Extreme Biology

by Stevie (AP Biology) 

Ha! I Don’t Need You!… Or Do I?

How does life exist on our planet without everything else? Is it possible for any living thing to survive without using the energy from or bi-products of another organism? This raises an even more extreme question- can any organism survive completely by itself, without any other matter at all? Of course not! Any and every living organism on this planet needs not only extra matter, but also other organisms to survive! This dependence that every living thing has on other organisms and other a-biotic factors in their habitats, or even the biosphere, is referred to as the “Interdependency of Nature.” The interdependency of nature exists on all different levels life in the biosphere! Let’s take a closer look at this concept in the following examples:

Molecular 

On a molecular level, every living thing depends on several key elements to survive. Some of these include oxygen, hydrogen, carbon, and nitrogen. All four elements make up numerous molecules and compounds that make up an organisms body or complex! (Of course there are others, but these are the main four). One simple, yet vitally essential, of these molecules is water.

Photo source

All organisms, no matter what species, have to meet a required amount of this substance of they will become desiccated, or dried up, and die. However, organisms must re-circulate water right? If there was only so much water on earth, all of it would have been used up a long time ago and we would never have even existed! All organisms, in many ways depend on water for survival. Many organisms actually break up the elements on water (hydrogen and oxygen) to use for their own ends, mostly in basic cell functions. But if so, won’t they just need more water to replace what they’ve already broken down to use? No! All organisms recycle water! In some way, all organisms resynthesize the hydrogen and oxygen molecules and return the water to nature to be used by other organisms! So we see here that even at the smallest level of existence all parts of nature depend on one another, living and Abiotic!

Cellular

When dealing with individual cells, there are millions upon billions of ways that all things in nature are interdependent upon one another. Take, for example, a nerve cell and the action potential of a nerve cell needed to send a message to another part of the body.What occurs in a nerve to send a message is really quite fascinating! First, a stimulus is picked up on by the dendrites of the cell. The stimulus causes a truly amazing reaction to occur in the cell! First, sodium ions rush into the cell through protein channels on the axon membrane, creating a positive charge inside the cell and a negative charge outside the cell called depolarization. Then, potassium ions rush out of the cell through protein channels on the axon membrane, thus creating a positive charge outside the cell again and a negative charge inside the cell (as it was at its resting potential). This process is called an action potential! The action potential then codes for the synaptic terminals at the end of the axon to expel molecules called neurotransmitters that continue the message throughout the body. This example serves to show that without the sodium and potassium ions, the nerve cell could not function to carry the message on to other parts of the body and the brain would never receive those signals! Thus, it shows us that without the sodium and potassium ions the nervous system could not properly function and meaning that we are dependent on sodium and potassium to survive! In turn, someday our bodies will decease and we can give back that when our bodies decompose, or even through the simple act of sweating!

Another example of the way cells are dependent on matter in nature is in the process of cellular respiration. Cellular respiration is the process by which cells break down glucose and oxygen into ATP (the cells main source of energy), water, and carbon dioxide using the mitochondrion organelles in the cell.

This proves that, like all consumers in the biosphere, we need outside sources to get our energy. Here we use the glucose that we get from consuming food by turning it into a compound called pyruvate and progressing through the three stages of cell respiration to come up with the end result of ATP. Our cells use the energy stored in ATP to perform almost all the cellular functions we need to have carried out in our bodies for them to function correctly. Once again, we depend on other things in nature obtain that energy we need to carry out the essential processes of life and survive! In turn, other organisms in nature, like decomposers, depend on all organisms to give back when they die and use the dead organisms as food for them to create ATP and carry out their own cell functions!

Organismal 

In the bodies of all colemate animals there are organs and organ systems in which those organs function. Not only do the organs within the organ systems depend on one another, but the organ systems themselves depend on one another! Take, for example, the circulation and respiratory systems in humans.

In a healthy human cardio-respiratory system, blood carries oxygen from the lungs to the rest of the body and excretes carbon dioxide from the rest of the body through the lungs. In basic terms, what occurs is the heart pumps blood into blood vessels in the lungs for gas exchange to occur. As you breathe in, you take a lot of oxygen into your lungs. As blood flows through, carbon dioxide on red blood cells is diffused through the membranes of the alveoli (shown above) and oxygen is diffused back across to attach to empty red blood cells and be carried to the rest of the body. Here, the heart is depending on the lungs to get rid of the carbon dioxide and replace it with oxygen and the lungs are inversely depending on the heart to displace and transport the oxygen that they have taken in and supply carbon dioxide for them to expel from the body! Both systems depend on one another to carry out their specific functions.

Population 

In a population members of the same species must depend on one another to reproduce to continue the population of their species. Take giraffes for example.

Each giraffe is an individual in a population that needs to look out for itself and even compete with other members of the same population to survive on the available resources (that is, if the resources should become scarce.) However, one of the two main purposes of life in biological terms is to survive and reproduce! Now, many organisms can reproduce through asexual methods without need of a mate or even another member of the population. But for those who cannot, they must have a member of the opposite sex in the population to mate with and produce fertile offspring and continue the survival of their own species. Hence these giraffes depend upon one another to mate and produce an offspring that will, in good faith, someday survive to reach maturity and find a mate of its own and do the same!

Community 

In a community several different species share the same general environment and must therefore compete with one another for resources. One resource that a species needs is in almost constant need of is food! And though Mother Nature is sometimes cruel, many species do indeed consume members of other species for food and, there-in, energy. Take for example the Great White Shark and the sea-lion.

Great White sharks live in virtually all oceans of the world, and spend a liberal amount of time near islands where their prey, sea lions, lives. The sharks of course consume the sea lions and depend upon them for the rich energy they provide. However, believe it or not, but the sea lions (as a population) benefit from this relationship as well. An ecosystem can only support so many members of a population until the population has reached its carrying capacity. Once this is reached, the ecosystem no longer has the resources to support the numbers of the members of the population, and therefore those not best fit to survive will die off and let those that are live on and reproduce to pass those best-fit traits on to their offspring. Well, in many cases, the sharks will have the same effect! The sharks will wait and pick a target that seems slower, weaker, or most vulnerable to take as prey. So they are also picking out those best fit to survive in the population and encouraging the shift towards higher percentages of those genes in the population from generation. Here we do see that the sharks depend on sea lions for food and energy, but the sea lions as a population depend on the sharks to enforce natural selection and encourage the evolution of the species!

Biosphere 

In the same way that different populations are dependent on one another in a community, so are all communities and the ecosystems they reside in. In the biosphere, all living things exist and carry out the functions that they need to survive. In any ecosystem and even the whole biosphere, plants and algae perform photosynthesis and all the leftover oxygen that they do not use for respiration is put back into the air or water. Well, who else uses that oxygen but consumers? They breathe (or filter) oxygen out of the air or water to use in respiration. The consumers, in turn, produce carbon dioxide as a bi-product of respiration that the plants can use to make their own food in photosynthesis! Here we see again dependency once more! But how does this apply to the biosphere? The neat about oxygen is that it is, in most forms, a gas and can therefore move very quickly and over great distances before it is ever used! An algae in the Gulf of Mexico could be supplying oxygen to a kangaroo in Australia, and a penguin in Antarctica could be providing carbon dioxide for a tree Central Park! Clearly we can see here that all aspects and parts of nature really do depend on one another, whether living or not!

Is there anything in nature that doesn’t depend on some other aspect of nature?  Should abiotic factors be observed as part of nature? Why or why not?  What other examples can you think of?

This entry was posted on Wednesday, May 7th, 2008 at 10:08 am and is filed under Student Post, AP Biology, Themes in Biology. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.