Phylum Cnidaria and Climate Change Lab objectives: 1) Understand the complexity of the life cycles in the phylum Cnidaria. 2) Apply Bauplan concepts when describing and analyzing cnidarian life cycles. 3) Compare the life cycles of two groups of cnidarians (Order Siphonophora) 4) Integrate invertebrate zoology concepts to ecological and climate change concepts (Class Anthozoa). Cnidarians are a diverse group of organisms, with very complex life cycles. Although the generalization is that many species have a dimorphic life cycle, meaning that there is a polypoid and medusoid life stages, not all species within the phylum exhibit such dimorphic life cycle. Some notable examples of these exceptions are some species within the order Siphonophora (subphylum Medusozoa, subclass Hydrodolina) and the class Anthozoa (such as corals). This exercise will explore some of these differences and help you understand the life cycles of these organisms. In addition, you will explore some consequences of global change and the ways this phenomenon may impact sessile organisms with a planktonic stage. PART I. SIPHONOPHORE LIFE CYCLES Siphonophores come in two general “flavors”: calycophoran and physonect siphonophores. There is a third, the cystonects, but little is known about them, so we will exclude them from this lab activity. In this portion of the lab, we will explore some external sources to learn their main differences, as well as the life cycles. Instructions: visit the following website (a treasure trove on siphonophore information) and answer the following questions. http://www.siphonophores.org/. Make sure to use the glossary in this site to learn about the weird names we use when talking about these weird, wildly fascinating organisms. Questions: 1. Explore the body plans of the two main groups of siphonophores and discuss the main differences between these two groups. Include a schematic of their body plans. 2. The zooids found withing the colony that constitute a single siphonophore organism are highly specialized, and they have distinct morphologies to accomplish their individual functions within the colony. But where do all these colonies come from? 3. Now that you know where the individual zooids descend from, discuss the life cycle of a calycophoran siphonophore and provide a schematic. 4. What is the main difference during the early development of calycophoran and physonect siphonophores? 5. Based on the observations you just made, do siphonophores have a polypoid and medusoid life stage? PART II. CORALS (CLASS ANTHOZOA), ZOOXANTHELLAE & CLIMATE CHANGE. A crucial symbiosis: although not exclusive to Anthozoans (specifically corals), zooxanthellae are notably recognized as critical symbiotic organisms for the functioning and survival of corals. In this part of the lab, you will learn about zooxanthellae, and very importantly what is their role within corals as well as how they are linked to their life cycles. In addition, this lab will explore the challenge corals face with global warming. Instructions: visit another treasure trove on corals (https://oceanservice.noaa.gov/education/tutorial_corals/welcome.html) and learn about the incredibly challenging life cycles of corals. Hint: you can use the questions below as a guide for your exploring the site, so you don’t get lost. In addition, you can find useful information on the following sites to answer questions related to the challenges of corals due to climate change: https://climate.nasa.gov/vital-signs/global-temperature/ as well as the sea level rise animation: https://sealevel.nasa.gov/news/108/new-study-finds-sea-level-rise-accelerating Questions: 1) Describe the generalized life cycle of corals. Provide diagrams to illustrate your answer. 2) How are the coral spawning events called? And what are the hypothesized long-term and short-term controls of coral spawning? 3) Why do corals exhibit this type of reproduction? In other words, what are the challenges that corals must overcome in order to successfully reproduce and thrive? 4) Corals are known to have critical symbiotic relationships with organisms called zooxanthellae. But what are they and how this symbiosis work? 5) How do corals acquire zooxanthellae? Make a diagram depicting the main forms of “acquisition” of zooxanthellae? 6) How are zooxanthellae related to coral bleaching? 7) There are natural and anthropogenic threats to corals. Please, list some of them. 8) What are some natural threats that might be exacerbated (made worse) by climate change? In what specific ways? Hint: look at the map of where coral reefs are found; you may want to look at the climate and sea-level NASA links as well. Bonus question: other than ecological importance and environmental services, why do we care about coral reefs? In other words, what coral reefs protect us from? 
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