The sexual life cycle of plants is alternation of generation, which is a half diploid and half haploid cycle of multicellular stages. Animals are diploid life cycle dominated. Fungi and protists are haploid life cycle dominated.

The hormone auxin also is responsible for roots growing downward (gravitropism) and growing toward water (hydrotropism).

The stoma, which is the place for exchanging gas, is controlled by two guard cells. The phloem is a passage for transporting nutrients and sugars, and the xylem is a route for carrying water and minerals. The cuticle is a wax layer for protecting epidermal cells. The epidermis is a place for producing wax to make the cuticle.

Both angiosperms and gymnosperms are seed plants contained in vascular plants. Flowering plants and producing fruit are characteristics of angiosperms. Naked seeds are characteristics of gymnosperms.

Mycorrhizae are specialized structures of fungi. It gives plants minerals or phosphate ions and takes organic nutrients into fungi from plants. Therefore, this structure forms a symbiotic mutual relationship.

Autotrophs, self-feeders, can produce their own food and organic molecules from CO₂. Sulfolobus of archaea can live in sulfur-rich volcanic springs by using CO₂ as a carbon source and sulfate as an energy source. Euglena and algae of protista have chloroplasts and can therefore produce their own food. Plantae which is photosynthetic organisms is autotrophs as well. Bacteria, such as gram-negative bacteria, include photoautotrophs or chemoautotrophs. Fungi are heterotrophs, which cannot produce their own food and have to obtain organic molecules from other organisms. 

The operculum is a bony flap that covers the gills. The siphon, which passes water in and out between valves, is characteristic of the class Bivalvia. The adductor muscle controls valves. The mantle is a sheath of skin covering the visceral mass.

Archaea, bacteria, and eukarya are three domains.

Zygotes, sporophytes, and sporangia are diploid, whereas spores, gametophytes, and gametes are haploid.

Oomycetes causing Irish potato blight have hyphae to absorb nutrients like fungi. They, however, have cell walls made of cellulose, so these organisms are not the same as fungi. Water mold and downy mildews are included in oomycetes.