Christopher Long Biology I Mr. Snyder December 20th, 2008
Natural Selection Lab Determine how natural selection acts on the color and size of a moth. Materials you will need: ! ! ! !
An environmental tray with a dark interior. An environmental tray with a light interior. One set of moths with nine varying intensities One set of various sized squares
1. Find a partner, and unpack two boxes, your squares, and your moths. Put the squares in the lighter box, and the moths in the darker box. There should be two people in each group, and all materials should be set up. 2. The members of each groups should take turns with each other, removing five squares at random, recording their size, and replacing them in the box. Once this is finished, they should do likewise with their moths. 3. The groups should then switch boxes, and perform the steps in #2 to the new boxes. Once a groups has recorded information from three boxes, they may cease working. Data: 1. The selection of moths with various intensities. White Number Selected
3
Total Class Count
25
Grey 4
2
2
59 16 14
Black
0
0
0
1
4
26
9
7
27
41
2. The selection of squares with various sizes. 1/2
3/4
Number Selected
5
0
Total Class Count
32
1
1
5/4
6/4
7/4
2
0
0
3
4
1
2
53
10
3 100
Study Questions: 1. If the rows of colored moths or different size squares are arranged in a single file from white to black or small to large, is there an equal number of object on either side of the middle object? !
Yes
2. Looking at the class data for which colored moths were selected, did the class select more lighter colored moths or more darker colored moths? !
More darker colored moths
3. How would you explain the class results? !
Lighter colored moths stand out more in the experimental environment chosen.
4. Looking at the class data for which different sized squares were selected, did the class select more smaller–sized squares or more larger–sized squares? !
More smaller sized squares.
5. How do you explain the class results? !
Experimental error.
6. Imagine that most of the trees in a forest of over 100 years ago had bark that was light in color. In addition, some of the birds in this forest fed on moths. What kind of moth would be eaten by birds more frequently? Explain why. !
Moths with darker colors, because they stand out.
7. If uneaten moths mated, what color offspring would tend to have a few more of? !
Lighter colored offspring.
8. Further imagine that after a number of years, the nearby city became more and more industrialized. Smoke poured out of the chimneys and settled on the tree trunks. What happened to the color of the tree trunks as time progressed? !
The trunks darkened.
9. What kind of moth would be eaten by the birds more frequently? Explain why. !
Lighter窶田olored moths, because they stand out more against the environment.
10. If uneaten moths mated, what color offspring would tend to have a few more of? !
Darker colored offspring.
11. As the years continued the trees became darker and darker. If the surviving moths of each generation were to continue to mate, what do you think in time would happen to the entire population? !
Lighter窶田olored moths would die out, and the entire population would become dark.
12. You might say the moths evolved from one color to another. What caused the change to take place? !
Environmental change occurred
13. To summarize, you have learned that individuals differ. Because of these differences, some will have a better chance of surviving. What differences give some individuals a better chance of survival? !
Traits better suited for an organism to survive in its environment.
14. It should be pointed out that there may be many differences that help an organism survive. A more favorable structure is not the only reason. Those that survive live to give birth to young that are more similar to the parents. This idea was observed, studied, and proposed, by Charles Darwin. He called it the Theory of Natural Selection. Some people also call it survival of the fittest. According to Darwin, what was nature selecting? !
Genes more favorable to an organism's survival.
15. The giraffe survives by eating leaves off of trees. The giraffe did not get its long neck by stretching its neck to reach taller and taller leaves. (as proposed by Lamarck). Using Darwin's theory, how would you explain how the giraffe got its long neck? !
A long neck is more conducive to the survival or giraffes. Thus, organisms with genes for this trait had a greater chance of survival, and gave birth to more live young.
16. In summary, according to Darwin, what kind of an individual survives? !
The individual most adapted to its environment.
17. Is the case of the peppered moth an example of microevolution or macroevolution? Explain. How could this example be used to illustrate macroevolution? !
Microevolution, because only color is changed. Furthermore, if steps occur on small scale, there is no reason why they cannot occur on large scale.
Christopher Long
The Clam Kingdom: Animalia Phylum: Mollusca Class: Bivalva Genus: Mya Species: Arenaria
I. Purpose: The purpose is to examine the clam internally and externally by dissection. II. Materials: 1. 2. 3. 4. 5. 6. 7.
