Mass Extinction in the late Devonian Period
Mass Extinctions in the Marine Fossil Record (David M. Raup. 1982)
In this paper, genera extinctions are discussed in terms of mass extinctions rates that are shown throughout earth's period. By graphing familial data from the fossil record against geologic time, scientists are able to calculate the rate of extinction. With fossil records, there have been four statistically significant mass extinctions that have happened within earth's time frame. These have shown to happen late in the Ordovician, Permian, Triassic, and Cretaceous periods, and have been identified in the fossil record by major changes in organismal diversity. With fossils, there must be various factors that allow for a fossil to even be made. As the paper describes, shale is the best place to find "shelly" and rarely preserved family fossils because of its fine-grained properties. It is shown that each different location of shale can contain different types of these fossils from different time periods related to mass extinctions. Out of all the shale, only the Burgess Shale really showed any large significance that was different compared to the extinction rates already known. This brings up the idea of normal or background extinctions compared to mass extinctions. With the Phanerozoic diversity curve, we see five mass extinctions, four of which were shown to be statistically significant in the paper. A fifth extinction event, occurring in the Late Devonian, is considered to be a “smearing” event, which means that the event could either be have been a real event with multiple stages or one that had errors added from inconclusive extinction times. The paper concludes that there are four mass extinctions that have been shown to differ from just normal or background extinctions.
Questions:
How could we tell if there was ever a mass extinction with organisms that do not meet the requirements to produce a fossil? Could we ever fully tell the total amount of species that have gone extinct?
Our research and knowledge of the fossil record has increased substantially in the previous years and continues to grow at an exponential rate. What do you think the chances are that more historic mass extinctions may become more evident as our research continues? Why?
Terrestrial-Marine Teleconnections in the Devonian: Links between the Evolution of Land Plants, Weathering Processes, and Marine Anoxic Events (Thomas J. Algeo. 1998)
In this paper, environmental and organismal changes during the Devonian time period really set the future pathway to more diverse and complex earth systems. Early earth life consisted of land plants that were small in body size and had simple body systems that allowed for the plant to survive in moist, lowland habitats. During the Devonian period, arborescence, or more tree-like plants, started to develop. The trees’ trucks became thicker and had more of a woody outer layer and their roots began to deepen and spread. There were shrub-like plants that were developing that allowed for ground cover and microenvironments to begin emerging within the soils and top ground levels. This allowed for chemical weathering to advance the soil environments and create a more stable habitat for organisms to further grow.
With the growth of aboveground body systems taking place, belowground systems had to keep up to support the central system. Roots were first characterized to be short in size and soil depth. There was an increase in soil penetration, along with an increase in lateral root growth. With the beginning of soil formation, root soil penetration started to evolve, and in turn the soil around the plant also showed beneficial impacts. The soils became richer in nutrients and allowed organisms to have a mutual relationship with the soil around them due to an increase in detritus recycling and positive feedback between the rates of soil formation and floral biomass.
As the terrestrial plant life started to evolve their body systems to function at greater capacities, the seeds created and produced were able to follow that same path. Plants were no longer confined to just small ranges of moist, lowland habitats. Seeds could now survive in drier environments, making them able to travel and extend their range. This allowed plants to start inhabiting once unsustainable and unreachable environments. Diversification of plants started to grow with the added benefit of pollination and plant movement from area to area. Once uninhabitable environments were now able to develop and create their own ecosystems. The hydrologic cycle was altered and more water was staying in the soil or plants and evaporating at lower rates than before. In addition, this increase in vascular plant life caused a decrease in atmospheric CO2 which continued to decrease with added growth to plant habitats.
The combination of seeds and root systems caused significant changes in the soil substrates, which lead to algal blooms in the oceans. Many different soil types associated with temperate forests increased during this time. Furthermore, the development of these denser vascular plants that were rooted allowed for the stabilization of land surfaces, which in turn allowed more time for weathering of these surfaces into finer grains. Due to this increase in vascular plants, a rapid draw-down of atmospheric CO2 occurred, later resulting in global cooling and a short glacial episode that set the stage for the Permo-Carboniferous Ice Age.
Marine organisms were affected drastically from the development of terrestrial land plants. The influx of nutrients from terrestrial plant litter into marine environments may have played a key role in the increase in marine productivity and overall organic matter accumulation. With added nutrients being put into the soil, mineral leaching would allow marine life to obtain those nutrients. This would also include additions of carbon compounds that most plants can’t survive without. However, this increase in marine productivity may have also been responsible for opportunistic algal blooms and bottom-water anoxia that placed severe environmental stresses within many marine ecosystems and could have ultimately helped lead to a mass extinction.
Questions:
There was a lot of great new developments during the Devonian time towards plant systems and their environment. What would you pick as the development that had the greatest impact on how the earth was shaped for future time periods to come? Why?
What do you think is the most significant factor in linking terrestrial and marine ecosystems? Why?
How do you image the earth would be today if seed development and arborescence would have not occurred? How different do you think the climate would be? Would animals have ever evolved?
