Assignment: Animal Structure and Diversity

Exercise 3 KINGDOM ANIMALIA: ANIMAL STRUCTURE AND DIVERSITY Student Learning Outcomes: At the conclusion of this exercise you should: (1) Be able to identify ​seven​important anatomical characteristics which are used to classify animals into different evolutionary groups. (2) Be able to apply a taxonomic key to classify animals according to specific anatomical characteristics. (3) Be able to analyze selected animal specimens and place them into their proper taxonomic groups. (4) Be able explain “adaptive radiation” in vertebrate appendages and provide an example. (5) Be able to categorize ten common San Diego County animals using an ecological classification. (6) Be able to understand the difference between using ecological criteria and evolutionary (phylogenetic) criteria when classifying organisms.

Introduction to the Phylogenetic Classification of Animals Today you will be learning the currently accepted evolutionary tree diagram (cladogram) for the 9 most common animal phyla in this lab (Figure 1). It includes a recent revision of groupings that has been determined using DNA sequence evidence. The most fundamental differences between groups are the same whether anatomical and embryonic characteristics or DNA data is used. The branching points in the phylogenetic tree (usually leading to clusters of animal phyla) are based on the presence or absence of unique ​ anatomical and embryological characteristics​that are thought to be most important.

You will spend a good portion of today’s laboratory looking at examples of these characteristics. 2 Exercise 3 – Kingdom Animalia Figure 1. Evolutionary Tree Diagram of Animals. 3 Exercise 3 – Kingdom Animalia Animal Origins and their Evolutionary Relationships The closest unicelled relatives of animals are unicelled Protists that have flagella as a means of locomotion. This suggests that animals may have originated as colonial flagellated protists about 700 million years ago. The oldest known animals in the fossil record are cnidarians (e.g. jellyfish/jellies) that appear in sediments dated at about 600 million years old. One fundamental characteristic distinguishing animal groups is the ​presence or absence of true tissues​. Sponges are the only animals that lack true tissues and are placed in their own group: The ​Parazoa ​(“beside animals”). All other animals are placed in the ​Eumetazoa​(“true animals”). A second major characteristic used in animal systematics is ​body symmetry​. The eumetazoans are subdivided into taxa that exhibit ​radial symmetry​(The ​Radiata​) and those that exhibit bilateral symmetry. ​We will examine these kinds of symmetry later in the activity.​​All eumetazoans, exclusive of Radiata (jellyfish) and Parazoans (sponges), are placed together in a clade (branch) called the ​Bilateria​. Associated with bilateral symmetry is cephalization which is the concentration of sensory organs at the anterior end of the animal. Several other important characteristics are related to events that occur during early embryonic development. Remember that the developing embryo passes through stages leading to development of a gastrula, or hollow ball of cells with a tube through it. Once the gastrula stage is reached by an embryo, ​two or three layers of cells​, called germ layers, arise that will develop into tissues and organs. Assignment: Animal Structure and Diversity

The radially symmetrical animals have ​ectoderm​and ​endoderm​, whereas bilaterally symmetrical animals have both these germ layers and a third layer called mesoderm​. Mesoderm forms between the ectoderm and endoderm and gives rise to muscles and those internal organs not formed by the endoderm. Therefore, the Radiates, which have only 2 germ layers are known as ​diploblastic​, whereas all Bilaterians have three germ layers and are known as ​triploblastic​. The major branching point within the Bilateria on the evolutionary tree of animals has to do with what happens to the blastopore during​​embryonic development.​This is the opening on the surface of the embryo that forms as gastrulation starts. At the end of gastrulation, the tube through the embryo forms another opening. In one group of Phyla, the blastopore becomes the mouth and the other opening becomes the anus. Assignment: Animal Structure and Diversity

