Which Of The Following Pairs Of Animal Phyla Are The Most Closely Related

Creature phyla

This page is office of a series introducing diverse animal phyla. For the offset twenty-four hour period of animal 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 wait at these ii phyla very briefly; I don't have separate pages for them.
• Arthropoda (including Insects)
• Chordata: Branchiostoma & Lamprey larva, forth another topics specific to vertebrates.

Objectives

• Identify members of the fauna phyla covered in lab.
• Describe the beast torso plan features on this page and identify them in the creature specimens you run into in lab. You lot won't see all of these features in one 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 relationship based on common ancestry. Animal phyla are also traditionally defined by the fact that all members of the phylum share a number of distinct morphological features, which are known as the body programme of that phylum. Thus, by studying the defining features of various brute phyla, you are also studying the fundamental features that define animal diversity.

Defining features of animal phyla

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

Embryonic tissue layers

As yous learned in the animal development lab, gastrulation forms three embryonic tissue layers, which later differentiate to go all the jail cell types of the mature animal. This type of development is known as triploblastic. This is truthful for most all animals, but you'll two exceptions in Bio 6A: the sponges (phylum Porifera), which don't have well-defined tissues at all, and the phylum Cnidaria (jellyfish, etc.), which class only two embryonic tissue layers (diploblastic evolution). Without three embryonic tissue layers to course a foundation for later evolution, the sponges and cnidarians are limited to very simple torso forms.

Symmetry

Humans are bilaterally symmetrical – our left and correct sides look more or less like mirror images of one another, while our fronts look quite dissimilar from our backs. Most of the animals yous're familiar with are besides bilaterally symmetrical, but some animals aren't. Jellyfish (phylum Cnidaria) are more or less round and don't have a left or correct side; they tin can move in whatever direction equally well. Cnidarians are radially symmetrical.

Sponges have no particular symmetry; they are non 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 most of the sensory organs. Cnidarians such every bit jellyfish don't take any 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 cavity

The body cavity is the place where digestive and other internal organs form. Many of your organs are hanging more than 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 trunk cavity is formed early in embryonic development, and has important furnishings on later development. With respect to the trunk cavity (or the lack thereof), animal come in three types:

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

Pseudocoelomate: The body contains a cavity (the pseudocoelom) that is not fully lined with mesodermal tissue, and in which major organs develop. This blazon of structure is establish in some less-complex animals, such every bit nematodes.

Acoelomate: No body cavity; the body is more or less a solid mass. Cnidaria and flatworms are acoelomate. Notation that the gastrovascular cavity (or other type of gut) is not a torso cavity. Acoelomate animals have simple body structures.

Division

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

Digestive tract

Aside from sponges, all animal phyla accept a digestive tract, or gut. Cnidaria and flatworms have a gastrovascular cavity, a digestive tract with a single opening. This could be chosen a 2-manner gut, since whatsoever boxy waste must come up out the same way it went in. For instance, some flatworms eat snails past sucking the entire snail into the flatworm's gastrovascular cavity through the throat, digesting information technology, then spitting out the shell through the pharynx. Most other animals take an alimentary canal (also chosen a complete digestive tract, or but a 1-mode gut), with a separate mouth and anus. This type of digestive tract allows for much greater complexity and specialization.

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

Circulatory organisation:

Fauna circulatory systems vary widely. Animals with a gastrovascular crenel don't have a split circulatory system; the gastrovascular cavity allows nutrients to be carried throughout the body, but does not perform other circulatory arrangement functions such as delivering oxygen. Animals with this type of torso programme must be fairly small-scale and have relatively low metabolic rates.

Larger, more complex animals may accept an open or closed circulatory system, equally you learned in lecture.

Exoskeleton

Animals such every bit crabs (phylum Arthropoda) have a hard external skeleton that both protects and supports the animal'southward body. An brute with an exoskeleton must typically molt, or shed its exoskeleton, in lodge to grow.  The technical term for molting is ecdysis. Nematodes (phylum Nematoda) accept a more flexible exoskeleton called a cuticle, but they must too molt in order to grow.

Animals come up in an immense range of different styles, and animal diversity can't be described in a few short paragraphs. However, the features listed above provide a way of categorizing creature phyla in terms of their trunk plans. These features create both opportunities and limits for the evolution of a grouping. For example, at that place aren't any large terrestrial animals that don't have some sort of hard skeleton.

Body program tabular array

This table summarizes some of the key trunk plan features of the fauna phyla covered in lab.

Study questions for animal phyla

You don't demand to plough in answers to these questions. However, you may want to think
about them to assist you prepare for the adjacent lab test. Some of the answers tin be found on this page, just others may be on other pages of this site or in Campbell.

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

Terms & Concepts to Remember

This list includes terms from all the phyla listed at the elevation of the page.

• Annelida
• Appendages: jointed, branched
• Arthropoda
• Bilateral symmetry
• Cephalization
• Colonial vs. private polyps
• Choanocyte
• Cnidaria
• Cnidocyte
• Coelom
• Cuticle
• Digestion: Intracellular vs. Extracellular
• Ecdysis (molting)
• Echinodermata
• Epidermis
• Exoskeleton vs. Endoskeleton
• Flagellated cells
• Free 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
• Partition; specialization of segments
• Spicules
• Interruption feeding
• Symmetry: radial vs. bilateral vs. no symmetry
• Tagma/tagmata (arthropods)
• Tissues
• Water vascular organisation of echinoderms

Sample multiple-choice questions

On the lab exam y'all'll run into slides of the various phyla listed on this folio. You might see multiple-choice (or make full-in) questions similar these:

1. What phylum is this?

2. This species has:

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

iii. What is the structure indicated by the arrow? (Answers could be any of the structures labeled on the animal phyla pages.)

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

References & further reading

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

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

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