what tissue do humans have that cnidarians do not?
The tissue that humans have, but cnidarians do not, is muscle tissue. Muscle tissue is responsible for movement and locomotion in animals.
To determine the answer, we can compare the general anatomy of humans and cnidarians. Cnidarians, such as jellyfish and sea anemones, have a very simple body structure called a polyp or medusa. They lack complex organ systems found in more advanced organisms, like humans.
Humans have three types of muscle tissue: skeletal, cardiac, and smooth muscles. Skeletal muscles are responsible for voluntary movements, such as walking or running. Cardiac muscle forms the heart and is responsible for its rhythmic contractions. Smooth muscle lines the walls of organs like the intestines and blood vessels, controlling involuntary movements.
In contrast, cnidarians lack specialized muscle tissue. Their movements are largely controlled by specialized cells called cnidocytes, which contain nematocysts capable of venomous stinging. These cells provide basic movement and defense mechanisms, but they are not true muscle tissue.
So, in summary, the tissue that humans have but cnidarians do not is muscle tissue, which allows for the complex movement and coordination observed in higher organisms like humans.