Sunday, December 2, 2007

FORUM TOPIC (Chapter 14, Page 323 - Critical Thinking Q2)

Scientists predict that the ocean will get warmer and the sea level will rise as a result of an intensified greenhouse effect. How might this affect coral reefs?
A prediction of how global warming will affect the marine environment is that the flow of some major ocean currents may change, affecting many marine ecosystems. Already stressed ecosystems such as mangrove forests and estauries will be flooded; coral reefs may not grow fast enough to keep up with rising sea levels.
Marine Biology Sixth Edition - Peter Castro/Michael E. Huber
Living in a Greenhouse: Our Warming Earth, pages 406 & 407

Coral Reefs Assignment - Chapter 14, Part II

1. Fringing reefs are reefs that form along a coastline.
2. Barrier reefs grow parallel to shorelines, but farther out, usually separated from the land by a deep lagoon.
3. Coral Atolls are rings of coral that grow on top of old, sunken volcanoes in the ocean.
4. Fringing reefs grow on the continental shelf in shallow water.
5. Coral Atolls begin as fringe reefs surrounding a volcanic island; then, as the volcano sinks, the reef continues to grow, and eventually only the reef remains.

1. Spur-and-groove formations develop primarily on reef slopes that are exposed to consistent strong winds which are found on atolls and some fringing reefs as well as barrier reefs.
2. All grow different types of corals
3. All consist of a reef flat and a reef slope
4. All are home to many different types of fishes
5. All are type of coral reefs


Coral Reefs Assignment - Chapter 14, Part I



1. How is each reef structure formed? “Coral” is a general term for several different groups of cnidarians, only some of which help build reefs. In reef-building, or hermatypic, corals the polyps produce calcium carbonate skeletons. Billions of these tiny skeletons form a massive reef. The most important reef builders are a group known as scleractinian corals, sometimes called the stony or “true” corals. Nearly all reef-building corals contain symbiotic zooxanthellae that help the corals make their calcium carbonate skeletons. It is the zooxanthellae as much as the corals themselves that construct the reef framework, and without zooxanthellae there would be no reefs.

2. Where is each reef structure found? There are three basic types of coral reefs; fringing, barrier and atoll. Fringing reefs are located very close to shore, and because of water run off they are typically high in nutrients and the water has a high turbidity. Barrier reefs are further from shore, with a lagoon between the reef and the shore. And finally atolls are a circular reef with a central lagoon and possibly small islands formed on the reef.

3. What is the trophic structure of a reef? The trophic structure of a reef is the recycling of nutrients. Coral reefs have among the highest rate of nitrogen fixation of any natural community. Coral reefs are very productive even though the surrounding ocean water lacks nutrients because nutrients are recycled extensively, nitrogen is fixed on the reef, and the zooplankton and nutrients that occur in the water are used efficiently. The reef is able to provide some of its own nutrients.

4. How does the location and type of reef influence the trophic structure? It is theorised that each of these types of reefs corresponds to a differing age of the entire reef structure. The youngest is the fringing reef, with the corals colonising a shallow water area close to the land. If the sea levels then rise or the land subsides, then the reef structure keeps up with this changing depth by growing upward. Eventually a shallow area with no coral growth will form behind the main reef, called a lagoon, giving a barrier reef. If the sea level or land subsides so much as to cause the land to disappear below the water surface, then an atoll is formed. The overall type of the reef whether it is a turbid, high nutrient reef where the stony corals are less common and algae abounds or crystal clear, low nutrient reef where the stony corals can dominate, is dependent of several factors. These include the proximity to land (therefore water run off which will be high in nutrients), proximity to river mouths (for the same reason as land proximity), and location of deep sea currents (which typically bring nutrient rich water. Each type of reef is also divided into various zones within each reef.

5. Give examples of the types of corals found on reefs. Corals are divided into two kinds and both are stationary on the ocean bottom. Hard corals such as brain, star, staghorn, elkhorn and pillar corals have rigid exoskeletons, or corallites, that protect their soft delicate bodies. Gorgonians, or soft corals, such as sea fans, sea whips, and sea rods, sway with the currents and lack an exoskeleton.

