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Historically, all living things were classified as either animals or plants [61] and botany covered the study of all organisms not considered animals. [62] Botanists examine both the internal functions and processes within plant organelles, cells, tissues, whole plants, plant populations and plant communities.
The classification of living things into animals and plants is an ancient one. Aristotle (384–322 BC) classified animal species in his History of Animals, while his pupil Theophrastus (c. 371 –c. 287 BC) wrote a parallel work, the Historia Plantarum, on plants. [7]
Other scientists did not consider all of them part of the animal kingdom, and by the middle of the century they were regarded within the groupings of Protozoa (early animals), Protophyta (early plants), Phytozoa (animal-like plants) and Bacteria (mostly considered plants). Microscopic organisms were increasingly constrained in the plant/animal ...
In seed plants (gymnosperms and flowering plants), the sporophyte forms most of the visible plant, and the gametophyte is very small. Flowering plants reproduce sexually using flowers, which contain male and female parts: these may be within the same ( hermaphrodite ) flower, on different flowers on the same plant , or on different plants .
A life form (also spelled life-form or lifeform) is an entity that is living, [1] [2] such as plants , animals , and fungi . It is estimated that more than 99% of all species that ever existed on Earth, amounting to over five billion species, [3] are extinct. [4] [5] Earth is the only celestial body known to harbor life forms. No form of ...
A multicellular organism such as an animal, plant, fungus, or alga is composed of many cells, often specialised. [22] A colonial organism such as a siphonophore is a being which functions as an individual but is composed of communicating individuals. [8]
Animals have several characteristics that set them apart from other living things. Animals are eukaryotic and multicellular. [14] Unlike plants and algae, which produce their own nutrients, [15] animals are heterotrophic, [16] [17] feeding on organic material and digesting it internally. [18] With very few exceptions, animals respire aerobically.
A plant defense is a trait that increases plant fitness when faced with herbivory. This is measured relative to another plant that lacks the defensive trait. Plant defenses increase survival and/or reproduction (fitness) of plants under pressure of predation from herbivores. Defense can be divided into two main categories, tolerance and resistance.