Lower invertebrates
How are Cnidarians more complex than Poriferans?
Cnidarians
Cnidarians come from the phylum Cnidaria. Phylum Cnidarian consists of three classes; Class Hydrozoa, which includes the Hydra species and the Obelia species, Class Anthozoa, which includes anemones and corals, and Class Schyphozoa which includes the Jellyfish. Cnidarians have radial symmetry and are diploblastic, have two germ layers, which are an outer epithelium (epidermis), and a inner epithelium (gastroderm). They also have another layer called a mesoglea which is a jelly like layer in between the two true tissue layers. Something that makes them more advanced than Poriferans is that they contain a nerve net nervous system while Poriferans do not have any nerves. Cnidarians have an alternation of generations life cycle and go through a sessile stage (polyp) and a motile stage (medusa). They get rid of their waste through diffusion and digestion takes place in their gastrovascular cavity. Cnidarians reproduce asexually via budding during the polyp stage and sexually via external fertilization (motile gametes) during the medusa stage.
Poriferans
Poriferans come from the phylum Porifera meaning pore bearer. Poriferans are the most primitive and simplest animals. This class consists of many different sponges including the Red Beard sponge, the Glass sponge, and the Giant Vase sponge. Unlike Cnidarians, Poriferans are asymmetrical and do not contain any germ layers. Like I said above, they also do not have a nervous system. To expel waste products, water is circulated through the body with the help of collar cells. Digestion is done through the collection of particles in water as it is circulated through the system via the collar cells. Poriferans can reproduce both sexually via internal fertilization, and asexually via budding and gemmules. Although there are many differences between the to Phyla, They also share some similarities. Both Phyla's live in marine and fresh water and both have a sac plan.
How are Platyhelminthes more advanced than Cnidarians?
Phylum Platyhelminthes consists of the Flatworms. The three classes include; Class Turbellaria which includes the Planaria, Class Trematoda, which includes the parasitic flukes, and Class Cestoidea, which are the tapeworms. Unlike Cnidarians, these worms are triploblastic, meaning they have three germ layers and also have bilateral symmetry. These worms are still primitive as they lack a body cavity. Another advancement Phylum Platyhelminthes has over Cnidarians is that they have a nerve ladder instead of a nerve net. Unlike Cnidarians, flatworms have developed flame cells to get rid of waste. Flatworms also have developed a ganglia or "simple brain" via cephalization. Similarly to Cnidarians, flatworms digest in their gastrovascular cavity, but use their pharynx to collect food.
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How is Phylum Nematoda more advanced than Platyhelminthes?
Nematodes come from the Phylum Nematoda. This Phyla consists of all roundworms. Some of the members in Phylum Nematoda include the Ascaris species, which are the intestinal roundworms, the Hookworm, the Pinworm, the Trichenalla worm, the Filaria worm, and the Guinea Stick worm. Nematodes are highly advanced compared to Platyhelminthes as they have a tube within a tube body plan, meaning they have a separate mouth and anus. The roundworms also compare to Nematodes as roundworms are pseudoceolomates and the flatworms are acoelomates. Similarly to Platyhelminthes, Nematodes are triploblastic, meaning they have three germ layers, and are bilaterally symmetrical. Unlike digesting in the gastrovascular cavity, Nematodes digest in a long tube like digestive tract.
