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Why was the the complete digestive system a major innovation? What was the selective pressure? What were its 2 advantages?
Major innovation since it increased digestive ability and efficiency in animals.
The complete digestive system allowed for more food to be consumed in a single opportunity. Unlike those animals with an incomplete digestive system, those with a complete digestive system could consume food while it was being digested. This was highly advantageous, especially in environments where food was scarce since it allowed more food to be consumed in a single opportunity.
It also allowed for more specialized digestive systems. Since food passed down the digestive tract in a sequential manner the digestive tissues could become more specialized since food was always encountered in a particular form in distinct regions. More specialized digestive tissues and structures allowed for more nutrients to be absorbed in less time making digestion significantly more effiecient.
The selective pressure was more efficient digestion
Why was the the circulatory system a major innovation? What was the selective pressure? What were its 4 advantages?
Major innovation since it allowed animals to overcome constrains on body size, adopt new body plans, efficient transport of nutrients and gasses, and more effective immune responses.
1. Animals could become larger and develop thicker tissues since circulatory system could deliver all gasses and wastes internally.
2. Animals could develop new body plans and structures that increased activity, protection, and predation since they no longer needed to conduct gas exchange through epidermal tissues, gastrovascular cavities, and flow-through systems. Internal and external structures could become more highly specialized since they did not need to also have the main responsibility of gas exchange.
3. The efficient delivery of oxygen allowed for higher activity to be possible. Active lifestyles require lots of energy and thus need lots of oxygen. The circulatory system made the exchange of gasses more efficient which was necessary for the increase in animal activity.
4. Animals could deliver more effective immune responses. Immune cells could be delivered directly to the site of infection for an increased immune response. This was not possible before the evolution of the circulatory system.
The two main selective pressures were the pressure to achieve larger body size, and the pressure to achieve more active lifestyles
Closed circulatory system, advantages and disadvantages
The closed circulatory system can deliver gasses and nutrients quicker since a constant pressure is maintained through blood vessels. Higher energetic cost to build.
Open circulatory system, advantages and disadvantages
The open circulatory system delivers nutrients slower since a lower pressure is maintained. However it costs less energy to build.
Why was the the respiratory system a major innovation? What was the selective pressure? What its 4 features across the independent evolution?
Major innovation since it allowed for more efficient gas exchange which was crucial to attaining more active lifestyles and larger body size.
1. Vascularized. The respiratory system has to be associated with blood vessels
2. Living and Moist. The coating of the respiratory system has to be moist in order for oxygen to be absorbed into the cell.
3. Morphology that increases SA. The morphology of the cells and structures in the respiratory system have to be of a design that maximizes surface area.
4. Positioned in a protective place. The vascularized structures that maximize SA for gas exchange are usually very fragile. Thus either the animal lives in a protected habitat or the animal has structures that protect the respiratory system.
Why was the the coelom a major innovation? What was the selective pressure? What were its 4 advantages?
The coelom was a major innovation since it allowed for support, circulation, held organs in place, and allowed for space for organs to develop.
1. The coelom allowed for a hydrostatic skeleton that could be pressurized to provide support in small to medium sized animals. This allowed for point of muscle attachment as well.
2. In some animals the coelom served as a circulatory system. The inside of the coelom is ciliated so this would allow the fluid to be circulated around. Thus, it served the functions of a circulatory system.
3. Mesentries held organs in place. The mesenteries of mesodermal origin held organs in place. This was an advantageous function since the organs would not be damaged as easily.
4. Space for organs. Since the organs were able to develop in fluid it allowed them the space to become more complex. This allowed for the digestive system, the coelomic organs, and the body wall to become more specialized. Since there was now space the digestive system could become more muscular, the body wall could become thicker and more rigid, and the coelomic organs could become more specialized. Since they were suspended in fluid. Also since the internal organs were suspended in fluid it made them less susceptible to damage.
Why was the molluska shell a major innovation? What are its advantages? What are the disadvantages?
The molluska shell is major innovation because it provided structure, protection, and
-The molluska shell provided structure for the body and
-served as a point of attachment for muscles. This was a huge advantage
-The molluska shell was covers most of the body and allowed for the internal organs to be protected which was a major advantage
-The molluska shell was energetically is costly produce
-The shell is quite heavy so it requires lots of energy to move with the shell
-The shell is hinders mobility in tight environments. The shell is large and oftentimes makes it difficult for the mollusk to move in the environment.
What is the advantages of spiral shells in the molluska?
Spiral shells are able to contain more of the body.
Spiral shells have less of a footprint which allows for better motility
Spiral shells have less suseptibility from forces in the environment
Why are conispiral shells better than planispiral shells?
Conispiral are stronger
Less susceptible to forces since they are lower.
What is the unique innovation of the Scaphopoda?
The capitula can be extended to capture food
Why was torsion a major innovation in the gastropods?
-the mantle cavity to be in the front of the body
-allowed the animal to have the oshphadium which is the chemosensory structure in the front fo the body. This allowed for a better detection of chemical stimuli.
-The gills were found in the front of the body which allowed for better control of the flow of water flowing into the gills.
-Torsion allowed for a better centre of gravity.
What was the innovation in the aplocophora? What did it allow?
The aplocophora had no shell and a vermiform body. This meant that there was less weight, less of an energy investment, and more motility.
What was the unique synapomorphy of the cephalopods, which other traits made them so successful?
The cephalopods have a modified muscular foot that allow allow for locomotion, adhesion, and food capture. They also have highly advanced nervous systems, a closed circulatory system, which is the only of its kind in the molluska, and a streamlined body. The dorsal was flattened to become the posterior and the ventral was the anterior. These traits all optimized the cephalopods to become highly effective predators with very active life.
What is segmentation? Why was segmentation a major innovation for those with vermiform bodies (3)? What are its advantages? What are the disadvantages?
Segmentation is the repetition paired structures of mesodermal or ectodermal origin. Segmentation was an innovation that was a result to live more active lifestyles.
1. Segmentation was a major innovation because it allowed for independent body movements. The repeated muscle structures and appendages allowed for more control of body movements since small muscles could be contracted and relaxed instead of just one or two large muscles
2. Segmentation was also an advantage because the repetition of structures meant that if one was damaged there were others that could take over the function. This allowed the organisms to survive better.
3. Segmentation allowed for more powerful movements. In vermiform worms that utilized peristalsis segmentation allowed for the coelom pressure to be localized resulting higher pressure localized in specific areas.
What is the downside to segmentation?
One larger structure that performs a function is more efficient than many smaller structrures which all contribute to do the same function.
Segmentation evolved four separate times.
1. Phylum Molluska: Monoplacophora
2. Phylum Annelida
3. Panardthopoda- 3 phyla in this phylum have segmentation
4. Phylum Chordata: only one phylum in the chordata which gave rise to the cephalachordata and vetebrata. Segmentated internal structures passed from ancestors.
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