6. Give examples of competition, predation, and grazing. Competition – Sessile coral reef organisms must compete for space. Corals and seaweeds compete for light as well. The two main ways in which corals compete for space are by overgrowing their neighbors and by directly attacking them. NOTES FOR STUDENT ONLY: Competition – The interaction that results when a resource is in short supply and one organism uses the resource at the expense of another. Predation – Predation on corals occur when a variety of animals eat corals, but instead of killing the coral and eating it entirely, most coral predators eat individual polyps or bite off pieces here and there. The coral colony as a whole survives and can grow back the portion that was eaten. NOTES FOR STUDENT ONLY: Predation – The act of an animal, or predator, eating another organism, or prey. A top predator is one that feeds at the top of the food chain. Grazing – Grazing is the process of transplantation, removal and caging. An example of the effects of grazing on reefs are damselfishes. Many damselfishes graze on seaweeds inside territories that they vigorously defend, chasing away other fishes that happen to venture inside. Many such damselfishes has actually “farm” their territories. NOTE FOR STUDENT ONLY: Grazer – An organism that feeds primarily on plants.

Marine Biology Sixth Edition, Peter Castro/Michael E. Huber - Chapter 14

Fish Resources - The Fate of the Ocean

The article on The Fate of the Ocean is 12 pages long and I would like more people to read it because it explains the importance of marine organisms in our daily lives as well as the abuse that we humans create for ourselves in the upcoming years. It is an informative article that is easy to understand. It also provides a lot of detailed explanation of how science works around us and how our actions affect marine life.
In this article, Scientists stated that, "From a scientific perspective, we now know enough to improve dramatically the conservation and management of marine systems through the implementation of ecosystem-based approaches." This statement is self explanatory to all but the problem is getting full cooperation from everyone. "Change" has always been close to impossible for many, which is why by the time people understand the importance of marine organisms, it is already to late. SAD, but TRUE!
I love the ending of this article which read, "AT NO TIME IN HUMAN HISTORY has so much scientific inquiry been focused so intensively in one direction: on the anthropogenic changes in our world. As a result, we are learning more, and more quickly then ever before, about the life-support systems of earth work. Science now recognizes that the ocean is not just a pretty vista or a distant horizon but the vital circulatory, respiratory, and reproductive organs of our planet, and that these biological systems are suffering. Much effective treatment is suggested by computer-modeling studies, which the Bush administration, with its fear of science, negates-even though computer models are the same powerful tools that enable us to put men into space, to run wars, and to forecast financial trends." In comparison of this statement, the Marianas, a perfect example of how powerful politicians can be, is the act of our former Governor, Governor Babauta, making the stateless individuals U.S. citizens. If only our politicians would concentrate on the more important matters, EDUCATION and HEALTH, anything can be accomplished!
While reading this article, I kept thinking, what if we completely stop the exporting of wild seafood around the world? Could this be a possible solution to some of the problems? My thoughts continued and came up with, no more exporting wild seafood = more tourists visiting places where wild seafood is overflowing = revenue = growth in wild seafood production. For example, if I am a wild seafood lover and one way to indulge in seafood is to visit a place where seafood is served daily, then I will definitely go there. I wish it was this simple!
The Last Days of the Ocean
News: We're Pushing Our Seas to the Brink. Can They be Saved? A Mother Jones special report.
March/April 2006 Issue

Fish Resources - "Only 50 Years Left" For Sea Fish

I think the article on “Only 50 Years Left” For Sea Fish make a whole lot of sense to me. One reason why I agree with the article is that my father was a fisherman his whole life and today I have three brothers that not only enjoys fishing as a sport but catches fish for food. The catch that my brothers have today even when combined does not even come close to the amount of fish that my father caught 25 years ago. One of the wonderful memories I have of my father when I was as young as 10 years old is when he goes out fishing from night until dawn and returns home with a truck load of fish. Not a cooler full of fish, but, a truck load of fish. Growing up I remembered that people were very generous and neighbors always help each other. When my father returns home from fishing, we already have all our neighbors waiting for their share of the catch, free of charge. With this type of generosity, all our neighbors would also share either their vegetables or animals (pigs, chickens, ducks, cows, goats) with us.

