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Birth Control and Contraception
Birth Control and Contraception

Different pregnancy and birth control and contraception strategies are described. Read this tutorial to learn each of th..

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Human Reproduction and Fertilization

For human species to obviate extinction, reproductive mature adults should be producing viable offspring in order to con..

Stem
Stems

Stems primarily provide plants structural support. This tutorial includes lectures on the external form of a woody twig ..

Freshwater Ecology
Freshwater Ecology

Freshwater ecology focuses on the relations of aquatic organisms to their freshwater habitats. There are two forms of co..

Homo Species
The Homo Species

The evolution of the species of the genus "Homo" led to the emergence of modern humans. Find out more about human evolut..

Pikas are an indicator species for climate change
Indicator Species and Endangered Species

Certain species are capable of expressing characteristics indicative of the state of the ecosystem they occupy. They are..