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Successful parasite vs successful free-living worm
Free-living worms:
Free living worms are not harmful to humans and do more positive things for us than negative. These worms live freely, and do not depend on a host. Free-living worms are very helpful as they are decomposers and break down waste into useful nutrients for others. An example of a free-living worm would be a Planarian which comes from the class Turbellaria. Characteristics of a Planarian are that they contain a ganglia or "simple brain", eye spots, a pharynx, which extends out the gastrovascular cavity and acts as the worms mouth, and a nerve ladder. They also have anterior and posterior ends as well as ventral and dorsal sides. Parasitic worms: Parasitic worms live inside a host and feed on blood, tissues and other parts of the host which can be very harmful. Most parasitic worms live and reproduce inside the hosts small intestine and their eggs come out in there feces to continue their life cycle. Other parasitic worms can live in your lungs, lower bowel, and even cause cysts in your muscle tissue. An example of a parasitic worm is the Trichenella worm. The Trichenella worm is obtained by a host by eating undercooked or improperly cooked pork. These parasites invade selected muscle tissues and form painful cysts inside them. A Trichenella worm has a tube within a tube body plan and a pseudocoelom between their mesoderm and endoderm. Reproduction for these worms is mostly sexual. |
Hookworm
Hookworms (Necator species) are parasitic roundworms that are also know as the itch worm. I find this worm particularly disgusting as they burrow into your toes causing you to itch, and then enter through the cuts made from scratching. The human hookworm feeds on blood inside the intestine and can drain 20ml of blood per day! A hookworm infection can cause appetite loss, loss of nutrients, nausea, fever, and intestinal cramps. Ways a hookworm can be treated include medication prescribed by your doctor, and sometimes ever surgery. Ways to prevent getting a hookworm is to always wear shoes when outside/walking through feces. A typical life cycle of a hookworm starts with the hookworm entering through the toes. This happens when someone walks barefoot outside or in feces that contain the worms. Once the hookworm has entered through your toes, it makes its way through the blood stream and up to the lungs. Once in the lungs, the worm is coughed up and re-swallowed and ends up in the small intestine. The worm, now once an adult, lays eggs in the small intestine and the eggs come out in your feces.
Ascaris dissection
Higher Invertebrates
Earthworm dissection
Analysis:
1. What is the name of the pumping organs of an earthworm? Like humans, the heart is a pumping organ in an earthworm. 2. In the earthworm, trace the parts of the digestive tract in which food passes. Food in an earthworm enters through the mouth, gets pushed through the pharynx, then down the esophagus. The food then enters the crop where it is stored and eventually moves to the gizzard where the food is absorbed. The waste from the food travels through the intestine and is excreted out the anus. 3. What of the parts of the earthworms body that you saw are included in the excretory system?
The nephridia is an organ that acts as a kidney to remove metabolic waste from the earthworms body. 4. Among the earthworms structural adaptations are its setae. How do you think the earthworms setae make it well adapted to its habitat? The earthworms setae keeps the worm from slipping when in motion and keeps it able to move forward. 5. How is the earthworms digestive system adapted for extracting relatively small amounts of food from large amounts of ingested soil? The gizzard breaks down soil and increases the amount of surface area. This allows food to be extracted more easily. The worms digestive system is also very long so it allows the food a lot of time to digest. 6. What did each germ layer develop into in the earthworm? The Ectoderm developed into skin/nerves The Mesoderm is the muscle and the circulatory system The Endoderm developed into the digestive tract The coelom is the cavity 7. What is the function of the nephridium? How does it complete this function? The nephridium's function is to excrete waste, (it acts as a kidney) 8. How is the sand worm different and similar to the earthworm? The sand worm is bigger and have obvious parapodia. Both the sand worm and earthworm are segmented and have a coelom. 9. How is the leech designed to live as an ectoparasite? What are the similarities and differences between the leech and earthworm? Similarities Differences ~Phylum Annelida ~Leeches live in water ~Same germ layers (ectoderm, ~They are parasitic mesoderm, endoderm) ~Feed on blood ~Have suckers to attach to their host (externally) |
Squid dissection
For this dissection I was away.