As stated by Steve Palumbi, Scientist from Stanford University, “Unless we fundamentally change the way we manage all the ocean species together, as working ecosystems, then this century is the last century of wild seafood.” I totally agree with his statement because without the cooperation of everyone, the abuse with fishing will continue not forever but rather only until all the wild seafood are gone which is not long from today.

For the Marianas, I will have to say that it will be very sad when the fish population do decline as predicted. Why? Well, one, because some of our people were born fishermen and they fish today for profit as their only way of making ends meet. Two, fish has always been a delicacy for our people and we could not imagine not having fish as part of our diet. An example would be, every year, during lent, we eat only seafood, mainly fish, everyday for 45 days until Easter Sunday. This has always been the practice for my family as part of our religion, Roman Catholics. Therefore, I believe that if people here in the Marianas were educated on the importance of our marine environment as well as to establish strict laws when dealing with our marine organisms, then wild seafood may still be saved and 50 years from today, everyone will enjoy what has always been enjoyed in the past, FISHING!
By Richard Black
Environment correspondent, BBC News website
Last Updated: Thursday, 2 November 2006, 19:01 GMT

Monday, November 26, 2007

Sea Floor Spreading

What is sea floor spreading? Sea-floor spreading is the process by which new sea floor is formed as it moves away from spreading centers in mid-ocean ridges.

What are some of the major land forms that are created from plate movement? Trenches, Mid-Ocean Ridges, Mountains & Volcanoes.

How were the Mariana Islands formed? The Mariana Islands were formed by volcanoes.

What evidence exists today that the plates are still moving and that the islands are ancient volcanoes? Plate Tectonics! The earth beneath our feet is not dead; it is constantly moving, driven by forces deep in its core. Nor is the planet's crust all of one piece; it is composed of numerous plates, which are moving steadily in relation to one another. This movement is responsible for all manner of phenomena, including earthquakes, volcanoes, and the formation of mountains. All these ideas, and many more, are encompassed in the concept of plate tectonics, which is the name for a branch of geologic and geophysical study and for a powerful theory that unites a vast array of ideas. Plate tectonics works hand in hand with several other striking concepts and discoveries, including continental drift and the many changes in Earth's magnetic field that have taken place over its history. No wonder, then, that this idea, developed in the 1960s but based on years of research that preceded that era, is described as "the unifying theory of geology."

What is an atoll? An atoll is a coral reef that develops as a ring around a central lagoon.

Why are atolls mainly found on the Pacific? Because atoll formation requires coral reef building, atolls are limited to tropical waters. Atolls are most commonly found in the Pacific and Indian Oceans.


Wednesday, November 14, 2007

Fish of the Marianas Waters

CN: Mahi Mahi SN: Coryphaenidae Hippurus

CN: Bluespine Unicornfish or Tataga SN: Naso Unicornis

CN: Atulai SN: Selar Crumenophthalmus

CN: Bluefin Trevally SN: Caranx Melampygus

CN: Malabar Trevally or Eiei SN: Carangoides Malabaricus

CN: Parrotfish or Palakse SN: Cheilinus Digraammus

CN: Red Snapper or Onaga SN: Lutjanus Campechanus

CN: Rudderfish or Guilie SN: Centrolophus Niger

CN: Skipjack Tuna SN: Katsuwonus Pelamis

CN: Snapper or Gindai SN: Pristipomoides Zonatus

CN: Tagafi - Red Phase or Red Bass SN: Lutjanus Bohar

CN: Two-spot Red Snapper or Tagafi SN: Lutjanus Bohar

CN: Mutibar Goatfish or Satmoneti SN: Parupeneus Multifasciatus

CN: Striped Surgeonfish SN: Acanthurus Lineatus

CN: Star Puffer SN: Arothron Stellatus

CN: Lattice Soldierfish SN: Myripristis Violacea

CN: Sabre Squirrelfish SN: Sargocentron Spiniferum

CN: Orangespine Unicornfish SN: Naso Lituratus

CN: Manta Ray SN: Manta Birostris

CN: Great White Shark SN: Carcharodon Carcharias


FORUM TOPIC (Chapter 1, Page 21)

Critical Thinking – Question 2

In Chapter 1 it was explained that the statement “There are mermaids in the ocean” is not a valid scientific hypothesis. Can the same be said of the statement “There are no mermaids in the ocean”? Why?

