In Chapter 7, Neil Shubin remarks that sponges are an "interesting" specimen, with its body consisting of silica and collagen. Even though their body structures are relatively simple, Shubin explains that their body reveals much about our own bodybuilding apparatus. Its cells have a division of labor, the cells can communicate with one another, and the array of cells function as a single individual, much like our human body. In this way, Neil Shubin emphasizes the possibilities of discovering our past through observations on other organisms.
Recall the Invertebrate and Vertebrate Unit:
Compare and contrast Vertebrates and Invertebrates.
What greatly differentiates us(vertebrates) from invertebrates, such as sponges?
What similarities do we share with invertebrates?
Consider the theme of Evolution:
What are specific structures/mechanisms that only vertebrates have developed?
What are specific structures/mechanisms that only invertebrates have developed?
Why was the development of these structures/mechanisms necessary to survive?
(Keigo Tanaka; tanakarus3@hotmail.com)
Invertebrates account for about 95% of known animal species on Earth. The massive variety of invertebrates means that there is a large amount of diversity among invertebrates since they have evolved for different conditions. Invertebrates are much older than vertebrates. The major phyla we studied are Cindarians, Calcarea and Siliceans, Platyhelminthes, Rofitera, Mollusca, Annedlida, Nematoda, Arthropoda, Echinodermata, and Chordata (Campbell 669). Each of these phyla is unique, but they also share common characteristics. All invertebrates have no spinal column or backbone, all are eukaryotic and don’t have cell walls. Without a backbone, most invertebrates cannot grow immense in size because they do not have the support and the nervous system requirements, although the giant squid is an exception. The giant squid also defies the fact that invertebrates are generally slow creatures because fast creatures need good support systems and a good oxygen delivery system, and most invertebrates have an open circulatory system, which wouldn’t work very well for that (Interesting Animal Staff 3).
ReplyDeleteVertebrates are different from invertebrates in many different ways. Vertebrates have neural crest cells, increased cephalization, a vertebral column, and a closed circulatory system for efficient energy exchange. All vertebrates also have a group of transcription factor genes called the Dlx family (Campbell 704). Because of the increasing complexity of vertebrate body plans, it can be inferred that a wider variety of genes started to emerge as well. The new genes probably emerged as a necessity because of the more complicated processes and the need for different proteins to be created through transcription and translation of mRNA.
There are similarities between vertebrates and invertebrates as well, although there are very few. Both can move, both are heterotrophs, both reproduce sexually, and both are found in a variety of environments. Besides this, there aren’t many similarities since there are 23 invertebrate phyla (Campbell 666).
Unique to invertebrates is the gastrovascular cavity, which is a sac with a central digestive compartment. This is used to digest food and also to excrete wastes. It functions as both an anus and as a mouth (Campbell 671). Also unique to invertebrates is an open circulatory system. Arthropods have open circulatory systems. For example, insects use tracheal tubes to absorb oxygen form the air. The air is then absorbed by the blood, or hemolymph, of the insect. The blood throughout the insect is partially oxygen-rich and oxygen-poor. Also unique to insects are the Malphigian tubules. These remove wastes from the hemolymph.
One ability unique to vertebrates is the increased ability to regulate systems. Vertebrates maintain homeostasis through a variety of unique mechanisms. Some use countercurrent exchange to maximize the diffusion of oxygen and carbon dioxide. Countercurrent exchange means that blood flows in opposite directions to exchange heat, keeping the oxygen-rich blood and oxygen-poor blood at similar temperatures (Thompson 7).
These mechanisms were developed in response to stimuli throughout the history of these animals. As a result, the animals with a certain selective advantage would survive and pass on their genes, and the gene pool would be slightly “improved” for the living conditions that the population lived in. Over time, these traits became exaggerated, and eventually became selective advantages for the species, so the species survived better with this trait, and the trait was passed on more and exaggerated more until the entire population had the trait. This evolution of certain traits are necessary to survive because of the constant stresses put on animals by the environment and other animals. Without constant adaptations, many species of animals wouldn’t be able to survive.
benitorosenberg12@comcast.net
http://www.interestinganimals.net/characteristics_of_invertebrates/characteristics_of_invertebrates.html
http://163.16.28.248/bio/activelearner/44/ch44c6.html
The first known specialized forms were the invertebrates. (Shubin 121) Therefore, it can be expected from the appearance of the first invertebrate to vertebrate, many characteristics would evolve and many differences would form. The main differences between Vertebrates and Invertebrates is the development of a backbone in vertebrates. All invertebrates are relatively small. This may be attributed to more primitive exchange systems, such as the open circulatory system, and in some cases, the lack of a proper digestive system in favor of directly absorbing nutrients from the source (Campbell 666)
ReplyDeleteSimilarities include specialized cells to make up existing systems (vertebrates contain more specialized cell than their invertebrate counterparts, but there is still specialization present in both organisms) as well as the start of cephalization in some invertebrates which became more defined and common in vertebrates.(Campbell 674) (http://animalkingdom.net/category/invertebrates/)
Through evolution, or continuity and change, both invertebrates and vertebrates developed unique characteristics to help them survive in their environment. One such example is radial symmetry, displayed in some species of invertebrates. This would make reproduction less energy consuming as it would allow a part of the organism to break off and form another separate organism, with the drawback of less genetic variation (http://www.geodakian.com/en/70_Asymmetry_en.htm) while a characteristic seen only in vertebrata would be the development of fully specialized and organized organ systems
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ReplyDeleteBoth vertebrates and invertebrates are a part of the phylum Chordata. As explained in Chapter 34 of Campbell, chordates are bilaterally symmetrical and contain a notochord. Thus, vertebrates and invertebrates are bilaterally symmetrical and contain a notochord. However, all vertebrates are deuterostomes and are formed anus to mouth during development. Only two groups of invertebrates are deuterostomes, the cephalochordates and the urochordates (698). Also, a main difference between invertebrates and vertebrates is the presence of a backbone within vertebrates. Vertebrates also contain a highly developed brain and an advanced nervous system (http://www.diffen.com/difference/Invertebrate_vs_Vertebrate). Thus, vertebrates are more developed as well as more complex. Invertebrates on the other hand have developed many different structures in different phylum. For example, Arthropods contain “segmented bodies, hard exoskeleton[s], and jointed appendages” (684). Jointed appendages allow for more flexibility and a greater range of motion for organisms with hard exoskeletons. With the evolution of jointed appendages arthropods were formed. Jointed appendages were necessary in helping the hard exoskeleton organisms to move. Without the jointed appendages, it would be hard for the organism to go about daily functions such as finding food because the organism would not be very flexible. Another example is the Cnidarians which contain 2 stages, polyp and medusa. The polyp stage contains an advantage because the polyp stage is the sessile stage of the cnidarian. Because it does not move, it is less likely to be chased by a predator and eaten. Also, Cnidarians contain nematocysts which aid the cnidarian in catching prey and food. Without nematocysts, cnidarians would be unable to catch food by stinging their prey. Nematocysts provide Cnidarians a way to live life easier because the nematocysts make it easier to catch food. Evolutionarily, vertebrates and invertebrates have advanced in a manner that allows for a more efficient and sustaining life style.
ReplyDeleteSources:
http://www.diffen.com/difference/Invertebrate_vs_Vertebrate
Campbell
Matt Micucci (coochqbk@sbcglobal.net)