Rat Dissection

A week ago, our biology class dissected rats. I have to say, this was probably the most exciting dissection. The purpose of this dissection was to familiarize ourselves with the anatomy of mammals and to provide a "hands-on" method of learning. Or, at least that is the textbook answer. This lab was more than that; it was an opportunity to delve into an unknown world. It's not everyday we get to explore the insides of animals without raising ethical issues.

Our uncut rat. 

For this dissection, we worked in groups of four people instead of our usual two. Our group had a female rat. Before we cut her open, we immediately noticed certain features that identified her as a mammal. First of all, she still had fur left over. She also had nipples which means she nursed her young. What really surprised me was the fact that she had twelve nipples! It showed us that while many animals are classified as mammals, there are still big differences between them. I was actually quite anxious and squeamish before the dissection. I was desperately praying that the rat was not pregnant; I don't think I could have handled that.

When we finally started cutting open the rat, we noticed that its anatomy was quite similar to humans: it had a rib cage, a heart, lungs, and a liver. There was also a long tangle of intestines. In class, we learned that another identifying feature of mammals is the diaphragm but it wasn't as obvious in the rat compared to the diagrams. In fact, all the organs were slightly shifted around, out of their standard positions. It almost felt like solving a puzzle. The respiratory, digestive, and circulatory systems greatly resembled human's. In fact, they seemed pretty standard for mammals. The rat had a four-chambered heart, like all mammals. That is also a trait it shares with birds and some reptiles. We also observed that the female reproductive system in rats is very similar, if not the same, as humans. The ovaries produces eggs which are fertilized internally. The development of the embryo of rats and humans occur in the uterus and finally, the babies are born through the vagina. However, one difference is that rats have a tendency to produce more babies than humans (more than 5) while humans tend to give birth to one or two at a time. In terms of body structure, the rat had a standard mammal's body: 4 legs, a head and a body. Some reptiles and amphibians also have this vague structure.

One thing about this dissection I regret was not actually being the one dissecting the rat. If I were to redo this dissection, I would want to be the one cutting the organs open. I feel like actually doing it would probably give me a different perspective compared to being a bystander. It was also a pity that I could not participate in the second day of the rat dissection but I am grateful I had this experience.

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For this dissection, we used our hands because no matter how well trained a person is using other instruments, hands are always going to be the most controllable (as it is the first "tool" we mastered).

We have labeled diagrams to aid us during dissection. That way, we can identify all the different organs of the rat.

The tail of the rat helps with balance and sensing. It is almost as long as the rat's body.

The vibrassae function as sensors. They are also commonly known as "whiskers."

The rat is bilaterally symmetrical, meaning that one said of the body mirrors the other. Bilateral symmetry occurs in organisms that are higher on the evolutionary chain.

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The sphincter is a ring of muscles at the beginning or end of some organs that control how much stuff and the time it can pass through.

The large intestines is bigger and shorter because it only absorbs the excess water and salts that have not yet been digested. On the other hand, the small intestines are thinner and much, much longer, resulting in greater surface area to absorb nutrients. The incredible length also ensures that the digested food will pass through for a long enough time for most of the nutrients to be absorbed.

The liver has many important functions including digestion and detoxifying and purifying the blood.

The word "duodenum' means "12 finger lengths" in Latin.

The appendix is involved with the digestion of cellulose in herbivores.

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The serous membrane functions as a protective covering over organs to prevent friction when the organs shift. This is especially important because of the expansion of the chest cavity.

The spleen removes old blood cells and contains a reserve of blood in case of hemorrhagic shock.

The diaphragm expands the chest cavity, aiding mammals to breathe.

The atria are the top two chambers in a four chambered heart. The atria have thinner walls and can not propel the blood very far while the ventricles are more muscular and can therefore pump the blood further with more force.

The left ventricle pumps the oxygenated blood to the rest of the body so as the result, it has the thickest walls of any chamber to accomplish this task.

The male and female reproductive systems produce haploid gametes as well as are bilaterally symmetrical.

Kidneys remove wastes from blood and are also involved with maintaining body fluid levels.

The thyroid, thymus and adrenal glands are part of the endocrine system. They release hormones that regulates mood, metabolism, growth and reproductive processes.

Squidissection

Last Thursday, our class dissected squids. Squids are members of the phylum Mollusca along with snails, slug, clams, oysters, scallops and octopi. It may seem strange that all these different organisms were grouped together into one phylum but they share similar characteristics. Mollusks are soft-bodied organisms that have an internal or external shell. Bivalves are known for their external shells while squids possess an internal shell (the pen). There are a few types of mollusks that lack shells. Snails, slugs, clams and squids are also grouped into one phylum because they share the same basic body structure: foot, mantle, and visceral mass. They also share similar developmental patterns (most produce free-swimming larvae called trochophores).