Yes, I believe that the same can be said of the statement “There are no mermaids in the ocean” as the statement “There are mermaids in the ocean” because neither statement is testable.

I grew up being told beautiful stories of mermaids in the ocean therefore I believe that because marine biologists could not prove that there are no mermaids in the ocean does not mean that mermaids do not exist.

On the other hand, marine biologists may state that the statement “There are mermaids in the ocean” is a testable hypothesis since they have searched for a mermaid without success. A testable hypothesis is one that at least potentially can be proved false. In this case, they can prove that there are no mermaids in the ocean because they have not found a single mermaid.

SEE FORUMS (Chapter 3, Page 69)

Critical Thinking - Question 2

Just for the fun of it, someone in Beaufort, South Carolina, throws a message in a bottle into the sea. Some time later, someone in Perth, on the west coast of Australia, finds the bottle. Referring to Figure 3.20 and fold-out map of this book, can you trace the path the bottle probably took?

The path the bottle probably took started from the warm currents of the Gulf Stream to the cold Canary Current where the winds would then take it to the Antarctic Circumpolar Current to where it was found in Perth, on the west coast of Australia.

This is very interesting. This reminds me a lot of one of my favorite shows; “Message In A Bottle” stars Kevin Kostner.

Tuesday, November 13, 2007

SEE FORUMS (Chapter 8, Page 179) - Questions

Question 1.

The only living representatives of a very ancient group is the hagfishes and lampreys (jawless fishes). Why do you suppose these jawless fishes do not live in our waters?

Question 2.

A Marine Biologist from Fish & Wildlife collected a deep-water female shark containing 20 eggs from our waters for the first time and did a detailed study on it. Do you think that the Marine Biologist will conclude that this shark species, although new, belong to the family of sharks already present in our waters? Would it be possible that this new female shark mated with one of our male sharks? Please explain your answers.

Question 3.

Parrot fish is one of the favorite fish of the local people. What are the advantages and disadvantages should parrot fish have an equal number of males as females present in our waters?

Thursday, November 8, 2007

SEE FORUMS (Chapter 8, Page 179)

Critical Thinking - Question 3
Individuals of some species of bony fishes change sex, some to maintain more males than females, others more females than males. What are the advantages and disadvantages of each situation? Are there any advantages and disadvantages in having an equal number of males and females?
In the deep sea finding a mate can be difficult – even harder than finding food therefore being able to change from a male to a female or a female to a male is advantageous for these types of fishes because there would be an increase in reproduction. Deep-sea fishes that are hermaphrodites guarantee the ability to breed. In at least some species of anemone fishes (Amphiprion), all individuals begin as males. Each sea anemone is inhabited by a single large female that mates only with a large, dominant male. If the female disappear or is experimentally removed, her mate changes into a female and the largest of the non-breeding males becomes the new dominant male. Males of some wrasses form harems of many females. If the male disappears, the largest dominant female immediately begins to act like a male and within a relatively short period of time changes color and transforms into one that is capable of producing sperm. A variation of hermaphroditism among fishes is sex reversal, or sequential hermaphroditism, in which individuals begin life as males but change to females (protandry), or females change into males (protogyny). These changes are controlled by sex hormones but triggered by social cues such as the absence of a dominant male. I believe that there are neither advantages nor disadvantages in having an equal number of males and females since protandry and protogyny are present within these fishes. The way I understand it, we will never run out of fishes that are hermaphrodites.

SEE FORUMS (Chapter 8, Page 179)

Critical Thinking - Question 2

A deep-water shark, new to science, is collected for the first time. The specimen is studied in detail, but its stomach is empty. How could you get a rough idea of its feeding habits? The specimen is a female, and its reproductive tract is found to contain 20 eggs. Can you tell the type of development characteristics of this species?

