The Animal Kingdom Quotes

“One feature shared by all animals is that they are ‘multicellular’. That is, their bodies are made of many specialized cells. By this criterion, single-celled organisms such as the familiar Amoeba are not considered to be animals, contrary to the views of a century ago. Indeed, many biologists now carefully avoid the term ‘protozoa’ for organisms such as Amoeba, since by definition an organism cannot be both ‘proto’ (meaning ‘first’ and implying one cell) and ‘zoa’ (implying animal).”
― Peter Holland, The Animal Kingdom: A Very Short Introduction

“The propensity of nematodes to live inside other organisms is described in a poetic, but somewhat exaggerated, 1914 quote from the ‘father of nematology’, Nathan Augustus Cobb:

If all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes and oceans represented by a thin film of nematodes. The location of towns would be decipherable, since for every massing of human beings there would be a corresponding massing of certain nematodes.

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― Peter Holland, The Animal Kingdom: A Very Short Introduction

“The distinctions between bilaterians, or triploblasts as they are also known, and the more ‘basal’ animal phyla have been noted for over a century. In 1877, the influential English zoologist Ray Lankester contrasted the embryos of bilaterians with those of cnidarians and sponges, and pointed out that in their early development bilaterians have an extra layer of cells destined to develop into the well-defined muscle blocks of the adult. The similarities seen within embryos and in body symmetry are certainly fundamental. Towards the end of the 20th century, biologists were astounded to find similarities that went far, far deeper – right down to the DNA. The discovery that all bilaterians use the same set of genes to build their bodies represents one of the most fascinating scientific breakthroughs of the 20th century, and one that has changed biological science from the 1980s onwards. It was a discovery with explosive impact, yet this was a revolution with a slow fuse.”
― Peter Holland, The Animal Kingdom: A Very Short Introduction

“Most comb jellies have little direct effect on humans, except through a minor role in marine food webs. One species, however, stands apart as the villain of the basal invertebrates. In the 1980s, the Atlantic comb jelly Mnemiopsis was accidentally introduced into the Black Sea, probably in ballast water carried by commercial shipping. Once in its new environment, away from natural competitors and predators, it reproduced rapidly – all the while consuming vast quantities of larval fish and crustaceans. Some (controversial) estimates placed the total seething mass of diminutive comb jellies in the Black Sea at over half a billion tonnes. The local anchovy fishery, already under heavy fishing pressure, was decimated. While ecologists debated what to do, a possible solution arrived, unplanned, in the shape of another accidental introduction. The newcomer was a second comb jelly, this time the voracious Beroe. Fortuitously, Beroe does not eat fish or crustaceans, but is instead a specialist predator of other comb jellies and nothing else. As the invading Beroe now feast on the Mnemiopsis, the fish stocks are showing gradual and welcome signs of recovery.”
― Peter Holland, The Animal Kingdom: A Very Short Introduction

“Remarkably, it is not only humans who use sponges as tools. In Shark Bay on the Western Coast of Australia, a population of bottlenose dolphins has learned to snap off pieces of living sponge and attach these to their snouts to protect themselves when foraging for food in the sandy bottom.”
― Peter Holland, The Animal Kingdom: A Very Short Introduction

“Although sponges have many different types of cells, most are not organized into organs with discrete functions, like kidneys, livers, or ovaries (although the choanocyte chambers could be considered simple organs). For this reason, sponges are sometimes described as having a ‘tissue-level’ organization. Some sponges have astonishing powers of regeneration, so extreme that they were the inspiration for regenerating aliens in the science-fiction television series Doctor Who. The defining experiments that revealed this property were published in 1907 by Henry Van Peters Wilson of the University of North Carolina, USA. Wilson mashed up a living sponge and passed it through a fine cloth, the sort used for sieving flour, thereby splitting most of it into individual cells. Wilson then observed that these cells gradually crawled back together and reassembled into a new sponge! Furthermore, if the cells of two different species were mixed together, they would sort themselves out and regenerate into the two original sponges again. Although regeneration is found in many branches of the Animal Kingdom, no other animals are as expert as some of the sponges.”
― Peter Holland, The Animal Kingdom: A Very Short Introduction

“For centuries, naturalists and philosophers have struggled to make sense of the range of life on Earth. One of the earliest and most pervasive ideas was that of a ‘Scale of Nature’ in which living, and sometimes non-living, things were arranged into a linear hierarchy. Each ascending rung on a ladder represented increasing ‘advancement’, based on a blend of anatomical complexity, religious significance, and practical usefulness. The idea had its origins in the thinking of Plato and Aristotle, but was crystallized by the work of the 18th-century Swiss naturalist Charles Bonnet. In Bonnet’s scheme, the Scale of Nature rose from earth and metals, to stones and salts, and stepwise through fungi, plants, sea anemones, worms, insects, snails, reptiles, water serpents, fish, birds, and finally mammals, with man sitting comfortably on top. Or almost on top, being marginally trumped by angels and archangels. It is easy to ridicule such ideas today, but Bonnet had a good knowledge of the natural world. For example, it was Bonnet who discovered asexual reproduction in aphids and the way that butterflies and their caterpillars breathe. Furthermore, the idea of a Scale of Nature still pervades much modern writing, with many scientists talking of ‘higher’ or ‘lower’ animals: language that bears an uncanny resemblance to this old and discredited idea.”
― Peter Holland, The Animal Kingdom: A Very Short Introduction