Lower Invertabrates
Lower Invertabrates
This unit in biology, we covered half of the kindgom Animalia. All member of the animal kingdom share characteristics. Those includes being heterotrophic {1}, multicellular, eukaryotic , does not contain a cell wall. The kingdom Animalia includes many pylums, but a certain amount are classfied as the lower invertabrates (meaning that they do not contain a backbone or vertebral column. ). These Lower invertabrate phylums are Phylum Porifera, Phylum Cnidaria, Phyum Platyhelminthes and Phylum Nematoda.
As the first phylum of Animalia, phylum Porifera is the most primitive and less advanced of all the phyla. It was the first of the animals to branch out and experiment in multicellularity for animals. The phylum Porifera, which in Latin means “pore-bearers”, includes the sponges. They are sessile, asymmetrical creatures with a simple body plan. They have lived along our water for at least 540 million years, making them the most ancient animals.
Changed little since they evolved Phylum Porifera Characteristics Tissue layers and organization -No true tissue layers, contains specialized cells which do not work cooperatively Development of a coelom -No coelom, diploblastic Symmetry -asymmetrical Reproduction -Sexual- internal fertilization- the hermaphroditic sponge releases it gametes (sperm/egg) and it fertilized in an organism -Asexual- budding and Gemmules Life cycles -not specified Bodies and any specialized structures -Feeding- filter feeders {51} -Excretion- circulates waste/ other unwanted particles out from the sponge by excreting them through the osculum {52} -Response and motility- no specified response, sessile Classes and examples of each -Calcarea- -Hexactinellida- -Demospongiae- - Sclerospongiae- Cephalization -does not undergo cephalization |
As the second phylum of animals, there isn’t much complexity, but cnidarians do showcase an array of interesting features. They are soft bodied organisms which have stinging cells, which they use to hut prey. They also go through alternations of generations, where they switch from being a sessile creature called a polyp to a motile organism named a medusa. In this phylum you see jellyfish, and other marine animals. Phylum Cnidaria characteristics Tissue layers and organization -diploblastic, has a ectoderm, endoderm and a fake middle layer, mesoglea Development of a coelom -does not have a coelom Symmetry -radial, in both polyp (not colony wise) and medusa Reproduction -Sexual- external fertilization -Asexual-Budding Life cycles -has alternation of generations, starts as motile gametes{------}, becomes a zygote, into a swimming larva called a planula, then becomes a polyp, which then buds to give off young medusas, which mature into adult medusas which releases the motile gametes Bodies and any specialized structures -Feeding- predators, caught prey in medusa stage as -Excretion- through mouth/anus -Response and motility- nerve net and jet propulsions Classes and examples of each Hydrozoa-Obelia/hydra Anthozoa-anemone, sea pen and coral Scyphozoan- Jellyfish Cephalization -not cephal |
Platyhelminthes, also known as flatworms, are creatures which stir in water and in organisms. As the first phylum with parasites, you see such creatures as tapeworms, and others such as a free living planaria. These worms are known to reproduce mostly sexually, and with a process called penis fencing {43}. These animals are also the first phylum known to be triploblastic {31} and bilateral symmetry {32}
Phylum Platyhelminthes characteristics Tissue layers and organization -triploblastic. With ectoderm, mesoderm and endoderm Development of a coelom -still no coelom developed Symmetry -bilateral symmetry Reproduction Sexual- penis fencing -Asexual- fission and regeneration Life cycles -liver fluke -tapeworm Bodies and any specialized structures -Feeding-parasitic (absorb through epidermis) and predators -Excretion-flame cells -response and motility-nerve ladder, motile Classes and examples of each Turbellaria-planaria Trematoda-blood/liver flukes Cestoda-tapeworm Cephalization -First phylum to undergo cephalization due to the bilateral symmetry |
Nematoda, also known as the parasitic phylum, is home to some of the worm parasites. Such roundworms like guinea stick worm, Trichinella and pinworm are found classified as a Nematoda. Even though the phylum is mostly parasitic, there are free living organisms. The free living organisms are decomposer which live off of soil and water. Nematodes are also the first phylum to contain a body cavity.
