You might be "As happy as" this mollusk that has a heart but no brain
Around 1905 it was discovered that the American eel spawns in this "sea" in the north Atlantic
Measles, mumps & rabies are not transmitted by bacteria, but by these
Linnaeus only recognized 2 biological kingdoms; everything was either plant or this
It's composed of the brain & spinal cord in vertebrates; scientists abbreviate it CNS
Muscles may connect directly onto bones or connect to them by these
A termite's intestinal tract can break down this plant substance; yours can't
They're a plant's anchor & can have a fibrous or tap system
Around 1940 scientists found that mutations in these chromosomal units result in defective enzymes
3 kinds of these are sensory, motor & mixed