Dissection tray Clam Dissecting Needle Dissecting Probe Scissors Forceps Scalpel
III. Methods: A. External: The dissector carefully looked over the clam, noting the tannish white color of it's dual sided shell, and the small growth lines on the surface, a long distance between which indicated that his clam had experienced an extended period of growth, before his eyes moved on to the white umbo, oldest part of the exterior, which appeared on either side of the shell. He turned the shell so that the umbo was to his left, and the opening of the clam was to his right. He then identified the anterior, which was pointier and longer than the posterior, which he identified by it's rounded end shape, and closeness to the umbo. As he touched the clam, he noted the rough texture of the exterior, and it's hard, rock-like surface. Next he identified the dorsal side of the animal, which judging from the location of the umbos, the anterior and the posterior, was the side he was looking at. He briefly turned the clam over, to look on the ventral side, and after he realized that the coloration was lighter, flipped the clam back to it's original position, and examined the hinges and ligament of the clam, nestled all along the space between the umbos, which were extremely dark, and green colored. Their texture was smooth, but felt a little scraggly. Nothing more was observable to him, so he sat the shell down, and prepared to examine the interior. B. Internal: The dissector dissector easily pried open his clam, whose adductor muscles were not strong enough to make a scalpel necessary. He carefully opened the shell, without affecting the clam, and examined the pearly layer of the shell, which was white in color, somewhat soft, and much smoother than the horny layer he had observed on the outside. He then cracked off a piece of the shell, so that he could observe e prismatic layer within, which was thicker than the pearly layer or the horny layer, and between the two in coloration. After he finished, the dissector removed the clam from it's hold on the other half of the shell, and examined both sides. All it's organs were covered entirely by the mantel, a dark-brown, smooth–textured material which excreted shell, and had been attached to the shell at the edges, before he detached it. The dissector, who desired to see past it, carefully detached the mantle from all organs on the clam's body, using a scalpel, and assorted tools. When he did so, a torrent of aqueous, pearly colored hemocoel, used in the animal's circulatory system, poured out of the shell. Next, the dissector examined the clam, and noted the major organs. Immediately, he examined the adductor muscles, located at each end of the clam, which looked like raspberry textured, dark pink circles, the anterior of which was slightly larger, and more circular than the posterior. He then began to inspect the clam's pair of gills, located at the ventral, and centered evenly between the the anterior and posterior. They were each slightly larger than an umbo, and hued a light yellow-brown. The ridges on their surface, used to increase to area for gas exchange were clearly visible, each consisting of several flaps of tissue. Alongside and slightly posterior to the them, the dissector could see the incurrent siphon, used to ingest water and small animals, located ventral to the gills, and the excurrent siphon, used for waste removal, located dorsal too them. Both siphons had a ridgy texture, and were black in color. The dissector then carefully removed the gills with a scalpel, and examined the visceral mass, murky green colored and smooth, that were attached to the shell primarily by the foot, which fit neatly into the shell. At the posterior of the clam, the dissector could see a small, red-colored mouth, well protected by two palps of the visceral mass's color, and to the anterior, he could see the anus, a small opening of darker color, but no different texture. Posterior this ran the rectum, of the visceral mass's color and texture. The dissector then extracted the foot from the shell and observed the black-lined hole through which it fit. At last the dissector sliced the visceral mass in half with a scalpel. Inside, he could see the translucent,
white-colored intestine, which connected to the stomach, and ran throughout the visceral mass, and the remains of the stomach, that was interior and connected to the mouth, and whose color and texture was unobservable. The dissector could not find observe the coelom, heart, nephridophore, gerital pore, or any of the ganglions, as they were to small, or destroyed in dissection. The dissector, after not locating these, found the gonads, which were green in color, and mushy in texture, distributed throughout the interior of the visceral mass. Finally, he located the digestive particles, located throughout the visceral mass, of mushy texture, and pale coloration.
IV. Observations: A. External Anatomy of a Clam
IV. Observations: A. External Anatomy of a Clam
V. Conclusions: 1. Why are clams called Bivalves? Clams are called Bivalved because their shell is divided into two halve divided by a valve 2. What is the function of the mantle? The function of the mantle is to secrete the clam's shell, and protect the visceral mass. The mantle also secretes nacre. 3. Describe the path of water through a clam. Water enters a clam through the incurrent siphon, and then proceeds to minute openings (or ostia) which line the gills. Lamellae (the many folds and ridges which make up the gills) eventually lead to the cloacal chamber, that empties out throughout the excurrent siphon. 4. Describe the filter-feeding process of a clam. The surface of the gills, mantle, and visceral mass are lined with cilia that beat in a coordinated manner. This movement causes water to enter the mantle cavity through the incurrent siphon. Along with water, zooplankton, phytoplankton, and organic detritus are carried into the mantel cavity. As the continuous stream of water passes along and through the gills, food particles become entrapped in the mucus that lines the surface of the gills. The food laden mucus is driven to the labial palps where the indigestible mater is separated and the food carried off to the mouth. The rejected material is moved to the mantle edge of the clam shell and expelled out the clam. 5. Which organs play a part in the digestive process of a clam? (answers in bold below) Food ingested through the mouth passes into the stomach. Here the food is broken up into fine particles and mixed with a digestive enzyme. This is accomplished by the rod-like organ within the stomach called the crystalline style. Digestible food particles are swept into the digestive gland that surrounds the stomach. Indigestible food particles are swept into the intestine. 