Philosophy and objectives of the course Overview of the Phylum Arthropoda D. L. A. Underwood Biology 316 - General Entomology A. Course format 1. Assignment of teams a. Pass out cards with numbers and letters. b. Assemble groups by number. c. Students write down their number and letter on a piece of paper for later reference. d. On the cards, students write their names, email (phone if they don t do email), favorite plant, favorite animal, favorite hobby. e. Group members introduce themselves to each other. 2. Team Project - A s take notes; B s speak a. List at least five questions the group has about the course, instructor, entomology, etc. B. Philosophy 1. Traditional methods of teaching vs. cooperative learning a. The format of this course will be very different probably from any other course you have taken (unless you've taken Ecology from me!). b. Every lecture will be broken down into mini-lectures and team projects. c. You will be asked to participate in lecture, rather than merely sit there like a halfasleep puppy and take notes. d. Studies have shown that students learn better by being actively involved during lecture. e. I have taught using both methods and I am sold on the cooperative learning method as a model for teaching in the new millennium. f. Hopefully you will approach this new way with an open mind. 2. Traditional methods of teaching general entomology a. Identification through dichotomous keys b. Insect collection focused on identification c. Emphasis on characters and morphology 3. It is not the 1900's anymore a. While keys are useful and a person must be able to use one, practical identification is often via field guides and reference books. b. Insect diversity is amazing but why not also try to tie taxa to habitat? c. Characters and morphology are obviously important, but aren't behavior, ecology, and species interactions worth something? Philosophy and overview of the Arthropoda - Page 1 of 6
C. Objectives 1. To gain an appreciation for insect species and ecological diversity. a. Of the approximately 1.1 million described animal species, insects comprise over 70% or approximately 814,000 species. b. The beetles alone account for over 30% (350,000 species) of the described animal species. c. It is estimated that the vast majority of the insects remain unidentified, especially in the tropics, and that the insects probably make up more than 90% of the animal species on earth. 2. To have a general understanding of insect museum techniques. a. Pinning b. Point mounting c. Using alcohol d. Spreading the wings of moths and butterflies e. Labeling 3. To be able to use standard keys for identifying insects to family and subfamily. a. The keys in your text are considered the industry standard. 4. To be able to sight ID the most common insect families and orders. 5. To understand basic principles of insect population dynamics and how this affects insect diversity in nature and our attempts at controlling insect populations in forests and fields. D. What makes an arthropod? 1. Team project - B takes notes, A speaks a. Without looking at your lecture outlines, come up with ten words or phrases that come to mind when you think of the Arthropoda. They don't have to be scientific terms; in fact, I prefer "gut reaction" types of words. 2. Exoskeleton of chitin Chitin Cellulose 3. Body wall of sclerites or hardened plates 4. Segmentation and the formation of tagmata 5. Jointed articulated appendages Philosophy and overview of the Arthropoda - Page 2 of 6
6. Ecdysis or growth by molting the exoskeleton 7. Team Project - C takes notes, D speaks a. Having an exoskeleton has its obvious benefits and drawbacks. List two of each. 8. Compound eye 9. Malpighian tubules (terrestrial forms only) 10. Tracheal system (terrestrial forms only) 11. No cilia 12. Open circulatory system with hemocoel and hemolymph E. Classification of the Phylum Arthropoda 1. NOTE: The text is still out of date with regard to the subphyla. Below is the currently accepted divisions of the Phylum Arthropoda. All page numbers refer to the lab textbook by Triplehorn and Johnson. 2. Five Subphyla a. Subphylum Trilobita b. Subphylum Chelicerata c. Subphylum Crustacea d. Subphylum Myriapoda e. Subphylum Hexapoda F. Subphylum Trilobita a. Trilobites lived during the Paleozoic (about 575 million years ago) and went extinct about 200 million years ago. b. They were the first arthropods to appear in the fossil record and exhibited Philosophy and overview of the Arthropoda - Page 3 of 6