With regards to the Raup paper- I don't think we will ever have more than an estimation of the rates of extinction and the number of species we lost to extinction just due to the fact that, like we discussed in class, the odds of becoming fossilized is extremely rare and the animal has to die in just the right conditions to be preserved. Some species are only present in environments which make that difficult, such as a lush jungle, where bacteria, scavengers, and acidic soils are prevalent- making the chances of just one individual of a species to become fossilized extremely rare, and then if one individual does become fossilized, the odds of a paleontologist or just someone in general finding that individual extremely unlikely. These reasons, I believe, are why extinctions are looked at in the family/genera level, opposed to the species level-- there is more data to examine a trend- whereas with a species they might only find a few individuals in total which gives almost no information about its longevity. Also, for the soft bodied animals-- if there is not enough data to know more discernibly how largely they were present, we could never really know if there was also a mass extinction largely involving them.
ReplyDeleteHow could we tell if there was ever a mass extinction with organisms that do not meet the requirements to produce a fossil? Could we ever fully tell the total amount of species that have gone extinct?
ReplyDeleteI believe that the fossil record will always be largely incomplete, and that there really is no way of quantifying possible extinctions of certain types of organisms. There is no doubt entire phyla that we have absolutely no record of. As we went over in class, you not only have to be of a certain bodily composition to have a significant chance of being fossilized, you have to die in the right places, and be able to be found. There must be various stretches of land where fossils are rarely found, if ever. Surely these areas had to have been occupied by species at some point in the course of history, which makes the question of how narrow our scope of knowledge really is a complete mystery.
There was a lot of great new developments during the Devonian time towards plant systems and their environment. What would you pick as the development that had the greatest impact on how the earth was shaped for future time periods to come? Why?
I would say that the evolution of seeds was an important development that largely impacted the future environment of the earth. This allowed for the dispersal of plants away from the water and the ability to colonize new areas of land. As the paper explains, this not only had major implications for terrestrial environments that were then transformed into new ecosystems, it also caused widespread changes to marine environments. It resulted in a wide variety of new interactions between the various biotic and abiotic components of the earth.
I think the chances of detecting other mass extinctions is small, because we rely on statistical models to identify them. As we gather more fossils, I think they will adhere to the current model of an overall trend toward decreasing extinction rate, punctuated with mass extinctions. We can only extrapolate, based on current estimates of taxa diversity, how many families were present at any given time. Raup and Sepkoski used marine fossils to construct a model for extinction rates, and their sample size of 3300 families is minuscule compared to the actual number of families that must have been present throughout the Phanerozoic. It is, however, reasonable to conclude that non-fossilized organisms, which evolved to a survive in those aquatic environments, would suffer the same fate as the fossilized.
ReplyDeleteMass Extinctions in the Marine Fossil Record (David M. Raup. 1982)
ReplyDelete1) I do not think we will be able to determine mass extinction events for organisms that do not meet requirements for fossilization as becoming a fossil is already a rare occurrence and fossilization of these organisms would be something close to a miracle. If the fossilization of such organisms did occur I feel that determining mass extinction for these organisms would be inaccurate as we would not have enough data to make such a distinction with in the fossil record. Since we can not include these organism and many other organism that met the requirements for fossilization but simply did not fossilize, I do not think we can ever have a true record of mass extinction that is very accurate and we can only make an attempt to determine extinction events for every organism.
2) I do not think that more historic mass extinctions will become apparent as I feel we would have to discover quite a bit more fossil records to make the case for another extinction that is significantly greater than background extinction events.
Terrestrial-Marine Teleconnections in the Devonian: Links between the Evolution of Land Plants, Weathering Processes, and Marine Anoxic Events (Thomas J. Algeo. 1998)
1)I believe the most significant impact was the development of a seed that could survive outside of water as this allowed plans to travel further and more soil to become suitable for growth and give later animals a source of food father from the water.
2)I think the factor that was important for linking the terrestrial and marine ecosystems was resources. I say this as the land was mostly not inhabited by many organisms so land had more space and less competition as no other organisms really where utilizing it so sunlight was abundant for plants. Once plants settled in there was again more resources in terms of less competition for herbivores so it was relatively beneficial to find resources there. I believe this pattern continued until land became dominated by life. I think animals would have continued to develop as there was resources in the marine environment, I think if the seed was not developed land would be barren and only have life near pockets of water and the ocean would have the concentration of life and have heavy competition as all of life would be concentrated there competing for resources.
Mass Extinctions in the Marine Fossil Record
ReplyDeleteI don’t believe the scientific community will ever be able to precisely determine the total number of species that have gone extinct. Even in present times, there is no exact number listing extant species, and this is further complication by some organisms, such as viruses, which are more hesitantly given the title of species. That being said, there are certain some well-rounded estimations and modeling techniques that can be used to address this issues, and Raup does just that in his paper. He states “Calculations were made separately for “shelly” taxa and for rarely preserved taxa. The effect of this segregation was negligible in most cases…”. I understood “shelly” fossils to be those ancient species which are most easily preserved by virtue of possessing a shell, while rarely preserved taxa were defined as the opposite. Raup seems to believe his calculations determining mass extinction events, based on “marine vertebrates as well as invertebrates and protozoans” can be applied to other animal groups.
