II. Read the following text paying attention to the highlighted words. Explain or interpret the contextual meaning of the underlined phrases

The earliest concepts of organismal classification were constrained within narrow boundaries that defined all life as either plant or animal. The Kingdom Plantae and Kingdom Animalia were the most basic dichotomy of Linneaus's (1753) classification of living organisms. Nevertheless, there were complex organisms, mainly microscopic and aquatic, with the greater characteristics of greenness of plants and the movement of animals that stretched those plant and animal boundaries.

In 1866, the German naturalist Ernst Haeckel (1834 – 1919) made the first of many proposals for a third kingdom of life. He named this third kingdom and the organisms contained within it the Protista, “the first of all, primordial“. Haeckel considered the Protista to be a “boundary kingdom intermediate between the animal and vegetable kingdoms” containing organisms “neither animals nor plants”.

In 1838, American biologist Herbert F. Copeland (1902 – 1968) proposed a four-kingdom classification of life. Its foundation was in the exclusion of the bacteria and the “blue-green algae” (cyanobacteria) from Haeckel’s Kingdom Protista into a separate kingdom he named Monera.

In 1957 Robert H. Whittaker (1924 – 1980) began a reassessment of Copeland’s four-kingdom system from an ecologist’s point of view. Whittaker based his kingdom groupings upon the three main modes of nutrition in natural communities: absorption, ingestion, and autotrophy. He also credited the evolutionary sequence of unicellular to multicellular with central importance to his classification scheme. Utilizing these criteria as the basis for classification, Whittaker returned the bacteria to Kingdom Protista (also based upon their unicellular nature) and placed all algae (green, brown and red) into Kingdom Plantae. Whittaker observed the absorptive role of the fungi in the natural environment. He rejected the common belief that the superficial resemblance of fungi to plants, with their non-motile habit and cell-walls, made them true plants and he erected the kingdom Fungi.

In 1969 Whittaker published a revision of his four-kingdom system to expand it to five kingdoms, now including a separate bacterial kingdom named Monera in recognition of the fundamental division of life as “prokaryotic” versus “eukaryotic”. After the removal of the bacteria and fungi, the Kingdom Protista typically contained the eukaryotic algae, the protozoa, the slime moulds and certain 'fungi' whose zoospores have heterokont flagella.

Protists are most often single-celled microscopic organisms but some, such as seaweeds, are multicellular, and others, such as slime molds, are ‘single cells’ (coenocytic plasmodia) but may become quite large in size. There is substantial diversity amongst the protists, regardless of size or number of cells. Photosynthetic (autotrophic) protists use a wide range of light–harvesting pigments that greatly exceed those pigments used by plants. Others are heterotrophic, engulfing prey (phagotrophs), absorbing organic molecules from the environment (osmotrophs), and digesting organic matter of living (parasites, symbionts) or dead (saprophytes) organisms. And, perhaps remarkably, some protists are mixotrophic, i.e. carrying out both photosynthesis and some form of active heterotrophic feeding activity simultaneously.

The modern history of protists began with the use of the electron microscope. For all protists, Corliss (1994) listed six kingdoms, 34 phyla (divisions) and 83 classes, a substantial increase over Haekel's (1866) Kindom Protista. Thus, the surge of ultrastructural data had profound effects on protistan classification, and probably the most important contribution involved the concept of endosymbiosis.

Molecular biology studies, especially those which compare the nucleotide sequences of genes, have offered little to our recognition of new classes, but they have contributed substantially to our understanding of evolutionary relationships among classes.

The knowledge gained from electronic microscopy and molecular biology caused the demolition of the traditional classification schemes of algae, fungi and protozoa. However, a modern classification of all protists based upon evolutionary relationships is only partially reconstructed in the place of the traditional classification.

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