I think one can get a rough idea of an unidentified deep-water shark's feeding habits by studying the feeding habits of other known sharks. In addition, sharks possess movable powerful jaws that have rows of numerous sharp, often triangular teeth, therefore, if the unidentified deep-water shark possess any of these features, then we can assume that their feeding habits would be the same as the sharks known today.
Yes, it is possible to tell the development characteristic of the unidentified deep-water female shark by studying the 20 eggs found in its reproductive tract. Since the eggs were found in the reproductive tract of the unidentified deep-water shark then this shark could be ovoviviparous, which are cartilaginous fishes that retains eggs inside their reproductive tract for additional protection and gives birth to live young.

SEE FORUMS (Chapter 8, Page 179)

Critical Thinking - Question 1

Hagfishes and lampreys are the only living representatives of a very ancient group. Why do you suppose there are still some of these jawless fishes around?

I suppose hagfishes and lampreys (jawless fishes) are still living today because of the simplicity of their way of life. Hagfishes feed mostly on dead or dying fishes while lampreys attach to other fishes and suck their blood or feed on bottom invertebrates. Both jawless fishes do not require much effort for survival.

Tuesday, October 23, 2007

Genetics/Cell Cycle

1. What is DNA? DeoxyriboNucleic Acid.
2. What are the 4 bases? A (Adenine), T (Thymine), C (Cytosine) & G (Guanine).
3. What 2 peices of information did the scientists need to solve the elusive structure of DNA? In order to solve the elusive structure of DNA, a couple of distinct pieces of information needed to be put together. One was that the phosphate backbone was on the outside with bases on the inside; another that the molecule was a double helix. It was also important to figure out that the two strands run in opposite directions and that the molecule had a specific base pairing.
4. What are the specific base pairs? G can only bind to C and A can only bind to T.
5. How does the pairing rule effect the shape and structure of DNA? According to the biochemist Erwin Chargoff even though different organisms have different amounts of DNA, the amount of adenine always equals the amount of thymine. The same goes for the pair guanine and cytosine. For example, human DNA contains about 30 percent each of adenine and thymine, and 20 percent each of guanine and cytosine. With this information at hand James Watson was able to figure out the pairing rules. On the 21st of February 1953 he had the key insight, when he saw that the adenine-thymine bond was exactly as long as the cytosine-guanine bond. If the bases were paired in this way, each rung of the twisted ladder in the helix would be of equal length, and the sugar-phosphate backbone would be smooth.
6. What does the DNA do during cell division? During cell division, the DNA molecule is able to "unzip" into two pieces. One new molecule is formed from each half-ladder, and due to the specific pairing this gives rise to two identical daughter copies from each parent molecule.
7. How many base pairs does E. Coli have? How long does it take to replicate? How is the DNA packaged in the cell? The DNA in E. coli bacteria is made up of 4 million base pairs and the whole genome is thus one millimeter long. The single-cell bacterium can copy its genome and divide into two cells once every 20 minutes. In order to fit, the DNA must be packaged in a very compact form. In E. coli the single circular DNA molecule is curled up in a condensed fashion.
8. How many base pairs does Human DNA have? How long does it take to replicate? How is the DNA packaged in the cell? The DNA of humans is composed of approximately 3 billion base pairs, making up a total of almost a meter-long stretch of DNA in every cell in our bodies. The human DNA is packaged in 23 distinct chromosome pairs. Here the genetic material is tightly rolled up on structures called histones.

1. What is RNA? How different is it from DNA? RiboNucleic Acid. DNA is made up of double strand while RNA is made up of a single strand. Also the base T (Thymine) in DNA is replaced by U (Uracil) in RNA.
2. How are the RNA messages formed? The alphabet in the RNA molecule contains 4 letters, i.e. A, U, C, G. To construct a word in the RNA language, three of these letters are grouped together. This three-letter word are often referred to as a triplet or a codon. An example of such a codon is ACG. The letters don't have to be of different kinds, so UUU is also a valid codon. These codons are placed after each other in the RNA molecule, to construct a message, a RNA sequence. This message will later be read by the protein producing machinery in the body.
3. How are the RNA messages interpreted? Every organism has an almost identical system that is able to read the RNA, interpret the different codons and construct a protein with various combinations of the amino acids. In fact every RNA word or codon, corresponds to one single amino acid. These codons and their correlation with the amino acids in a protein sequence is what defines the genetic code.

