Plants belong to the PLANT KINGDOM, one of the
five kingdoms of living things. Plants are classified into smaller groups,
according to shared characteristics. All plants share certain features. They
are made up of many cells. They also produce their own food by a chemical
process called photosynthesis, using water, carbon dioxide, and the energy of
sunlight. As a by-product, they release life-giving oxygen into the
air.
Plants are green because they contain a green pigment called
chlorophyll. Chlorophyll captures some of the energy in sunlight and uses this
to make food. This process is called photosynthesis. Most plants make food this
way, but a small number also digest other living things.
THE FIVE KINGDOMS OF LIFE
The moneran kingdom includes the simplest, single-celled organisms.
Protoctists are more complex single cells and include green algae, which
contains the chlorophyll that is also found in plants. Fungi, plants, and
animals are thought to have evolved from protoctist ancestors. The kingdom
containing the most known species is the animal kingdom.
BIOGRAPHY: CAROLUS LINN`AEUS Swedish, 1707-1778
Naturalist Linnaeus devised the first uniform, scientific way of
defining and naming plants and animals. His system is still used as the basis
for classification today. The first part of a Linnean name indicates the genus
(group). The second part gives the particular species.
Within the plant kingdom, plants are divided into two
main groups. The largest group contains the plants that produce seeds. These
are flowering plants (angiosperms) and conifers, Ginkgos, and cycads
(gymnosperms). The other group contains the seedless plants that reproduce by
spores. It includes mosses, liverworts, horsetails, and ferns. So far,
scientists have named 400,000 separate plant species. Around 300,000 of these
are flowering plants.
Table 21. CLASSIFYING A LESSER CELANDINE
| Class | Magnoliopsida (dicotyledons) |
| Order | Ranunculales |
| Family | Ranunculaceae |
| Genus | Ranunculus |
| Species | Ranunculus ficaria |
From the fossilized remains of ancient plants, we know that the
first plants probably developed from algae and lived in water. Mosses and
liverworts appeared on land around 475 million years ago (mya). Next came
clubmosses, horsetails, and ferns, between 390 and 350 mya. Cone-bearing cycads
and conifers evolved much later, and flowering plants most recently of all.
A rose begins life as a seed that germinates (sprouts), growing
roots and a shoot. The shoot puts out leaves to produce food and flowers to
produce seeds. Seeds develop after pollination (when a male sex cell, carried
in pollen, fertilizes a female one). Fruits called hips grow around the
developing rose seeds. Birds eat hips and disperse seeds away from the parent
plant.
Plants are found in most of the world’s habitats, including
wetlands, grasslands, forests, and polar regions. By far the richest plant
habitats are tropical rainforests. Tall, broad-leaved trees reach for the
sunlight. Far below, ferns and mosses thrive in the warm, damp conditions.
There are also flowering plants, often brightly coloured to attract animals
that will help to pollinate them.