The purpose of this dissection was to acquaint ourselves with the anatomy of a squid and to compare it with other mollusks. We noticed how the tentacles and arms were really just a modified version of a standard foot  and how the squid had an internal shell in comparison to clams and oysters who have external shells. Squids also possess radulas which are common to all mollusks except for bivalves. One glaring difference between squids and other mollusks was their well-developed compound eyes. I dissected one of the eyes and learned that the lens of the squid was actually quite large compared to its body (picture below).

 While squids are colour blind, they have highly developed sight and can somehow control their cromatophores to blend in with their environment. Unlike many sessile mollusks, squids are motile and agile. They use their funnels and jet propulsion to move themselves. This adaptation allows them to hunt effectively.

During the dissection, we were also able to find the ink sac. Many cephalopods squirt out a cloud of ink when they are threatened. This allows them to make a quick getaway. They squirt out ink from the funnel.
It was very interesting to try to write with squid ink. Unlike normal ink in our pens, it is not as fluid but quite dotty.

The squid we got had 8 arms and 2 tentacles. All of them have suckers to aid the squid catch prey.

The shorter arms grab and hold prey. They also bring it to the squid's mouth. The longer tentacles are for capturing prey that are further away. 

The squid moves by releasing water from its funnel (blue arrow) which propels itself in the opposite direction of where the funnel is facing.

The squid uses its arms and tentacles which are lined with suckers to capture and immobilize its prey. 

Another adaptation that helps the squid's predatory life are pigment cells called chromatophores. Chromatophores expand or contract to display or hide different colours which helps the squid surprise its prey or hide from predators. 

Squids, like many other mollusks, are bilaterally symmetrical and are coelomate. 

Another trait that squids have in common with other mollusks is the basic body structure. They all have a foot, a mantle that covers the body, and the visceral mass containing most of the organs. 

Squids have one pair of feathery gills for respiration (outlined in yellow).

The ink sac empties into the funnel. When the squid is agitated or feels threatened, the squid will shoot ink out of its sac and funnel, into the water to create a smokescreen of sorts to escape. 

The pen is the squid's internal shell. It supports the mantle, keeping the squid upright, allowing it to float in water. If the squid did not have a pen, squid's body would have no support and would just flop around. 

Solid waste exits the squid through the anus out of the siphon. Waste produced from cellular metabolism is removed from the blood by tube-like organs called nephridia. 

While it was difficult to distinguish the inner organs from one another at the beginning, everything became clear after we identified the ink sac. I had a very interesting time comparing the different structures of the squid to other mollusks. Its quite amazing to see how a basic body part could adapt into so many different forms depending on the purpose. The only thing that disappointed me in this dissection was the fact that we could not eat the squid afterwards. We threw out all the squid which could have been a delicious lunch.

On an end note, I think the squid would win: dinosaurs are extinct because they were unable to adapt to changes in the environment while squids are still around today. And the whale is too apathetic to get involved. Or maybe I'm just rooting for the squid because it is the cutest. 

Earthworm Dissection

After learning about Annelids in class, we all had a chance to dissect a earthworm. While it sounds like no big deal, I was pretty close to panicking; I am completely terrified of anything that creeps, crawls or slithers. To add to that, we were told that no gloves would be provided so we had to touch the worm with our hands. I almost died. Well, not really, but I wasn't too keen on the touching part, no matter how interested I was in the worm's anatomy. In the textbook, we saw many simplified diagrams of worms. So, naturally, this lab was aimed to let us find and observe these anatomies in a real specimen. It was a simple "look at the diagrams and identify the parts in the worm" kind of lab. However, this proved to be more challenging than I expected. I don't think any of us realized how simplified the diagrams were until we started dissecting the worm. The pictures in the textbook barely resembled the real anatomical structures. It was very tough to figure out what structure was what. In fact, some organs weren't even in the correct (standard) position due to our scalpels messing everything inside up. Also, the diagrams in the textbook were 2-D so we could see all the organs clearly. However, in the real specimen, the organs were layered one over one another and intertwined with others. This lab proved to me that while these worms may be considered primitive and are simple-looking, their appearances were deceiving as their anatomies were quite complex. It made me wonder just how complex and puzzling human bodies must be.

In this picture, we see the worm's five hearts which are also known as "aortic arches." They pump the blood through the worm's closed circulatory system. 

The digestive system starts at the mouth where the food enters. The pharynx pumps the food through the esophagus, through the crop (where it may be stored, to the gizzard (where the food is ground up). It then passes through the intestine and the waste is eliminated through the anus. 

Brain blocked by pin. Standard area of brain pointed out. 

The worm's "brain" is made up of paired ganglia (cluster of nerve cells) which are connected to the rest of the body by the ventral nerve cord. 

