Biology: Age 15

13 illustrated Biology lessons for Age 15.

The DNA double helix DNA is made of two long strands that twist around each other like a spiral ladder. The strands are held togeth…
The DNA Ladder DNA is shaped like a long, twisted ladder made of two strands winding around each other. The rungs that connec…
Marmot Hibernation To survive winter, marmots rely on stored fat and let their body temperature and heart rate drop sharply. They…
Muscle Energy Loop Muscles use ATP as an immediate energy currency for contraction. Cells continually rebuild ATP from glucose be…
From Ear to Brain Sound enters the ear and becomes electrical pulses. The auditory nerve sends these pulses to the brain, which …
Alcohol and the Teen Brain Alcohol reaches the brain quickly and can disturb a brain that is still growing. It can make learning, memory,…
Chromosome Pairs Most human cells contain 46 chromosomes arranged in 23 pairs. An extra copy of one chromosome causes a conditi…
Plants in Ice-Free Pockets During ice ages, glaciers covered most mountain ranges. A few rocky pockets stayed free of ice, and the plants…
Tree family sugar sharing Some trees may share sugars with related seedlings through underground fungal networks. This extra sugar can h…
Gut bacteria at work Gut bacteria break down parts of food that the body cannot digest on its own. This releases nutrients that pas…
Sliding Filament Segment Muscle fibres contain repeating units built from thick and thin protein strands. During contraction, the thin …
Running Heart and Lungs When you run, your leg muscles burn through oxygen and fuel much faster than when you sit still. Your heart be…
One Cell Becomes Two Before a cell divides, it copies every chromosome so there are two matching sets. The sets are pulled to oppos…