Phylum Nematoda characteristics Tissue layers and organization -triploblastic, with ectoderm, mesoderm and endoderm Development of a coelom -pseudocoelom Symmetry -bilateral symmetry Reproduction Sexual- mostly Asexual- rare Life cycles Parasitic life cycles-ascaris, hookworm, pinworm, Trichinella, wurchereia bancrofti and guinea worm stick Bodies and any specialized structures- Feeding-complete digestive system (tube within a tube) Excretion-out anus Response and motility-lateral nerves Classes and examples of each Free living-decomposers Parasites- ascaris, hookworm, pinworm, Trichinella, wurchereia bancrofti and guinea worm stick Cephalization -are cephal |
Vocabulary
{1} –Sessile- non motile, attached to some surface
{2}-Motile- can move
{3}-Polyp-a generation which members of phylum Cnidaria undergo, the sessile stage where they reproduce asexually and grow in colonies. May stay dormant for 50 years before producing medusas.
{4}-Medusa- a generation which member of phylum Cnidaria undergo where they bud from a polyp and become motile, hunt for prey and release gametes for external fertilization
{5} Alternation of Generations- In cnidarians, a member undergoes two different life cycles as a medusa and polyp, alternating to each
{6} Choanocytes-
{7}-Tentacles-a structure which cnidarians have that are found extending into the environment and attacking prey with toxins
{8}-Cnidcytes- Stinging cells which line the tentacles and have nematocysts which latch unto prey and release toxins
{9}-Nematocyst- stinging capsule which contain a thread lined with barbs that penetrates prey and releases toxins in order to kill or paralyze
{10}-Gastrovascular cavity
{11}-Tissues- a type of material which plant and animals are made of
{12}-Diploblastic-Two germ layers (tissue), ectoderm and endoderm (mesoglea is cellular middle layer in cnidarians)
{13}-Ectoderm-outermost germ/tissue layer (skin)
{14}-Endoderm- innermost germ/tissue layer (organs)
{15}-Mesoglea- middle cellular layer in cnidarians, not a true tissue layer
{16-mesoderm- middle germ/tissue layer muscles)
{17}}- Asymmetrical- no symmetry
{18}-Radial symmetry- symmerty around a central axis
{19}- Asexually- reproducing with only one parent and one set of genetic material thereby making an offspring identical to the parent
{20}-Sexually-reproducing with two separate parents and making an offspring with genetic diversity
{21}- Budding- forming a new bud off of a mature adult which contains the exact DNA
{22}- Gemmules- a group of ameobocytes covered by a hard outer covering
{23}-Fragmentation- a process where an organism is broken and regrows
{24}- Internal fertilization- when an egg is fertilized by sperm inside of an organism
{25}-Gametes- sex cells (egg and sperm)
{26} -hermaphrodite- an organism which contain both male and female reproductive organs and gametes
{27}- External fertilization- when an egg is fertilized by sperm outside of an organism
{28}-Nerve net- a collection of nerves loosely encased in a body, unorganized nervous system
{29}- Coelom- a body cavity which is found between the mesoderm and endoderm
{30}-Cephalization-the concentration of nerves ad sensory organs in the anterior region
{31}-Triploblastic-three complete germ/tissue layers, ectoderm, mesoderm and endoderm
{32}-Bilateral symmetry- able to be dived into symmetrical halves, split into an anterior, posterior, ventral and dorsal end
{33}-Anterior Region- Top part of a bilateral organism
{34}-Posterior Region- Bottom part of a bilateral organism
{35}-Ventral Side-Front side of a bilateral organism
{36}-Dorsal side-back side of a bilateral organism
{37}-Statocysts- sensory organ which detects the force of gravity
{38}-Ocelli- sensory organ which detects light
{39}-Nerve ladder- nervous system arranged in a ladder pattern
{40}-Ganglia-Primitive “brain” found in anterior region
{41}-Flame cells- act like a primitive kidney and excrete waste
{42}-Pharynx- A structure which is part of the digestive tract, in Platyhelminthes extend out into environment from the mouth and sucks up nutrients
{43}- Penis Fencing- Platyhelminthes way of sexual reproduction, a fight between hermaphroditic flatworms, which the victory releases its sperm onto he loser and the loser must bear motherhood
{44}-Parasite- an organism which lives in other organism, dependent for food and thereby harming the host organism
{45}- Free Living- An organism who lives independently out in an environment
{46}-Endoparasitic- a parasite which lives inside a organism
{47}- Malnourishment- lack of proper nutrition, caused by not having enough to eat, not eating enough of the right things, or being unable to use the food that one does eat.
