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Some male birds and mammals congregate in communal courting grounds called leks.
The testes. In addition to producing sperm, the testes secrete the male sex hormones, primarily test
Endocarditis. The human heart has been sectioned to reveal the left ventricle and origin of the aort
Diphtheria. The bacteria that cause this disease, called Corynebacterium diphtheriae, proliferate in
The heavily worn, and sometimes cutmarked, anterior teeth of Neadertals suggest that these teeth wer
A Gaucher cell showing accumulated fat stored in structures called lysosomes