Algae are a large and diverse group of eukaryotic (complex-celled) photosynthetic organisms. The green algae are primitive members of kingdom Plantae, though other types of algae are outside the kingdom entirely. Land plants evolved from green algae about 500 million years ago. The algae are a paraphyletic group, meaning they did not descend from a common ancestor. Algal groups have independently evolved several times in life on Earth, representing a beneficial strategy adopted by parallel evolutionary paths. It is also an attractive food source because it is high in protein and other essential nutrients; when dried, it is about 45% protein, 20% fat, 20% carbohydrate, 5% fiber, and 10% minerals and vitamins.