{48}- Pseudocoelom- a fake body cavity which is not complete because it is not covered completely in muscle.
{49}-Acoelomate- an animal which does not have body cavity/ coelom
{50}-Encysted- encased in a cyst.
{51}-Filter feeding- a process of getting nutrition by filter particles through and collecting the ones needed for the organism. In sponges, they circulate water throughout, from their Ostrum, through the centre of the sponge, where Choanocytes causes a current which pulls the particles towards them, collecting these particles. The unwanted particles or waste is excreted through the osculum.
{52}- Osculum-the osculum is a structure in the sponge which is a large opening where excretes the waste, water and unwanted particles from the top of the sponge.
{2}-Motile- can move
{3}-Polyp-a generation which members of phylum Cnidaria undergo, the sessile stage where they reproduce asexually and grow in colonies. May stay dormant for 50 years before producing medusas.
{4}-Medusa- a generation which member of phylum Cnidaria undergo where they bud from a polyp and become motile, hunt for prey and release gametes for external fertilization
{5} Alternation of Generations- In cnidarians, a member undergoes two different life cycles as a medusa and polyp, alternating to each
{6} Choanocytes-
{7}-Tentacles-a structure which cnidarians have that are found extending into the environment and attacking prey with toxins
{8}-Cnidcytes- Stinging cells which line the tentacles and have nematocysts which latch unto prey and release toxins
{9}-Nematocyst- stinging capsule which contain a thread lined with barbs that penetrates prey and releases toxins in order to kill or paralyze
{10}-Gastrovascular cavity
{11}-Tissues- a type of material which plant and animals are made of
{12}-Diploblastic-Two germ layers (tissue), ectoderm and endoderm (mesoglea is cellular middle layer in cnidarians)
{13}-Ectoderm-outermost germ/tissue layer (skin)
{14}-Endoderm- innermost germ/tissue layer (organs)
{15}-Mesoglea- middle cellular layer in cnidarians, not a true tissue layer
{16-mesoderm- middle germ/tissue layer muscles)
{17}}- Asymmetrical- no symmetry
{18}-Radial symmetry- symmerty around a central axis
{19}- Asexually- reproducing with only one parent and one set of genetic material thereby making an offspring identical to the parent
{20}-Sexually-reproducing with two separate parents and making an offspring with genetic diversity
{21}- Budding- forming a new bud off of a mature adult which contains the exact DNA
{22}- Gemmules- a group of ameobocytes covered by a hard outer covering
{23}-Fragmentation- a process where an organism is broken and regrows
{24}- Internal fertilization- when an egg is fertilized by sperm inside of an organism
{25}-Gametes- sex cells (egg and sperm)
{26} -hermaphrodite- an organism which contain both male and female reproductive organs and gametes
{27}- External fertilization- when an egg is fertilized by sperm outside of an organism
{28}-Nerve net- a collection of nerves loosely encased in a body, unorganized nervous system
{29}- Coelom- a body cavity which is found between the mesoderm and endoderm
{30}-Cephalization-the concentration of nerves ad sensory organs in the anterior region
{31}-Triploblastic-three complete germ/tissue layers, ectoderm, mesoderm and endoderm
{32}-Bilateral symmetry- able to be dived into symmetrical halves, split into an anterior, posterior, ventral and dorsal end
{33}-Anterior Region- Top part of a bilateral organism
{34}-Posterior Region- Bottom part of a bilateral organism
{35}-Ventral Side-Front side of a bilateral organism
{36}-Dorsal side-back side of a bilateral organism
{37}-Statocysts- sensory organ which detects the force of gravity
{38}-Ocelli- sensory organ which detects light
{39}-Nerve ladder- nervous system arranged in a ladder pattern
{40}-Ganglia-Primitive “brain” found in anterior region
{41}-Flame cells- act like a primitive kidney and excrete waste
{42}-Pharynx- A structure which is part of the digestive tract, in Platyhelminthes extend out into environment from the mouth and sucks up nutrients
{43}- Penis Fencing- Platyhelminthes way of sexual reproduction, a fight between hermaphroditic flatworms, which the victory releases its sperm onto he loser and the loser must bear motherhood
