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Principle The liver is the central organ of human and animal metabolism. It influences, for example, the blood sugar level, synthesizes various blood proteins, and decomposes toxic metabolic products and other toxicants taken up with the food. The bile which the liver produces accumulates ...
Many animals of rather simple structural organization, for example, paramecium or the earthworm, take up oxygen for all vital processes over their entire body surface. In the fishes, numerous skin folds have developed in the course of evolution, the so-called gills. Water flows past ...
Most insects possess 1 or 2 pairs of membranous wings. Their venation may differ distinctly. Similarities in the venation pattern indicate a close genetic relationship of the species. Compare the venation pattern of various insect species.
The insects have developed various mouthparts in the course of evolution, depending on their mechanism of food intake. Examine the mouthparts and explain the structures.
Principle
Planarians belong to the class of the free-living flatworms (Turbellaria) and these, in turn, belong to the phylum of platyhelminthes (flatworms). They occur in both freshwater and marine environments, feeding as predators, for example, on the eggs of fishes and shrimps in ...
Threadworms (nematodes) are whitish or colorless roundworms of very simple organization, which occur almost everywhere in moist soils, in water, and also as parasites in plants, animals and humans.
Benefits
There is a genus of very small crustaceans living in salt lakes. These animals feed on other microscopic organisms such as algae and bacteria. The brine shrimps lay eggs from which larvae develop. These grow up to juvenile crustaceans within a few weeks. When salt lakes dry up ...
Water fleas are not actually fleas but belong to shield shrimps (branchiopods) just like the brine shrimps do.
In numerous animals, the surface of mucous membranes is ciliated similar to the bronchial mucosa in humans. Mussels not only breathe with their gills but they are also able to feed themselves by using them. The cilia growing on the surface of their gills produce a water current. ...
Weedy fern plants are often found in moist forests. In the tropical regions, however, there are even tree ferns that can be up to 10 meters tall. The ferns do not belong to the flowering plants and therefore do not produce any seeds. Like the mosses, they reproduce by spores. On ...
Principle Surely you have seen on several occasions that molds have grown on food. Molds live on organic matter composed of carbohydrates, fat, and protein. As foodstuffs contain these substances and the required moisture, they make an ideal substrate. The macroscopically visible ...
Principle Life in the aquarium is more variegated than one may perceive at first glance. You can not only see how fish feed but also observe the movements of gill covers and how water flows through a fish's body. Besides you can observe mating behavior and territorial fights among the ...
Principle A microscopic water analysis predominately reveals unicellular organisms. But occasionally you can also see groups of algae that resemble a mulberry. They consist of a number of single algae which are held together by mucilage. Such an assemblage is referred to as a colony. The ...
Principle Many people are afraid of the dangerous moor because one might sink and drown in it. For others, however, this is an interesting place. Archeologists find traces of early settlements in moors. Paleobotanists search for pollen which plants left behind in prehistory. Botanists find ...
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