WELCOME TO THE DISCUSSION GROUP FOR THE BOOK "YOUR INNER FISH" BY NEIL SHUBIN. PROMPTS AND POSTS ARE STUDENT GENERATED. THIS IS A COLLECTIVE EFFORT TO ENGAGE IN DISCUSSIONS THAT CONNECT THE THEORY OF EVOLUTION WITH THE BIOLOGICAL CONCEPTS AND THEMES DISCUSSED IN OUR COURSE THROUGHOUT THE YEAR.
Monday, April 4, 2011
Operculum No More
In the afterword, on page 206, Shubin talks about how Tiktaalik lost its operculum. In what ways did this specific change in the structure of Tiktaalik effect its movement and how does this show the evolution of land animals from aquatic animals?
In fish, the operculum is the protective bony flap that covers the gills. Fish are able to “breathe by drawing water over four or five pairs of gills…by movement of the operculum and contraction of muscles surrounding the gill chambers” (Campbell 708). In the Tiktaalik, this operculum was lost causing a change in breathing patterns, but also surprisingly causing a change in movement. Because the operculum was lost, the Tiktaalik became an “aquatic animal specializing to breathe air” (205). However, the loss of the operculum also caused a major change in movement for the Tiktaalik. The operculum is also a bone that helps to attach the head of a fish to its body. This causes the head to not be free from the body so “when a fish wants to move its head, it needs to move its body” (206). However, since the Tiktaalik lost the operculum, its head was able to move independently from the rest of its body. It was now known to have a "true neck".
This new adaption was a factor that shows evolution from aquatic animals to land animals. The lack of an operculum is a selective advantage for animals living on land because they are “supporting [themselves] on solid ground” (206). It would be difficult and annoying for us humans to always have to move our bodies in the direction we wanted to look. Instead, because we don’t have an operculum and because we have a neck, we are able to look around without having to move our entire body in that same direction. Fish don’t need a neck because they are “readily able to orient the body to position their mouth toward prey” (206). So, the loss of the operculum in the Tiktaalik was a first step for animals being able to live on land and support themselves with a “true neck”. It also displays how the Tiktaalik shows the connection between aquatic animals and land animals.
Sources: Your Inner Fish Campbell http://www.speroforum.com/a/16462/First-land-animals-shared-neck-structure-with-fish
According to Shubin, the operculum "is a series of bones that serve to attach the head to the body in the fish" (206). Because of the operculum, the head and the body of the fish are connected, therefore one cannot move without the other moving along with it - in other words, movement of the head and body of a fish are always synchronized. Tiktaalik was found to lack the operculum, which means that there was no bone structure that connected the head and the body, therefore they could move independently of each other. In other words, "Tiktaalik [had] a true neck" (206).
As Danielle stated above, the operculum in bony fish is a hard, bony flap that functions in protecting and covering the gills. The operculum consists of four bones that are fused together: the opercle, preopercle, interopercle, and subopercle. These four bones were derived from separate gill-slit covers of ancient fish species. The posterior end of an operculum functions in preventing reverse water flow during respiration by utilizing its flexible and ribbed structure as a seal. The operculum is also very important in the process of obtaining oxygen. The operculum is opened as the mouth is closed which results in a pressure drop inside the fish. Water flows from the high to low pressure across the gills of the fish, allowing for the oxygen in the water to be absorbed. In other words, the operculum is vital in helping fish breathe under water.
Like Danielle said before, the selective advantage of Tiktaalik not having an operculum is that it is able to move its head and neck independently from each other. Living on land, this is very important because the animal's range of motion would be very limited which would become a disadvantage when looking around in search of prey or protecting itself from predators. Also, animals without necks that live on land would have trouble reaching places there could be food. Evolution over the course of millions of years and many generations led to terrestrial animals such as humans with well developed necks from fish with operculum that could not move their bodies and heads independently. Another great selective advantage of terrestrial mammals having no operculum would be that they could obtain oxygen without using as much energy. The process of obtaining oxygen through the operculum is much less efficient than the process of obtaining oxygen in the air, mostly because the concentration of oxygen in the water is much smaller than the concentration of oxygen in the air, which is also the reason why the operculum is needed in the fish to breathe in water.
