Life takes many forms, what life lives on your planet
Planning what form your life will take: We will look at 3 types of life, but you can research others, then students can bud their own life-forms to populate their planet.
Life forms that like more stable conditions.
Mammals take many forms on Earth, these life forms are not very good at surviving extreme environments, a mouse for example requires a temperature around 15 – 30 degrees, any warmer or colder and the mouse does not thieve and as you get closer to 0 or 40 degrees the mouse would soon perish.
To maintain the energy need for a mammal to keep warm and active they breath. The Oxygen in air is used to change the food they have eaten into the energy they need to survive (sustain homeostasis), the process is known as Aerobic Respiration as it involves the use of Oxygen. Animals that use oxygen take many forms and can be different shapes and sizes, but the chemicals involved are the same for all.
The process is chemical and to understand what is happening Lego blocks can be used to show the electrons different sized atoms want to share.
To begin we have the basic blocks to show Hydrogen (One Electron but wants to give it away, as it is in the first column of the periodic table) shown using 2 stud bricks, Oxygen (Eight Electrons, but wants to gain two more, as it is in the sixth column of the periodic table) shown using 4 stud bricks and Carbon (Six Electrons, but wants to give or gain four more, as it is in the fourth column of the periodic table). We start with 12 Hydrogen, 18 Oxygen and 6 Carbon. The Colours do not matter it is how many studs long the bricks are, in this case. Hydrogen 1-Blue, Oxygen 2-White and Carbon 4-Red.
Next build the molecules (Collections of Atoms), All studs should be covered. This builds a sugar (Glucose) molecule or C6H12O6 (to show what atoms it contains) and 6 Oxygen molecules O2 as the two Oxygen atoms share electrons.
Inside the cells of your creature the sugar is broken down and the energy stored in the Sugar released. Break up the sugar and give the Carbon atoms oxygen. Much like burning wood produces Carbn Dioxide so does turning food into energy. This builds 6 Carbon Dioxide Molecules or CO2 and each Oxygen gets the electrons they want and the as the Carbon gives 2 to each. The remaining oxygen binds with the hydrogen atoms receiving one election from each Hydrogen forming 6 Water or H2O Molecules.
Life Forms that can survive extreme conditions.
Smaller lifeforms such as the Tardigrade or water bear can survive harsher environments, these creatures are barely visible, about half a millimetre (mm) on a ruler. They are made up of around 40,000 cells which may seem big, but the mouse contained around 12,000,000,000 cells.
They have organs like larger animals and can be male or female. Unlike larger creatures however they can survive much harsher environments, going to sleep (Lowering their metabolism) in extreme temperatures and even surviving for years when nearly completely dehydrated (loosing 99% of their water). These are therefore very good for surviving on planets with long cold nights or long periods of draught.
They also breath Aerobically and eat like larger creatures.
Lifeforms that thrive in Extreme Conditions, these Extremophiles are the most likely to exist on other planets or moons within our solar system.
One of the more likely candidates for life on Mars are Methanogens, a simple life form found on Earth in places with little oxygen such as the intestines of mammals.
These tiny spherical or rod shaped (See picture) single cell sized organisms are anaerobic (Without Oxygen) and most cannot survive in aerobic conditions (With Oxygen) are ideal for planets with no or very little oxygen.
The ExoMars mission is looking for signs of this type of life, so what are they made of?
Inside the body of the Methanogen there is no Nucleus like in most cells, instead the DNA is free inside the Cytoplasm of the Cell. Designing such life is not about adding organs as you would a mammal, but Cell Walls, ribosomes and other parts that make up a cell.
Respiration is how an Animal or more technically its cells produce energy, inside a Methangen this is in the form of Methanogenesis a type of Anaerobic respiration.
The process is again chemical and so is best described using blocks as before.
In this case we start with four Hydrogen molecules and one Carbon Dioxide molecule as shown, Hydrogen has one electron and wants to give it away. But like the Oxygen in the aerobic reaction previously, it will settle on sharing with a second Hydrogen. So Hydrogen form bonds with itself forming H2, There will be four pairs of Hydrogen atoms required for the Methanogen to make energy. Then there is the Carbon Dioxide or CO2 where the Carbon atom wants to gain or give four more elections and each of the two Oxygen want to gain two.
The Hydrogen want to give up their electrons and so the Carbon Dioxide is broken down inside the Methanogen cell to form new molecules where each Hydrogen can give an electron to an atom that wants one, in this case the two Oxygen atoms forming two Water molecules H2O and one Carbon atom forming Methane CH4
Build your own lifeform
Using what you have learnt decide based on how extreme the environment of your world is decide on what the best form of life is and build a lifeform that could live there. This can be any shape you like, but don’t make it to big to survive on your planet.
Online Starter or Plenary (End) Activity