These are called the ​protostomes​(which means “first mouth”). In the deuterostomes​(which means “second mouth”), the blastopore becomes the anus and the second opening becomes the mouth. Many other characteristics are correlated with being either a “protosome” or a “deuterostome”. Molluscs, annelids, and arthropods are protostomes while chordates and echinoderms are deuterostomes. Within the Protostome groups, the recent DNA evidence has suggested a major split between two groups of taxa that was not previously recognized. The important characteristics that 4 Exercise 3 – Kingdom Animalia scientists have decided to separate these taxa are that one group of Phyla have a kind of larva called a ​trochophore​while the other group lack this kind of larva and go through the process of ecdysis​or molting. The ​trochophore larva​(Figure 2.) is able to swim with the band of cilia around its middle and feed, since it has a digestive tract. This larva is found in groups that are marine or freshwater and has been lost in groups like the earthworms that are terrestrial. ​Ecdysis is found in animals that have a non-cellular toughened outer body coating (the cuticle or exoskeleton), which they have to break out of and shed (or molt) in order to grow, as insects do. The last characteristic shown on the branches of the tree diagram is the presence of a ​segmented body​. ​ Assignment: Animal Structure and Diversity

This feature is thought to be an important morphological characteristic that can be used to determine evolutionary relationships. It is observed in both the protostome and deuterostome groups and is thought to have evolved independently in both of these branches (See Figure 1). The characteristic called out in the text box below the tree diagram is the ​presence or absence of an internal body cavity (or “coelom”)​ . An internal body cavity, or ​coelom​, is always associated with mesoderm germ tissue found only in animals with all 3 germ tissues. Triploblastic animals, lacking a coelom (body cavity) are ​acoelomate ​(“no cavity”). Flatworms are acoelomates. Animals with a coelom that is only partially lined with mesoderm are said to have a pseudocoelom ​(“false coelom”) and are described as “pseudocoelomates”. Nematodes are pseudocoelomates. An animal with a coelom (“body cavity”) completely lined with mesoderm tissue is said to have a ​true coelom​and called a ​eucoelomate​.

Molluscs, annelids, arthropods, and chordates are examples of eucoelomates. The presence/absence and kind of coelom used to be used to distinguish evolutionary groupings, but the DNA evidence suggests that the trochophore/ecdysis distinction is more informative of evolutionary history. With the exceptions of body symmetry and segmentation, the characteristics that we have just reviewed are difficult to observe on whole adult animals in the laboratory. Today we will also learn some more easily observable characteristics that will enable you to distinguish between specimens of the 9 Phyla shown in Figure 1. 5 Exercise 3 – Kingdom Animalia Application: Look carefully at the following 6 “make-believe organisms”. Try to classify them into ​four different groups. What ​one​simple observational criterion could you use? Question 1. Write ​one ​obvious characteristic of body form which you could use to “slot” the six different animals above into ​4​groups. (The characteristic should have 4 types or variations.) Replace this text with your answer. Question 2. Give a descriptive name to each of your four groups. List the different “animals” above (A-F) which would fall into each of your four groups: Descriptive Name of Group Animals in Group In this example, what was your purpose (objective or goal), in using the criterion you chose? It is very likely that you were ​not ​trying to say anything about the organism’s ancestral (evolutionary) relationships! Your objective was simply identification and nothing more. Assignment: Animal Structure and Diversity

If you were “into” legs you might have used leg number as a criterion. On the other hand, you might have used general body shape or body size as the basis for your classification system. As discussed earlier, during the seventeenth and eighteenth centuries, investigators were faced with a problem very similar to the one you were just asked to deal with: New and exotic plants and animals were being brought back to European ​taxonomists​(biologists who classify) in enormous numbers by world explorers. Just as with our example, different biologists used different criteria to classify their specimens. This obviously led to a great deal of confusion when one tried to determine whether he was describing a new type of animal or not. People could not be sure whether they were talking about the same organism. Since it was vogue in the eighteenth 6 Exercise 3 – Kingdom Animalia century for the western European aristocracy to have their own museum collections of organisms, there must have been a good deal of pressure to develop a universally acceptable classification system. Since then, zoologists and botanists have continued their struggle to develop an objective approach to classify organisms into their proper evolutionary groups. Currently, the Cladistic approach is considered the most useful biological classification technique. Although there is an almost infinite diversity in the shapes of living things, certain physical and chemical characteristics common to large groups of animals and plants become apparent when they are seen together. Assignment: Animal Structure and Diversity

