Biomes are terrestrial sets of ecosystems characterized by rainfall, temperature, and the dominant form of vegetation. A single biome occupies a large geographic area and usually is found on more than one continent. 

• Tropical Rainforests - contain at least one-half of the world's species of plants and animals and are dominated by tall, broad-leaved trees. Tropical rainforests are wet and hot year-round and have nutrient poor soil (most of the nutrients are held in the vegetation).
• Savannas - dry grasslands with widely spaced broadleaf, deciduous, and evergreen trees. Savannas are characterized by low rainfall or prolonged periods of drought. Herds of migratory grazing animals and fire are important in maintaining savannas.
• Deserts - lack of water is the most influential feature. Vegetation is limited and life is based on water conservation. Many animals are active at night to avoid high daytime temperatures.
• Temperate Grasslands - sometimes called prairies. Summers are hot and wet, winters are cold. Fire, seasonal drought, and grazing are instrumental in maintaining grasslands, recycling nutrients and preventing the succession of shrubs and trees. Temperate grasslands have extremely fertile soil and have been converted to some of the richest agricultural areas on earth. Grasslands usually lie in a zone between temperate deciduous forests and deserts, and intergrade with both biome types.
• Temperate Deciduous Forests - warm summers, cold to moderate winters, plentiful rainfall, and rich soils. Hardwood and deciduous (shed leaves in winter) trees are characteristic of this biome type.
• Coniferous (Evergreen) Forests - cold winters, seasonal dry periods, and nutrient poor soils. Cone-bearing trees such as the Douglas Fir, redwoods, spruce, hemlock, and pines make up the dominant vegetation. The northern coniferous forest, or taiga, is the largest terrestrial biome.
• Arctic Tundra - cold temperatures, strong winds, and permanently frozen soil (permafrost). Dominant vegetation types are grasses, mosses, and lichens.

In the five-kingdom classification system, Plantae refers to green plants, excluding the green algae.  The Kingdom Plantae includes the mosses, seed ferns, conifers, flowering plants and related groups.  Plants are multicellular organisms that develop from embryos. Plants have cellulose in their cell walls that gives strength and structural support, and use chlorophyll a and b to transfer energy from the sun to chemical energy, a process called photosynthesis. 

In the life cycle of plants, the two multicellular body forms, the gametophyte (1n) and sporophyte (2n), alternate. The predominant form and pattern of this cycle is a key characteristic of differing plant groups.

Plants are adapted primarily for life on land and have had to overcome problems of water loss and transport. Various groups of plants approach the problem of reproduction, support and transport with ingenious adaptations of vascular tissue, roots, stems, leaves, pollen, seeds, fruits, and flowers.

The Plant Kingdom is often separated into bryophytes (mosses and liverworts), pteridophytes (ferns), and seed plants. Seed plants are divided further into two groupings, gymnosperms and angiosperms.  Gymnosperms are the cone-bearing plants such as pines and conifers. Angiosperms are the flowering plants, which are traditionally divided into monocots or dicots. 

Bryophytes are plants that lack vascular tissue, true roots, stems, and leaves. They reproduce by dispersing large amounts of spores. These plants are small because of water transport problems, and they depend on diffusion and osmosis for movement of materials throughout the plant.  The gametophyte (1n) generation is predominant. Examples of bryophytes are mosses, hornworts, and liverworts.

Pteridophytes have conducting tissue for nutrients, water and the products of photosynthesis. In this group, the sporophyte (2n) generation is dominant. The spores of these plants are resistant to drying.  Examples include ferns, club mosses, and horsetails.

Evolution of the seed allowed plants to move further away from water, and to tolerate harsher climates.  The seed offered new survival advantages for the embryo, such as protection, nourishment, dispersal, delayed growth. 

Gymnosperms include pines, junipers, cycads, and gingkoes. The gymnosperm seed, often described as "naked," is not enclosed in a fruit. Wind dispersal of pollen means that large amounts of seeds are needed to insure fertilization. In the gymnosperms, the sporophyte (2n) generation is predominant.

Angiosperms are flowering plants that produce seeds surrounded by a fruit barrier. What we think of as fruit is actually a mature ovary. Fruits are classified as simple (like an apple), aggregate (like a strawberry), or multiple (like a pineapple). The most recent group to evolve, angiosperms produce pollen and seeds. Angiosperms are traditionally divided into two groups, monocots and dicots, but scientists are now considering adding a third group, the eudicots. Some examples of monocots are lilies, orchids, yuccas, grasses, and grain crops. Examples of dicots are oaks, maples and sycamores.  Eudicots are sometimes referred to as euangiosperms and are classified based mainly on their pollen structures. Recently, phylogenetic analyses, based on both structural data and molecular sequences, have begun to unravel higher-level phylogenetic relationships within the eudicot group. Eudicots make up approximately 75% of all existing angiosperms.