Terrestrial-Marine teleconnections in the Devonian: links between the evolution of land plants, weathering processes, and marine anoxic events
The development on a cycle of nutrient transport seems to be one of the key developments on the Devonian Period. Without the appropriate chemical precursors, no organism is able to obtain energy through any energy source, so even with the application of light as energy and water as a medium, life is limited by access to key nutrients. Taking a step back, it seems that the major development on the Devonian was an efficient method of distributing these valuable nutrients. Increased arborescence allowed for the stratification of nutrients into the canopy, and the development of the seed habit enabled the progression of plants inland, transporting nutrients from watery areas to more dry environments. Newly formed soils sequestered these nutrients and further enabled to transportation nutrients inland, and allowed the cycle to continue by being washed back toward water sources during rainfall events.
Mass Extinctions in the Marine Fossil Record (David M. Raup. 1982)
ReplyDeleteI believe that in this current time there is no way for scientists to measure how many total species have gone extinct. In order for us to measure which species have gone extinct, we use records of fossils to record the estimation of which species have gone extinct as well as the time the frame of their extinction. Many factors play a role in becoming a fossil which include having hard body parts, biotic factors such as not getting eaten or stepped on, have death occur in the right place and physical components including avoiding wind and finding the right sediments. Also the chances of a fossil being found plays a paramount role in being able to calculate species extinction. Based on these criterions, the fossil record is most likely incomplete and making it hard to estimate the exact number of species that have gone extinct. The current models in Rupps paper have extinction rates that are trending downwards. If we were to assume things are trending in the same directions as the models displays extinction in the future will also decrease.
Terrestrial-Marine Teleconnections in the Devonian: Links between the Evolution of Land Plants, Weathering Processes, and Marine Anoxic Events
As plants began to evolve on terrestrial lands, I believe seed dispersion was the biggest role player in this major event. With dispersion of seeds, plants were no longer confined to certain regions and seeds could now be dispersed to undesirable conditions and habitats. Seed dispersions contributed to a multitude of phenomena including changing soil textures, decreasing atmospheric CO2 levels and creating larger root systems where the plants inhabited. If seed dispersal would not occur it would be hard for animals to evolve. If plants are not able to disperse and cover more surface area this will also greatly impact the environmental climate. Many animals today such as humans are oxygen dependent and without oxygen humans may not exist. As we all know plants are significant and are vital in producing oxygen to the atmosphere, and without them the climate would still have significant amount of CO2. Larger amounts of CO2 would lead to warmer temperatures in the earths atmosphere. With warmer temperatures and higher amounts of CO2 instead of oxygen in the atmosphere, many species of oxygen dependent animals that we know today would not have evolved.
In regards to questions on the first paper, I do not think we will ever have a comprehensive data set of all the species to have ever existed throughout earth’s history. It seems that a large number of species are currently unrepresented in the fossil record due to the limitations the criteria for an organisms becoming fossils poses. I believe that the best way to work around this and obtain the most data possible was to resort to studying organisms from broader taxonomic levels. As to the discovery of more mass extinctions, again, I feel that it is unlikely. The amount data we hope to ascertain from the fossil record is limited by the number of organisms that were “lucky” enough to become fossils and the amount of unexplored/undisturbed land we have left to explore. The human population is still increasing exponentially and we are encroaching on more and more land as a result of this. Already there are issues in analyzing the stratification from which fossils are pulled from and as more land is overturned and disturbed it seems the hope of ever unscrambling the order becomes unlikely.
ReplyDeleteIn regards to the questions on the second paper, I believe that it was the increase of size in land plants that led to the greatest changes in earth’s environment. I think that the sheer size of the plants allowed for more carbon dioxide intake and more diversification of the surrounding soils and nutrients. In turn, I believe it is clear to see a link between the nutrients produced in the soils due to the diversification and the bloom of marine life that eventually led to anoxia. Marine ecosystems in our oceans now can be significant impacted by supplementing limiting nutrients such as Iron into the water. The organisms response (usually bacteria and algae) follow a pattern: a bloom in productivity resulting in increased O2 intake and carbon sequestration, followed by a drop off in productivity as nutrients are used up. I believe the anoxia event that occurred was following this same pattern in response to the nutrient runoff from the soil the land plants had created.
Pertaining to the Raup paper. I think that is what is so exciting about the fossil record is that it is always changing. We never know what we are going to find! We are at a huge loss when it comes to knowing the amount of species diversity that lived in the past. So 96% of all life lost in the great dying was just 96% of what we currently know. That is changing all the time. Paleontology and geology are not my forte but I do think that as research continues we will not more historic mass extinctions. I believe there is already enough evidence for the ones that we know about and we probably would have found something else by now. (But who knows?) I do think however with continued research that we will see more minor extinction events because more than likely the research will increase our species diversity record.