As Sujin and Danielle have previously stated, the loss of the operculum in the Tiktaalik allowed for this animal to have an increased range of motion as it could simply move its neck rather than its whole body. In addition to the fact that no operculum in the Tiktaalik allows for easier movement (that also requires less expenditure of energy), the loss of structure also relates to the fact that the Tiktaalik has structures such as joints: it is a fish "with shoulder, elbow, and wrist joints" (Shubin 23), which corresponds with the fact that the Tiktaalik is a vital link between acquatic and terrestial animals. Thus, because the Tiktaalik was one of the animals on its way to becoming mainly land-dwelling, the loss of the operculum was another step in evolution that would eventually happen. This can be attributed to the fact that the operculum is mainly used to facilitate water movement over the gills (Campbell & Reece 708), which is why it is also present in osteichthyans, since fish frequently need to be taking in water from the environment, mainly to maintain an osmotic balance with the either freshwater or saltwater environment. Going further on the point that Sujin made that the operculum is vital for underwater breathing, this becomes the reason for which the operculum is no longer necessary in the Tiktaalik. Like land-living animals, this "hybrid" (the link between water-living and land-living animals) came to rely on "mov[ing] air in and out of its lungs solely by mouth pumping" just like frogs do (Shubin 206). Furthermore, this also relates to how us humans breathe-- through our mouth and also through changes in the shape of our chest cavity. There is contraction of both the intercostal muscles as well as of the diaphragm, causing it to move downward, which increases the volume of the thoracic cavity and decreases its pressure; thus, this lowered air pressure in the lungs causes air to move in from the environment, from high to low pressure (http://people.eku.edu/ritchisong/301notes6.htm). As animals moved from water to land, there was less need for structures such as the operculum to assist in moving water into the body because air could be moved through different measures, such as this contraction of the thoracic cavity to allow for air to move down the pressure gradient and into the body.
We’ve seen how the structures facilitating breathing have changed over time, depending on the need and the environment of the animal (Tiktaalik didn’t need the operculum, while other animals, such as fish, do), another interesting step forward is in how we as humans will possibly change our breathing habits and capabilities over time. A study’s results released in PNAS started out as how algae enters developing salamander eggs and becomes part of the growing fetus, and is even present in the adult, meaning that salamanders are part-algae. This algae DNA is then passed on over generations. The algae “snacked on nitrogen in the embryo's waste, while the embryo benefited from the oxygen in the algae's waste” (http://io9.com/#!5789151/future-humans-with-algae-implants-could-breathe-underwater). Therefore, this symbiotic relationship between the algae and the salamander embryo allowed for its survival and eventual passing on to future generations. This study can be taken a step further when it is related to humans—it is possible that, with algae implants, we could more easily pull “oxygen from the water” (http://io9.com/#!5789151/future-humans-with-algae-implants-could-breathe-underwater), and therefore we could eventually develop the ability to breathe underwater. While this may seem like a stretch, it could be possible—as we’ve observed the great structural changes that have already occurred over time (from fish, to Tiktaalik, to humans) and the new functions constantly emerging, this may be the next logical step in how we can expand our capabilities as related to breathing. Sources: Your Inner Fish Campbell & Reece http://people.eku.edu/ritchisong/301notes6.htm http://io9.com/#!5789151/future-humans-with-algae-implants-could-breathe-underwater
In fish, the operculum is the protective bony flap that covers the gills. Fish are able to “breathe by drawing water over four or five pairs of gills…by movement of the operculum and contraction of muscles surrounding the gill chambers” (Campbell 708). In the Tiktaalik, this operculum was lost causing a change in breathing patterns, but also surprisingly causing a change in movement. Because the operculum was lost, the Tiktaalik became an “aquatic animal specializing to breathe air” (205). However, the loss of the operculum also caused a major change in movement for the Tiktaalik. The operculum is also a bone that helps to attach the head of a fish to its body. This causes the head to not be free from the body so “when a fish wants to move its head, it needs to move its body” (206). However, since the Tiktaalik lost the operculum, its head was able to move independently from the rest of its body. It was now known to have a "true neck".
ReplyDeleteThis new adaption was a factor that shows evolution from aquatic animals to land animals. The lack of an operculum is a selective advantage for animals living on land because they are “supporting [themselves] on solid ground” (206). It would be difficult and annoying for us humans to always have to move our bodies in the direction we wanted to look. Instead, because we don’t have an operculum and because we have a neck, we are able to look around without having to move our entire body in that same direction. Fish don’t need a neck because they are “readily able to orient the body to position their mouth toward prey” (206). So, the loss of the operculum in the Tiktaalik was a first step for animals being able to live on land and support themselves with a “true neck”. It also displays how the Tiktaalik shows the connection between aquatic animals and land animals.
Sources:
Your Inner Fish
Campbell
http://www.speroforum.com/a/16462/First-land-animals-shared-neck-structure-with-fish
Danielle Webb (dwebb456@gmail.com)
According to Shubin, the operculum "is a series of bones that serve to attach the head to the body in the fish" (206). Because of the operculum, the head and the body of the fish are connected, therefore one cannot move without the other moving along with it - in other words, movement of the head and body of a fish are always synchronized. Tiktaalik was found to lack the operculum, which means that there was no bone structure that connected the head and the body, therefore they could move independently of each other. In other words, "Tiktaalik [had] a true neck" (206).