6. Describe how clams reproduce. Generally, when clams reproduce, eggs are lodged in the gills while sperm is released into the surrounding waters via the excurrent siphon. Water carrying sperm passes through the gills and fertilizes the eggs. Early embryonic growth occurs here. When embryos are large enough they are passed on to develop independently of the parent. 7. Describe the nervous system of a clam. Clam's have three pairs of connected ganglia, each pair of which is a source of nerve fibers that lead to adjacent organs. There is also a pair of minute sense organs which detect changes in equilibrium called statocysts, located posterior to the pedal ganglions. 8. Describe how a clam uses its foot to move. In order to move, the clam extends it's foot, and then expands it, to form and anchor. Then, the clam allows it's body to move forward, pulled by the extended foot. The clam then retracts its foot, or continues to move. 9. Describe the development of the freshwater clam. The fertilized eggs of the clam develop within the gills of the female and become larval clams known as glochidium. The larval clams superficially resemble their parents with two chitinous halves joined by a hinge. These halves are held together in an open position by a single adductor muscle. The open end of the valved have teeth which are hook shaped. When the glochidium reach a particular size they are expelled by the parent into the surrounding waters. Here the larva either sink to the bottom or become suspended in the water. In either case the glochidia remain with their valves gaping waiting for a fish to brush against them. The larva are sensitive to their fish host and clamp tightly onto any superficial fish tissues they touch. If the larva do not attach themselves to a host
within a few days of leaving their parents they die. When the glochidia is attached to a fish the tissues of the the fish soon grow around it. During this encystment the larva undergoes marked changes and the adult organs are formed. After a period of 10 to 30 days the young clam breaks free of its host, falls to the bottom and begins the juvenile phase of its existence. The juvenile phase lasts until the clam becomes sexually mature in one to eight years. 10. Briefly summarize your experience your experience in one paragraph. My experience of this dissection was as good as I think any dissection could be, and although I admittedly dislike dissecting in general, everything went very well. The only way it could have been a better was if the clam was much larger, and all the organs were visible. Before the dissection began, I was worried that it would feel like I was dissecting a mammal, but once it started, I felt more as if I were taking apart a rubber toy, laced with water. I can't really say whether that's a good thing or not, but it certainly is strange. Ultimately, despite perfect instructorial care, I can't say I look forward to the next one— and I hope that I never have to dissect a creature who's flesh looks human, but I can say this: I experienced a pleasant thrill from using an instrument so precise as the scalpel, and I am glad to have had the experience.
Christopher Long
The Earthworm Kingdom: Animalia Phylum: Annelida Class: Oligochaeta Genus: Lumbricus Species: terrestris
I. Purpose: The purpose is to examine the Earthworm internally and externally by dissection. II. Materials: 1. 2. 3. 4. 5. 6. 7. 8.
Dissection tray Earthworm Dissecting Needle Dissecting Probe Scissors Pins Forceps Scalpel
III. Methods: A. External: The dissector began by measuring the worm, which he determined to 25 cm, and estimated the worm to be about 130 segments long, he performed a general bodily analysis of the worm. First, he located the clitellum, a smooth-textured light pink organ, located about 5 cm from one end of the earthworm, which he then determined to be the worm's anterior. He used his dissecting probe to briefly analyze the mouth, a small opening at the anterior, before he examined the anterior parts of the worm as a whole. He noticed that the anterior end of the worm was somewhat conic in shape, by comparison with the posterior, that was slightly flattened, and that the coloration tapered from dark brown on the anterior, to medium-grey at the posterior, where the anus, a small opening at the anterior was located. He then examined the anus of the worm with his dissection probe, and began to perform a general analysis of the the worm's dorsal side. The worm was segmented, and the texture was bumpy, however the animal was covered in a thin, translucent cuticle, which secreted mucus to protect the worm. With his dissection needle, the dissector scraped a small part of the cuticle on the worm, and observed it, before he noted the dorsal blood vessel, which ran underneath the worm's skin from the top to bottom, along it's center. The dissector than turned the worm over, and examined it's ventral side, which was sicklywhite, and slightly flatter than the skin of the front. About 15 segments down the worm, he could see two small sperm vents, at running diagonally into the worm's body, that were used in reproduction. Next the dissector brushed his finger over the edges of the worm, and felt something bristly, that he reasoned to be the setae. Having nothing further to observe, the dissector turned the worm over, and prepared to begin his dissection. B. Internal: The dissector began by placing one of his pins into the dorsal-posterior of the worm, and then placing the other three segments from the anterior of the worm. Next, he counted five segments down from the clitellum, and placed a final pin. After the dissector fasted the worm to the dissection tray, he proceeded to make an incision with his scissors, starting at the segment immediately behind the clitellum, and passing through to the segment three from the anterior. He could observe a small amount of translucent, puseous-white colored body fluid, but not enough to hinder his observations. The dissector observed that the integument was still attached to the worm's body by small septa on the interior of the worm's body. The dissector held the sides of the earthworm apart with his forceps, while he used his dissection needle to sever the septa from the integument. The dissector then pinned the earthworm's integument to his dissection tray, observing that its interior was pale white, and began to observe the earthworm's coelom, starting at the posterior most part he had dissected, the intestine, a protracted organ that was blackish in coloration, and bumpy in texture. Using his scalpel, the dissector made an incision along the length of the intestine, and