Crayfish dissection
1. How many pairs of appendages did your crayfish have?
Our crayfish had 29 appendages (2 chelipeds, 2 antennae, 2 antennules, 8 walking legs, 10 swimmerets, 4 uropods, and 1 telson) 4. What is the sex of your crayfish? Our crayfish was a male, we knew this because the first pair of swimmerets were long and stiff unlike females. 5. Why is there so much surface area on the gills of a crayfish? So it can exchange gases and CO2 with water. With a greater surface area oxygen can be exchanged more quickly. This allows the crayfish to move faster as well. 6. Draw the digestive system and label the structures food would pass through. Food enters through the mouth with the help of the mandibles and maxillipeds. It then travels down the esophagus and into the stomach where it is broken by digestive acids produced my the digestive gland. The partially digested food enters the intestine where the nutrients are absorbed and then the waste is excreted out the anus. 7. Which appendage(s) is used to: ~Sense: compound eye and antennae, antennules ~Defend: chelipeds ~Mate: pseudo penis in males , swimmerets in females ~Eat: chelipeds ~Chew: mandible ~Move backwards: tail ~Move forwards: walking legs ~Swim: swimmerets 8. How are arthropods more advanced than other phyla that we have looked at thus far? They have specialized appendages that help them defend and eat, the chilipeds, help them move, the walking legs, and help them swim, the swimmerets. They have a single improved hear and a tough exoskeleton that protects them. Some arthropods have wings and can fly. They also all mate sexually. Arthropods have adapted to breath on land using either book lungs, in arachnids, and tracheal tubes, in insects. 9. Why are insects so prolific while the crayfish are not. Insects are more prolific than crayfish because of multiple reasons. First of all they are tiny and can easily hide, which makes it hard for predators to find them. Also, since they are so small, they do not eat much. Secondly, insects have evolved the ability of flight, which can also contribute to escaping predators. |
Sea star dissection
1. What type of symmetry did your sea star have?
5-part radial symmetry, or pentaradial symmetry.
2. How many arms does your sea star have?
Our sea star had five arms.
3. Label the central disk, arms, spines, eyespot, and madreporite on the diagram below.
5-part radial symmetry, or pentaradial symmetry.
2. How many arms does your sea star have?
Our sea star had five arms.
3. Label the central disk, arms, spines, eyespot, and madreporite on the diagram below.
4. What is the upper surface of the starfish called?
The dorsal side is called the aboral surface.
5. What is the lower surface of the starfish called?
The ventral side is called the oral surface.
6/7/8/9.Label the oral spines, mouth, ambulacral groove and tube feet/ Label the pyloric caeca, stomach,central disc, gonads, ampulla and ossicles/ Label the lateral canal, ring canal, stone canal, and madreporite, and the path of water flow.
The dorsal side is called the aboral surface.
5. What is the lower surface of the starfish called?
The ventral side is called the oral surface.
6/7/8/9.Label the oral spines, mouth, ambulacral groove and tube feet/ Label the pyloric caeca, stomach,central disc, gonads, ampulla and ossicles/ Label the lateral canal, ring canal, stone canal, and madreporite, and the path of water flow.
10.On which surface are these parts of the sea star visible:
Mouth: Oral Madreporite: Aboral Suckers: Oral Oral spines: Oral Eyespots: Aboral (end of arms) Ambulacaral groove: Oral 11.What part of the tube foot creates suction to open clams whenever the sea star feeds? The ampulla controls the water that enters and moves the tube feet and create a suction force strong enough to open clam shells. 12.Why do the gonads sometimes appear larger The gonads are the reproductive glands in a sea star. During mating season the gonads appear larger. 13. What type of skeleton, endoskeleton or exoskeleton, does the sea star have? A sea star has an endoskeleton that is made up of calcium-carbonate. 14. What bony plates make up its skeleton? The bony plates in a sea star are called ossicles. They are made up of calcium-carbonate. These plates make up the skeleton and allow for flexibility and easy movement for the starfish. 15. What is the function of the pyloric caeca? The pyloric caeca produces digestive juices to help break down food and fully digest it. The pyloric caeca is connected to the pyloric stomach. 16. Where is the stomach of the sea star located? What can the sea star do with its stomach when feeding on clams and oysters? There are two stomachs inside a sea star that are located inside the central disk. The pyloric stomach stays inside the sea star to digest food. The cardiac stomach is vomited out of the mouth of the sea star, and into a clam or oyster shell that is partially opened. The cardiac stomach, once inside the shell, ingests the soft inside of its prey. The stomach is then pulled back inside the sea star to finish digestion. |