Do All Bilaterally Symmetrical Animals Have Cephalization, Circulatory Systems , Digestive System

Animal phyla

This folio is part of a series introducing various animal phyla. For the showtime day of brute phyla, you should await at these pages:

• Animal phyla
• Porifera
• Cnidaria
• Platyhelminthes
• Nematoda
• Annelida

On other lab days, we'll await at some other animal phyla:

• Mollusca and Echinodermata. We'll look at these two phyla very briefly; I don't have carve up pages for them.
• Arthropoda (including Insects)
• Chordata: Branchiostoma & Lamprey larva, along some other topics specific to vertebrates.

Objectives

• Identify members of the animal phyla covered in lab.
• Describe the animal body program features on this folio and identify them in the fauna specimens you run into in lab. You won't see all of these features in i lab day.

Specimens

The specimens are listed on the pages for the specific phyla.

What is an animate being phylum?

An animal phylum (plural: phyla) is a high-level taxonomic group, describing a group of species sharing a phylogenetic human relationship based on common ancestry. Beast phyla are besides traditionally divers by the fact that all members of the phylum share a number of distinct morphological features, which are known as the body plan of that phylum. Thus, past studying the defining features of various animal phyla, you are besides studying the central features that define animal diversity.

Defining features of animal phyla

The fundamental features that define animal phyla are based on early events in beast development, such equally gastrulation. These early events change rarely in evolution, and in many cases set the stage for later on developmental events. Features that announced later in development, such as feathers or pilus in vertebrates, are more than likely to be defining features of clades within a phylum.

Embryonic tissue layers

As y'all learned in the animal development lab, gastrulation forms three embryonic tissue layers, which afterward differentiate to become all the cell types of the mature animal. This type of development is known as triploblastic. This is true for almost all animals, but you lot'll ii exceptions in Bio 6A: the sponges (phylum Porifera), which don't have well-defined tissues at all, and the phylum Cnidaria (jellyfish, etc.), which form only two embryonic tissue layers (diploblastic development). Without three embryonic tissue layers to course a foundation for afterwards evolution, the sponges and cnidarians are limited to very elementary torso forms.

Symmetry

Humans are bilaterally symmetrical – our left and right sides look more or less similar mirror images of 1 another, while our fronts look quite different from our backs. Most of the animals y'all're familiar with are also bilaterally symmetrical, but some animals aren't. Jellyfish (phylum Cnidaria) are more than or less round and don't have a left or right side; they can move in any direction every bit well. Cnidarians are radially symmetrical.

Sponges take no particular symmetry; they are not radially or bilaterally symmetrical.

Cephalization

Cephalization means having a caput. For humans and many other animals, our head is the part of the body that has the brain and almost of the sensory organs. Cnidarians such as jellyfish don't have whatsoever cephalization; their nerves and sensory organs are distributed all around their bodies. Jellyfish don't have brains; they also don't have a front or a dorsum. Cephalization only occurs in bilaterally symmetrical animals.

Body crenel

The body cavity is the place where digestive and other internal organs form. Many of your organs are hanging more or less freely in 2 large cavities in your body: the intestinal cavity (containing the intestinal tract) and the thoracic cavity (containing the lungs). The body cavity is formed early in embryonic development, and has important effects on later on development. With respect to the body cavity (or the lack thereof), animal come in three types:

Coelomate: the body contains a cavity (the coelom), fully lined with mesodermal tissue, in which major organs develop. This blazon of structure is found in the virtually circuitous phyla of animals, including arthropods and chordates.

Pseudocoelomate: The body contains a cavity (the pseudocoelom) that is non fully lined with mesodermal tissue, and in which major organs develop. This type of structure is found in some less-circuitous animals, such as nematodes.

Acoelomate: No body cavity; the body is more or less a solid mass. Cnidaria and flatworms are acoelomate. Notation that the gastrovascular crenel (or other blazon of gut) is non a body crenel. Acoelomate animals take simple body structures.

Segmentation

Many animals' bodies are divided into segments. Segmentation is obvious in a segmented worm such every bit an earthworm (phylum Annelida) or in an insect (phylum Arthropoda); division is also visible in repeated trunk structures such as the backbones of vertebrates (phylum Chordata). On the other mitt, some animals, such equally planarians (phylum Platyhelminthes) or jellyfish (phylum Cnidaria) are not segmented at all.

