1. Introduction to Plants and Botany

Botany is the scientific study of plants. It is difficult to define precisely what a plant is. Most plants have green leaves, stems, roots, and flowers. Conifers, cactuses, succulents, ferns, and mosses are also plants. Some botanists include green algae with plants; others exclude them. Fungi are not considered to be plants.

Plant biology is governed by a small number of basic principles:

  1. Plant metabolism is based on the principles of chemistry and physics.
  2. Plants must have a means of storing and using information. Genes are the primary means of storing this information.
  3. Plants reproduce, passing their genes and information on to their descendants. Offspring resemble parents.
  4. Genes, and the information they contain, change. Mutations occasionally occur. Variation exists in populations.
  5. Plants must survive in their own environment. They must be adapted to the conditions in the area where they live. Also, plants do not exist in isolation.
  6. Plants are highly integrated organisms. The structure and metabolism of one part have some impact on the rest of the plant.
  7. An individual plant is the temporary result of the interaction of genes and environment. There are differences between an individual plant and the plant’s species.
  8. Plants do not have a purpose or decision-making capacity. It is inaccurate to attribute anthropomorphism and teleology to plants.

Photosynthesis first arose about 2.8 billion years ago in a cyanobacterium. Organisms that acquired chloroplasts evolved into algae and plants. The most recently evolved plant group consists of the flowering plants, which originated about 100 to 120 million years ago.

More than 297,000 species of plants exist today.

All living beings have all of the following characteristics; if even one is missing, the material is not alive.

  1. Metabolism involving the exchange of energy and matter with the environment.
  2. Nonrandom organization.
  3. Growth.
  4. A system of heredity and reproduction.
  5. A capacity to respond to the environment such that metabolism is not adversely affected.

In addition to these absolute requirements of life, two features are almost certainly associated with all forms of life. (1) Organisms develop, such that young individuals and old ones have distinctive features, and (2) species evolve, changing with time as the environment changes.

—July 2020
—July 2023