ReplyDeleteAs Danielle stated above, the operculum in bony fish is a hard, bony flap that functions in protecting and covering the gills. The operculum consists of four bones that are fused together: the opercle, preopercle, interopercle, and subopercle. These four bones were derived from separate gill-slit covers of ancient fish species. The posterior end of an operculum functions in preventing reverse water flow during respiration by utilizing its flexible and ribbed structure as a seal. The operculum is also very important in the process of obtaining oxygen. The operculum is opened as the mouth is closed which results in a pressure drop inside the fish. Water flows from the high to low pressure across the gills of the fish, allowing for the oxygen in the water to be absorbed. In other words, the operculum is vital in helping fish breathe under water.
Like Danielle said before, the selective advantage of Tiktaalik not having an operculum is that it is able to move its head and neck independently from each other. Living on land, this is very important because the animal's range of motion would be very limited which would become a disadvantage when looking around in search of prey or protecting itself from predators. Also, animals without necks that live on land would have trouble reaching places there could be food. Evolution over the course of millions of years and many generations led to terrestrial animals such as humans with well developed necks from fish with operculum that could not move their bodies and heads independently. Another great selective advantage of terrestrial mammals having no operculum would be that they could obtain oxygen without using as much energy. The process of obtaining oxygen through the operculum is much less efficient than the process of obtaining oxygen in the air, mostly because the concentration of oxygen in the water is much smaller than the concentration of oxygen in the air, which is also the reason why the operculum is needed in the fish to breathe in water.
Sujin Ko (sujinko93@gmail.com)
Sources: Shubin
http://en.wikipedia.org/wiki/Operculum_(fish)
As Sujin and Danielle have previously stated, the loss of the operculum in the Tiktaalik allowed for this animal to have an increased range of motion as it could simply move its neck rather than its whole body. In addition to the fact that no operculum in the Tiktaalik allows for easier movement (that also requires less expenditure of energy), the loss of structure also relates to the fact that the Tiktaalik has structures such as joints: it is a fish "with shoulder, elbow, and wrist joints" (Shubin 23), which corresponds with the fact that the Tiktaalik is a vital link between acquatic and terrestial animals. Thus, because the Tiktaalik was one of the animals on its way to becoming mainly land-dwelling, the loss of the operculum was another step in evolution that would eventually happen. This can be attributed to the fact that the operculum is mainly used to facilitate water movement over the gills (Campbell & Reece 708), which is why it is also present in osteichthyans, since fish frequently need to be taking in water from the environment, mainly to maintain an osmotic balance with the either freshwater or saltwater environment.
ReplyDeleteGoing further on the point that Sujin made that the operculum is vital for underwater breathing, this becomes the reason for which the operculum is no longer necessary in the Tiktaalik. Like land-living animals, this "hybrid" (the link between water-living and land-living animals) came to rely on "mov[ing] air in and out of its lungs solely by mouth pumping" just like frogs do (Shubin 206). Furthermore, this also relates to how us humans breathe-- through our mouth and also through changes in the shape of our chest cavity. There is contraction of both the intercostal muscles as well as of the diaphragm, causing it to move downward, which increases the volume of the thoracic cavity and decreases its pressure; thus, this lowered air pressure in the lungs causes air to move in from the environment, from high to low pressure (http://people.eku.edu/ritchisong/301notes6.htm). As animals moved from water to land, there was less need for structures such as the operculum to assist in moving water into the body because air could be moved through different measures, such as this contraction of the thoracic cavity to allow for air to move down the pressure gradient and into the body.
(continued from last post...)
ReplyDeleteWe’ve seen how the structures facilitating breathing have changed over time, depending on the need and the environment of the animal (Tiktaalik didn’t need the operculum, while other animals, such as fish, do), another interesting step forward is in how we as humans will possibly change our breathing habits and capabilities over time. A study’s results released in PNAS started out as how algae enters developing salamander eggs and becomes part of the growing fetus, and is even present in the adult, meaning that salamanders are part-algae. This algae DNA is then passed on over generations. The algae “snacked on nitrogen in the embryo's waste, while the embryo benefited from the oxygen in the algae's waste” (http://io9.com/#!5789151/future-humans-with-algae-implants-could-breathe-underwater). Therefore, this symbiotic relationship between the algae and the salamander embryo allowed for its survival and eventual passing on to future generations. This study can be taken a step further when it is related to humans—it is possible that, with algae implants, we could more easily pull “oxygen from the water” (http://io9.com/#!5789151/future-humans-with-algae-implants-could-breathe-underwater), and therefore we could eventually develop the ability to breathe underwater. While this may seem like a stretch, it could be possible—as we’ve observed the great structural changes that have already occurred over time (from fish, to Tiktaalik, to humans) and the new functions constantly emerging, this may be the next logical step in how we can expand our capabilities as related to breathing.
Sources:
Your Inner Fish
Campbell & Reece
http://people.eku.edu/ritchisong/301notes6.htm
http://io9.com/#!5789151/future-humans-with-algae-implants-could-breathe-underwater
Kathy Li, kathy2132@gmail.com