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Biology and extraterrestrial life

Frequently we can read on the news newly discovered planets that could harbor extraterrestrial life. Often we have new information about Mars, other worlds with water and extremely resistant living beings, like tardigrades. But is life possible outside the Earth? What is life? What is needed to sustain life? Astrobiology tries to answer this questions. Do you want to find out more?

ASTROBIOLOGY AND EXOBIOLOGY

Astrobiology is a set of different scientific disciplines that studies the existence of life in the universe. To achieve this it combines knowledge of biology, physics, chemistry, astronomy, ecology, geography, geology, planetary science and molecular biology. Within astrobiology, exobiology studies the possibilities of life outside our planet. It should not be confused with ufology, a pseudoscience. Astrobiology tries to answer such exciting questions as:
– What is life?
– How did life appear on Earth?
– How does life evolve, and what is its adaptability?
– What is the future of life on Earth and other places?
– Is there life in other worlds?

No, neither is this a Martian nor is it astrobiology. Source: Quo

WHAT IS LIFE?

Although it seems like a banal question, life is not easy to define. Apparently, we can recognize if something is alive or not if it can perform certain functions and has certain features. Living beings have vital functions:

  • Nutrition: they can obtain energy from the environment to grow, survive and reproduce.
  • Reproduction: they can create copies similar to themselves.
  • Interaction: they can perceive what is going on the environment and inside themselves.
  • Organization: living beings are formed by one or more cells
  • Variation: variability between individuals allows species to evolve.

Problems begin when with beings that don’t have all the characteristics. The most classic example would be viruses: they are unable to reproduce on their own and lack cellular structure. Another example would be erythrocytes (red blood cells) of mammals, cells without genetic material or mitochondria.

Microphotography of the Ebola virus under electronic microscope (Public photo of the CDC)

WHAT IS NEEDED FOR LIFE TO EXIST?

We only know one type of life: the terrestrial one. This is why astrobiologists need to take it as a reference to know what to look for elsewhere. Could there be other forms of life different than terrestrial? Maybe, but it would be almost impossible to recognize them. If you do not know what you are looking for, you may find it but do not realize it.

It is considered that in order for life to appear and develop, it is necessary:

  • A liquid where chemical reactions take place: on Earth, it is water.
  • An element with ease to form stable compounds: on Earth, it is carbon.
  • A source of energy: on Earth, it is the Sun.

We are looking for planets or satellites with these characteristics, although other possibilities such as liquid methane (in the case of Titan, a satellite of Saturn), ethane, sulfuric acid, ammonia or acetic acid as solvent are being considered. Life-based on other elements such as silicon, it is a recurring topic in science fiction stories.

Artistic representation of Titan’s methane lakes. Credit: Steven Hobbs

WHAT IS NEEDED TO SUSTAIN LIFE?

The celestial body has to fulfill a series of characteristics so that life can be sustained:

  • An abundance of chemical elements such as carbon, hydrogen, oxygen, and nitrogen to form organic compounds.
  • The planet/satellite has to be within the habitability area of its star (orbiting at a distance that allows a temperature suitable for life).

planet, star, habitable zone
Habitability area (green) according to the temperature of the star. Red: too hot, blue: too cold. Source: NASA / Kepler / D Mission. Berry

  • A source of energy enough to maintain the temperature and allow the formation of complex molecules.
  • An appropriate gravity to keep an atmosphere and not crush the living beings of the planet.
  • A magnetic field to divert the radiation incompatible with life.

The Earth’s magnetic field protects life from the solar wind. Source: ESA

In our Solar System, the candidates that possibly fulfill these characteristics are Mars, Europe and Ganymede (satellites of Jupiter), Enceladus and Titan (satellites of Saturn) and Triton (satellite of Neptune).

WHY CARBON?

Living beings are formed by cells, and if we reduce the scale, by molecules, and atoms (like all matter). Why is life-based on carbon?

In fact, in the constitution of organisms 26 elements are involved, but 95% of living matter consists of carbon (C), hydrogen (H), nitrogen (N), oxygen (O), phosphorus (P) and sulfur (S). We can imagine them as the “bricks of life”: by combining these building blocks, we can obtain complex organisms. These bricks can be joined to others by covalent bonds. Metaphorically, atoms can be imagined as spheres with hands which can be grasped by other hands. For example, the main energy source molecule for all living things is ATP (Adenosine triphosphate, C10H16N5O13P3).

enlaces químcos, moléculas, sulphur, phosphorus, hidrogen, oxigen, carbon, nitrogen, chemical bond
Schematic representation of carbon, hydrogen, oxygen, nitrogen and phosphorus atoms and their valences (possible bonds). Own production based on figure 6.3 of “Life in space” (see references)

The candidate element to sustain life would have to be an abundant element able to form a great amount of bonds with itself and with other elements. The 5 most abundant elements in the universe:

  • Helium: does not form compounds
  • Hydrogen and oxygen: they have 1 and 2 hands: they can only form very simple compounds
  • Nitrogen: can bind to 3 atoms, but no chains of several nitrogen atoms are known.
  • Carbon: it has 4 hands so it can be strongly bonded to other carbons with single, double, or triple bonds. This allows it to form long chains and three-dimensional structures and can still join to other atoms. This versatility allows constructing molecules chemically active and complex, just the complexity that makes life possible.