Digestive tract

Bated from sponges, all creature phyla take a digestive tract, or gut. Cnidaria and flatworms have a gastrovascular crenel, a digestive tract with a unmarried opening. This could be called a 2-fashion gut, since any indigestible waste must come up out the same style it went in. For case, some flatworms eat snails by sucking the entire snail into the flatworm'south gastrovascular cavity through the pharynx, digesting it, then spitting out the beat out through the throat. Most other animals have an alimentary canal (as well called a consummate digestive tract, or merely a one-style gut), with a carve up mouth and anus. This type of digestive tract allows for much greater complexity and specialization.

Alimentary canals are simply found in animals with triploblastic development and a coelom or pseudocoelom.

Circulatory organisation:

Animal circulatory systems vary widely. Animals with a gastrovascular cavity don't have a divide circulatory arrangement; the gastrovascular crenel allows nutrients to be carried throughout the body, merely does non perform other circulatory system functions such equally delivering oxygen. Animals with this type of trunk plan must exist fairly pocket-sized and have relatively depression metabolic rates.

Larger, more complex animals may take an open or airtight circulatory system, as you lot learned in lecture.

Exoskeleton

Animals such equally venereal (phylum Arthropoda) have a difficult external skeleton that both protects and supports the animal'south body. An animal with an exoskeleton must typically molt, or shed its exoskeleton, in guild to grow.  The technical term for molting is ecdysis. Nematodes (phylum Nematoda) have a more flexible exoskeleton chosen a cuticle, just they must also molt in order to abound.

Animals come up in an immense range of different styles, and animal variety can't be described in a few short paragraphs. Withal, the features listed to a higher place provide a way of categorizing brute phyla in terms of their torso plans. These features create both opportunities and limits for the evolution of a group. For example, there aren't any large terrestrial animals that don't have some sort of hard skeleton.

Body programme table

This tabular array summarizes some of the fundamental body plan features of the animate being phyla covered in lab.

Study questions for animate being phyla

You don't demand to turn in answers to these questions. Notwithstanding, you lot may want to think
most them to help you prepare for the next lab exam. Some of the answers tin can be institute on this page, but others may exist on other pages of this site or in Campbell.

1. Why does it thing how many embryonic tissue layers are nowadays in a phylum? (In this lab, you've seen fauna phyla with either two or three embryonic tissue layers.)
2. How is body plan with a true coelom different from one with no body cavity or with a pseudocoelom?
3. Compare & contrast the skeletons (or lack of skeletons) in the 3 phyla from these labs.
4. Which phyla take motility, and how does it work?
5. Which phyla have muscles?
6. Which phyla take circulatory systems? Why would an animal have a circulatory system? How tin can any animate being survive without one?
7. Which phyla take specialized excretory organs? Why would an animal have them? How can any fauna survive without i?

Terms & Concepts to Call back

This listing includes terms from all the phyla listed at the top of the page.

• Annelida
• Appendages: jointed, branched
• Arthropoda
• Bilateral symmetry
• Cephalization
• Colonial vs. individual polyps
• Choanocyte
• Cnidaria
• Cnidocyte
• Coelom
• Cuticle
• Digestion: Intracellular vs. Extracellular
• Ecdysis (molting)
• Echinodermata
• Epidermis
• Exoskeleton vs. Endoskeleton
• Flagellated cells
• Gratuitous living vs. parasitic
• Gastrovascular cavity
• Hydrostatic skeleton
• Larva
• Drapery cavity (molluscs)
• Medusa
• Mesoglea
• Metamorphosis
• Mollusca
• Nematocyst
• Nematoda
• Nerve cords
• Neurulation
• Notochord
• Pharynx
• Phylum (plural: phyla)
• Platyhelminthes
• Polyp
• Porifera
• Pseudocoelom
• Radial symmetry
• Segmentation; specialization of segments
• Spicules
• Suspension feeding
• Symmetry: radial vs. bilateral vs. no symmetry
• Tagma/tagmata (arthropods)
• Tissues
• Water vascular arrangement of echinoderms

Sample multiple-choice questions

On the lab test y'all'll run across slides of the various phyla listed on this page. You might see multiple-selection (or fill up-in) questions like these:

1. What phylum is this?

ii. This species has:

1. No body cavity.
2. Pseudocoelom.
3. True coelom.

3. What is the structure indicated past the pointer? (Answers could be any of the structures labeled on the animal phyla pages.)

iv. How many embryonic tissue layers does this species course?

References & further reading

Campbell Biology, Chapter 33: An introduction to the invertebrates.

Source: http://brianmccauley.net/bio-6a/bio-6a-lab/animal-phyla

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