ReplyDeleteIn the first paper it's interesting to think about how many species we don't know about because they are not preserved in the fossil record. We are lucky to have some evidence of poorly preserved species in things like Lagerstätte and other well preserved fossil sites around the globe. I don't think there would be a "mass extinction" that wouldn't at least show up in other taxon that we would be able to see but it may be possible that there were times where many species went extinct and had a poor fossil record so we would know nothing about it. Since most metazoan forms show up by the Cambrian I think its safe to say that we know a lot about the diversity of life and its many forms since the Cambrian explosion but there surely are a lot of specific species we will never know about. I think that over time we will discover more and more fossil evidence that supports the 5 mass extinctions we know about today and provide more insight into the background radiation that is always occurring but I find it extremely unlikely that we will discover another mass extinction that we don't know about already or have some evidence for presently.
ReplyDeleteFor the second paper I would pick the development of seeds and their evolution as one of the most important events in the timeline of terrestrial plants. Surely they had a profound effect on the diversity and distribution of terrestrial plants which gave way to soil and nutrients which in turn created a waterfall effect for a lot of biology. I think that nutrient flow from the terrestrial ecosystems to the aquatic ecosystems had a huge effect on the ocean and its diversity. Nutrients play an important role for marine life today and that process would have began when terrestrial plants started to dominate the landscape outside of the oceans. Terrestrial life would be much different today if seeds didn't evolve. I don't think that would have stopped terrestrial life from taking root on land because open niche space is almost always filled and life would find a difference way around its problems. There would definitely still be animals at least in the form of aquatic life such as fish and reptiles.
Mass Extinctions in the Marine Fossil Record (David M. Raup, 1982)
ReplyDeleteWe can compare the amount of sediment in rock formations left by a time period of life on Earth to the overall pattern of sediment available. This would reveal relative times of mass die off by the measurable amount of sediment present that is characteristic of old life. With this evidence and limited fossil availability, we cannot know exactly how many species have gone extinct, only how much biomass had to be present to produce such characteristics in rocks.
Evidence of extinction may become more available with the development of increasingly telling technology and exactness of dating may improve our record of life on earth. However, it is unlikely that many, or any, more mass extinctions in recent time – perhaps in the last 500 million years – will be revealed to have occurred since we have collected much of the fossil record present. In terms of increasingly archaic time on Earth, more than 500 million years ago, more evidence of how life began may be collected. Such evidence may be of early microorganisms which define the beginning of life on Earth. Small and delicate organisms from an incredibly long time ago may only be discoverable with new technology.
Terrestrial-Marine Teleconnections in the Devonian: Links between the Evolution of Land Plants, Weathering Processes, and Marine Anoxic Events (Thomas J. Algeo, 1998)
I would say that the development of carbon fixation in plants and the down-draw of CO2 out of the atmosphere was particularly important and significant. CO2 is a significant greenhouse gas and the changing of its levels in a planet’s atmosphere can significantly, or even drastically, change the climate of that planet. This use of CO2 by and efflux of O2 from photosynthesis allowed the continued development of aerobic respiration in organisms which then allowed the continued complexification and evolution of animals.
If seed development and arborescence had not occurred, plants would not have reproduced and developed as effectively. We can say this because we know that the evolution of seeds allowed for the displacement of plant genetic material away from the parent plant through the opportunistic use of wind and animal diets. Additionally, arborescence increased the durability and lifespan of tree-like plants, meaning they could age and grow significantly longer, with an increasing ability to pull CO2 from the atmosphere and provide O2 among many other niches in an ecosystem such as providing shelter for small animals and insects. Without the ability to spread and photosynthesize at a greater rate, the climate of Earth may have remained heavily CO2 dense and, subsequently, warm and wet. Animals likely would not have evolved at nearly the same rate because of the lack of O2 availability and challenging climate.
Regarding the Raup paper, I don’t think we could ever fully tell the total amount of species that have gone extinct. I think that because, like you said, there must be various factors that allow for a fossil to be made that there is a very low possibility that we would be able to find evidence of every species that has gone extinct. It would be highly unlikely that every species that existed and went extinct went extinct in a place that would allow for fossils to form and stay intact long enough for us to find them in the present day. Regarding your other question for this article, I think there is a slim to zero chance that more mass extinctions would become evident as our research continues. I think that the likelihood of finding more fossils that would lead to the discovery of another mass extinction is very low.
ReplyDeleteMoving on to the Algeo paper, I think that the development that had the greatest impact on how the Earth was shaped for future time periods to come was the fact that seeds could now begin to survive in drier environments. I think that this was the greatest impact that shaped the Earth for future time periods because it allowed for vegetation to grow and prosper in environments that before this time were not able to do so. With vegetation and trees growing this would allow for herbivores to follow suit and then carnivores and this would lead to a new environment forming allowing for more parts of the world to be a place to live for all diverse kinds of organisms. I think that without seed development and absorbance that there would be a lot of barren places around the world that there would be little to no life living. This would have limited the amount of species that would be able to live on earth due to limited space which means that animals and plants would have needed to evolve at a faster rate due to so much competition happening at once in a small area. I also think that the climate would be a lot more arid and hot and there would be a lot less variability across the world.
