Characteristics of Life
What defines something as being living?
This is THE most fundamental question surrounding life. For from our answer then derives what we study and why we study it. Unfortunately the debate is still out, as no true consensus has been identified. However, most scientists agree on the following, with a few places of contention:
This is THE most fundamental question surrounding life. For from our answer then derives what we study and why we study it. Unfortunately the debate is still out, as no true consensus has been identified. However, most scientists agree on the following, with a few places of contention:
- Reproduce- sexual or asexual
- Grow and Develop - has a life cycle (born, grow, die)
- Metabolize: chemical reactions in a cell
- Respond to their environment/ stimuli (Adapt to environment)
- Homeostasis: maintain a stable internal environment - regulate their systems (ex. blood pressure or heart rate)
- Nutrition: obtaining food, providing energy
- Excretion: get rid of waste products
- Evolve: change over time within groups
- Many scientists group this one into life. However, it can be extremely hard to observe in most organisms. Is it also a requirement to change/ evolve to be alive?
- Made of Cells- single or multiple
- Cells are considered the smallest unit that has the characteristics of life. By that definition the question comes from can they also be required to be alive?
- DNA- genetic material (DNA or RNA)
- It is a bit of a contention. Does it fit under another category, such as cells or reproduction, or is it essential in and of itself?
- It is a bit of a contention. Does it fit under another category, such as cells or reproduction, or is it essential in and of itself?
- Some pull out response and adaptation as two separate characteristics, others put the together.
What are viruses?
Virus Explorer- HHMI Biointeractive |
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HOw do Virus' Replicate
Numbers coordinate to picture
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Cell Theory
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The cell theory attempts to explain life through the existence of cells. It states:
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Exceptions to the Cell Theory
There are a few exceptions to the above cell theory:
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