1. Describe cell cycle. The cell cycle, or cell-division cycle, is the series of events that take place in a eukaryotic cell leading to its replication. These events can be divided in two broad periods: interphase—during which the cell grows, accumulating nutrients needed for mitosis and duplicating its DNA—and the mitotic (M) phase, during which the cell splits itself into two distinct cells, often called "daughter cells". The cell-division cycle is an essential process by which a single-celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed.
2. What is nuclear division. The division of the nucleus and its genetic information into more than one cell deriving from a parent cell, either via meiosis or mitosis.
3. What is interphase. A phase of the
cell cycle, defined only by the absence of cell division. During interphase, the cell obtains nutrients, and duplicates its chromatids. Most eukaryotic cells spend most of their time in interphase.
4. Cytokinesis. Cytokinesis is the process whereby the
cytoplasm of a single cell is divided to spawn two daughter cells. It usually initiates during the late stages of mitosis, and sometimes meiosis, splitting a binucleate cell in two to ensure that chromosome number is maintained from one generation to the next. In animal cells, one notable exception to the normal process of cytokinesis is oogenesis (the creation of an ovum in the ovarian follicle of the ovary), where the ovum takes almost all the cytoplasm and organelles, leaving very little for the resulting polar bodies, which then die. In plant cells, a dividing structure known as the cell plate forms across the centre of the cytoplasm and a new cell wall forms between the two daughter cells.

5. Homologous chromosomes. (Science: genetics) a pair of chromosomes containing the same linear gene sequences, each derived from one parent. The chromosomes tend to pair or synapse during meiosis. They have the same genes, in the same location, but the genes have different versions (not like in sister chromatids that are exact replicas).
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6. Phases of mitosis (5 of them).
1. Prophase – In prophase, the
chromatin condenses into discrete chromosomes. The nuclear envelope breaks down and spindles form at opposite "poles" of the cell.
2. Metaphase – In metaphase, the chromosomes are aligned at the metaphase plate (a plane that is equally distant from the two
spindle poles).
3. Anaphase – In anaphase, the paired chromosomes (
sister chromatids) move to opposite ends of the cell.
4. Telophase – In this last stage, the chromosomes are cordoned off in distinct new nuclei in the emerging daughter cells.
Cytokinesis is also occurring at this time.
Interphase – G1 phase: The period prior to the synthesis of DNA. In this phase, the cell increases in mass in preparation for cell division. Note that the G in G1 represents gap and the 1 represents first, so the G1 phase is the first gap phase. S phase: The period during which DNA is synthesized.

7. Phases of meiosis and how it is different from mitosis.
Meiosis begins with Interphase I. During this phase there is a duplication genetic material,
DNA replication. Cells go from being 2N, 2C (N= chromosome content, C = DNA content) to 2N, 4C. Cells remain in this active phase 75% of the time. The chromatin remains in a nuclear envelope while a pair of centrioles lies inside a centrosome.
During Prophase I, the
chromatin condenses into chromosomes, the nuclear envelope disappears, and a spindle apparatus begins to form. Each chromosome consists of a pair of chromatids connected by a centromere. Cells are now 4N, 4C. The major occurrence in this phase is the coupling of these homologous chromosomes. Two double-stranded chromosomes form a four-stranded tetrad. In some cases, there is crossing-over of the two middle strands, at a site called the chiasma, such that there is genetic recombination. This process is extremely important for creating genetic diversity.
In Metaphase I, the tetrads line up on the "equator" of the cell. The centrosome has replicated and one has moved to each pole. Microtubules that extend out of each centrosome attach to kinetochores in the center of each side of the tetrads that have lined up on the equator.
Anaphase I occurs as the microtubules pull the pairs of homologous chromatids toward each pole, as the tetrad is divided. The cell begins to lengthen.
During Telophase I, the nuclear envelope begins to reform and nucleoli reappear. The cell begins to split, forming a cleavage furrow in the middle.
In Cytokinesis I, the cells finally split, with one copy of each chromosome in each one. Each of the two resulting cells is now 2N, 2C.
Interkinesis has not replication, unlike the previous Interphase I and the interphase of mitosis.Prophase II, Metaphase II, Anaphase II, and Telophase II repeats the same steps as Prophase I-Telophase I, with half as much genetic material.
Cytokinesis II is the final step of meiosis, where each cell splits into two daughter cells, for a total of four
gametes, each with half the number of chromosomes. Each of the four resulting cells is 1N, 1C. (30)
In Meiosis the first phase is Interphase but in Mitosis it is last. In addition, Meiosis process are seven stages while Mitosis process are five phases.
8. Describe the process and purpose of crossing over. Crossing over occurs when the sperm and egg chromosomes pair up and swap genetic information, reducing the number of chromosomes to a complete set. It is important because it makes the number of chromosomes the normal number and also allows the genetic information to remain present in the cell.