The most fascinating thing about fossils is the fact that we have been able to gain so much from them already, and that we even understand anything at all. That being said, thinking forward and considering the second question regarding the 1982 Raup paper and the chances of uncovering more mass extinctions, I would say anything is possible. Paleontological research has truly tested the concept of science as a process of using supporting and contradicting evidence to determine truth, and modern perspectives on the history of Earth have changed drastically and with much contention over time. We have no way of knowing how complete the fossil record truly is, and therefore we can never be completely confident that we have all the answers sorted out regarding species diversity and durations for given time periods; however, the extent to which the fossil record is known today may be a significant reflection of the extinction patterns of the past. Adelene makes a good point when she says "we would have to discover quite a bit more fossil records to make the case for another extinction that is significantly greater than background extinction events." If additional mass extinctions are uncovered and are not uncovered as a result of miscalculations or inaccurate modeling, the compilation of enough fossil evidence may inhibit a timely reveal of any solid conclusion.
ReplyDeleteIn reference to the second paper, I would agree with many of my classmates in saying roots and seeds are the most significant factor in linking terrestrial and marine ecosystems. Roots allowed greater nutrient uptake and survival away from water while seeds ensured the possibility of moving away from water in the first place. In addition, I think the dispersal of plants away from water had a large impact on how Earth developed over time because the dispersal of plants allowed for the diversification of plants and the animals that eat them.
Mass Extinctions in the Marine Fossil Record (David M. Raup. 1982)
ReplyDeleteI do not think it is possible to find evidence of a mass extinction if organisms never fossilized and I do believe that there is never going to be a certain amount of organisms that have gone extinct. With little information to go off of, it is only certain that we will only have a rate and not a total amount of how many species have gone extinct. Without fossilization of organisms there is little to go by indicating that a mass extinction happened because there are no fossils to show record of particular organisms disappearing. We may have information for a certain time period and some organisms may have been able to leave traces that they were there, but there is not always a way to prove that it is a mass extinction because we wouldn’t have known exactly what lived or how many lived in that time period when there are no fossilizations to help understand where the organisms went.
Terrestrial-Marine Teleconnections in the Devonian: Links between the Evolution of Land Plants, Weathering Processes, and Marine Anoxic Events (Thomas J. Algeo. 1998)
I think the main development that had the greatest impact on how earth was shaped was the fact that there were so many plants evolving at the time of the Devonian period. Larger plants that began to evolve helped with the spread of more plants and eventually organisms could evolve based on what was available to survive. The most significant factor linking terrestrial and marine ecosystems I think is that of plants growing larger and spreading to other available areas of land. With more plants, it has changed how the marine life lives and mainly how terrestrial life lives but it brings them together because certain criteria to live like carbon dioxide and oxygen levels have changed. If earth did not have the seed development and arborescence occurrence, I do not think it would be as developed as it is today with all the plants that have developed. I think the climate would be cooler based on how plants usually make a climate more warm and without plants or a lot of plants, the warmth would not occur. I do believe animals would be able to survive and evolve based on there still being marine life. I think marine life should still be able to evolve as they did when terrestrial plants evolved.
My response to the questions on the first paper are as follows:
ReplyDeleteI believe that there were families that went extinct, but we have no idea about what they were, where they were, etc. This is because they did not become fossils, as there are many ways to become a fossil, there are also many ways to avoid becoming a fossil, such as having a soft body, and not dying in the right place, such as the Burgess Shale area. As we continue to find fossils, some of these families may surface and be added to the fossil record, recording additional mass and minor extinctions. This is because the study of extinctions is a relatively new branch of science and techniques or methods are still being developed to find these elusive creatures.
My response to the questions on the second paper are as follows:
The development that had the greatest impact on how plant development shaped the earth was the structural support systems that plants developed to hold themselves upright. This required a vascular system to distribute water and nutrients throughout the plant body. Moving from an aqueous environment to dry land required plants to determine how to not dry up, how to distribute water throughout themselves from resources in the soil instead of just absorbing moisture through their outer membranes, and how to reproduce without distributing pollen and eggs through water, but through air. Seed distribution systems were very important in how the plants colonized the available land masses.
The most important factor linking both aqueous and land environments seems to be the harsh UV rays of the sun. The developing ozone layer was instrumental in protecting both animals and plants from the harmful UV rays, allowing them to crawl out of the deeper water and begin living on earth. If plants had not developed their seed distribution systems, life would have been restricted to wet areas, both in the water and just along the edges of it. The carbon cycling of plants would have been limited, and the ozone layer would not have developed as it did, nor the oxygen rich atmosphere. Animals would have only been able to be small, without the available oxygen, and most of life would have been in deeper waters, protecting animals and plants from the UV rays.
Raup Paper Answers
ReplyDeleteIf there was a mass extinction with organisms that don’t produce a fossil of themselves when they die, we could find out about their existence by using trace fossils and bio markers that they may have left behind instead of their bodies. These could be impression of where they had walked or a nest they had built if they laid eggs, or even just the presence of a chemical reaction that only took place because of their existence and the chemicals they made.
Sadly we will never know exactly how many species have gone extinct over Earth’s history as we only have so many opportunities to find fossils and even if we have fossils of them at all we may misclassify something as we really only have morphology to lean on to tell different species apart. It’s a two part problem in the fact that not everything can be seen in a fossil record and even when we do have one, it is not all the information we would need to properly classify every specimen.
