The vast majority of living plant species belong to the group called the Angriosperms or flowering plants. The term denotes the common characteristic of having seeds encased in an ovary and differentiates them from the gymnosperms, in which the seed is ‘naked’. Angiosperms are wonderfully diverse but all share that primary characteristic of having the developing ovules and then seeds encased in a protective ovary within a flower.
Angiosperms are the most numerous plants on the planet these days and are the most important plants in human agriculture. Mosses were probably the first land plants but they lack true roots and stems and so are still tied to water and cannot get very big. Ferns were the first vascular plants or tracheophytes and during the first age of dinosaurs were the dominant land plants but they were soon facing competition from two newcomers; the Gymnosperms and the Angiosperms. By the second age of dinosaurs there were many cone-bearing trees competing with ferns for space and feeding the dinosaurs, but the land still lacked the vibrant colours that would come with the evolution of flowering plants. By the last age of dinosaurs the flowering plants and their attendant insects and birds were starting to change the color of the world.
Flowering plants are divided into two groups: monocotyledons (monocots for short, plants with one seed leaf) and dicotyledons (dicots for short, plants with two seed leaves). The monocots are small, relatively simple flowering plants but very important agriculturally. The Grass family, Poaecea, provides us with not only the grasses for our lawns and fields but all the important grains in our lives as well: wheat, rye, barley, rice, sorghum and corn to name a few. And what garden would be complete without lilies, irises, orchids and other beautiful monocot flowers?
However the dicots became the dominant group because of their ability to produce woody tissues, allowing them to grow into large trees. Most of the great tree species and all of our flowering shrubs, forbs and herbs are dicot angiosperms. Now, except in the colder climates where conifers still dominate, the world’s forests are filled with dicots: maples, eucalypts, acacias, oaks, ash and beech, magnolias and all the fruit and nut trees from apples to pecans. And so many of the herbs, shrubs, bushes and vines from the under-stories now grow in our gardens; from berries to roses and zinnias, dicot Angiosperms every one.
Angiosperms are very sexy plants, because flowers are sexual organs and they need to be fertilised. Since plants cannot move around, they use animals to do the work for them. Pretty clever for beings without brains! Flowering plants have evolved to get themselves fertilised and to do this they offer attractive and nutritious food sources to an incredible multitude of insect, bird and mammal species in a variety of different biomes and ecosystems to fit all conditions on terra firma. From deserts to tropical rainforests, from grasslands to temperate forests, grasses, flowering herbs and shrubs and trees attract animals for food and shelter, from leaves and flowers to pollen and nectar to grains and fruits and berries, flowering plants offer animals the foods they need to survive and in return, plants get fertilised and dispersed to new habitats.
Of course, the plants also have to have mechanisms to ensure that they don’t become extinct from overconsumption. Some, like the grasses, grow quickly and die after flowering. Annuals we call them. Others grow too large to consume or have chemicals to keep off many herbivores or tough bits to protect their vital tissues. Animals too have evolved to maintain themselves and not destroy the plants that feed them. Thus we see the great migrations of hoofed herbivores in Africa which allows plant species time to recover from heavy grazing and droughts. We see species that are generalists and move from food species to food species whilst in other situations we see species which are specialists, designed to eat plants that others cannot touch.
In all of these ecosystems, Angiosperms are key species, the main producers that are the basis of their systems and on which all the consumers depend for their survival. It was like that back in the Triassic and Jurassic ages also, with ferns and conifers playing the producer role and the dinosaurs playing the roles of the consumers, but it was a green world with very few other colours. Then came the flowers and suddenly the world was glittering with yellows and whites, reds, purples and pinks among the green and then all the brightly coloured birds and insects that evolved with them.
The result is a world full of beautiful flowers, from the flowering maples and oaks of the Northern Hemisphere to the Eucalypts of Australia. From roses in our gardens to apples and cherries in our orchards. The flowers we buy for the sick, the dead and the beloved. The fruits we eat and the grains and the vegetables. All of these are Angiosperms, flowering plants, without which our world would be a poorer and less colourful place indeed.