carefully observed the interior. He could see the intestine's black typhlosole, responsible for augmenting digestion, which was normally held aloft in the intestine, as well as green food particles undergoing the process of digestion. Anterior to this the dissector observed the gizzard, which was much harder and larger than the intestine, and colored lighter grey, and the crop, which was slightly smaller than the gizzard, softer than it, and located anterior to it, but otherwise shared the same traits. To the anterior of this, the dissector observed both the large, tubular, seminal vesicles, and the smaller, less elongated, dot like seminal receptacles. Both sets of organs were smooth, white, and located dorsally of the five, circular, black aortic arches, which the dissector moved the reproductive organs aside with his dissection needle to see. Located underneath these, the dissector saw the tubular, grey colored esophagus, which connected the crop to the pharynx, a grey, muscular organ responsible–
for sucking earth into the worm's body through the mouth, to which it connected. The dissector then examined the dorsal blood vessel, a small, black tube which ran the worms length, over the dorsal side of the organism. It was connected by the aortic arches to the ventral blood vessel, an organ on the ventral side of the organism, which the dissector analyzed immediately thereafter, and found to have the same properties. After he examined both the ventral and dorsal blood vessels, the dissector examined the worms nervous system. The dissector first observed the very small, white, ventral nerve cord, which ran the length of the worm, that the dissector observed to be connected to the integument. The dissector followed the nerve cord this to the anterior end of the organism, where, in the top two segments, it suddenly expanded, ventral to the mouth, and formed the cerebrial ganglion, which was white in color, bumpy and texture, and extremly small. Finally, the dissector located the slits he had seen on the interior, called spermal vents, ventral to the clitellum. The dissector then ended the dissection, as there was nothing left to examine.
IV. Observations: A. External Anatomy of an Earthworm
IV. Observations: B. Internal Anatomy of an Earthworm
V. Conclusions: 1. List the characteristics shared by all annelids. The characteristics shared by all annelids are that they have a body divided into segments or metamers know as somites, display well developed cephalization (sense organs concentrated at anterior or “head” end, an elongated body, and a closed circulatory system with hemoglbin and amebocytes. 2. What is the function of Setae? Setae are briscles located on the ventral side of the body which are asscociated with muscles that can push them out or retract them, and aid in providing traction for locomotion. 3. What is another name for the body segments of an earthworm? Another name for the body segments of an earthworm is metemeres. 4. What is the function of the Clitellum? The clitellum is a glandular organ that produces mucus for copulation and secretes the cocoon into which the eggs are deposited. Eggs emerge from paired oviducts, small opening on the ventral surface of somite 14. Sperm ducts are on somite 15. 5. How many hearts does an earthworm have? There are five pairs hearts, named aortic Arches, located around the esophagus from segments 7 to 11. These arches pump blood throughout the worm in a closed circulatory system consisting of the large dorsal and ventral blood vessels, connecting vessels and capillaries. 6. Describe the process of digestion in an earthworm? Food is taken in through the posterior of an earthworm, at the mouth, sucked in by the muscular pharynx, and then transported a short time along the esophagus, until it reaches the crop, a thin walled swelling in which food is stored temporarily before entering the gizzard. After this, the organ enters the gizzard, a muscular organ that uses particles of soil to help grind up food for digestion, and then passes into the intestine, a long tube where food is digested, and nutrients absorbed. Finally, indigestible matter is excreated from the posterior of the animal through the anus. 7. What is the function of the typhlosole? The typhlosole is a ridge or fold hanging inside the intestine from the dorsal side. It enlarges the surface area of the intestine which increases the efficiency in absorbing food. 8. What is the term given for the slowing down of an earthworm's bodily functions? Soil moisture is an important factor in determining good earthworms habitat. Earthworms have no respiratory organs. They obtain oxygen by diffusion through their moist skin. When the skin dries, oxygen cannot diffuse into the worm, causing death. Earthworms have adapted to survive moderately dry soil periods by slowing down their body functions in a period know as diapuse. As much as 70% of the worm's body fluid may be lost during this period before it dies. If the worm survies the dry period, it can quickly reabsorb water and resume activity. 9. Distinguish the different families of class oligochaeta. The members of the family Aeolosomatidae are microscopic oligochates which are exclusively fresh water worms. They reproducer aesexualy and feed on algae. The family Tubificidae contains the tubifext worms (sometimes called “bloodworms due to their bright red pigmentation”) that are popular as fish food. These fresh water worms can be seen on the muddy bottoms of ponds and streams and occur in large wiggling clumps. Tubifex worm wave their cranial ends back and forth collecting floating–
detritus which is then ingested. The family Enchytraeidae includes both aquatic and terrestrial species. They are up to 25mm long, and are whitish in appearance. The relatively common Enchytraeus albidus live under debris along the seashore. 10. Summarize your dissection experience in one paragraph. My dissection was remarkably successful, and far easier than that previous, yet at the same time, had a larger disgust factor. On the one hand, all of the internal organs were easy to locate, and I could observe the body process's of the worm with great detail (including setae, which were intriguing to the touch), and the body layout was clear, but on the other side, I found the similarities between myself, and this fellow terrestrial organism to be disturbing, especially in the layout of their digestive tracts, which followed a plan very close to our own. Ironic, I suppose, considering that mollusks are closer to us. With exception of a slight setback in time, and a few small slips of the dissection needle, everything else was alright, and in the end I certainly have no right to complain. Things went well.