I believe that one or two more mass extinction events may be found through study of the fossil record and improving our understanding of it. This is due to my skepticism that anything is ever truly, one hundred percent, correct and the fact that we really just started looking at this data in the last century or so, and I believe that these mass extinction events will be found in the earlier parts of the Earth’s life, as it is harder to get a clear picture of it from a fossil record for many reasons and because it is viewed by many as less interesting and important so it receives less scrutiny and funding to study it.
Algeo Paper Answers
I believe that the most important development discussed in this paper that happened in the Devonian was that smaller shrubs allowed ground cover and the formation of microenvironments. This is because these micro environments allowed the soil to become more rich and nutrient dense thus allowing plants to spread over almost all land mass at one time or another in Earth’s history, and it allowed them to become bigger so as to sustain almost all of the ground life for the rest of history as well. These microenvironments probably also allowed the first creatures to walk on land a place to live that more closely resembled the ocean they had just crawled from while still being firmly on land just not completely exposed to it.
If seed development and arborescence did not occur when they did, then the Earth would be unrecognizable to us from what it is like today. The climate wouldn’t be nearly as oxygen rich as it is now or has been in the past which is half the reason life on land exists. There would definitely still be animals on Earth but I believe they would all be based in the water as that is the area that would still have food and thus life in the form of algae and other water plants, but little to any life would occur on land I think.
In regards to the Raup paper, I think its first important to remember that we have other types of fossils that we can look at to identify dying off of un-fossilized organisms. If a specific organism doesn't leave a fossil behind we can examine common ancestors of the organism to understand extinction events. We can also use fossils with similar life niches to predict if an organism was likely to go extinct. Lastly, we can use trace fossils such as trails left behind from the organism. I don't believe that we can ever fully tell the exact number of species that went extinct. I think, it is more important to understand general extinction trends than to find the exact number of species dying off in an extinction. I do believe more mass extinction will be identified as we get more sophisticated methods of identifying fossils. I predict, that new mass extinction will not be as large as the five that have already been identified but they will still be larger than background extinctions.
ReplyDeleteIn response to Raup's paper:
ReplyDeleteI also believe that we will never be able to come close to knowing all of the species that have gone extinct in Earth's history. Not only is fossil formation (our best identification process yet) highly limited for hard-bodied organisms, but it also does not account for most soft-bodied organisms. We will also never be able to know what may have been lost due to erosion or destruction prior to the beginning of our fossil hunt. Therefore, it seems that we will never know every species that ever walked the Earth. However, technology is forever growing, and what seems impossible now may be attainable for the future. With what we have right now, new mass extinctions seem unlikely, but not at all impossible. It would not be surprising to me if a new mass extinction was found, I just don't know how we would go about finding it.
In response to the Algeo paper, seed formation and the dispersal of plant life further inland seemed to be a huge step. Not only did this affect the soil, climate, and marine life, but it also extended a food source and created newly (or differently) habitable areas. However, if seed formation had never occurred, I find it hard to believe that the niche would have never been filled. I believe plants and/or animals would have evolved to have different tactics to colonize the inland areas. Who knows, perhaps they tried and were out-competed by seeding plants and the critters that followed!
In answering the question to the Raup paper, I believe we maybe able to tell if there was a mass extinction to organisms that do not meet the requirements to produce a fossil by studying the changes in organismal diversity before, and after a mass extinction. We may be able to identify what organisms may have gone extinct by tracing a lineage that may have evolved from the extinct organism, or the ancestors they are descendants from. But, to fully tell the total amount of species that have gone extinct I do not believe we will ever be able to tell the exact amount of extinct species.
ReplyDeleteThe most important development in plants during the Devonian would be the increase development in the root system, because plants are unable to move they need to be able to reach a water source, and find nutrients that support their growth and reproduction.
The most significant factor in linking marine ecosystems to terrestrial would be competition. The plants, and animals that move to land were most likely being out competed by lack of oxygen, and nutrition exposing a niche for these organisms to survive on land.
If the development of seeds, and arborescence did not occur earth's atmosphere would still be developing, temperatures would be warmer than they are today, which may cause animals to evolve at a slower rate.
Although the concept of a fossil is pretty easy to understand, having the requirements to become a fossil is pretty difficult. If the organism does not have hard parts, that organism can not make a body fossil and can only possibly make trace fossils. Even if the organism does have hard parts, the requirements to becoming a fossil include dying in a location where there is no oxygen, where there is no acidity, dying in the right sediment, and before all of this, being sure to not get eaten by predators. So being able to tell if there is a mass extinction with organisms that never became fossils would be difficult. The only way to tell if there were organisms would be through trace fossils, chemical fossils or true form fossils, which are the rarest of all the fossils.
ReplyDeleteBeing able to tell the total amount of species that have gone extinct would be impossible, in my opinion. As of today, we do not know all of the species that live on current earth, so the idea of being able to know the total amount in earth's history is implausible. I believe we could get estimates that are relatively close because we have the technology to do so but if some creatures did not leave any fossils, it would be difficult to even know they existed.