The nephridia deals with waste resulting from cellular metabolism. They remove waste products from body fluids and carry them to the outside. Solid waste is passed through the anus which is connected to the digestive system. 

We can assume the earthworms eat soil because of the large concentration of soil in the earthworm's digestive tract. If we wanted to test this theory out,  we can simply place a worm in an environment that only contains soil. If the worm survives, we can conclude that it eats soil. Or we can simply google what earthworms eat. 

Setae are tiny bristle-like hairs on the earthworm that help it anchor itself and move through the soil.

Photo Credit: http://images.tutorvista.com/content/animal-nutrition/digestive-tract-earthworm.jpeg

The small gizzard grinds up the relatively small amounts of food. The large amount of undigested ingested soil passes through the long intestinal tube. The difference in proportion between the gizzard and the intestine indicates the adaptation of the earthworm's digestive system.

While my dissection of the earthworm did not go past segment 32, I expect to see more of the intestine and the undigested food if I were to dissect the remainder of the worm/

Earthworms are hermaphroditic so they possess both male and female reproductive organs. The ovaries produce eggs and the testes produce sperm. However, worms do not self fertilize so it must join with another worm to reproduce. They connect at the clitellum and the sperm is released through the male genital pores, along the sperm grooves to the female genital pores to internally fertilize the eggs of the other worm. The clitellum then secretes a mucus ring into which the eggs and sperms are released. Then the ring slips off the worms and develops into a cocoon that shelters the fertilized eggs. 

While this lab was kinda icky in my opinion, I enjoyed the dissection immensely. I felt like a surgeon from a hospital drama. Through this lab, not only did we learn about the anatomical features of an earthworm, we also learned that creatures are more complex than textbooks make them out to be. 

Phylum Platyhelminthes 

This beautiful pink flatworm is known as Prostheceraeus giesbrechtii (roseus). It is found in the Mediterranean Sea near Sicily, Italy. 

This is from the pseudoceros genus. It is found in the Gulf of Thailand. 

This flatworm is pseudoceros zebra. It can be found near South Africa, Tanzania and the Red Sea. 

Phylum Porifera

The orange puffball sponge is spherical in shape with a flat bottom. When parts of the sponge becomes infected, the sponge is able to use its spicules to isolate the infected part and expel it from the main body. Then, it is able to regenerate the shed part. 

The giant barrel sponge is usually found in the Caribbeans. It has a lifespan of up to 2000 years. 

Glass sponges form reefs off the coast of British Columbia and Washington State. 

Phylum Cnidaria 

This massive Normura jellyfish looks like it came straight out of a Japanese horror movie. They lurk in the Yellow Sea and East China Sea and can grow up to 2m in length. 

The flower hat jellyfish has shiny tentacles that it uses to hunt small fish for food. It lives off the coast of Argentina, Brazil and Southern Japan. 

The Bathykorus Bouilloni is the only species in the genus bathykorus. It was discovered in 2010 in the deep waters (below 1000m) of the Arctic Ocean. 

(Somewhat) Magic School Bus: Day at the Aquarium

     After a 3-year absence, I am back at the Vancouver Aquarium. This time, I was with my friends and my Biology class. The purpose of this trip was to give us the opportunity to see the creatures we are learning about which we may not see in our everyday lives. I was very excited to see all the different types of poriferans, and cnidarians, especially because there were specimens from all over the world. Unlike the pictures in our textbooks, the formerly inanimate creatures were swimming, breathing and thriving all around us. This trip gave us a better understanding of how the sea creatures interacted with their environment. Before going to the aquarium, we just learned facts about the porifera or the cnidaria but at the aquarium, we saw not only the sponges, but we saw a small piece of a whole ecosystem that the sponge played a part in. 

An ecosystem made of different sponges, each playing an important role. 

    

 For the rest of the morning, we wandered through the aquarium, taking pictures of anything that struck our fancy. At the same time, we tried to find the different creatures outlined in our scavenger hunt. 

                                     

Photo Credit: Alan Zhong

Clownfish and sea anamones form symbiotics relationships to survive. The sea anemone provides protection for the clownfish using its toxic tentacles while the clownfish lures prey to the sea anemone. The clownfish also protects the sea anemone from any predators that are immune to its poison. 

 

At one time sea otters could be found all along the coast of British Columbia, all the way up to Alaska but now they are quite rare because they were hunted for their pelt. A sea otter's fur is so dense that water never reaches a sea otter's skin in a lifetime. One square inch of the otter's skin has more hair (fur) than a human's head. Sea otters clean their fur meticulously to remove the oils that would cause the fur to clump together. If it does clump together, it no longer serves its purpose in keeping the sea otter's skin dry. 

There were many sea anemone at the aquarium but I did not notice the ones near the sea otter tank. However, I did manage to take a picture of these bright green sea anemone. They are growing on purple-ish rocks. 

