Why don't animals have wheels?

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Made by Eve Parkin, Fred Burton, Orla Macalpine and Lou Eung

Why don't Animals have Wheels?

Richard dawkins

The wheel may be one of those cases where the engineering solution can be seen in plain view, yet be unattainable in evolution because it lies [on] the other side of a deep valley, cutting unbridgeably across the massif of Mount Improbable.

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However...

Examples of wheels in bacteria

Examples of wheels in plants

Examples of wheels in animals

Mechanical Drawbacks

Evolution

Introduction

Index

• Wheels are a ubiquitous part of our everyday life, since the invention of the wheel, humanity has rolled into a new age of invention.
• However, this commodity is not observed in the natural world, despite all of its benefits. Why is that?
• In the presentation we explore this idea and more, touching on similar adaptations from nature!

Introduction

Evolution

SECTION 01

Natural Selection

All living organisms elvolve and develop through the process of natural selection. This works through the random mutation of the genome, altering small aspects of an organisms genotype and phenotype completely by chance. A small proportion of these mutations are beneficial, granting the organism a greater chance of survival. Beneficial traits are extrememly varied, and result in slight improvements in survival

Through this mechanism, animals developed the most efficient limbs for their environment, meaning that legs had a better chance of survival than a rolling limb in animals. This reason, in part is one of the numerous explanations of why animals lack wheels!

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Darwinism vs Lamarckisim

A common misunderstanding of the theory of evolution is that adaptations occur through an organism adapting to its environment and passing that on to their offsrping. This is an example of Lamark's theory. However, our best explanation of evolution stems from natural selection, through random mutations. Creating a functional wheel from a single mutation would be very difficult, and would most likely result in an early death, stopping that gene from being passed on. For this reason functional wheels would be difficult to evolve, as that stepping point would be extremely challenging to overcome.

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Mechanical Drawbacks

SECTION 02

However, every exterior part of the body must be covered with a seamless layer of skin, as it is a main defence against disease, as well as a way to protect against impacts. Rotating a wheel that is connected to the main body would be impossible as it would stretch the skin too much. Additionally, large animals cannot gain speed very quickly because it is more difficult for muscles to pull against a large inertia that would be caused by the wheels.

Tension

The drawbacks of wheels don't only stem from the evolutionary disadvantage it provides. From mechanical standpoint, wheels make little sense for an animal. A wheel must be able to freely rotate about an axis, and with the socket joints and muscles of animals, this could possibly be acheivable.

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In different areas, surfaces such as ice and mud would impede wheels functionality.

To function properly, wheels must be on a flat plane, which may be not be attainable in all ecosystems.

Animals exist across the globe

World Map

Examples of "wheels" in animals

SECTION 03

Whilst clear animals lack wheels, it is certainly interesting to note where similar mechanical systems are introduced. The process by which a bird flaps its wings closely resembles a circular motion, similar to that of a wheel. They do this to reduce energy loss by flapping its wings as one continous motion. The main difference here is that the wings are not free to move around its hinge, and has a narrow degree of freedom compared to that of a true wheel. Through this, birds do not deal with added problems such as overstretched tissues.

Wing Mechanisms

Armadillos and pangolins are marsupials with the unique ability of being able to curl up into a ball. This adaptation is used as a method of defence, with its hard exterior protecting its vital organs! The curved shape of the shell adds greater difficulty to biting into it. Additionally, the spherical shape is great for rolling! Different from a wheel, due to the whole animal rotating, its ability to roll comes in great aid when running away, or traversing the difficult terrain of the hilly jungles where they inhabit.

Armour Plating

Examples of "wheels" in plants

SECTION 04

Contrary to animals, plants have many expamples of "wheels", mainly as a method of evenly spreading their seeds. Many fruits are round in order to use the force of gravity to move further away from their parents. Tumbleweeds use the wind in order to further disperse their seeds, degrading over time. One reason why plants exhibit this adaptation is that this method of rolling is used to do its unpredictable nature, spreading the plants as far as possible. This may not be suited for individual animals, who cannot rely on producing tens of thousands of off-spring, for only a few to survive.

Seed dispersal

Examples of "wheels" in bacteria

SECTION 05

Flagellated bacteria all share a common rotary nanomachine. The bacterial flagellar motor is powered by the gradient of ions across the membrane, called the ion motive force (IMF) and rotates the flagellar filament to generate thrust to propel the cell body. Embedded in the membrane, the flagellum is joined to the motor by a hook substructure. Being the only evidence of a wheel in a living organism, the adaptation of the flagellum is advantageous to bacteria as they need to move quickly for colonisation of new environments and discovery of new resources for survival.

Bacterial Flagella Motor

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Despite these examples of wheels in certain orgamisms, there is no known multicellular organism that can spin a part of its body while keeping the rest of its body still.

However...

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We hope you enjoyed our presentation on why animals don't have wheels!

Eureka!

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Where do we all come from?

Did you know that every living organism today comes one common ancestor? And they're called LUCA!LUCA stands for our "Last Universal Common Ancestor", here's what we know about them

• An organism with a lipid bilayer
• It lived over 3 billion years ago!
• LUCA lived on hydrothermal vents

Absurdism, Lamarckism

Despite being a very advanced theory of evolution (written before Darwin's theory of evolution)Lamarck's theory had some major drawbacks, which now would be seen as extremely absurd!

• All animals came from a "fountain of life
• All animals originally evolved from a type of worm!

The world of the micro!

Bacteria are some of the smallest living organismsEukaryotic cells are around 10x smaller than human cells. They have to be this small in order to:

• Colonise host cells
• Break through the plasma membrane
• Have a greater surface area to volume ratio