Wednesday, October 17, 2007

Virtual Dissection - Crayfish

Internal anatomy of a crayfish: edible freshwater crustacean, with pincers on the two forelegs.
Encephalon: site of the mental functions of a crayfish.
Stomach: part of the digestive tract between the esophagus and the intestine.
Heart: blood-pumping organ of the crayfish.
Gonad: sex gland of a crayfish.
Extensor muscles: muscle that extends the tail of the crayfish.
Anus: outlet of the digestive tract.
Flexor muscle: muscle that bends the tail of the crayfish.
Digestive gland: glandular organ that produces digestive enzymes.
Ganglion of ventral nerve cord: budge related to a collection of nerves of the abdomen of a crayfish.
Ventral nerve cord: collection of nerves in the abdomen of a crayfish.
Maxilliped: pair of appendages of a crayfish used for holding prey.
Esophagus: part of the digestive tract between the mouth and the stomach.
Mandible: lower jaw.
Mouth: entrance to the digestive tract.
Green gland: antennary gland.
Eye: sight organ of a crayfish.

Taxonomy - Crayfish are members of the Decapod crustaceans.
External Anatomy

Female crayfish "In-berry".

Juvenile crayfish attached to the abdomen of a female.


Virtual Dissection - Squid

External Morphology
1 – This is the squids's dorsal surface. 2 – This is the squids's mantle.
3 – This is the fin portion of the mantle.
4 – This is the collar portion of the mantle.
5 – This is an eye.
6 – This is one of ten arms.
7 – This is one of a pair of tentacles.

1 – This is the squid's lateral surface.
2 – This is the squids's mantle. 3 – This is the fin portion of the mantle.
4 – This is the collar portion of the mantle.
5 – This is an eye.
6 – This is one of ten arms.
7 – This is one of a pair of tentacles.

1 – This is the squid's ventral surface. 2 – This is the squids's mantle.
3 – This is the fin portion of the mantle.
4 – This is the collar portion of the mantle.
5 – This is an eye.
6 – This is one of ten arms.
7 – This is one of a pair of tentacles.
8 – This is the squid's funnel; the equivalent of the clam's excurrent siphon.
9 – This is an incision that was made in preparation for injecting the circulatory system of the squid.

Funnel Area
1 - This is the collar area of the squid's mantle.
2 – This is the squid's funnel.
3 – This is the squid's eye.
4 – The arrows point to the two funnel retractor muscles.
5 – The arrow points to the squid's rectum. The two small flaps are called rectal papillae.
6 – The left arrow points to one of a pair of cartilaginous ridges in the mantle that fits into grooves on the funnel (right arrow).

Buccal Mass
1 – The arrow points to a sucker on one of the squid's arms.
2 – This is a part of the buccal membrane.
3 – This is the buccal mass, a muscular organ with chitinous teeth and a radula for masticating prey to prepare it for digestion.
4 – The arrow points to tissues associated with the squid's salivary glands.
5 – The arrow points to the esophagus. The tissue surrounding the esophagus is associated with the liver.

1 – This is the funnel area of the head. 2 – The arrow points to the right gill.
3 – The arrow points to the left funnel retractor muscle.
4 – The arrow points to the squid's rectum.
5 – The arrow points to one of the squid's branchial hearts. They receive deoxygenated blood from the precavae and the posterior vena cavae and pump it through the gills.
6 – The arrow points to one of the squid's precavae. These vessels containing the kidneys, receive deoxygenated blood from the head area via the anterior vena cava and direct it to the branchial hearts.
7 – The arrow points to one of the squid's posterior vena cavae. These vessels receive deoxygenated blood from the mantle area and direct it to the branchial hearts.
8 – The arrow points to the squid's caecum, a large chamber receiving masticated food from the stomach. Much of the digestion occurs here.
9 – The arrow points to the squid's single testis. Usually, it is partially covered by the caecum.