Christopher Long
The Crayfish Kingdom: Animalia Phylum: Arthropoda Class: Crustacea Genus: Cambarus Species: s.p
I. Purpose: The purpose is to examine the clam internally and externally by dissection. II. Materials: 1. 2. 3. 4. 5. 6. 7.
Dissection tray Crayfish Dissecting Needle Dissecting Probe Scissors Forceps Scalpel
III. Methods: A. External: The dissector began his observations by measuring the length of his crayfish, and found it to be approximately 8 in. long, from the anterior to the posterior. He then flipped the crayfish to its ventral side, without making observations, and used his dissecting probe to probe the crayfish's anus, located at the posterior-most segment, called the telson, before flipping the crayfish once more, so that the dorsal side faced upwards. The dissector then examined at the segmented exterior of the crayfish, which was smooth, pink, shiny, and hard to the touch, but slightly flexible, and covered in small, translucent,sharp hairs, especially the edges of appendages. Located at the exterior of the organism was the largest segment, known as the carapace, that covered the entire cephalothorax of the crayfish, and at the animals anterior, spiked sharply, to form the conical rostrum. The carapace was dived by the line of fusion between the head and the thorax, and indention known as the survical groove. The dissector used his dissecting probe to carefully lift the side of the carapace, and observe the feathery, translucent gills, which it protected. Posterior to the carapace, the dissector observed the seven segments which composed the abdomen of the crayfish, five of which were similar to each other in appearance, but decreasing in size, followed by by one smaller, flatter segment, to which was attached the telson, which was paddle-like. Branching from the segment anterior to the telson were two pairs of uropods, shaped like the heads of a canoe paddle, that extended to either side of the telson, which he found spreadable. Both the telson and the uropods were extremely bristly. The dissector then turned to the anterior most part of the crayfish, and examined the long, segmented black antennae, which were rough to the touch, and rested below the rostrum, to either side. In between these, he could also see small appendages known as antennules, that were much thinner and shorter than the antenna, colored red, and smooth. Above both these pairs of appendages, immediately underneath, and to either side of the rostrum, the dissector could see two black, compound eyes, that rested on movable eyestalks. Next, the dissector observed the celipeds of the crayfish, that were thick, slightly rough appendages with approximately five joints, and extended horizontally in front of the organism. They were of white coloration on the ventral side, and ended in large pincers called celae at the anterior, which the dissector subsequently removed for measurement, and found to be about 1.5 inches in length, before he opened and closed them, noting that they were very inflexible, and covered in sensory hairs. The dissector proceeded to examine the four pairs of walking legs, located posterior to the chelipeds, that were much smaller, moderately shorter, and considerably more flexible then them, due to the presence of a varying number of additional joints, but like the chelipeds were white on the ventral side, and pink on the dorsal side. The first pair of walking legs ended in tiny claws, used to hold on to grasp small objects and the others were spike-tipped. All the crayfish's joints were translucent white in color. Next, because the dissector had fully observed the dorsal side, he turned the crayfish to its posterior, and began an examination of the swimmerets; five pairs of small, leg-like appendages connected to the underside of the first five abdominal segments, which due to being tucked in, indicated that the crayfish was a female. The dissector removed the swimmerets with his forceps, and observed that the underside of the abdominal sections was a stained, murky translucent color, and rubbery in texture, that rose in ridges in those areas where two segments met, and vanished into the cephalothorax. Through it, he could make out the thin, black, ventral nerve chord. The dissector then examined the posterior section of the cephalothorax, where the walking legs and chelipeds were attached to the body by large, gray, joints. It was of harder texture, and had a slightly varied, murky color. The dissector pulled both the legs, and the chelipeds from the cephalothorax with his forceps, and then moved to the anterior of the cephalothorax, directly posterior to the mouth, which he probed using his dissection probe. Here, the dissector could observe several pairs of maxillipeds, and examined them in turn. The dissector first examined the longest pair,