These characteristics form the basis for our modern system of classification and are the backbone of evolutionary theory that suggests that all animals have descended from common ancestors. It is this universally accepted classification system which is being used when someone says: “There goes a bird, fish, crab, worm, spider, human, starfish, etc.” 7 Exercise 3 – Kingdom Animalia Vertebrates and Invertebrates The nine Phyla in the Animal Kingdom that we are studying are broken down into 2 broad groups: the ​Vertebrates ​and ​Invertebrates. ​(The word “phylum” is singular; “phyla” is the plural version.) The ​vertebrates​, all of which belong to the ​Phylum Chordata​, are animals that have a column of vertebrae for a backbone and they include those animals which are probably most familiar to you. You are to learn the 7 Classes of vertebrates in the Phylum Chordata. Assignment: Animal Structure and Diversity

They are listed below: 1. Phylum Chordata (7 groups to learn in this Phylum) a. Superclass Agnatha (the “jawless fishes” which include the lamprey and hagfish Classes) b. Superclass Gnathostomata (fish with true jaws) Class Chondrichthyes (the cartilage fishes like sharks and rays) Class Osteicthyes (the bony fishes like bass and tuna) c. Superclass Tetrapoda (​vertebrates with 4 appendages rather than fins): Class Amphibia, the amphibians (frogs, and salamanders, etc.) Class Reptilia, the reptiles (lizards, snakes, turtles, etc.) Class Aves, the birds Class Mammalia, the mammals. The ​invertebrates​, which of course have no vertebral column, are members of many​​different phyla. The most common invertebrate groups that you might expect to run into include the following 8 phyla: 1. 2. 3. 4. 5. 6. 7. Phylum Porifera (sponges) Phylum Cnidaria (also called Coelenterata) (sea anemones and jellyfish, etc.) Phylum Platyhelminthes (flatworms​,​like planaria) Phylum Nematoda (round worms) Phylum Annelida (segmented worms like earth worms) Phylum Mollusca (bivalves, snails, octopi, etc.) Phylum Arthropoda (crabs, insects, and spiders, etc.) 5 groups to learn here: a. Class Arachnida (spiders, mites, ticks and scorpions) b. Class Insecta (flies, grasshopper, butterflies etc.) c. Subphylum Crustacea (old grouping: Class Crustacea) includes crabs, shrimp, lobster, barnacles, etc. d. Class Chilopoda (the centipedes) e. Class Diplopoda (the millipedes) 8. Phylum Echinodermata (starfish, sea urchins, sand dollars etc.) 8 Exercise 3 – Kingdom Animalia We will now investigate the anatomical characteristics that are used to categorize animals into the various evolutionary groupings mentioned above. I. Anatomical Characteristics Used in Phylogenetic Classification of Animals The characteristics that are described in Sections 1-7 below are more or less natural criteria which have become apparent to taxonomists after many years of observation of animal morphology (shape). Assignment: Animal Structure and Diversity

The physical characteristics of many animals were observed and recorded (accumulation of facts) and natural relationships were perceived. The search for order (“​patterns​ ”) which is characteristic of science, led to the construction of a system of classification into which each kind of animal more or less ​naturally​fits. Procedure: Go to the appropriate station​(that matches the section number) and observe the examples of what is meant by each of the anatomical characteristics. In order for you to identify “unknown” animals later in this exercise you must know this material well. Note:​ Not all of these characteristics will be equally apparent in all animals and some would be obvious only after dissection of the animal to be identified. Section 1. Type of Body Symmetry Observed in Animals Most animals you will observe are either ​bilaterally or radially symmetrical.​The bilateral animals are characterized by the fact that there is only one plane in which you can cut them in two and obtain mirror images. Assignment: Animal Structure and Diversity

Thus, a dog can be divided into identical (but reversed) halves by cutting it between the eyes, through the middle of the body, and then through the tail to obtain mirror images. If we cut across the abdomen from the left to the right side, however, one-half would have a tail and the other half a head. Obviously, these halves are not identical. Question 3.​Give three examples of organisms that exhibit bilateral symmetry. 1. 2. 3. The ​radially symmetrical​animals can be cut in half several different ways, however, and still obtain two mirror images (provided only that the “cut” is made through the center of the animal). 9 Exercise 3 – Kingdom Animalia Question 4.​Give 4 examples of organisms with radial symmetry. 1. 2. 3. 4.

