A species
Giant kelp
Macrocystis pyrifera
A super-fast giant that looks like a plant but is not one.
You and the giant kelp last shared an ancestor about 1.8 billion years ago (on 28 July, if life's history were one year).
Giant kelp looks like a leafy plant, with parts that look like roots, stems and leaves. But it is not a plant at all. It sits in a loose big grouping often called the protists. Its cousins on this tree are a surprise: diatoms, most too small to see without a microscope.
This is one of the fastest growers known. It can shoot up by about half a metre a day. Many grow to about 30 metres long, as tall as a ten-storey building. Small gas-filled floats lift most ribbons toward the surface, where the golden-brown ribbons can catch the light.
A cone of root-like grippers anchors it to rock, but it does not soak up food like a root. It lives in cool, sunlit, surging seas. Many strands rise from one shared base, and many kelps together form tall underwater forests. Like a rainforest, they have a floating roof and layers below that give food, shelter and a nursery for young fish.
Ice cream helper
Something taken from kelp is used in paper, toothpaste and ice cream, where it keeps texture smooth and helps freezing and melting stay even.
Spores first, then eggs
The big kelp you can see does not make eggs and sperm. It makes tiny spores on small ribbons near its base. Some grow into tiny male forms that make sperm and others into tiny female forms that make eggs.
Otters guard the forest
Sea otters were hunted out of the Channel Islands by about 1900. Without them, sea urchin numbers grew fast and ate down the kelp, leaving wide bare patches.