which bore a resemblance to the walking legs, possessing a pinkish color, much increased length, and a hard, jointed exterior, before he removed them with his forceps, and examined the second pair of maxillipeds, that were small, smooth, white, and of similar size and texture to the antennules. After removing them with his forceps, the dissector examined the final pair, which was similar to the second but slightly smaller, and removed them with his forceps. Now the dissector could see clearly see the small, murky colored, feathery appendages, of the maxillae, that were located on the head section of the crayfish, and covered the mouth. He removed them with his forceps, and finally, observed the pair of white, plaque stained mandibles, located on the lower jaw of the crayfish, each about the size of a human tooth. The dissector then prepared to examine the interior of the crayfish. B. Internal: The dissector the dissection by making a small incision with his scissors alongside the lower side of the sixth abdominal segment, about 1 cm from the gill line, and continuing to cut along this path until he was within 1 cm of the eye, before cutting horizontally to the other side, and then back the length of the crayfish. Once this was completed, the dissector carefully lifted the exoskeleton from both the cephalothorax and the abdomen, before using his scissors to remove the telson. The dissector then began his inspection of the interior, starting at the posterior. The dissector first observed the intestine, a thin, black tube which traveled the visible length of the crayfish to the anus, and the white, semitransparent, rubbery tail muscle that surrounded it on either side. The dissector then recognized that a long, very thin white tube known as the dorsal abdominal traveled dorsal to the intestine, for the depth of the abdomen, and vanishing into the cephalothorax. The dissector next lifted the tail muscle with his gloved hand, in order to examine what lay ventral to it, and in the process penetrated a slight remnant of the epidermis, a thin layer of semitransparent tissue which had covered the entirety of the organism, until much of it separated from the interior, when the dissector removed the exoskeleton, which upon seeing the tissue, he briefly examined, and found clear of anything notable. The dissector then located a small, white, ventral nerve chord, which akin the dorsal abdominal, also ran the visible length of the organism. Because the dissector could not observe anything further in the abdomen, he turned his observations to the cephalothorax, and examined the organs there. Firstly, the dissector found a large concentration of small, tapioca-like, orange-colored eggs, which broke into pieces on contact with a dissection probe, but were moderately firm. The dissector allowed them to remain, and examined the sides of the crayfish, attached to which were many overlapping, feathery gills of translucent tan color, that had been connected directly to the crayfish's legs. Next, the dissector removed the eggs, and then examined what lay ventral to them; a small, red organ, which due its connection to the abdominal artery, he recognized as the heart. The dissector then moved the heart to one side with his dissection probe, and upon examination of what was ventral to it, located the crayfish's gray, soft digestive gland, which ran under the intestine, and split into two spiky, white testes near the organ's posterior. Located anterior to this, the dissector could see a black, bulging, and soft to the touch organ known as the stomach, which filled most of the remaining anterior, and was connected to the mouth by a small, similarly colored esophagus. The dissector carefully removed the stomach, and observed the interior surface of the cepholothorax's interiors anterior, which consisted of a few muscles running vertically, a small remnant of the epidermis, and to either side, the gills, which he had already observed. Anterior to this cavity space, the dissector examined the mandibular muscles, two pairs of light-purple muscle concentrations that felt extremely dense, and anterior to those, he probed the crayfish's green gland using his dissection probe, and found it to be felt relatively soft. Ironically, the dissector noted that the green gland was tinted yellow. Finally, the dissector followed the ventral nerve cord to the brain around the two circumoesophagial nerves. The dissector removed it, and observed that it was a small white sphere of rubbery tissue located slightly dorsal, and anterior to the green gland. The dissector the ended his dissection, as there was nothing else to examine.