It was really interesting to read how plants evolved into the type of plants that we are similar with today. They had to evolve quite a bit. Having to choose the development that had the greatest impact is difficult because I believe they all worked in harmony. I think the most impactful would be the development of the seed. Before the seed, plants had to be in aqueous environments in which a sperm had to swim over to the egg, allowing them only to live in moist lowland habitats. After developing a seed, this allowed plants to disperse in various habitats because they no longer relied on the sperm-egg. This allowed plants to grow in highlands, deltas and other environments that would have otherwise been off limits. With this, also came diversification of the plants, which allowed for greater spread.
Raup paper response:
ReplyDelete-I don't think that there is a definitive way to tell if there are mass extinctions with organisms that don't fossilize. Because there is no physical evidence left by fossils for a number of past species, it is impossible to state that we as humans have an exact record of every living organism in the history of life. The fossil record is definitely able to give us insight on a larger scale, and we have more reliable information about animals that have fossilized. I think that this alone gives humans substantial data that allows us to connect the dots in terms of how history is aligned. Patterns and trends are important in knowing more about past organisms.
-As science becomes more advanced and research of fossils continues, I think that our knowledge of the fossil records will increase. We don't really know the limitation of where science can take us and what we can discover about the past.
Algeo paper response:
-I would agree with most of my classmates that the most impactful development would be the evolution and development of the seed. The dispersal and durability of seeds allowed for widespread plant growth which ultimately led to a higher survival rate for animals. Plants would provide animals with both a food and oxygen source, which was key to survival and development.
-The most significant factor linking marine and terrestrial ecosystems was probably competition driven processes. Evolution of marine animals towards land due to a higher demand for oxygen was a probable cause for this. Competition for food and other resources could have led to this linking as well.
-Earth would have looked quite barren if seed development and arborescence had not occured. Especially inland, where seeds dispersed to away from shorelines. Life would be limited because of more competition in areas with more plants, and the climate would be higher in carbon dioxide concentration lower in oxygen. This would not allow for the evolution of more terrestrial species. Marine species would be dominant and the marine ecosystem would be in a state of heavy competition for resources.
Re: Raup paper
ReplyDeleteI can think of a couple ways to suggest there was a mass extinction. One would be a sudden, radical change in the environment at the time, suggesting anything living would face severe hardships that would potentially drive up extinctions. This is obviously more speculative, however, since abundance and diversity aren't known. The only way we could know whether such critters existed would be via trace fossils or some sort of biomarkers that were left behind. However, I don't think it would be possible to know what species went extinct without some way of knowing they existed in the first place. Given the challenges involved in creating a fossil, it's reasonable to presume there are numerous creatures that have existed and gone extinct that we're completely oblivious to. Similarly, the more the fossil record is detailed, the more we should be able to determine the scope and range of extinction events because we will have a better idea of how long species were around and whether their disappearance from the fossil records coincides with extinction events that rise above the background rate.
Re: Algeo paper
I found this paper particularly intriguing because it outlined how developments that we take for granted, and depend upon, likely contributed to a mass extinction because of how radically they impacted contemporary ecology. Determining which development had the greatest impact is admittedly difficult. Clearly the adaptation of plants to a terrestrial environment had a massive impact, from vascularization, sunlight and CO2 processing, water retention, seeds, and altering the soil composition. Narrowing down developments beyond that get tricky and unnecessarily argumentative, since they all likely went hand-in-hand and collectively contributed to Earth's history. This impact is immediate in terms of mineral and nutrient transport and the proposed anoxia event, but also dictated how all future life evolved adaptations to the atmosphere and environment the plants were essentially colonizing. This also plays into the most significant factor linking terrestrial and marine ecosystems; the new/altered methods of water, nutrient, and mineral exchange re-shaped both environments in terms of their nutrient availability as well as potential new feedbacks such as runoff and the anoxia even that plagued water columns, choking off oxygen from the deeper organisms that hadn't yet adapted to the dangers of sunlight. Again, this dictated how all future life would evolve. Imagining how the planet would look without these developments is an interesting thought experiment. I'd suspect that the planet would be more akin to Mars: cold and with an inability to retain a significant atmosphere, leading to more impact events without an atmosphere to burn up or reduce the bolides. Water would probably become trapped in polar and surface ice, with whatever life being microbial and relegated to the depths.
Unfortunately without any fossils, it would be very difficult to tell if there was a mass extinction with organisms that do not meet those fossil requirements. The easy way to answer would be to say to look for something else LIKE a fossil, just not the organism itself- such as a trace fossil. However, even with a huge amount of trace fossils, it would still be difficult to tell just what went extinct. So no, we would probably never really tell the total amount of species that went extinct, but at least we could make educated guesses and theories.
ReplyDeleteI am not completely sure if we might discover more mass extinctions- it is always possible, especially if we ever get access to new land mass via technology, but it is hard to say. The reasoning behind why I say this is that a mass extinction wipes out a lot of life, and life at that point needs time to build up again- there are only so many mass extinction events that could have ever happened, so who's to say it wasn't just 5? Or more, or even less if we have new findings. I really can't say.
However, it would be interesting if we could access more fossils, wherever they may be!
