Gen Bio III Lab 7 Animal Diversity Part II

Transcription

1 Gen Bio III Lab 7 Animal Diversity Part II Introduction Last lab you were introduced to animals and provided with some ways to think about them (body plan, phylogenies and trait mapping, adaptations for feeding/respiration/locomotion, etc ). This week we will look in detail at more of the major animal phyla. You goal is to recognize these groups, understand their evolutionary relationships, and learn their key morphological features. You will not see these animals in lecture until next week. This lab is meant to introduce you to some major themes on the structure and function of animals using some organisms you may already be familiar with. You will understand the lab better if you read Chs. 33 and 34 before you come to lab. Lab Organization Today s lab is laid out as a series of stations that introduce you to some common themes in the evolution and morphology of protostome and deuterostome animals. Visit each station and use the material at that location to help you understand what you have read in Chs. 33 and 34. We have included a list of new vocabulary important for understanding animals formatted in bold on the station cards. These are provided in the list below. Body Plans One fundamental way that animals can be categorized is by reference to their body plan, the basic features of its structural and functional design. Remember that there are four major elements to the body plan (tissue layers, symmetry, presence and formation of coelom, and cleavage patterns). In addition to these, animal phyla are often characterized by unique derived features added to an ancestral the body plan. In today s lab you will see some of the features that define the major phyla of animals and understand their importance for body architecture. You will also appreciate some ways that the features of a body plan may be constraints on evolution. Functional Morphology Another way to study animals is to focus on how their body form helps them to accomplish basic life functions. Remember that some key challenges for all animals include respiration, feeding, locomotion/attachment, and reproduction. As you view the stations today be sure you understand the function and importance of the new morphological features you will view. Important topics will be include life cycles within the parasitic groups, the transition from juvenile to adult in insects, and the types of body support ( skeletons ) scattered through the phyla. You will may be surprised by some of the ways organisms deal with these fundamental challenges. Evolutionary Relationships Because all animals are descended from a common ancestor, it is useful to organize the diversity of animal groups using a phylogeny. Bring the phylogeny of major animal groups from the Animal Diversity I handout, or a similar phylogeny in your text (Fig ). Although we will not ask you to memorize groups below the phylum level, you will see phylogenetic trees that zoom in on differences among subphyla or classes. These will illustrate important concepts, such as evolutionary radiation, the relationship of symmetry and cephalization, or other trends in animal evolution. Derived metazoan phyla This week we will concentrate on a subset of phyla that illustrate key innovations in the Animalia. We will look at three major clades within animals: the lophotrochozoa (Phyla Mollusca and Annelida), the ecdysozoa (Phyla Nematoda and Arthropoda), and the deuterostomes (Phyla Echinodermata and Chordata). This week s stations will cover each of these groups in detail, highlighting selected key features.

2 Hands-on Activity You will investigate the relationship between body size and metabolism in mammals using a selection of our study skins. You will use measurements of body size to calculate basal metabolic rate (BMR). BMR is the amount of energy required by a resting, inactive organism to simply maintain the body. This value tends to be higher in endothermic animals, like mammals, since they consume energy to maintain their body at a constant temperature. BMR is an important physiological parameter that affects animal architecture, since it is strongly correlated with the type and amount of food required by an organism. Method: Collect basic measurements of your selected study skin. o Determine the snout-vent length (SVL) of the specimens. SVL is measured from the tip of the snout to the base (not tip!) of the tail. Record this value in cm. o Determine the circumference (C) of the animal by measuring around the body at the midpoint between the forelimbs and hindlimbs. Record this value in cm. Put your data on the board, and record the data taken by other students for the remaining study skins. Calculate the surface area and volume of each animal by approximating it s shape as a cylinder. o The formula for the surface area of a cylinder = 2(C 2 /4π) + (C * SVL) o The volume of a cylinder = (C 2 /4π) * SVL Approximate the body mass of the living organism using observed data on the density of humans. The density of an average human (assuming about 13% body fat) is 1.07 g/cm 3. Calculate the estimated mass (M) of each specimen by multiplying the body volume (in cm 3 ) by this density. Next, use a formula proposed by White and Seymour (2003) to calculate the basal metabolic rate (BMR) of a mammal. Using data from 619 species of mammals, they determined that BMR = 4.34M 0.67 (ml O2 per hr) Create a graph showing the dependence of BMR on body mass implied by this equation. You might find this graph easier to interpret if you use a log scale for both the x and y axes. Next, calculate the SA/V ratio for each animal. Plot SA/V against body mass for the class dataset. Finally, plot BMR against SA/V using the class dataset. Lab Write Up Your lab write up should include notes on the information at each station, as well as your answers to any questions found in the station notes. You should also include relevant sketches or diagrams to help you learn and remember the key concepts of today s lab. You should also include a properly labeled graph of the data collected by the class during the experiment on scaling in mammal architecture. Be sure you can interpret the shape of the curve you generated of SA/V vs. metabolic rate. Then answer the following questions: We approximated the shape of the mammals by considering them cylindrical. Does this make sense based on the tube-winthin-a-tube design mentioned in lecture? Does this make sense based on the shape of the animals revealed by the study skins?) We approximated body mass using data from humans. Is this realistic? Why/why not? Last week you learned that rate of diffusion was positively related to the SA/V ratio. If you think of heat diffusing, instead of water, which mammal will loose heat most quickly? How do you think this impacts the amount of food needed to maintain the body? When you consider this graph, as well as the computer activity examining body size in arthropods, can you explain how changes in body size beyond certain minimum and maximum limits have to be accompanied by fundamental changes in body shape and body plan?

3 Vocabulary Animalia Bilateria Protostoma Deuterostoma Lophotrochozoa trochophore larvae lophophore teloblastic growth Annelida prostomium peristomium setae parapodia clitellum Mollusca radula mantle ctenidium mollusc foot HAM (hypothetical ancestral mollusc) SA/V ratio metameric/metamerism diploblastic Echinodermata water vascular system pentaradial symmetry ossicles tube feet Chordata notochord dorsal hollow nerve cord pharyngeal gill slits post-anal tail endostyle amphioxus ammmocetes larvae BMR SA/V evolutionary constraint squid dissection: tentacles pen ink sac beak Ecdysozoa ecdysis Arthropoda exoskeletin chitin compound eye antennae tagmosis/tagmata

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