By Vanessa Salvia Updated March 12, 2021
The earliest plants were very simple algae that lived in the sea. Plants that use cones to house their seeds, known as "cone-bearing plants," came along early in the Mesozoic era, giving rise to the seed plants that came later. Before seed-bearing plants evolved, the only vegetative life consisted of mosses, liverworts and ferns.
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The difference between cone-bearing plants and fruit-bearing plants is that cone-bearing plants, called gymnosperms, develop a seed that is part of a cone structure. A gymnosperm seed is not protected inside a fruit, as is the case with fruit-bearing plants that came later.
The Earliest Plants
Scientific research and the fossil record support the theory that plants evolved from early single-celled aquatic algae. It was only much later that plants evolved features that allowed them to live and reproduce on land, such as stems, seeds and flowers, explains FlexBooks.
When plants were able to move out of their watery home, animals were already the dominant species on land. The first plants may have left the water about 700 million years ago. These probably resembled modern plants called liverworts, which are small, simple plants that reproduce through spores.
Spore-bearing plants include mosses, ferns and fungi. Since plants evolved from living completely in water, one of the challenges they had on land was absorbing enough water to stay alive. This kept the earliest plants small, close to the ground and living in wet environments. The next stage in evolution involved plants that looked similar to ferns.
Cone-Bearing Plants, or Gymnosperms
Common cone-bearing plants examples are ginkgos and conifers, like pine trees, redwoods and palm trees. These types of plants are called gymnosperms, and they were the first of the seed-bearing plants to evolve. According to Encyclopedia Britannica, the earliest plants with seeds seen in the fossil record are from about 382.7 to 358.9 million years ago. The seed coating helped protect the seed and prevented it from drying out, which led to greater reproductive success.
Gymnosperms are also called "naked-seeded plants." The seeds are considered "naked" because they are not protected inside a fruit, as is the case with flowering or fruit-bearing plants that came later, but instead develop on the cones with no protection from the environment.
Gymnosperms produce seeds located on the upper surface of scales, which are usually parts of cones. Conifer trees, such as pines, spruces, firs, cedars, sequoias, redwoods and yews, are the most abundant gymnosperms today. Rather than leaves, gymnosperms often have long, thin structures that we call "needles."
Fruit-Bearing Plants, or Angiosperms
Angiosperms, which evolved between 250 and 200 million years ago, are the most common type of plant on Earth today, making up 80 percent of all plant species. Angiosperms produce seeds that are enclosed within a fruit, many of which are the foods that we commonly consider fruits, but also included are other foods, such as maple seeds, acorns, beans, wheat, rice and corn, says Biology Dictionary. Flowers are a major part of their reproduction process. Many of them are pretty and colorful and smell good, but not all flowers are showy.
When the plants evolved enough to encase their seeds within fruits, that also provided extra nourishment for animals and helped them spread, as animals enjoyed eating them. The fruits and flowers of angiosperms are most often designed to attract animals and to make them attractive for pollination. Although many gymnosperms, like palm trees, are important in some ecosystems, many of the gymnosperms that lived throughout the geological time periods on Earth have become extinct because their reproduction was not as successful or easy as that of the flowering and fruit-bearing plants.
Pollination of Gymnosperms and Angiosperms
In gymnosperms, male cones have structures that create pollen. Female cones have structures that create eggs. Later, the female cones develop seeds on the scale structures of the cones. Cone-bearing gymnosperms are designed to be pollinated by the wind, with male cones frequently arranged on branches above the females.
Fruit-bearing angiosperms, on the other hand, are often pollinated by insects, birds or small mammals. By using animals to transfer pollen, angiosperms are more likely to be successfully fertilized by compatible pollen because their pollinators apply pollen directly to the sexual organs.
Flowers are unique to angiosperms and attract pollinators, offering a food reward in exchange for pollination. The flower houses all the sexual organs, including the ovary, which contains many ovules that when successfully fertilized cause the ovary to enlarge into a fruit. Gymnosperms have no flowers, instead producing cones that are either male or female.
