On page 117 in Subin's book, he goes on to define 'a body'. Explain in your own words what defines a body. In addition, explain when did bodies arise, how did they come about, and the significance of bodies. Describe the differences between a cluster of random bacteria cells and a cluster of cells creating a human.
Nikhil Pereira (nikhil.pereira3@gmail.com)
Shubin defines a body as something whose "component parts work together to make a greater whole". In essence, he is differentiating between individuals of humans and other multicellular organisms and unicellular organisms. The dictionary provides a biologically valid definition of "individual", defining it as "separate and distinct from others of the same kind". A more appropriate definition for this context is an organism which can live independently from other organisms of the same species. The difference between a colony of bacteria and a fish is that while both are collections of cells, the colony is a group of individual cells as opposed to the fish, whose cells are all part of one individual. Also, in colonies of bacteria, none of the cells are vital to the survival of the others. This is not the case in animals, or other organisms with bodies. In multicellular organisms, some cells are vital to the survival of the whole individual, and if removed, all the other cells will die.
ReplyDeleteMulticellular bodies began as protists over 600 million years ago, from which animals eventually developed. The first animals evolved into organisms with locomotion. This is one of the defining characteristics of animals. Locomotion came to be because moving allows for a better way to cope with environmental pressures like lack of food and temperature fluctuations. Moving allowed the first bodies to seek out their food instead of waiting for their food to come floating along.
The first animals were soft-bodied, showing no adaptations which would protect modern-day animals from predators. As the millions of years went on, animals developed hard shells as protection. The first animals still had sac-like openings for digestion. As the millions of years went on, animals developed a more efficient system for digestion, evolving into triploblastic creatures with a uni-directional digestive system. From these earliest organisms, we have covered the rest of evolution thoroughly in the novel and in this blog. It is interesting to note that once the first bodies came into being, the rate of diversification into different types of bodies increased dramatically. Knowing that from the first cells of life to the first bodies was a period of about 3 billion years, thinking about the diversity of bodies that has occured in the past 600 million years is quite dramatic.
http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookdiversity_7.html
Jeremy Solomon
imabum14@gmail.com
A body is composed of many different systems, operated by multiple organs, that work together to efficiently carry out an organism’s daily processes. Bodies started showing up on planet Earth as soon as resources became plentiful enough to support their lifestyles, around 600 million years ago. With all of the cells working together at the same time, species with bodies require much more energy than species without bodies. Also, as the conditions of Earth improved more to sustain bodied life, more complex organisms started emerging. However, these complex organisms did not just come out of nowhere, but they are derived from simpler organisms that obtained selective advantages for survival. These simpler organisms were able to maintain their newly obtained traits by taking advantage of the Earth’s resources. Organisms with bodies came from organisms without bodies through this same process of evolution, with the Earth’s resources to allow this huge change.
ReplyDeleteThe main difference between a cluster of random bacteria cells and a cluster of cells creating a human is that the bacteria cells are each its own organism, while the cluster of human cells is part of a single body, working together in one organism. Each bacteria cell is independent of each other, so communication between different cells is not nearly as frequent as it is inside a body. For example, inside the human body, each system can only function properly if all of the cells that are a part of a system are communicating and sending each other positive and negative feedback. Through this homeostasis, the body’s functions can be controlled, reducing excess energy usage where it is unneeded. An example of communication in the human body is apparent in the digestive system. As food particles enter the stomach, the hormone gastrin stimulates the production of gastric juices, which contain pepsinogen and HCl. Pepsinogen is converted by HCl into pepsin, which chemically digests proteins. Also, when the food reaches the dudodenum of the small intestine, CCK “stimulates release of enzymes from the pancreas and of bile from the gallbladder” (Campbell 888). Early, bodiless organisms like bacteria have no use of this communication because they do not need it, due to their lack of organized systems.
Sources:
Campbell
Shubin
http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20102/bio%20102%20lectures/digestive%20system/digestive%20system.htm
Austin Lee (austinklee7@gmail.com)
As Jeremy said, there is a long history behind what made a body. One could say it started with the cell clumping that happened during the conditions of early life on earth. Cells could be a lot more efficient in energy use if they worked together, showing an early start to combining cells for a purpose. From there, after a long period of time, at one point a prokaryotic bacterium entered a pre-eukaryotic cell, becoming one part functional cell and one part energy powerhouse, the eukaryotic cell(http://facstaff.gpc.edu/~pgore/students/w96/joshbond/symb.htm). This idea of an endo-symbiotic theory shows the beginnings of cells specializing to be used for certain things. This is advantageous because it saves energy, and allows for each part of the body to be in charge of one thing. From here, the building blocks were set, allowing groups of cells to organize and distribute the workload.
ReplyDeleteAt this point, cells needed a way to “stick together” in a way, and groups of cells that developed these functional units proved to be at an advantage. Some functional units included “the rivets that hold cells together; the various devices that help cells signal to one another; and many of the molecules that lie between cells” (132). As time went on, some organisms needed more and more of these molecular ties. As Shubin later says, starfish have a fraction of the amount of rivets than chordates.
In this way, the idea of cells being held together by other cells was the original body. With each part being in charge of a process and a system for holding up the organism, one could say that the origins of the body started in simple cells working together in order to live through the harsh conditions of the planet.
(Alex Sapozhnikov marijio@gmail.com)
As Jeremy and Austin stated, the main difference between a random cluster of cells and a body is the concept that a colony or cluster of cell is simply a group of individual entities located in the same area. However, a body constitutes many different cells working together to cooperate and make sure that an organism lives in the most efficient and healthy way possible. I also agree with the point that Jeremy hit on; that in clusters of non-connected cells, if some of the cells are removed or killed, the others are virtually unaffected. On the contrary, in a body, the cells work together to perform specific functions, which when done properly and in unison, allow the body to function at its highest level. Shubin gives an example of this on page 117 when he explains that removing some cells from a mat of bacteria will just give you a lower quantity of bacteria, whereas if you remove cells from the heart or brain of some animal, you could potentially create a fatal void in the animal's body. In a way, it is a somewhat "selfish" vs. "non-selfish" relationship: individual cells only execute processes that will benefit them, while cells in a body are programmed to do a specific job and play a role in maintaining homeostasis.
ReplyDeleteA central theme involved in the discussion of bodies is the relationship between structure and function. Bodies are much more than just clusters or balls of cells that form an organism. Instead, cells in bodies form organs and tissues, which all have specialized roles. This connects to the theme of regulation; that the body's cells are constantly doing their jobs, that are encoded into their DNA, to make sure that the body remains in homeostasis, and is able to perform functions necessary to life. These organs are structured to be able to carry out their specific functions, which in turn helps to regulate the body. The different groups of specialized cells working together is what differentiates a body from a colony or cluster of individual cells. The themes of structure and function, and regulation, help to connect the idea that groups of cells in bodies are shaped together in a specific way to help perform a certain function, and thus regulate the body and maintain homeostasis.
As both Austin and Jeremy stated, bodies arose around 600 million years ago when organisms began to develop higher energy needs, and more complex organization. When multicellular tissues and organs began to form to accommodate specialized functions, bodies truly began to form.
I think that bodies signify evolution's progress and how new animals are developing much more complex and advanced systems, to help gain a selective advantage to ultimately survive and reproduce. Evolutionary history and progress has led to the point where brains in humans now have more interneural connections than the number of atoms in the universe. The ever increasing complexity and adaptations of bodies drives the pace of evolution, and as bodies are able to do more and more, animals gain more selective advantages to survive and reproduce.
Sources:
Campbell
Shubin
Matt Kim
(matthewkim0803@gmail.com)