DNA chemical structure, double helix
DNA chemical structure where we can see the importance of carbon bonding to form rings and chains. Source

Could there be life in another place based on a different atom?

ALTERNATIVES TO CARBON

SILICON EXTRATERRESTRIALS

Since establishing 4 links is so useful, silicon is the first candidate for biologists and science fiction writers, even if it is not as abundant as carbon. Silicon (Si) can also form 4 bonds and is abundant on rocky planets like Earth, but …

  • The Si-Si bond is quite weak. In an aqueous medium, life based on silicon would not be sustained for a long time as many compounds dissolve in it, although it could be possible in another medium, such as liquid nitrogen (Bains, W.).
  • It is very reactive. Silane, for example (one silicon atom bonded to 4 hydrogens) spontaneously ignites at room temperature.
  • It is solid at most temperatures. Although it can easily form structures with oxygen (silica or silicon dioxide), the result is almost always a mineral (quartz): too simple and only reacts molten at 1000ºC.
  • It does not form chains or networks with itself, due to its greater size compared to carbon. Sometimes it forms long chains with oxygen (silicones), that perhaps could be joined to other groups to form complex molecules. The alien of the movie Alien has silicone tissues. The beings formed by silicones would be more resistant, which leads to speculate what kind of extreme conditions they could withstand.

Horta, a silicon-based form of life featured in the science fiction series Star Trek. Source

NITROGEN AND PHOSPHORUS EXTRATERRESTRIALS

Let’s look at some characteristics of nitrogen and phosphorus:

  • Nitrogen: can only form 3 bonds with other molecules and is poorly reactive.
  • Phosphorus: its bonds are weak and multiple bonds uncommon, although it can form long chains. But it is too reactive.

By combining the two, stable molecules could be obtained, but the beings based on nitrogen and phosphorus would have other problems: the nitrogen compounds, from which they would have to feed, are not abundant in planets and the biological cycle would not be energetically favorable.

BORON, SULFUR AND ARSENIC EXTRATERRESTRIALS

The most unlikely biochemistries could be based on these elements:

  • Boron: can form long chains and bind to other elements such as nitrogen, hydrogen or carbon
  • Sulfur: can form long chains, but because of its size is highly reactive and unstable.
  • Arsenic: is too large to form stable compounds, although its chemical properties are similar to those of phosphorus.

In 2010, the journal Science published a scientific research in which researchers claimed to have discovered a bacterium (GFAJ-1) capable of living only in arsenic, lethal to any living being. It broke the paradigm of biology by not using phosphorus (remember ATP and DNA structure) and opened up new study lines for astrobiology. In 2012, two independent investigations refuted the theory of researcher Felisa Wolfe-Simon and his team. Phosphorus remains essential for organisms to live and develop on Earth.

GFAJ-1 bacterium. Source

At the moment, these hypothetical biochemistries are nothing more than speculations, so astrobiologists are still looking for carbon-based life, although we already know that science never ceases to amaze us. Although we could identify life based on other elements if we ever find extraterrestrial life (or vice versa) the revolution will be so great that it won’t matter if they are carbon-based beings.

REFERENCES

 

MIREIA QUEROL ALL YOU NEED IS BIOLOGY

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Flowers wearing turban, the Tulip fever

The spring beginning has allowed some of you to enjoy the beautiful colours of those flowers that have already bloomed. This time I’m going to talk about one of the most colourful, simple, but wonderful flowers you probably already will have had the opportunity to observe in many gardens or in nature. It is the tulip. Besides introduce you this plant, in this article I will make a more detailed description of its morphological parts. I think it’s a good example to start learning vocabulary, because its structure is quite clear and simple. Therefore, if you are interested in learning some technical vocabulary, now it’s a perfect chance. But, do not think I’m just going to talk about the technical aspects, because reading this article you will also be able to learn the history behind the tulips. And as you will see, these flowers caused a good fever!

tulipes
Artistic image of several tulips (Photo taken by Adriel Acosta).

 INTRODUCTION

The tulips (Tulipa sp.) are flowers that when are closed seem a turban. This plants have been very popular and well-known for very long time, because of its high ornamental interest.

