Please note that the images are copyright protected and can only be used for educational and training purposes. If want to use your drawing commercially, you have to work as much from your own photos, go out into nature or set up a still life at home. Search out your own subject matter from real life wherever possible. Use an A4 sketchbook and always jot down the date of your drawing and take notes.
Do each task regardless of agreeing with the subject, this will teach you to push through problems. Or if you have already something planned to use as a motif that suits you, the better. Never be overwhelmed by a subject that seems far too intricate for 10 minutes, the images are just indicative just do what you can and leave the drawing unfinished and whenever you feel like it go back to it.
Images of the following books have been used, which I recommend as the best source for this drawing challenge. You can order most of them Online. If you want to buy only one book, I advice to get "The Art of Basic Drawing" by William F. Powell.
William F. Powell - The Art of Basic Drawing, Walter Foster (Publisher)
Arthur Guptill - Sketching and Rendering in Pencil
Andrew Loomis - Successful Drawing
J.D. Harding - On Drawing Trees and Nature: A Classic Victorian Manual
Joe Weatherly - The Weatherly Guide to Drawing Animals