The greatest impact on how the earth was shaped for future time periods might be the fast that forests became large and impactful. The production of oxygen in the atmosphere paved the way for terrestrial life forms to flourish. Without the oxygen in the atmosphere, life may have ended up staying in the ocean.
Without seed development and plants being able to spread further and into harsher areas, we would have seen a huge lack of them. Plant life spreading led to a lot of oxygen production and the lessening of carbon dioxide in the atmosphere, leading to (relatively) cooler climate.
However, without the oxygen in the atmosphere, life may not have evolved the way it did anyway. All there really is to say is that without everything happening the way it did specifically, the earth might be completely different than it is now; however, it is very difficult to imagine, like asking a person to think of a new color.
Mass Extinctions in the Marine Fossil Record (David M. Raup. 1982)
ReplyDelete1) I don't think it would be possible to determine if I mass extinction event had occurred for organisms who do not meet the requirements necessary to become a fossil. The fossil record today is a collection of many organisms but there are always more being discovered. The process for an organism to become a fossil is not so easy because certain conditions need to be met as well as having it be preserved over long periods of time is also a necessity. I don't think we could ever fully tell the total amount of species that have gone extinct because not all organisms have a fossil record.
2) I don't think the chances of finding evidence to support that more historic mass extinctions had occurred is likely because we would need to find much more fossils in our research to distinguish the findings from just being a part of the background extinction events. Extinction has occurred throughout history and a lot of evidence would need to be found to support a claim of another mass extinction event.
Terrestrial-Marine Teleconnections in the Devonian: Links between the Evolution of Land Plants, Weathering Processes, and Marine Anoxic Events (Thomas J. Algeo. 1998)
1)I would pick the development of the seed as having the greatest impact on how the earth was shaped for future time periods to come because it allowed new dispersal ways in which the seed could travel and find areas in which there were not a lot of other plant species present. It would allow the plant to have less competition for resources and allow it to flourish. Also, the seed also allows the plant to survive in other conditions, such as a fire.
2)I think the most significant factor in linking terrestrial and marine ecosystems is looking at how the smaller shrubs were able to inhabit the ground and allowed formation of microenvironments to happen. These shrubs helped the soil become more rich in nutrients and allowed more plants to grow larger in other areas, allowing them to survive for long periods of time. If seed development and arborescence would not have occurred I think the Earth today would look pretty similar. I think that there wouldn't be trees or forests but rather something else like Fungus species could be dominate which could influence what organisms (maybe we would have more hybrid organisms) evolved or even how we as humans would have evolved. As far as our climate, the types of components in which dominate the air today could be different: we might not have as much oxygen in the air which could limit the amount of organisms in which could populate the Earth over time.
In regards to the Raup paper, in order to tell if there was a mass extinction with organisms that did not meet the requirements, I would have to say one would need to look at the geological record looking at other groups that were similar to those that were suspected to have a similar anatomy, and guesstimate on how many species could have been lost. Though there is no real way of knowing how many species were really lost, in other words the geological fossil record will always be incomplete. There will never be a way to know what was living millions of years ago. I think the chances of finding more mass extinctions may be very slim due to the fact that there are a wide variety of species that do not meet the requirements to become a fossil. Unless scientists and others come up with a way to detect these undetectable species then we many never find other mass extinctions.
ReplyDeleteDuring the Devonian, I would have to say that the best development would have to be the ability to have plants on land. Allowing for oxygen and other needed organic compounds needed to sustain life. This was a huge event that changed the upcoming time periods allowing for a change in diversity on land, and even more in marine fauna.
Raup et al. 1982
ReplyDelete1.) If species cannot be fossilized, then we cannot identify whether they even existed. Therefore, we could never question whether or not a mass extinction occurred in the unknown species. In my opinion, we will never be able to tell the total amount of species that have gone extinct because some species may have not left any indication of their existence.
2.) I think the likelihood of finding evidence of more mass extinctions is unlikely. The reason being is that though we lack a fair amount of material in the fossil record, it still isn't that bad. If there were other mass extinction, especially if the criteria for a mass extinction must meet a 75% die off of species, we would have probably already seen it.
Algeo et al. 1998
1.) I would propose that seed dispersal had the greatest impact on how the earth was shaped for future time periods. The reason why is because it allowed life to extended further and further onto terrestrial environments. More dispersal meant a great abundance of vegetation which ultimately helped with increased oxygen concentrations in the atmosphere. Increased atmospheric oxygen allowed for more life to evolve and diversify, leading to marine organisms inhabiting terrestrial habitats.
2.) The most significant factor linking terrestrial and marine ecosystems was nutrient cycling. As vascularized plants invaded land, their roots broke up rock and exposed hidden nutrients. Eventually, these nutrients found their way into stream, rivers, and eventually the oceans. The increased nutrient loads into the oceans may have caused massive marine extinctions but it also allowed for marine organisms to diversify and possibly, force them out of a system that was unsafe (anoxic conditions from algal blooms; possibly a reason for fish to evolve to terrestrial animals?).
3.) If seed development did not occur, the landscape would look bare like Mars. I think the climate would have been arid and hot. Eventually, I believe animals would have evolved, but in a different way than they did before. They would have evolved into more rugged creatures is my guess.