Its genus is distributed in the central and western Asia, in the Mediterranean and in Europe. It is known that its origin belongs to the centre of Asia and, from there, their distribution has been expanded naturally and by human actions. And, although about 150 species are known in the nature, human intervention has greatly increased the species list. Caused both by hybridization (forcing the offspring of two interesting species) and by selective breeding (choosing the offspring which has more value).

Tulipa_cultivars_Amsterdam
Tulip crop in Amsterdam (Photo taken by Rob Young). 

 THE TULIP FEVER

As already mentioned above, tulips are one of the most ornamental plants used, both in decoration as in landscaping. And while the tulip crop is rather old, the boom occurred in Europe during the seventeenth century. Giving rise to what is known as Tulip mania or the Tulip fever. In those moments, especially in Netherlands and France, a high interest in the cultivation of these plants awoke. The fever was so great that people were selling goods of all kinds to buy tulip bulbs, even reaching up to sell the most valued as the house or farm animals.

The cause of this was originated in the Netherlands, where the single-coloured tulip bulbs were being sold at that time. But afterwards, the Eastern bulbs that give rise to flowers with variegated colours appeared. And they were very attractive. Although the cause was uncertain in that moment, it was known that if a single-coloured bulb touched other marbled-coloured bulb, the first one would turned into a marbled-coloured bulb. This caused the tulip’s price began to increase and soon after occurred the first speculative bubble in history.

Nowadays, we know that the cause is due to a virus which is transmitted from some bulbs to others; this virus is known as Tulip breaking virus.

Semper Augustus Tulip 17th century
Anonymous gouache on paper drawing, 17th century, of the “Semper Augustus”. A representation of one of the most popular tulips which was sold at record price in Netherlands (Public Domain).

MORPHOLOGICAL CHARACTERS

 The plant

 Tulips are geophytes, that is, they have resistance bodies underground to survive during unfavourable seasons, the winter. These organs are bulbs, which have been used on crops to preserve these plants.

Its leaves are linear or linear-lanceolate, i.e., they are long, narrow and acute. Parallel venation can be observed on its leaves, so a nerve is by side other and with the same direction. Their arrangement is usually in rosette: this means that the leaves are born agglomerated in the bottom of the plant above the bulb, and at the same level. Even so, you can sometimes see some leaves along the stem, cauline ones. These are sessile, without petiole, and wrap a little the stem.

To cultivate tulips, we can use their bulbs or fruits. These seconds are capsules, a dried fruits, opened due the action of some valves. At first, the seeds are hooked inside these capsules and then are released and distributed on the environment.

20150329_165102[1]
Tulip (Photo taken by Adriel Acosta).

The flowers

Tulips appear in early spring, due they are plants adapted to very dry Mediterranean climate or cold areas.

As you have seen, the flowers are solitary or appear to 3 gathered in one stem. They are usually large and showy, hermaphrodite, therefore, they have both male and female reproductive organs, and are actinomorphous, that is, they can be divided symmetrically for more than two planes of symmetry.

These flowers have 3 inner tepals and 3 external that are free among them, without being bound or fused. We talk about tepals when the sepals (calyx pieces) and petals (corolla parts) are similar between them. In this case, the tepals are petaloid, because they adopt typical colours and shapes of the petals.

In the inner part of the flower, we can see 6 stamens divided equally into 2 whorls; being these two closely spaced between them, so they seem to arise from the same point. And right in the centre, surrounded by these stamens, there is the gynoecium, female part of the flower. This gynoecium consists of the ovary and 3 stigmas attached to this directly. The stigmas are this part of female reproductive organs where it should arrive pollen to fertilize the ovaries.

part tulipa
Parts of tulip flower: 1. Sepal, 2. Petal, 3. Stamen, 4. Female reproductive organ (ovary and 3 stigmas) (Photo taken by Adriel Acosta).

 As you have seen in this article, some flowers have caused curious stories and a great impact on our society. Also, you have had the opportunity to observe in detail the tulip’s structure. One more time, I wish you liked it.

Difusió-anglès

REFERENCES

  • A. Aguilella & F. Puche. 2004. Diccionari de botànica. Colleció Educació. Material. Universitat de València: pp. 500.
  • Bolòs, J. Vigo, R. M. Masalles & J. M. Ninot. 2005. Flora manual dels Països catalans. 3ed. Pòrtic Natura, Barcelona: pp. 1310.
  • Notes of Phanerogamae and Applied Plant Physiology, Degree of Environmental Biology, Ambiental, UAB
  • F. Schiappacasse. Cultivo del tulipan. http://www2.inia.cl/medios/biblioteca/seriesinia/NR21768.pdf
  • Fundación para la Innovación Agraria; Ministerio de Agricultura. 2008. Resultados y Lecciones en Tulipán. Proyecto de Innovación en XII Región de Magallanes. Flores y FOllajes/ Flores de corte (11).

Sharks: predators as prey

Today we will talk about a sensitive topic. This topic is shark finning, an unsustainable and macabre practise that happen in our waters. 

