Got Pellets?

Rabbits. Those little, adorable balls of fluff that you just love to cuddle. They may be cute, but there's nothing particularly interesting about them, right? Wrong. In fact, rabbits have an absolutely fascinating digestive system...

http://www.flash-screen.com/free-wallpaper/happy-2012-easter-day-cute-rabbits-wallpaper/lying-cute-rabbit,1366x768,64155.html

Unlike us, rabbits can eat a wide variety of plant material. They can process and extract nutrients from many plants that are indigestible to us because of their cellulose. How on Earth do they manage this?

Rabbits are herbivores, meaning they only feed on vegetation. A rabbit has a mouth, esophagus, stomach, and intestinal tract, just like other mammals. So, how are they able to break down cellulose where other mammals are not? Well, relative to their size, rabbits have a large stomach, which allows them to eat large amounts of plants quickly. Their digestive process begins just like ours: in the mouth. The rabbit grabs the plant with its lips, rips it with its front incisors and then chews it with its molars and swallows it.

Rabbits have a very large sac called a cecum, located where the small and large intestine join together. In this sac live a diverse population of bacteria, yeast and other organisms that help the rabbit digest its food. When the food in the small intestine reaches the cecum and large intestine, the materials that need to be digested further are diverted into the cecum. The other materials pass through the large intestine as waste and leave the body in the form of little, round droppings.

http://www.therabbithouse.com/diet/rabbit-digestive-system.asp

What's happening in the cecum, you ask? The microorganisms in the cecum break down the indigestible fibre, turning into digestible nutrients. In order for the rabbit to use these nutrients, it must take these nutrients through its digestive tract once more. So, at certain times of the day the material in the cecum is packaged into small, moist pellets, called cecotropes. The rabbit's brain then signals the rabbit that these delicacies are ready to be passed out of the body, and it eats them as soon as they emerge. Delicious, eh?

Carbon, Carbon, Carbon

Life as we know it, depends on the existence of molecules built around chains of carbon atoms. We, and all other living organisms, are carbon based life. Although living organisms are mostly water, which is made of hydrogen and oxygen, carbon and these two elements, along with nitrogen, phosphorus, calcium and sulphur, form the bulk of the compounds found in living things.

http://www.randolph.k12.nc.us/schools/whs/Teachers/jkube/Pages/BiologyCourseDescription.aspx

Carbon forms the four main macromolecules in our bodies: carbohydrates, lipids, proteins and nucleic acid. The reason carbon can form so many different molecules is due to its versatility. Carbon has the potential to form millions of different chains and molecules, each with its own role to play in allowing things to function.

http://www.montmorillonite.info/Page%204_acid%20chart.htm

H2"wOah"

Like all matter, water is made up of atoms, which bond together to form molecules. Nearly everyone knows water consists of two hydrogen atoms bonded to one oxygen atom, but what people don't know is that water has several properties that make it very unique... 

Polarity:

When electrons in a covalent bond are not shared equally, the molecule is called polar. Water molecules are polar, meaning although the water molecule is neutral as a whole, one end of the molecule is slightly positive and the other end is slightly negative. The oxygen end has a slight negative charge and the hydrogen end has a slightly positive charge. Although polarity is relatively common in nature, the reason it is so important for water is because water's polarity is responsible for the "stickiness" between molecules. 

http://www.bcscience.com/bc8/pgs/quiz_section8.3.htm

Cohesion/Adhesion:

Cohesion and adhesion is what makes water "sticky". Cohesion is the attraction between water molecules, while adhesion is the attraction between water molecules and other molecules. Cohesion is what allows this water strider to run on top of the water's surface, without falling through. It creates surface tension, which almost acts as an invisible skin.

Cohesion and adhesion are also responsible for capillary attraction, which is the ability of water to move upwards in small spaces. Plants use this, along with transpiration, to make it possible for them to pull water from their roots up to the rest of the plant. We also use capillary attraction for things as simple as sucking a drink out of a straw.

Density:

As a substance undergoes phase changes, the density also changes. In most cases, as a substance changes from its liquid state to its solid state, its density increases. Strangely, when it comes to water, it's the exact opposite! Solid water is actually less dense than liquid water, which is why ice floats. The reason this occurs is because as water freezes it forms a crystalline structure that creates more space between the water molecules. This creates more volume, which in turn, causes the ice to be less dense than water. The fact that ice floats is essential for the survival of aquatic ecosystems and life on Earth. Can you imagine what the world would be like if ice sank? Lakes and ponds would freeze from the bottom up, killing many fish and aquatic life. Frozen water in the polar regions would sink, killing the animals living on top and causing ocean levels to rise, which would lead to floods. 

Heat and Solvency: 

Water has a very high specific heat capacity, meaning it requires a lot of heat to raise the temperature of 1g of water by 1C. This is extremely important because it allows water to resist changes in temperature, which in turn moderates temperatures on Earth. It also means water heats and cools slowly, allowing life inside the water to survive as temperatures slowly change.

"Water is life's mater and matrix, mother and medium. There is no life without water."

   - Albert Szent-Gyorgyi (Hungarian Biochemist)

Themes in Biology

Biology is a vast subject, and with it come a variety of themes. Three of these themes are evolution, relationship of structure to function and interdependence in nature.

Evolution is the core of biology and relates to the change of populations over the generations. It occurs in all animals and plants on Earth and allows species to adapt and change as the  environment around them does, allowing them a chance at survival. Through studying evolution, scientists hypothesize that all organisms alive today share a common ancestor. Although this may sound bizarre and unlikely, scientists have already proven that animals as different as spiders and monkeys belong to the same family trees. Furthermore, when DNA strands from different animals are examined, it becomes clear that there are many similarities. It seems likely that a very, VERY long time ago, all living organisms were the same single-celled organisms.

http://www.dailymail.co.uk/sciencetech/article-1070671/Evolution-stops-Future-Man-look-says-scientist.html

Many people have seen pictures such as the one above, depicting the evolution of men, from monkeys.

http://afterhardship.blogspot.ca/2012/01/pledge-under-tree.html

However, evolution is not the only large concept in biology. Everyday, we see examples of how the way an object functions is directly related to the structure of that object. The structural levels from molecules to organisms ensure successful functioning in all living organisms and systems. For example, DNA is composed of a double helix. Each step in the strand of DNA is a base-pair, consisting of a base in one chain attracted to an opposite base by a hydrogen bond. This hydrogen bond allows the DNA to be easily separated and put back together, allowing the creation of new DNA to form new life to be simple. An even easier example is looking at giraffes. Giraffes with longer necks will find it easier to reach high branches to get at food, whereas giraffes with shorter necks will have a harder time. Therefore, giraffes with structurally longer necks can function better and have a better chance at survival.

Finally, many animals living in an ecosystem are strongly dependent on one another.  There are many different reasons organisms may depend on each other, but one thing that is common is that their lives are so strongly interlocked that, without one, the other would not survive. Examples of interdependence can be seen in plants that need insects or animals to pollenate them to carnivores that need the meat and sustenance provided by prey. In the end, all living things are connected to each other in a cycle of dependencies.