{44}-Parasite- an organism which lives in other organism, dependent for food and thereby harming the host organism
{45}- Free Living- An organism who lives independently out in an environment
{46}-Endoparasitic- a parasite which lives inside a organism
{47}- Malnourishment- lack of proper nutrition, caused by not having enough to eat, not eating enough of the right things, or being unable to use the food that one does eat.
{48}- Pseudocoelom- a fake body cavity which is not complete because it is not covered completely in muscle.
{49}-Acoelomate- an animal which does not have body cavity/ coelom
{50}-Encysted- encased in a cyst.
{51}-Filter feeding- a process of getting nutrition by filter particles through and collecting the ones needed for the organism. In sponges, they circulate water throughout, from their Ostrum, through the centre of the sponge, where Choanocytes causes a current which pulls the particles towards them, collecting these particles. The unwanted particles or waste is excreted through the osculum.
{52}- Osculum-the osculum is a structure in the sponge which is a large opening where excretes the waste, water and unwanted particles from the top of the sponge.
Comparing Phylum Advancement
In the evolution of animals, we have an array of complexity. Those who branched early in the evolutionary process were less advanced, and more primitive in their functions and body plan. As we scale the branches, or phylum’s, of the kingdom Animalia, we see more characteristics that separate each phyla. These characteristics are used to judge them based upon if they carry this characteristic. The way I have learned to classify the phylum is
Tissue layers and organization
Development of a coelom
Symmetry
Reproduction
Life cycles
Bodies and any specialized structures-feeding-excretion-response and motility-reproduction
Cephalization
Why Cnidarians are more advanced than Poriferans
Two examples of phyla’s which are similar but differ in complexity are phylum Porifera and phylum Cnidarian. Porifera, being the first phylum of Animalia, is the most basic, while phylum Cnidaria has shown promising evolutionary progress, separating the two. Cnidaria is much more advanced the Porifera. Cnidaria was the first huge step of creating the intricate animals of today, including us. Porifera is only a sessile {1} creature for its entire life cycle, while cnidarians have both motile {2} and sessile generations they experience. Cnidarians life cycle includes an alternation of generations{5], living as both polyp {3} and medusa {4}, Porifera lives only in a sessile stage as a sponge, not living through another identity of an organism. When feeding, Porifera filers water throughout its body, collecting particles through their Choanocytes{6}, while cnidarians are predators which use their tentacles {7}, Cnidcytes {8} and Nematocysts {9} as weapons to grasp prey and pull them in to their enzyme filled Gastrovascular cavity {10}. Phylum Porifera does not have any true tissues{11}, but do contain specialized cells which allows for functions to be completed. Cnidaria however ae diploblastic {12}, meaning they have two true tissue layers, a ectoderm{13} and a endoderm{14}, and a mesoglea{15}, which is not a true tissue layer, but acts as the true second layer, mesoderm{16}. Symmetry wise they also do differ, Porifera being asymmetrical {17} and cnidarians being radially symmetrical {18}. In reproduction they share both being able to produce asexually{19} and sexually{20}, but Porifera reproduces asexually through budding{21}, Gemmules{22} and fragmentation{23} and sexually through internal fertilization {24} with releasing gametes{25}, also phylum Porifera is hermaphroditic{26}. Cnidarian reproduce sexually through external fertilizations {27} in their medusa{28] stage, and asexually as a polyp{3] with budding{3}. In the matter of nerves, though both do not have a structure which acts as a brain per say, the cnidarians have a more advanced nervous system called a nerve net {31} Though both do not contain a coelom {32}, and have an opening that both acts as a mouth and an anus, and both are do not undergo cephalization{33}.
