The present chapter reviews the approach of the book towards the issue of the metamorphosis of the European Economic Constitution, departing from the analysis and the evolution of its micro- and macro-economic structure. Alongside the development of the arguments in the text, it provides an understanding of how this metamorphosis has been induced by the measures taken to counter the economic crisis and reflects over the place of the Economic Constitution within the composite constitution of the European Union.
Lesson Objectives and Overview: Metamorphosis teaches students about the process by which certain insects and amphibians change from birth to adulthood. Students will learn that there are two types of metamorphosis and will be able to explain the stages of both. The lesson is for students in 3rd grade, 4th grade, and 5th grade.
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The Teacher Notes page provides an extra paragraph of information or guidance. It explains that students may understand the general concept of change but not necessarily how some specific animals mature in different ways. This section recommends that you use one or more videos that demonstrate the stages of metamorphosis to enhance the lesson. Use the blank lines on this page to write any additional ideas or notes you may have as you prepare the lesson for your students.
Students will next learn that in the United States alone, there are around 91,000 different species of insects. In the world overall, there are over 10 quintillion individual insects alive. Basically, there are about 200 million insects for every one human! These bugs are everywhere, and about 90% of them undergo complete metamorphosis. These include butterflies, moths, bees, and flies. The four stages are egg, larva, pupa, and adult.
Some insects undergo incomplete metamorphosis, the stages of which are egg, nymph, and adult. This is true for dragonflies and grasshoppers. The egg stage is basically the same as in complete metamorphosis. Similar to the larva stage in complete metamorphosis, the nymph stage is the young stage during which most of the feeding and growing occurs. Insects at this stage eat the same foods as the adult forms and look like miniature versions of the adults, but they have no wings. After molting four to eight times (the instar period), they grow bigger and bigger until they arrive at adulthood and get their wings.
Students will then discover that each stage of metamorphosis includes certain adaptations that help the species survive. Without these stages and adaptations, the species would die. The lesson then summarizes the information that students learned.
The homework assignment also contains several sections. The first section requires students to tell whether 10 statements are true (T) or false (F). Next, they will name the stages of metamorphosis in order for five different organisms. Finally, they will answer five questions using what they learned during the lesson.
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In species with complex life cycles, size at metamorphosis is a key life-history trait which reflects the complex interactions between costs and benefits of life in the aquatic and terrestrial environments. Whereas the effects of a deteriorating larval habitat (e.g. pond desiccation) on triggering an early metamorphosis have been extensively investigated in amphibians, the consequences of the resulting reduced size at metamorphosis on fitness in the post-metamorphic terrestrial stage remain poorly understood. We tested the hypothesis that a smaller size at metamorphosis negatively affects performance and survival in the ensuing terrestrial stage. Using as model a tropical amphibian (Ceratophrys stolzmanni) showing a large phenotypic plasticity in metamorphosing traits, we evaluated the effects of size at metamorphosis on fitness-related trophic and locomotor performance traits, as well as on growth and survival rates.
Our results support the hypothesis that a larger size at metamorphosis is correlated with better survival and performance. The survival rate of large metamorphosing individuals was 95%, compared to 60% for those completing metamorphosis at a small size. Locomotor performance and gape size were positively correlated with body size, larger animals being more mobile and capable to ingest larger prey. However, smaller individuals achieved higher growth rates, thus reducing the size gap.
Overall, size at metamorphosis affected profoundly the chances of survival in the short term, but smaller surviving individuals partly compensated their initial disadvantages by increasing growth rates.
Species with complex life cycles, such as biphasic amphibians and insects, are able to exploit different ecological niches and optimize their life-history in discrete developmental stages [1, 2]. The transition occurring at metamorphosis usually requires dramatic and irreversible morphological transformations, and is frequently accompanied by a complete change of the ecological niche [3, 4]. Pond-breeding amphibians, which in their post-larval stages become terrestrial, represent ideal models to investigate the independence of pre- and post-metamorphic life-stages and the presence of carry-over effects from one stage to the other, affecting the overall fitness of individuals [5]. The most evident trade-off between the aquatic and terrestrial stages is reflected in body size at metamorphosis. When the aquatic larvae are confronted with unfavourable conditions, such as food shortage [6, 7], high density [8], desiccation risk [9] or predation [10, 11], they can leave the aquatic environment by undergoing metamorphosis. However, this is usually done at a smaller size, which allows them to escape the immediate aquatic threats faster, but in turn exposes them to different selective pressures on land [1].
