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How does an animal choose what food to eat?

By: HWC, Views: 6150

One might assume that natural selection has influenced the foraging behaviors of animals, and that most animals forage efficiently, spending the least energy to gain the most nutrients. This is the underlying assumption of optimality modeling, a scientific approach to studying foraging behavior. ...

Green alga life cycle Animation

By: HWC, Views: 1266

Chlamydomonas zoospores are haploid flagellated cells. As long as conditions are favorable, these cells reproduce asexually. As many as sixteen cells may form by mitosis within a parent cell. Daughter cells escape when the cell wall ruptures. When conditions become less favorable, the...

Introduction to Genetics

By: Administrator, Views: 9517

Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms. Gregor Mendel, a scientist and Augustinian friar, discovered genetics in the late 19th-century. Mendel studied "trait inheritance", patterns in the way traits are handed down from p...

Body plan of euglena Animation

By: HWC, Views: 1002

Euglenoids are single-celled organisms that live in lakes and ponds. A contractile vacuole pumps out the water that diffuses into the cell from its hypotonic surroundings. The body is covered by a translucent pellicle composed of flexible strips of a protein-rich material. Light passe...

Polysaccharides

By: HWC, Views: 6225

More complex sugars are called polysaccharides (from "poly" meaning "many" and "saccharum" meaning "sugar"). Many things in nature are made of polysaccharides. Here we show one of the polysaccharides in corn, another in wood, and another in the exoskeletons of insects like grasshoppers. How are a...

Anaphylaxis Animation

By: Administrator, Views: 9422

Anaphylaxis is a serious, life-threatening allergic reaction. The most common anaphylactic reactions are to foods, insect stings, medications and latex. If you are allergic to a substance, your immune system overreacts to this allergen by releasing chemicals that cause allergy symptoms.

Plant Defense Mechanisms from Pathogens

By: HWC, Views: 6113

Plants and pathogens have coevolved such that pathogens can recognize plants by the sugars, or other molecules, they produce. Plants, in turn, can recognize pathogens by the molecules they produce. The ability to recognize pathogens allows plants to activate defense systems that can prevent wides...

Diversity of Living Creatures - Charles Darwin & the Beagle's Voyage

By: HWC, Views: 6409

As we look around at the living creatures on Earth, we see a great amount of diversity. In some cases, the differences are quite noticeable, like the differences between plants and animals. Some differences are not as easy to see, like the differences between two species of lizard. How did all...

Four Giant Convection Cells oF Earth

By: HWC, Views: 5975

Earth Has Four Giant Convection Cells Earth's climates range from dry and cold at the poles to wet and warm at the equator. These climates are dictated largely by the amount of solar radiation that a region receives. Solar radiation warms the Earth and the surrounding air, setting up convection c...