Bending your head back until it hurts is an example of

Could someone me with number one you

1. isogamy 1 organisms with gametes of the same size and shape 2. anisogamy organisms with gametes of different sizes and shapes 3. oogamy 2 organisms with gametes of the same shape but different sizes 4. gonads gamete-producing organs in lower plants 5. gametangia gamete-producing organs in animals

Why do you suppose the structural polysaccharide cellulose does not contain branches?