Category Archives: Biology

Articles relating to biology

Weird animal #2 – the pink fairy armadillo

Time for a second instalment of my ‘weird animal’ series! This time, something a little more cuddly: the pink fairy armadillo.

The Pink Fairy Armadillo

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Are humans still evolving?

Paranthropus boisei; a recent cousinHumankind has undergone a dramatic shift over the past few centuries. A combination of industrialised farming and modern medicine has allowed us to completely overcome our biology. We exist in record populations, live for longer than ever, and, most crucially are able to survive a wide range of situations that would have previously killed us. We are a social species. We naturally collaborate and help each other, and don’t stand by while others suffer. As a result of this, we no longer live under the law of ‘survival of the fittest’ – we exist as ‘survival of everyone’.

Evolution needs two things in order to work: genetic variation and selective pressure. Genetic variation is inevitable. It will always exist amongst living populations. Even if you had a theoretical population of exact clones, variation would arise over generations due to DNA copying errors, recombination and genetic drift.

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What happens after we die?

There are differing definitions of death, but it is clear that if a person is unconscious, their heart has stopped and their brain ceased to function, that person has died. They are beyond resuscitation, and their body, now just an object that resembles a person, meets none of the criteria for life. The body is no longer a series of self-sustaining chemical reactions; through the same miraculous processes that allowed it to live, it will begin an inexorable return to the ecosystem from whence it came.

Following death, pallor mortis is the first stage in the process of post-mortem disembodiment. As the heart has stopped, blood no longer circulates, and the red blood cells (being denser than the plasma) drift downwards, away from the upper surface of the body. This is the cause of the paleness of dead skin, and happens within the first half-hour of death.

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Weird animal #1 – the giant isopod

This is the first in a series of articles about the weird and wonderful of the animal kingdom. You may or may not know about the animals; some will be common, other rare, but all with be noteworthy for possessing an unusual trait or two. The first is about a deep-sea beastie, one that is familiar is shape but not at all in size: the giant isopod.

The giant isopod is a close relative of the common household woodlouse, only massive: the biggest yet found weighed 17 kg and was 76 cm long. They live a solitary life deep at the bottom of the sea, where they scavenge for dead fish and whales in the muddy gloom.

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What is life?

At my high school, we were taught that the defining life is easy. Living things obey the seven life processes – those being: movement, reproduction, sensitivity, nutrition, excretion, respiration and growth (the mnemonic being “Mrs Nerg”). Movement can include anything from physically ambling around to microscopic movements of cellular machinery. Reproduction is the production of offspring by parents. Sensitivity is the ability to detect one’s surroundings. Nutrition is the acquisition of materials for use by the body and respiration is the conversion of nutrients into energy; the products of this conversion are either excreted by the organism or used to help it grow.

This exclusive definition of life is simple: anything that does not adhere to every single process is not alive. It is a good working definition for GCSE biology, and one that belies the historical belief that living things and non-living things are entirely separate.  This is no longer the case, as scientists have realised the boundary between life and death is much more blurry…

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Why are there so many species?

Tens of millions of species inhabit the Earth. From the massive Californian redwood, to the tiny crescent-cup liverwort; the rare blue whale and its prey, the common krill; and from the primitive E. coli to its complex human host, the variation of the natural world is astounding. Surely, on our pale blue dot, there’s only limited room for species to live, so how is it that organisms have evolved to be so diverse?

Speciation is the process by which new species arise. There are several recognised modes, although in reality it works under more of a sliding scale. At one end is allopatric speciation, when members of the same species are geographically separated (through continental drift, etc.). At the other is sympatric speciation, where the organisms are isolated not geographically, but genetically, through processes such as genetic polymorphism. Polymorphism involves relatively small variations in DNA that have such a profound effect on the phenotype that two organisms with slight differences in their genotype are prevented from reproducing, and a single species is effectively split into two daughter species, which evolve separately.

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What is a species?

Having discussed how difficult it is to define ‘species’ in my last post, I feel I should stress that biologists still absolutely must use the concept all the time. There is no good in studying an animal, or group of animals, if you don’t name the group to which they belong.  Members of a species should always be more closely related to one another that they are to any member of any other species: as an example, doves all look more like each other than they look like a pigeon. This much is objectively true, but the subjective problem lies in where exactly you draw the line.

So doves all look more like each other than they look like pigeons  (and vice-versa) but the dove-pigeon grouping all look more like each other than they look like crows (and vice-versa). Are doves and pigeons and crows three distinct species or are dovepigeons and crows two distinct species and doves and pigeons are subspecies of dovepigeons? The more species you add, and the deeper back in time their genetic split goes, the more complex this gets.

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