extraordinary diversity. There are over 1500 genera described to date! c. Most trilobites ranged in size from 5 to 7 cm, but some very large fossils exceeding 65 cm have been found. d. They had a pair of large, compound eyes, one pair of antennae, and up to 27 segments. e. All lived in marine environments. Most were seafloor dwelling, but some were believed to be free swimming. f. They were primarily scavengers. However, some forms were predaceous while others were filter feeders. G. Subphylum Chelicerata (see pages 101-136) a. Six pairs of appendages b. The first pair of appendages are the chelicerae. c. Lack antennae d. Lack mandibles (mouthparts) e. The body is divided into two distinct tagma (regions), the prosoma (cephalothorax) and the opisthosoma (abdomen). f. Most chelicerates suck liquid from their prey. 2. Class Merostomata - horseshoe crabs (see page 102, Fig. 5.2) a. Marine animals that occur in the coastal waters of the Atlantic Ocean. b. They are predaceous on worms that live in the mud. 3. Class Arachnida - spiders, mites, ticks, scorpions, whipscorpions, etc. a. Primarily terrestrial and predaceous, there are over 70,000 described species worldwide with about 8,000 being found in North America. b. Arachnids were the first arthropods to move into terrestrial environments. Scorpion fossils appear in Silurian deposits (420 million years ago). c. In addition to the chelicerae, arachnids also possess a pair of pedipalps (the second pair of appendages). d. They usually have sucking mouthparts or a strong sucking pharynx used to ingest prey fluids. e. We will cover the major orders of arachnids in detail at a later date. H. Subphylum Crustacea (see pages 136-141) a. Two pairs of antennae b. Biramous appendages c. They have mandibles. d. Most crustaceans are aquatic, either freshwater or marine. Philosophy and overview of the Arthropoda - Page 4 of 6
2. Class Branchiopoda - brine shrimps, tadpole shrimps, and clam shrimps 3. Class Maxillopoda (the text depicts an older classification) - copepods, barnacles. 4. Class Malacostraca - shrimp, lobsters, amphipods, and pillbugs a. There are two fairly common terrestrial malacostracans. i We will cover them in lab as many people confuse them with insects. ii Respiration is via gills that are protected by the abdominal appendages. iii They are restricted to moist environments. b. Order Amphipoda we have one terrestrial form of amphipod here the L. A. basin. (See page 140, Fig. 5-26) c. Order Isopoda - the terrestrial forms include the common pill bug or roly poly. (See page 141, Fig. 5-27) I. Subphylum Myriapoda (within the "Atelocerata" in the text) a. They have one pair of antennae. b. They have mandibles. c. The appendages are uniramous. d. Body lacks clear development of tagmata. 2. Class Diplopoda - millipedes (Figs. 5-29 and 5-30) a. Most body segments bear two pairs of appendages. b. They are cylindrical in shape and often curl when disturbed. c. Millipedes are restricted to moist places and most are scavengers or feed on decaying plant material. Some attack living plants. d. Millipedes do not bite people, but many secrete a fluid that is offensive. 3. Class Chilopoda - centipedes (Figs. 5-31 and 5-32) a. Most body segments bear one pair of appendages. b. The body is dorso-ventrally flattened. c. All are predaceous, quick moving, and bite. Most of the centipedes you are likely to encounter are small and unable to pierce your skin. d. Behind the mandibles are two pairs of maxillae. The first pair of maxillae is leg-like while the second is claw-like and function as poison jaws. J. Subphylum Hexapoda - insects and their close relatives (within the "Atelocerata" in the text) a. The body is divided into three distinct tagmata, the head, thorax, and abdomen. b. The head bears one pair of antennae, one pair mandibles, and one pair of maxillae. c. The thorax is home to three pair of legs. Most insects also have two pair of wings. Some insects lack wings, however. Philosophy and overview of the Arthropoda - Page 5 of 6
d. In most insects, the abdomen is devoid of walking appendages and bears only structures related to mating. 2. Class Entognatha (to be covered later) 3. Class Insecta (to be covered later) Philosophy and overview of the Arthropoda - Page 6 of 6