gastrovascular cavity absorb the nutrients. Cnidarians have an incomplete digestive system with only one opening; the gastrovascular cavity serves as both a mouth and an anus.

Porifera and Cnidaria are organisms which share similar characteristics with one another. -They are both multicellular, they consist of many cells working together. They are both eukaryotic, they have DNA in the form of chromosomes contained within a distinct nucleus.

Movement. Although adult sponges are fundamentally sessile animals, some marine and freshwater species can move across the sea bed at speeds of 1–4 mm (0.039–0.157 in) per day, as a result of amoeba-like movements of pinacocytes and other cells. Juveniles drift or swim freely, while adults are stationary.

283 days

Farmers order semen from genetics firms that “mate” top-quality bulls with artificial cows to collect semen. Freeze and ship. The bull’s semen is divided and packed into plastic straws, each containing about 20 million sperm, along with nutrients and glycerol to help it survive freezing.

It usually works out that cows are giving birth every 12-14 months. With the life span of U.S. dairy cows averaging 4-6 years, most cows have 2-4 calves in a lifetime.