Coevolution

Survival of an organism is dependent upon its ability to thrive in an environment with other organisms. In a predator-prey relationship, the hunter is favored by evolving traits that aid in killing its prey. To counter these advantages, the prey must evolve traits to avoid detection and to successfully escape, sometimes by utilizing physical or chemical defenses. Examples of such oneupmanship have been aptly referred to as an “evolutionary arms race.”

Based on the theory of natural selection, if the predator evolves enhanced offensive capabilities, the prey’s survival necessitates the evolution of a commensurately improved defense. Examples of evolved traits exist in plant-insect relationships. Plants may employ chemical defenses to ward off culinary advances by insect herbivores. Insects, in turn, may evolve metabolic capabilities that neutralize the noxious plant chemical. The plant reciprocates by evolving a more effective chemical deterrent.

Moth-pollinated plants and moths (such as this hummingbird hawk moth) have coevolved such that the length of the plant tubes exactly matches the moth’s pollinating proboscis.

By contrast, some of the classic examples of coevolution result from mutually beneficial specialized relationships between plants and pollinator insects (as bees) and between a number of species of flowering plants with specific pollinators, such as bats and insects. Moth-pollinated plants and moths have coevolved such that the plant tubes are the exact length of the moths’ “tongue.” Upon examining the size and shape of a Madagascar orchid, Darwin predicted the existence of a pollinating moth with an 11-inch-long (28 centimeter) proboscis. Some forty years later, decades after Darwin’s death, such a moth was discovered.

Coevolution refers to reciprocal evolutionary changes that occur between pairs of species as they interact with and are dependent upon one another. Charles Darwin commented briefly on this phenomenon in Origin of Species (1859) and far more extensively in his The Descent of Man (1871). In the latter work, Darwin quoted the German biologist Hermann Müller, a pioneer in the study of coevolution, and his studies on bees and the evolution of flowers. These were described in Müller’s work, The Fertilization of Flowers, appearing first in German in 1873 and in an English translation a decade later.

The Unique Features of Angiosperms: An Overview

Angiosperms, or flowering plants, are the largest group of plants on Earth, with over 300,000 species. They have many unique features that set them apart from other plant groups, such as gymnosperms.

One of the most notable features of angiosperms is their flowers. Flowers are specialized structures that serve to attract pollinators and facilitate reproduction. They come in a wide variety of shapes, colors, and sizes, and often have unique adaptations to their specific pollinators. For example, some flowers have long tubular shapes to accommodate hummingbirds, while others have landing platforms for bees.

Another unique feature of angiosperms is their fruits. Fruits are the mature ovaries of flowers and serve as a means of dispersing seeds. They come in many shapes and sizes, from small berries to large, fleshy fruits like apples and peaches. The diversity of fruit types in angiosperms is unmatched by any other group of plants.

Angiosperms also have a specialized vascular system that allows them to transport water and nutrients efficiently throughout the plant. This system consists of xylem, which transports water and minerals from the roots to the leaves, and phloem, which transports sugars and other nutrients from the leaves to the rest of the plant.

One of the most significant evolutionary advancements of angiosperms is their ability to coevolve with insects and other animals. Many species of angiosperms have formed close relationships with specific pollinators and have evolved adaptations to attract and reward them. This coevolution has allowed angiosperms to diversify rapidly and dominate terrestrial ecosystems.

Finally, angiosperms have a unique double fertilization process that allows them to produce endosperm, a nutrient-rich tissue that supports the developing embryo. This process involves two sperm cells, one of which fertilizes the egg cell to form the embryo, while the other fuses with two other cells to form the endosperm.

Angiosperms are a remarkable group of plants with many unique features that have allowed them to diversify and dominate terrestrial ecosystems. Their flowers, fruits, vascular system, coevolution with animals, and double fertilization process are just a few examples of the fascinating adaptations and evolutionary advancements that have made them so successful.