IV. Observations: A. External Anatomy of a Crayfish
IV. Observations: B. Internal Anatomy of a Crayfish
V. Conclusions: 1. Identify at least four animals that belong in subphylum Crustacea. Four animals that belong to subphylum Crustacea are crayfish, lobsters, crabs, and shrimp. 2. Identify at least three distinguishing characteristics of subphylum Crustacea. Three distinguishing characteristics of subphylum Crustacea are bodies covered by a chitinous exoskeleton strengthened with calcium salts, two pairs of antennae, and a pair of maxillae and of mandibles. 3. What characteristics do Annelids share with Arthropods? Both Annelids and Arthropods are metamorphic (their bodies are segmented) although in some Arthropod groups such as ticks the metemerism is greatly reduced, both have a brain which is located cranially and dorsally but is followed by a ventral nerve chord with a ganglionic swelling in each segment, and lastly, primitive Arthropods show paired appendages which can be compared with the paired parapodia (or setae in the earthworm of each metamere in the Annelids.) 4. What distinguishing characteristics do Annelids share with Arthropods? Arthropods are characterized by having hard, protective body covering: the exoskeleton. Coinciding with the evolution of this skeleton, the muscles for movement had to change. The locomotory muscles evolved from a simple body musculature like that of the earthworm (composed only of longitudinal and radial muscles) to a complex series of specialized muscles to control the limbs and tail. The circulatory system has changed from the Annelid's closed type to an open circulatory system where the hemolymph (blood), is forced away from the heart in arteries, but flows back to the heart through open venous cavities or sinuses. The heart in Arthropods has evolved from the five dorsal aortic arches of the annelids to a single distinct dorsal heart. 5. Identify/describe all the mouthparts found in a crayfish. There are three pairs of small mouthparts originating from the the head (the mandibles and two pair of maxillae). There are three more sets of mouthparts originating from the head (the mandible and two pairs of maxillae). There are three more sets of mouthparts, the maxillipeds that arise from the thorax in the region nearest the mouth. These small appendages function as touch sensors and help to hold and manipulate food. 6. Identify the five major arteries found in a crayfish. What organs are supplied by those arteries? The five major arteries extending from the heart are the Opthamolic, Antennary, Dorsal Abdominal, Hepatic, and Sternal Arteries. The opthamolic artery aries from the medial portion of the cranial ends of the heart. It proceeds straight toward the head and supplies the head and esophagus. Arising from either side of the opthamolic artery and extending anteriorly to the green gland are the antennary arteries. These supply the stomach, green glands, antennae, and lateral portion of the head. The dorsal abdominal artery is a large artery extending causally from the heart. It supplies the intestine and the tail muscles. The hepatic arteries branch from the ventral surface of the heart and supply the hepatopancreas. The sternal artery extends from the ventral side to the ventral nerve chord where it branches. The anterior branch is the ventral thoracic artery and the caudal branch is the ventral abdominal artery. The ventral thoracic artery supplies the leg and the ventral abdominal artery supplies the tail muscles. All of the arteries divide into smaller vessels and capillaries, but the crayfish has no veins to return the hemolymph to the heart. Instead, the hemolymph is returned to the heart through a series of open sinuses. 7. Identify the habitats of a crayfish. Crayfish are found in freshwater ponds and streams all across the globe.
8. Identify the four genera of a crayfish. The are four genera of crayfish, Procambus, Orconectes, Cambarus, and Astacus. There are about 100 species in the United states, and probably around 300 species worldwide. In the United states, Procambus sp. are the most common west of the Rocky Mountains, Orconectes sp. and Cambarus sp. are the most common to the east, and Astacus sp. in the south 9. What do crayfish eat? The diet of crayfish consists of snails, tadpoles, insects, aquatic and terrestrial plants, and decaying organic matter. 10. Briefly summarize your experience in one paragraph. This dissection was probably the hardest one I've had so far, simply because of the quantity of information to parse, however I did manage to observe everything relevant to the dissection. It would have been interesting to look at the mouthparts with bit more detail, as I found them extremely interesting, however it was still a good (if not “pleasant”) experience to examine them in person. My general dislike of dissection now carries on only for invertebrates, and in particular, mammals, as I have come to find dissecting Crustaceans to be somewhat interesting, and in a diminished sense, enjoyable. From a technical view, the dissection went extremely well, and the only holdup was a slight delay in my recognition of the eggs. On a related note, several months back for my birthday I was served sushi mixed with a type of orange caviar, so when I noted the color of the crayfish's eggs, I was slightly amused. Obviously I didn't eat crayfish eggs, but it is strange what ends up in the stomach…
Christopher Long
The Starfish Kingdom: Animalia Phylum: Echinodermata Class: Asteroidea Genus: Asterias Species: s.p
I. Purpose: The purpose is to examine the Starfish internally and externally by dissection. II. Materials: 1. 2. 3. 4. 5. 6.