In which echinoderm is it most difficult to identify radial symmetry? One group of animals, the sponges, may be ​asymmetrical​—not having any plane across which they are mirror images. Question 5.​Observe the sponges, and draw two examples below. Replace this text with your answer. Section 2. Segmentation in Some Animals Many animals have structures or body parts which are linearly repeated, like the cars of a railroad train. These parts are called segments. A clear example of this characteristic is the repetitive arrangement of the external body parts of the sandworm, ​Nereis,​or the earthworm. In some animals the segmentation has been secondarily lost, or so modified that the repeated parts are no longer similar in appearance. It is sometimes possible to find clear segmentation in the embryo or in the adult’s internal anatomy when external observation suggests that no segmentation exists. The crayfish and, to a greater degree, the human animal are examples of organisms in which segmentation has been modified or lost during the organism’s evolutionary history. Segmentation can still be observed in the human embryo as well as in the adult’s repeating vertebrae which make up the backbone or vertebral column. Question 6.​How are the segments in the crayfish modified? Replace this text with your answer. 10 Exercise 3 – Kingdom Animalia Section 3. The Type of Skeleton in the Animal Some animals like the crayfish or grasshopper have an ​exoskeleton​(outer skeleton). There are no bones beneath their hard outer “shells.” The vertebrates, however, have an ​endoskeleton (internal skeleton) made of bone or cartilage. Assignment: Animal Structure and Diversity

Many creatures like the protozoans (single-celled animals), jellyfish, planaria (flatworm) and earthworms (segmented worms) have no skeleton at all. Animals without any true skeleton usually maintain their shape using water pressure (​hydrostatic “skeleton”​). Question 7.​Give one example of an organism with an exoskeleton. Replace this text with your answer. Question 8.​Give one example of an organism with an endoskeleton. Replace this text with your answer. Question 9.​Give one example of an organism with a hydrostatic skeleton. Replace this text with your answer. Section 4. The Number of Paired Locomotive Appendages in the Animal The number of locomotive (walking, flying, etc.) paired appendages an animal has is a very important criterion for classifying animals into different evolutionary groups. For example, the human animal and other primates, as well as other vertebrates, have two pairs of appendages, while grasshoppers and other members of the insect class have three pairs of appendages. Assignment: Animal Structure and Diversity

Moreover, 4 pairs of appendages are found in Class Arachnida, including spiders, mites, and scorpions.​​This criterion is appropriate only for animals with bilateral symmetry. Question 10.​Give two examples of animals with 2 pairs of locomotive appendages. Replace this text with your answer. Question 11.​Give two examples of animals with 3 pairs of locomotive appendages. Replace this text with your answer. Question 12.​Give two examples of animals with 4 pairs of locomotive appendages. Replace this text with your answer. 11 Exercise 3 – Kingdom Animalia Section 5. The Type of Digestive Tract in the Animal Various digestive tract strategies have evolved in different animal groups to aid in the absorption of food molecules. Animals have either: no digestive tract​, instead absorption occurs through “body” surfaces (protozoans and sponges, etc.). a ​sac-like or incomplete digestive tract​with only one opening by which food enters and wastes leave (jellyfish,​​flatworms). a ​tube-like or complete digestive tract​where food enters at one end (called the mouth) and wastes leave at the other end (called the anus), such as annelids, arthropods, chordates (including humans), molluscs, and nematodes. Question 13.​What organism is shown with a complete digestive tract? Replace this text with your answer. Question 14.​What type of digestive tract do humans have? Replace this text with your answer. Section 6.

The Type of Respiratory System in the Animal All animal cells require oxygen gas (O​2​) in order to breakdown molecules like glucose and obtain needed energy (Cellular Respiration). In turn, animal cells give off carbon dioxide gas (CO​2​) during the molecular breakdown process. As a consequence,​all​multicellular animals have some membrane area specialized for the exchange of gases between the circulatory fluid (“blood”) and the outside air or aquatic environment. Pouch-like internal membrane systems called ​lungs​are often found in terrestrial organisms. Other terrestrial animals like insects and some spiders have many branched membrane-lined tubes (called ​tracheae​) with external openings (​spiracles​) in the abdominal region. In these animals, gas (air) is moved in and out of the tubes by abdominal movements. Aquatic animals like crabs and fish usually have many membrane systems called ​gills​while animals like salamanders and starfish exchange gases throughout their exposed skin surfaces. Question 15.​Draw a simple grasshopper, and draw and label its spiracles. Draw by hand, take a picture, and then replace this text with your drawing (Insert > Image). 12 Exercise 3 – Kingdom Animalia Section 7. Degree of Nervous System Development in Animal Some animals, such …