1 – This is the funnel area of the head. 2 – This is the squid's rectum. It is terminated by two ear-like flaps.
3 – This is the left funnel retractor muscle.
4 – The arrow points to one of the squid's gills.
5 – The arrow points to the ink sac. This melanin-containing sac is dorsal to the intestine an empties into it.
6 – The arrow points to the squid's pair of nidamental glands. They secrete material that becomes the egg casings.
7 – The arrow points to the squid's left branchial heart. They receive blood from the vena cavae and pump it through the gills.
8 – This is the squid's ovary. It occupies much of this part of the mantle cavity and covers the caecum.

1 – This is the head area, seen laterally.
2 – This is the dorsal groove in the collar. The cartilaginous ridge in the head fits into it. The groove is supported internally by the pen.
3 – This is the collar.
4 – This is the stellate ganglion, a mass of cell bodies with giant motor axions that innervate the muscles of the mantle for rapid swimming.
5 – This is the squid's left gill. It has been injected with red latex.
6 – This is the left funnel retractor muscle.

Latin.mollis = soft)
This phylum is one of the largest marine groups with over 80 000 species. All comprise of a soft, unsegmented body, consisting of an anterior head, a dorsal visceral mass and a ventral foot.The body is more or less surrounded by a fleshy mantle (an outgrowth of the body wall) and nearly all species in the group secrete a lime shell that covers and protects the body. All, except the class Bivalvia, have a ribbon-like rasping tongue (radula - unique to this phylum) with small chitinous teeth that processes the food. Most mollusks are free living, but slow moving creatures, showing a close association with the substrate. Some attach to rocks or shells, others burrow, others float, octopuses and squids swim freely.
1. Body usually short and partially or wholy enclosed by a fleshy outgrowth of the body wall called the mantle, which may be variously modified. Between the mantle and the visceral mass is a mantle cavity containing components of several systems (secondarily lost in a few groups).
2. A shell (if present) is secreted by the mantle and consists of one, two or eight parts. the head and the ventral muscular foot are closely allied (the foot being variously modified for burrowing, crawling, swimming, or food capture).
3. The digestive canals are complete and intricate with ciliary canals for the sorting of particles. The mouth with a rudula bearing traverse rows of minute chitinous teeth to rasp food , except in Bivalvia. The anus opening in the mantle cavity. A large digestive gland and often salivary glands are present.
4. The circulatory system is open, except in Cephalopoda and usually includes a dorsal heart with one or two atrias and one ventricle. This is situated in a pericardial cavity. An anterior aorta and other vessels and many blood spaces (hemocoels) exist in the tissues.
5. Respiration occurs via one to many uniquely structured ctenidia (gills) in the mantle cavity (secondarily lost in some), by the mantle cavity, or by the mantle.
6. Excretion by kidneys (nephridia), one or two or six pairs, or only a single one. They usually connect to the pericardial cavity and they exit in the mantle cavity. The coelom is reduced to the cavities of the nephridia, gonads and pericardium.
7. The nervous system is typically a circumesophageal nerve ring with multiple pairs of ganglia and two pairs of nerve cords (one pair innervating the foot and another the visceral mass). Many poses organs for smell, or touch, or taste. Eyespots or complex eyes present. A statocyst for equilibration present.
8. The sexes are usually seperate(some are monoecious, a few are protandric). Gonads add up to four, two or one, all with ducts. Fertilization occurs externally or internally. Most species are oviparous. Egg cleavage determinate, spiral, unequal and total (meroblastic in Cephalopoda). Trochophores and veliger larvae form, or a parasitic stage occurs(Unionidae), or the development is direct (Plumonata, Cephalopoda).
9. Unsegmented (except Monoplasophora). Symmetry bilateral or asymmetrical.


Prepared by the BioG 101-104 Course Staff.Comments to Jon C. Glase: jcg6@cornell.eduAll contents © 2000 Cornell University. All rights reserved.Revised: April 5, 2000URL: