What are atoms of the same element that differ in their numbers of neutrons called?
opposites
reactions
organisms
isotopes
The first plants were probably similar to the stoneworts in Figure below . Stoneworts are green algae. Like stoneworts, the first plants were aquatic. They may have had stalks but not stems. They also may have had hair-like structures called rhizoids but not roots. The first plants probably had male and female reproductive organs and needed water to reproduce. In stoneworts, sperm need at least a thin film of moisture to swim to eggs.