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Why Platyhelminthes are more advanced than Cnidarians
Phylum Platyhelminthes, the flatworm phylum, is an evolutionary step above phylum Cnidaria, and therefore more advanced. While Platyhelminthes and Cnidaria are both motile{2} predators which ingest prey in their gastrovascular cavity{10}, both have an incomplete digestive system. Also the lack of a body cavity (coelom {29} ) also proclaims them together less advanced then other phyla, but comparing Cnidaria to Platyhelminthes shows many characteristic advancements which Platyhelminthes has over Cnidaria. In the terms of a germ layer (also known as tissue), we have discovered that phylum Cnidaria is diploblastic{12} and lack a true tissue middle layer (mesoderm {16} ). Instead they have a cellular layer between their ectoderm{13} and endoderm{14} known as the mesoglea{15}. Platyhelminthes however, do contain a complete set of germ layer, making it triploblastic{31} and has a true mesoderm. Also in Platyhelminthes, the organisms have bilateral symmetry {32}, which means the organism can be separated into an anterior region {33}, a Posterior region {34}, a Ventral side {35} and Dorsal side {36}. While animals of Platyhelminthes have such complex symmetry, cnidarians have a more timid symmetry, which is radial {18}. Radial symmetry is primitive a very primitive division. This advancements in symmetry over cnidarians are what we humans are based upon, leaving us with a region for our heads, a region for our legs and front and back sides. In terms of nervous system, Platyhelminthes also more complex. The phylum Cnidaria has a less complex and organized nervous system called a nerve net {28}, and the loose jumble of nerves leaves a lack of many sensory organs, excluding its statocysts {37} and ocelli {38}. In phylum Platyhelminthes, we are shown a more organized and advanced nervous system, which because of the way it’s organized is called a Nerve Ladder {39}. This nerve ladder extends around the Platyhelminthes body and at the anterior region, all the sensory organs are compact. This is called cephalization {30} and is another advancements over Cnidaria. Also in this concentration of sensory organs (such as ocelli and statocysts) we have a primitive brain called the Ganglia {40}, which is the first known structure to act as a brain in the early phylum’s, therefore not included in Cnidaria. Another structure which became present in only Platyhelminthes and not in Cnidaria or Porifera is the beginning of an excretory system. Since it is was only the first signs of some sort of excretory system, it’s very simple, and has been called a primitive kidney. This primitive kidney is called Flame cells {41}, which extend throughout their body and excrete waste through pores. Cnidarians do not have a separate system for excreting waste, and has a single opening which acts as both a mouth and an anus. In Platyhelminthes, they have a pharynx {42} which extends out of the mouth to capture nutrients and after being digested is excreted through the flame cells. Another system which had advanced in Platyhelminthes is reproductive, and in this phylum reproduction is mostly sexual, only reproducing asexually through fission and regeneration and sexually through “penis fencing” {43}. Phylum Cnidaria shares asexually and sexually equally through its generations. Lastly, Platyhelminthes includes species which are parasitic{44} and free living {45}, while cnidarians only includes their free living medusas and polyps.
