A dog is alive and a stone is not. That is easy. But a mule cannot reproduce, and a salt crystal does grow. In this course we study growth, reproduction, metabolism, cells and the response to the surroundings. We find which of them is true of every living thing, and which has exceptions.
3 lessons, about 1 h 30 min3 simulations11 problems6 practice questionsPython in every lesson
Created by StemPy LabBiology is the science of life forms and living processes. Growth, an increase in mass and in the number of cells, is a feature of living things, but it is not a defining one. Living things grow from inside, and non-living things grow only by material that piles up on the outside. In a single-celled organism, growth and reproduction are one event.
Reproduction is the making of new individuals like the parents. It can be sexual, or asexual by binary fission, budding, fragmentation, spores and regeneration. A mule or a worker bee does not reproduce, so reproduction is not the defining feature. Metabolism, the sum of all the chemical reactions in the body, is found in every living organism and in no non-living object, so it is a defining feature of life.
Every living organism is made of cells, and every one senses its surroundings and responds to stimuli that may be physical, chemical or biological. Human beings are also aware of themselves. A living organism is a self-replicating, evolving and self-regulating interactive system that is capable of responding to external stimuli. Metabolism, cellular organisation and the response to the surroundings are found in all of them.
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