Dissection tray Crayfish Scissors Dissecting Probe Dissecting Needle Forceps
III. Internal and and External Anatomy of a Starfish:
IV. Conclusions: 1. In what ways are Starfish unique to other invertebrates you have studied so far? Starfish are unique among the vertebrates I have studied thus far (clams, earthworms, crayfish) in that Starfish and other Echinoderms are Deuterostomes as opposed to being Protostomes. 2. What are the major differences between protostomes and deuterostomes? In protostomes, segmentation is complete, the brain is located above the gut, while the nerve chord is below the gut, a mesodermal skeleton is never present, embryonic cleavage is determinite, and the blastoplore becomes the mouth. In deuterostomes, segmentation is incomplete, both the brain and the nerve chord are above the gut, a mesodermal skeleton is often present, embryonic cleavage is indeterminate, and the gastropore becomes the anus while the “second mouth� forms as a new opening. 3. Where do all Echinoderms live? The phylum Echinodermata is composed of many familiar marine animals and is distinguished by pentamerous radial symmetry, a calcareous dermal endoskeleton with projecting spines, and also a system of coelomic canals and tube feet (the water vascular system) that is used in slow locomotion and manipulation of the food. 4. Identify five classes of Echinoderms; give an example of an animal that belongs to each class. Echinoderms consist of two subphyla, the Pelmatozoa and the Eleutherozoa. The primitive Pelmatozoa contains one class, the Crinoidea (sea lilies). The Eleutherozoa contains four classes, the Ophiuroidea (brittle stars), the Holothuroidea (sea cucumbers), the Echinoidea (sea urchins and sand dollars), and the Asteroidea (starfish). 5. How many species of Starfish are there? About 1700 species of starfish have been described, living in marine coastal waters from the north to the south poles. 6. Identify at least four external characteristics of a starfish. The opening of the water-vascular system, the madreporite, is a large button-like structure that is located off center on the disc between two arms. The inconspicuous anus is in the center of the disk, and both structures are located on the upper, aboral surface of the starfish. The mouth is in the center of the underside, or oral surface of the starfish's anatomy. On the oral surface of each arm are open ambulacral grooves extending from the mouth to the tip of each arm. These deep furrows contain two or four rows of tube feet, podia, with protruding suckers; features unique to the echinoderms. 7. Describe the process of water movement through a starfish's water vascular system. Water enters the system through the sieve-like madreporite in the aboral surface and passes through the stone canal into the ring canal which encircles the mouth. Nine sacs, Tiedemann's bodies, are located on the inner edges of the ring canal. These sacs are the breeding grounds of amoeboid cells that are found in the fluid of the water-vascular system. Extending out from the ring canal are five radial canals, one into each arm, through which water then travels. At regular intervals water passes into lateral canals, which branch off the radial canal and lead to ampulla, which are muscular bulbs located along both sides of the ambulacral ossicles. When the ampulla contract, water is forced into the tube feet, extending them, and enabling them to attache to substratum with their suckers. Excess water is excreted from the body of the starfish via the anus.
8. Identify the digestive organs of a starfish. Just under the dorsal endoskeleton are located large paired organs, hepatic ceca. There are a pair in each arm and they function as secretory glans to aid digestion which involves aversion of the stomach and external digestion. There is a connection between the hepatic ceca and the disk, the hepatic ducts, which all secrete into the small aboral pyloric stomach. Dorsal, or above the pyloric stomach is a small pair of lobed rectal ceca, which function in waste consolidation before excretion through the hard to see anus. Underneath, or ventral to the pyloric stomach is the large, bag-like cardiac stomach, which protrudes through the mouth while feeding. The everted stomach engulfs the prey and can insert itself into a slit in a shellfish only 0.1 mm wide. Digestion can begin outside the body until the cardiac stomach is retracted by five pairs of retractor muscles, one in each arm. 9. Describe the skeleton of a starfish. The aboral surface of the starfish is an arrangement of calcareous plate or ossicles of endoskeleton that allow both lateral, and up and down movement. Numerous spines portrude from the surface of the endoskeleton and give the body a spiny appearance, hence the name echinoderm— spiny skin. Small, moveable spines are covered by a thin layer of epidermis. The inner pattern of a starfish's endoskeletal framework is also composed of ossicles. The largest ossicles, ambulacral ossicles, support the ambulacral groove, and provide attachement for the tube feet. 10. Briefly summarize your experience in one paragraph. I began my dissection in the mistaken belief it wouldn't be quite so easy as the dissection guide portrayed, but upon starting, carried out the dissection in total leisure, and later, jokingly questioned whether I had perpetrated one at all. Rather than the carefull distinctions, and delicate machinery of a crayfish, I found clearly distinct, and almost brutally obvious internal organs, which easily detached from each other. The water vascular system in particular proved much easier to distinguish than I'd thought; within a few seconds, I located the stone canal, perhaps the starfish's least distinguishable part. After the dissection proper concluded, I did run into one difficulty, but I easily re-did my defective slide, and upon examination, discovered the gender of my starfish. (Eggs!) The smell, which affected some immediately, only irritated me while I cleaned my tray, but came on strong. Thank heaven for allergies! Without them, I probably would have seen the previous day's food. In any event, it was a good dissection— so good, in fact, it leaves me a bit wary about the next one.
Christopher Long Biology I Mr. Snyder Feb. 25, 2009
Analysis and Conclusion Questions: 1. What characteristics are shared by all vertebrates? !
All vertebrates posses vertebrae, bones or cartilage that surround and protect the dorsal nerve chord and form the spine, a cranium, which protects the brain, and an endoskeleton composed of bone or cartilage.
2. What key characteristics separate classes Osteichthyes and Chondrichthyes? !
Member of class Chondrichthyes posses jaws and fins, but their skeletons are composed of cartilage, and not bone and they are covered by unique scales. Members of Class Osteichthyes posses jaws, but most have skeletons which consist entirely of bone.
3. What adaptations lead to the divergence of mammals? !
The extinction of the dinosaurs led to the rise of new species, such as mammals, who gradually distinguished themselves from other species by traits such as hair, and the nursing of live young.
4. Which two groups of vertebrates share the most recent common ancestor? !
Classes Reptilia and Aves share the most recent common ancestor.