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Insects: The class Insecta, in the phylum Arthropoda, whose members are characterized by division into three parts: head, thorax, and abdomen. They are the dominant group of animals on earth; several hundred thousand different kinds having been described. Three orders, Hemiptera; Diptera; and Siphonaptera; are of medical interest in that they cause disease in humans and animals. (From Borror et al., An Introduction to the Study of Insects, 4th ed, p1)

Osmoregulation in Insects

JoVE 10990

Malpighian tubules are specialized structures found in the digestive systems of many arthropods, including most insects, that handle excretion and osmoregulation. The tubules are typically arranged in pairs and have a convoluted structure that increases their surface area.

Malpighian tubules extend from the digestive tract, typically the area between the midgut and hindgut, into the hemolymph—a mixture of blood and interstitial fluid found in insects and other arthropods, as well as most mollusks. Unlike other excretory systems, the excretory processes of Malpighian tubules lack a filtration step. Metabolic wastes, like uric acid, diffuse into the tubules from the hemolymph. The tubules are lined with a layer of transport epithelia. These specialized epithelial cells contain pumps that actively transport ions, like sodium (Na+) and potassium (K+), from the hemolymph into the interior of the tubule, called the lumen. Osmosis allows water to follow ions into the tubules passively. From the tubule lumen, water, ions, and waste travel from the intestine to the rectum. Tiny, protruding microvilli lining the inside of the tubules help maximize solute-water coupling and the propulsion of uric acid crystals through the tubules. In the rectum, specialized glands pump many of the ions back into the hemolymph. Osmo

 Core: Biology

Inductive Reasoning

JoVE 10650

Inductive reasoning is a type of logic in which premises lead to a conclusion. Inductive reasoning is uncertain and operates in degrees to which the conclusions are credible. As such, inductive arguments can be weak or strong, rather than valid or invalid, and conclusions can be used to formulate testable, falsifiable hypotheses.

In inductive reasoning, collected evidence of an often small sample is used to draw a conclusion. It allows for the possibility that the conclusion is false. This is unlike deductive reasoning, which starts with a hypothesis and looks at the possibilities to reach a specific, logical conclusion. For example, if all fish in a pond are observed squirting water into the air towards insects that they then retrieve and eat, inductive reasoning would indicate that all fish must be able to project water as a method of preying on insects. Because this conclusion is credible, it can be used to formulate a testable, falsifiable hypothesis—that all fish project water to catch their insect prey. In general, this is a weak argument considering that not all types of fish are present in this particular pond. Then, in order to test this hypothesis, the researcher could collect multiple types of fish from the pond—in addition to other types of fish that eat insects from other water sources—and observe how they behave in a

 Core: Biology

Eusociality and Division of Labor- Concept

JoVE 10617

Social Organization

Varying levels of social organization are observed within the animal kingdom, ranging from simple to highly complex. These systems can greatly enhance the survival and reproductive success of an individual or a population. Of these, eusociality is the highest level of social organization, involving divisions of labor based on social castes. However, this system …

 Lab Bio

Species Distribution and Biogeography- Concept

JoVE 10603

Species Distribution

Biogeography is the study of species distribution across geographic space and the processes that shape these distributions. This discipline is based on the assumption that each species within a location must have immigrated from another geographic area or evolved from a local species. Within each habitat, a variety of biotic and abiotic factors act on…

 Lab Bio

Extinction- Concept

JoVE 10594

The History of Life on Earth

Fossils of organisms that were different from anything alive today had been documented as early as the 17th century, but it was not until the early 19th century that scientists began to recognize that the successive layers of fossil bearing rocks were like successive pages in the history of life on earth. Although this recognition gave rise to the birth of…

 Lab Bio

Comparative Excretory Systems

JoVE 10998

Animals have evolved different strategies for excretion, the removal of waste from the body. Most waste must be dissolved in water to be excreted, so an animal’s excretory strategy directly affects its water balance.

Nitrogenous wastes are some of the most significant forms of animal waste. Nitrogen is released when proteins and nucleic acids are broken down for energy or conversion into carbohydrates and fats. Proteins are broken down into amino acids and nucleic acids into nitrogenous bases. The nitrogen-containing amino groups of amino acids and nitrogenous bases are then converted into nitrogenous wastes. Typical nitrogenous wastes released by animals include ammonia, urea, and uric acid. These excretory strategies involve tradeoffs between conserving energy and water. The various nitrogenous wastes reflect distinct habitats and evolutionary histories. For example, most aquatic animals are ammonotelic, meaning they directly excrete ammonia. This approach is less energy-intensive than converting ammonia into urea or uric acid before excretion, but also requires more water. For terrestrial organisms, which face perhaps no more significant regulatory threat than dehydration, water conservation is worth the extra energy cost. Ureotelic animals, like mammals and sharks, convert ammonia into urea before excretion. Urea is less tox

 Core: Biology
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