Why don't we grow back body parts?
Let’s re-visit the problem from the start of the week: our 15 year old’s amazing question:
“If a whole plant can be grown from a plant leaf that’s left on a window sill in a jar of water, why can’t we grow a complete human from a piece of a finger?”
An answer to this question will draw upon your understanding of cell division, stem cell biology, cell differentiation and the persistence of totipotency in plant stem cells but not in animal stem cells. However, as we all know, one amazing question often inspires another, so how will you respond to the student who asks:
“Why do plant stem cells remain totipotent but animal stem cells do not?”
Which areas of the Biology curriculum would you need to link to in order to explain your answer?
The answer to this question is based on the simple observation that plants can’t run away, but (most) animals can. Plants are rooted into the ground and have evolved adaptations that allow them to survive predation instead of escaping from it. If a grazing animal eats one part of a plant, it is important that the plant can re-grow the tissues that have been removed. The presence of totipotent plant stem cells in the meristems in the each of the plant’s many growing root and shoot tips allows this re-generation of tissues and organs vital to the plant’s survival.
Watch this video for some thought provoking ideas to help you to answer this question: Plant survival strategies
This is an additional video, hosted on YouTube.
The video discussed current ideas about how plants co-ordinate the growth responses necessary for their ‘stay-put’ survival strategy. It introduced you to for some thought provoking ideas and topics to consider and discuss with your students in answer to this question about differences in totipotency in plant and animal cells.
How could you use these ideas in the classroom to help students consolidate their understanding of previous learning and make those important links?
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