INTRODUCTION

Sharks, together with rays, are included in the elasmobranchii group. They are characterized by a cartilaginous skeleton and several teeth rows, which are continuously renovated. Sharks are predators because they are in the top of food chains. It means that they devour but they aren’t devoured. Nevertheless, we will see that is not completely true, as there is a species that has the ability to capture them, cut their fins and then to throw them to the sea.

WHAT IS SHARK FINNING?

Shark finning consists on cutting and saving shark fins and discard the rest of the body.

4145Fisher cutting a shark fin (Foto: Gary Stokes; Sea Shepherd, Hong Kong).

The animal usually is still alive when is thrown into the water, so it can swim and sink slowly to the deep sea; where, still alive, will be food for other animals. Fishers only save the fins because its economical value is much bigger than the meat of the animal so, discarding the body, they have more space in the ship for fins. In the next video, which is very hard to see, we can watch this activity:

IS THAT ILLEGAL?

Shark finning is a forbidden activity around Europe since 2003, with the passing of the Council Regulation (EC) No 1185/2003 of 26 June 2003 on the removal of fins of sharks on board vessels, but this law allowed to discharge fins without its body, with a permission, and in the case that the fin weight was lower than 5% of the total weight of the animal. This means that, despite the law, finning was taking place. This regulation had some legal vacuums, thanks to 4th article, that allowed to give special permissions to cut fins on board of the vessels and discharge these fins and the rest of the body in different harbours, what meant a big difficulty to control finning.

For all this reasons, in 2011, European Commission proposed the obligatory nature to discharge fins together with the shark body, what was well received by conservationist organisations, most of the scientific community, general public, Committee of Ministers of EU and the Environment Committee of EU. Nevertheless, Spain and Portugal, whose shark fisheries are by far the most important in EU, express their opposition to this reform. Both countries have a fishing line fleet in the North Atlantic.

Finally, in June 2013, it is approved the reform of the European reform about finning, Regulation (EU) Nº 605/2013 of the European Parliement and of the Council (of 12 June 2013), amending Council Regulation (EC) No 1185/2003 on the removal of fins of sharks on board vessels. In this regulation, it is mandatory to discharge sharks with their fins. This measure has been successfully to fight against finning in other parts of the world. Portugal and Spain were put up it because it reduces their benefits, so holds are full sooner.

WHY IS THAT HAPPENING?

This practise was expanded due to the high price of shark fins in the Asiatic market to do shark fin soup and in traditional cures. Every single kilo of fresh or frozen fin costs 20 €, while in the case of meat the value is just 1€. EU captures sharks in the Mediterranean and the Atlantic, Indian and Pacific oceans. It is the first worldwide power in shark fishing, with a 17% of declared captures in 2009, and the biggest fin exporter at Hong Kong and China.

_MG_7002Shark fins spread in the ground to be dried (Gary Stokes; Sea Shepherd, Hong Kong).
_MG_7411Shark fins spread in the ground to be dried (Gary Stokes; Sea Shepherd, Hong Kong).

WHICH SPECIES ARE THE TARGET?

Nowadays, many species are target of fishing because, despite 28% of the species are considered threatened by IUCN, just some of them are protected. In Spain and Europe, there are just 9 protected species. In addition, catch shares don’t exist and, for this reason, fishers can fish till extinction. Why do not exist catch shares? The reason is that fishing regulation in EU is conditioned by Spain and Portugal. However, specialists estimates that every year are killed 100 million sharks for their fins.

Blue shark is the main species in the Atlantic fishing line feet. If we have a look in the capture statistics of this shark in Vigo harbour (Spain) (2468 tones and more than 3 million euro of benefit, according to Puerto de Vigo), we can observer that is a great benefit: is legal, there aren’t catch shares and fins are well-paid in Hong Kong market.

WHICH IS THE IMPACT OF SHARK FINNING?

Shark finning has the following impacts:

  • Loss and devastation of shark populations around the world. Experts estimate that within a decade, most species of sharks will be lost because of longlining.
  • Unsustainable fishery. The massive quantity of sharks harvested and lack of selection deplete shark populations faster than their reproductive abilities can replenish populations.
  • Threatens the stability of marine ecosystems.
  • Obstructs the collection of species-specific data that are essential for monitoring catches and implementing sustainable fisheries management.
  • Wasteful of protein and other shark-based products. Up to 95 per cent of the shark is thrown away.

REFERENCES

ACKNOWLEDGEMENT

I wouldn’t finish this article without give thanks for her help and patient to Mónica Alonso Ruiz, who is communication responsible and Madrid responsible of Alianza Tiburones Canarias, who informed me and give me most of the information and data present here.

If you find this article interesting, you can share it in Social Networks to dissiminate this problem. The goal of this blog is to inform people about science. 

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