PLANTS AMD ANIMALS

1. The distinction between plant and animal life is not sharply drawn, with some categories of life that stand between or across the two. Originally Aristotle divided all living things between plants, which generally do not move, and animals. In Linnaeus’ system, these became the kingdoms Vegetabilia (later Plantae) and Animalia. Since then it has become clear that the Plantae as originally defined included several unrelated groups, and the fungi and several groups of algae were removed to new kingdoms. However, these are still often considered plants in many contexts. Bacterial life is sometimes included in flora, and some classifications use the term “bacterial flora” separately from “plant flora”.

2. Among the many ways of classifying plants are by regional floras, which, depending on the purpose of study, can also include “fossil flora”, remnants of plant life from a previous era. People in many regions and countries take great pride in their individual arrays of characteristic flora, which can vary widely across the globe due to differences in climate and terrain.

3. Regional floras commonly area divided into categories such as native flora and agricultural and garden flora, the lastly mentioned of which are intentionally grown and cultivated. Some types of “native flora” actually have been introduced centuries ago by people migrating from one region or continent to another and become an integral part of the native, or natural flora of the place to which they were introduced. This is an example of how human interaction with nature can blur the boundary of what is considered nature.

4. Another category of plant has historically been carved out for “weeds”. Though the term has fallen into disfavour among botanists as a formal way to categorize “useless plants”, the informal use of the word “weeds” to describe those plants that are deemed worthy of elimination is illustrative of the general tendency of people and societies to seek after or shape the course of nature. Similarly, animals are often categorized in ways such as “domestic”, “farm animals”, “pests”, etc. according to their relationship to human life.

5. Animals as a category have several characteristics that generally set them apart from other living things, though not traced by scientists to having legs or wings instead of roots and leaves. Animals are eukaryotic and usually multicellular, which separates them from bacteria, archaea and most protists. They are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls.

6. With a few exceptions, most notably the sponges, animals have bodies differentiated into separate tissues. These include muscles, which are able to contact and control locomotion, and a nervous system, which sends and processes signals. There is also typically an internal digestive chamber. The eukaryotic cells possessed by all animals are surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. This may be calcified to form structures like shells, bones, and spicules, a framework upon which cells can move about and be recognizes during development and maturation, and which supports the complex anatomy requires for mobility.

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