Select features of plants that are unique to gymnosperms and angiosperms.

The plant kingdom has not always had the diversity we know today.  It has taken hundreds of millions of years of evolution to bring about the diverse, complex group of flowering plants known as angiosperms.  And for many millions of years prior to the emergence of angiosperms, the plant kingdom consisted of primarily of gymnosperms.  

Today, these two branches of the plant family tree represent the primary dividing factor among land plants, with angiosperms much more abundant than their earlier kin, the gymnosperms.  So, what are the major differences between angiosperms and gymnosperms and what factors lead to the incredible success of the angiosperms? 

To step back even further in time, prior to emergence of the gymnosperms, plant life on earth began in the oceans. Recent research suggests that the first plant life to inhabit land dates back to almost 500 million years ago.  These early terrestrial plants were nonvascular, meaning they did not have a vascular system of conductive tissue (think of the circulatory system in humans) to circulate water and nutrients among cells.  Mosses, hornworts, liverworts and some kinds of algae are modern day nonvascular plants and representatives of early plant life on land

The development of a vascular system was a major step forward for the plant kingdom, occurring around 430 million years ago.  Next came reproduction from seeds, which was yet another huge step forward at around 350 million years ago that ultimately lead to the emergence of the first gymnosperms in the fossil record around 319 million years ago. 

Somewhere around 240-205 million years ago, the gymnosperms began to dominate the landscape on earth.  Their conquest was fueled by the development of both seeds and pollen, which were major innovations in plant reproduction.  Pollen grains could travel great distances to spread plant genes and seeds provided a protective coat around embryos.  Seeds also built in a higher resistance to drought, allowing germination when conditions were optimal.   These factors pushed gymnosperms to expand into much drier terrestrial environments. 

Around 150 million years ago, the angiosperms emerged in the fossil record.  They are most commonly known for the development of a more specialized seed that forms inside the ovary of a flower, surrounded by a protective fruit.  With the development of flowers, the angiosperms began to incorporate and attract other life in their reproductive process.  Pollinating insects became major players in the evolutionary history of angiosperms assisting them in and explosion of diversity around 100 million years ago.

Today, angiosperms dominate the plant world with an estimated 300,000-500,000 species, compared to a mere 1,000 species of gymnosperms.  The angiosperms include all the fruits and vegetables we eat, all of our native, deciduous trees and shrubs, as well as so many other plants that we encounter on a daily basis.  Beyond the development of flowers and fruits, they also established more advance methods to transport water and sugars within their vascular tissue as well as other improvements in physiology that gave them an advantage over gymnosperms. 

The biggest difference between gymnosperm and angiosperms lies in their seeds.  Gymnosperm seeds are typically formed in unisexual cones and are known as “naked” seeds since they lack the protective cover angiosperms provide their seeds.   In angiosperms, individual flowers can be unisexual, with separate male and female flower structures, or bisexual with both male and female parts on the same flower.  While both groups use pollen in reproduction, angiosperms have developed an incredible diversity of strategies for pollen dispersal and, in combination with their insect friends from the animal kingdom, have went on to expand into the most diverse group of plants on earth.

Photo Caption: Gymnosperms, like this Colorado blue spruce, are a group of nonflowering plants that emerged several hundred million years before flowering plants (angiosperms) entered the evolutionary history of the plant kingdom.

Updated June 26, 2019

By Mary Dowd

Life as we know it would not exist without plants to convert sunlight and inorganic compounds into food energy. In Kingdom Plantae, plant species are classified according to their method of reproduction.

One group is the "seed plants," which can be divided into two subgroups called angiosperms and gymnosperms.

Angiosperm derives from the Greek words for "vessel" and "seed." Angiosperms include vascular land plants and hardwood trees with flowers and fruit. They reproduce by making seeds that are enclosed in an ovary.

Gymnosperm derives from the Greek words for "naked seeds." Gymnosperms include vascular land plants and softwood trees that do not have flowers and fruit. They are cone-bearing and reproduce by making naked seeds on cone scales or leaves.

Plant life evolved millions of years ago from primitive algae in the sea. Nonvascular mosses, liverworts and hornworts then arrived on the scene. These types of living species reproduce by fragmentation or spores. Next came seedless vascular plants like ferns and horsetails.

Plants with a vascular system were stronger and able to grow taller. Gymnosperms, like conifers and ginko biloba, appeared during the Paleozoic Era and reproduced by dispersing “naked seeds” not imbedded in flowers or fruit.

Angiosperms evolved later during the Mesozoic Era. Angiosperms adapted to a challenging terrestrial ecosystem by developing a complex vascular system, flowers and fruit. They reproduced by seed and spread quickly on land.

Gymnosperms and angiosperms are more highly evolved than nonvascular plants. Both are vascular plants with vascular tissue that live on land and reproduce by making seeds.

They are also classified as eukaryotes, meaning they have a membrane-bound nucleus.

Only angiosperms are known as flowering plants. Many have beautiful petals, fragrant blossoms and fruit that contains dozens of seeds. Angiosperms typically drop their leaves when the seasons change and chlorophyll production ceases.

By contrast, gymnosperms such as pine trees produce bare, uncovered seeds, usually in pine cones. Most gymnosperms have green, needle-like leaf structures; angiosperm leaves are flat_._ Angiosperm leaves are seasonal in their life cycle while gymnosperms are generally evergreen.

	Angiosperm	Gymnosperm
Vascularity	All angiosperms are vascular plants	All gymnosperms are vascular plants
Land Plants	All land angiosperms are plants	All gymnosperms are land plants
Reproduction Method	By seeds	By seeds
Type of Cells	Eukaryotic	Eukaryotic
Seeds	Enclosed in ovary in fruit or flower	Not enclosed, considered bare or “naked seeds” usually housed in cones
Wood Type	Hardwood	Softwood
Pollination Methods	Rely on pollinators (usually animals) as well as on wind/water	Rely almost solely on wind
Leaf Structure	Flat leaves	Needle-like leaves
Seasonal/Cycle	Seasonal	Evergreen

The flowers of angiosperms have male and female reproductive parts. Stamens are male sex structures that make pollen on their anthers.

Pollination occurs when pollen grains from the anther reach the pistil, which is the flower’s female structure. A pollen tube in a structure called the style helps the generative cell in pollen reach the ovarian embryo sac.

The generative cell in pollen splits into two sperm cells. One fertilizes the egg, and the other one helps make endosperm through a process known as double fertilization. Fertilized eggs mature into seeds protected inside fruit.

Sporophytes in gymnosperms make male and female gametophytes. For instance, male cones have male gametophytes (pollen), and they are smaller than cones with female gametophytes.

Wind carries pollen from male to female cones. The fertilized female gametophyte produces a seed on a scale inside the cone.

Pollination methods of angiosperms differ somewhat from those of gymnosperms.

Angiosperms rely on bird, bees and other pollinators, as well as abiotic factors such as wind and water. Gymnosperms rely solely on the wind to carry pollen between male and female reproductive parts.

Unlike angiosperms, some species of gymnosperms have been around since the days of the dinosaur. For example, cycads (in the division known as Cycadophyta) look like palm trees, but they are actually close relatives of Coniferophyta (conifers) and Ginkgophyta (the division that contains Ginkgo biloba).

Gnetophyta, like the Welwitschia mirabilis desert plant, have existed for at least 145 million years based on fossil evidence. The Welwitschia can live up to 1,500 years. DNA shows that it is closely related to conifers and other gymnosperms, although the plant also has flower parts. It has been speculated that angiosperms may have evolved from gnetophytes.