Even though Alan didn't choose me as his favourite vertebrate, I still chose him as mine. My favourite invertebrate, however, is the moon jelly. 

Not only are they beautiful, they are quite well-adapted for survival. They have many tentacles, each equipped with nematocysts, to capture prey or fight off enemies. They also have 8 special sensory organs to tell the jelly fish where in the water column they are. In short, not only do that have the beauty, but thay also have the brains and brawn.

Here are the two belugas (also known as delphinepterus leucas) at the Vancouver Aquarium; one is named Aurora and the other, Qila. 

Photo Credit: http://magicporthole.org/wonders/Potbelly-Seahorse.jpg

The potbelly seahorses use their tiny fins to propel them. Because they are not really good swimmers, they usually prefer to stay in the same general area. However, they are able to move up and down, forwards and backwards.

Photo Credit: http://upload.wikimedia.org/wikipedia/commons/thumb/5/56/Brain_coral.jpg/220px-Brain_coral.jpg

The brain coral looks like a human brain (which is the centre of the nervous system. There are many different types of corals and they all belong to the family Faviidae. 

Moon-jellies move by contracting its bell, then opening. This opening-closing movement and along with jet propulsion from its tentacles propel the moon-jelly. This method of travel is not very efficient and the moon jelly relies heavily on water currents. The moon jellies feed on plankton by using its nematocyst-laden tentacles to capture prey. It then wraps its prey with mucus and brings it to the gastrovascular cavity to be digested by enzymes. 

Photo Credit: http://dive.bc.ca/pictures/octo/octo03.jpg

The white suctions cups on the Pacific Octopus' tentacles sucks and sticks onto its prey. They are one of nature's best predators because they are are very good at camouflaging and surprising their prey. They also use venom to anesthetize their prey, rendering them harmless. Their strong beak and constricting tentacles also contribute to their formidable reputation. 

Photo Credit: Ron Niebrugge / WildNatureImages.com

Steller sea lions feed on fish such as mackerel, herring, salmon, cod, and rockfish and invertebrates such as squid, octopus, bivalves and gastropods. They usually hunt for their food but female sea lions with pups usually feed at night, switching to foraging during daytime after breeding season.

This caiman is from South America.

This ferocious beast is a crocodile. It is earthy, brownish-green in colour and its rough texture blends in with the murky waters that it dwells in. This adaptation is useful for survival because it blends in with its environment so nothing can see it and kill it. 

Photo Credit: Alan Zhong

The Arapaima is the biggest fish in the Vancouver Aquarium. They are found in South America and can reach more than 2m  long.

The tambaqui is a vegetarian fish as it eats fruits, grains and decaying plants. They are often confused with piranha because of their similar appearances.  

Photo Credit: http://allamazingfacts.com/pictures/Piranh_390_piran.jpg

Piranhas are the biggest threat to humans when they are bleeding in the water. 

An intersting fact about sharks is that they actually have no bones.

Some other animals found in the shark tank are sea turtles, common bluestripe snapper, and laced moray. 

Photo Credit: http://www.alaska-in-pictures.com/data/media/1/sea-urchin_1566.jpg

These Giant Red Sea Urchins have movable spikes to protect them from predators. These sea urchins also have five teeth that help it ingest algae and break down other food. 

Archerfish gathers water and using its mouth, it shoots water at insects, making them fall in the water. Then, it just eats it. 

The sea turtle in the Tropic Zone is named Schoona. 

Here are some of the flamingos we saw in the Amazon exhibit. We did not know they could fly until they swooped down right above our heads. 

Here is a marmoset that was also in the Amazon exhibit. 

The variety of fish and colours make this picture fantasy-like.

The penguins with their puffed out chests reminded me of Penguins of Madagascar.

And here is the giant penguin stuffy that I wanted but couldn't afford.

Kriselda and I <3

 This was my all-time favourite photo!! S/He was just so adorable that i had to make him/her my wallpaper on my phone.

During the afternoon, we did the wet lab. We got to touch many different sea creatures from different phylums. My favourite were the cnidarians and the echinodermata. I liked the cnidarians because when  you touched them, the tentacles left a sticky feeling (which was actually the nematocysts burrowing into your skin). It was a very interesting sensation. I liked touching the sea cucumbers because unlike its spiky appearance, sea cucumbers are actually very soft and velvety. Even the spikes were soft! It had a very soothing feeling. After our wet lab, we got ready to go home.

I enjoyed my day at the aquarium very much. Before, while I liked walking around and looking at the creatures, I did not really understand them. Now, I am more excited because I can recognize the stuff we already learned in class and link it to the living sea creatures around me. This trip to the aquarium really changed my perspective on sea creatures. So much so that once I started on my blog, I just couldn't stop. There is just simply too much to say!!