How members of Nematoda are more advanced than Platyhelminthes
Phylum nematode, the last of the lower invertebrate phylum’s and the most advanced, is especially more advanced than its fellow lower invertebrate phylum, Platyhelminthes. Though both include an array of parasitic members, there are many huge characteristic differences between the flatworms (Platyhelminthes) and the roundworms (nematode). While Platyhelminthes includes the parasitic classes of trematoda and cestoda, nematoda’s majority is parasitic roundworms. Also these roundworms are much more serious in their harmful effects. For example the guinea stick worm, found in nematode, is a life threatening and painful parasitic worm, while the Platyhelminthes endoparasitic{46} tapeworm causes malnourishment{47} at worst. The most major difference between the phyla is the fact that nematode has the first sign of a body cavity in all lower invertebrates. It is only a pseudocoelom{48} and therefore not complete, having the body cavity not complete covered by muscle. .But it is still found between the germ layers of mesoderm and endoderm. Having a pseudocoelom is much more evolved then being an acoelomate{49} like phylum Platyhelminthes and containing no body cavity whatsoever. Also, inside the tube like form on nematode, we find a complete digestive system with separate opening for mouth and anus. This “tube within a tube” digestive system is largely diverse from Platyhelminthes incomplete digestive system with flames cells as an excretory system. Also in nematode we have specific genders and structural differences between male and female and that hermaphroditic trait in Platyhelminthes is no longer used. Besides these major structural differences, they share many similarities. In one phylum difference there is very huge evolutionary change. Though as we continue down the phylum of animals, we will get more complexity until we reached humans, which overpower all other animals in their vast advancement.
Questions
Parasites vs Free Living
A parasite, being of a simple nature and not in need of many complex structures, can be successful without any of the characteristics of the free living worms, which do in fact need more advanced structures. However, they both do share some characteristics, and of course, differences. Free living lives outside of other organisms, therefore there need for complexity is hefty and by the means of natural selection the more beneficial the traits are, the more abundant they will be. SO compared to parasites they have more functional structures and greater need. Parasites are tiny organisms which lives off of another organism absorbing their nutrients and traveling throughout, thereby harming the hot organism. In parasites, they lack many things. They have no opening where they could ingest food even though serious cases cause malnourishment. Instead they absorb nutrients trough their epidermis and since their epidermis is a larger surface area then a mouth would be they are capable of absorbing a large amount. Also they do not have proper sensory organs like ocelli or statocysts like free living do because their need to see and understand gravity is useless because they are born knowing how to maneuver and anything besides that does not benefit them. Having the ability to detect light d n understand gravity is way more important in free living since they do everything independently and most manoeuver throughout different environments besides other organisms digestive, respitory and circulatory systems.
Trichenella
Trichinella is a type of parasitic roundworm fund in the phylum nematode. Like all nematodes, they contain a pseudocoelom, have a complete digestive tract and are not hermaphroditic. They also have a very primitive and simple structures because they are provided with many needed things such as nutrition and oxygen inside other organisms. Trichinella is cause by eating infected undercooked pork, and its life cycle only includes a primary host, no intermediary host. It invades selected tissue muscles forming encysted larva, causing trichinosis. It starts with ingesting the infected meat which has been poorly prepared and still contains the larva in the pig’s muscles. Once inside, the encysted larva is broken down by the enzymes in the stomach and is released in the small intestines. They mature inside, and grow to their adult form. Then they are deposited in mucosa and circulate through the bloodstreams to the muscle, where they become encysted {16} and causes pain. There it will stay until treated or the muscle ingested by another organism. To prevent this infection of the Trichinella worm
Just like in humans, in pigs, the encysted larva is passed only through cannibalism. They get it the same way and it enters and spreads throughout. Other animals who ingest the meat of an infected pig or another organism that has gotten the infection will also be infected without proper preparation. |
Ascaris Dissection
In class, we partook in a dissection on one of the nematoda species, Ascaris. Objective of this dissection was to discover and explore the anatomy of this parasitic worm. We had chosen females becuase they have a larger body then the males, due to the fact hat they arry eggs. Males typically have a hooked posterior which is used to grasp the females for reproduction. Females have a straight the shape.