Larger size in freshly metamorphosed individuals is correlated with improved traits, like locomotor abilities and metabolic rates [12], endurance [13], resistance to desiccation [14], feeding success [15], and dispersal success [16]. Although the paradigm model [17] assumes that body size at metamorphosis is a good predictor of subsequent fitness, there are authors [e.g. 3, 18] who assert that this is not always the case. Since in amphibians a substantial percent of the adult body size is gained after metamorphosis, and because age of sexual maturity is variable, the relationship between body size at metamorphosis and fitness is more complex, especially in unpredictable environments [19]. For example, if smaller individuals have compensating mechanisms, such as more intense growth rates, metamorphic size may not have a significant effect on adult traits like mortality, age and size at first reproduction, or fecundity [20, 21]. The detrimental consequences of a small size at metamorphosis can also be compensated by changes in the morphology of juveniles [22, 23]. For example, the small froglets can have, proportionally to their body size, larger heads or longer legs than the bigger individuals. Such modifications would be beneficial because leg length influences locomotor (i.e. jumping) performance [23, 24], which in turn has been shown to positively affect food acquisition [25], predator avoidance [26] and dispersal [27]. In a similar manner, a large head width favours the swallowing ability, which is a limiting factor in prey selection [28, 29].
Life-history switch-points such as metamorphosis, that require major and irreversible changes in morphology, anatomy, physiology, and habitat and resource use, have a profound effect on individual fitness and involve trade-offs [17, 32, 33]. Our study reveals that individuals making the transition from aquatic larvae to the terrestrial stage at a large size experience higher survival rates during the first activity season. Even under favourable experimental conditions, with no predation or competition, and ad libitum food resources, the juveniles that metamorphosed at a small size had a higher mortality rate. It is expected that in the natural environment, smaller size would result in a further increase in mortality due to exposure to predators [34] and desiccation [14]. Our results imply that, although developmental plasticity can allow tadpoles to escape an unfavourable aquatic environment (e.g. drying pond, high density, reduced food availability) before reaching an optimal size, thus avoiding mortality in the larval stage, it has a direct cost on survival in the terrestrial stage. The lower survival rate of smaller juveniles in terrestrial habitat is consistent with observations made by some authors [6, 15], although in other cases no significant long-term benefits for larger size at metamorphosis in terms of survival was found [21, 35].
Although size at metamorphosis is predicted to have a large impact on size at maturity [32], in some species it was shown that, if environmental conditions are optimal for growth, smaller juveniles can compensate by growing faster and the differences in size eventually fade away [7, 36]. Indeed, our study showed that individuals metamorphosing at a small size are able to increase their growth rate compared to larger individuals, and thus diminish the size gap over time. However, long-term capture-mark-recapture surveys are needed to confirm this pattern in natural conditions.
Pacific horned frogs showed one of the widest range of sizes at metamorphosis reported for any amphibian in their natural population, individuals differing by up to 100% in body size and 890% in body mass. This range is broader than previously reported intrapopulation variation in the literature [31, 43]. Pond permanence [30], food availability [44], temperature [45] and presence of predators or competitors [46, 47] are known to have a profound effect on individual metamorphosing size in anurans, and the interaction between various selective pressures can determine a large spectrum of sizes. Additionally, in the case of anuran species reproducing in ephemeral ponds, individuals are less capable to delay their metamorphosis or further increase their larval growth rates, which are already close to the physiological limit [48]. This implies that differences in larval environment will produce a large variation in metamorphic body sizes, such as the one we report here. In the natural habitat, a high diversity of sizes is likely to reduce food competition amongst froglets and allow for a more rapid growth for both large and small individuals [49]. 2ff7e9595c
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