Question

   You and your crewmates have finally landed on your chosen planet. It is now time to begin exploring it. Remember that you are seeking out signs of life. In order to cover the most territory, your group decides to split up and explore different areas, with each of you agreeing to bring back samples of anything that looks like it might contain life or evidence of life.

            After putting on protective space suits, you go out and explore. The first thing you notice is that the planet is very different from Earth. Nothing looks familiar, and you realize that any life forms on this planet are likely to be very different from anything you’ve seen before. How can you tell if something is living or not? After exploring for awhile, you see some objects that look very interesting, so you collect a few samples and head back to the ship.

            When you get back you learn that several of your crewmates have also brought back samples, so you and your crewmates examine them. Now comes the hard part. You must decide if the samples are living things, or evidence of living things, or non-living. How will you decide this? What will you look for? What experiments might you conduct on these samples to decide?

This is totally hypothetical. For this assignment, you must post at least two responses to the discussion board. One response is you responding to the question posed and the second should be a comment or response to one of your classmates posts.

Answer 1

All living organisms will show certain features.

• They will respond to their surrounding environment: Living organisms move or attack or show some response if u touch or tamper with them. They show adaptations to adjust to the environment so that they have better chances of survival and reproduction.
• The process of growth and change will take place: Under the appropriate favorable conditions, a living organism will grow.
• Living organisms reproduce by producing offsprings and transfer their traits to them: Living organisms make more organisms like them to maintain the population of their species otherwise they will become extinct.
• Their molecular reactions and metabolic processes are complicated and very specifically regulated: Both flower (living) and crystal (nonliving) might have complex chemistry but a close look will reveal the dynamic processes going on internally like for example, transportation of water through petals, pigment production process, energy production by the breakdown of sugars, etc.
• They tend to maintain homeostatic balance: Living organisms can maintain a stable internal environment through various physical, physiological, biochemical, and behavioral processes despite changes in the surrounding external environment. For example, in an extremely cold outside environment, a living organism will not transform into ice, instead, it will try to keep the body warm by shivering and various other processes to maintain the body temperature.
• Any living organism is formed of a basic unit of life i.e., cells. If a thin section of a living sample is examined microscopically, the presence of one or more cells can be appreciated. It is the basic unit of structure and function in a living organism. Atoms form molecules that form larger molecules further forming organelles. These work all together to maintain a cell.
• Living organisms excrete the waste so that any toxicity because of unwanted waste material is prevented and the cell remains healthy.

How can you tell if something is living or not?

For instance, while exploring, you step on something. If it moves or snaps at you, it must be living. If it just lies there without showing any response then it can be nonliving because a response to a change in the surrounding environment is the basis of determining living form.

You must decide if the samples are living things, or evidence of living things, or non-living. How will you decide this? What will you look for? What experiments might you conduct on these samples to decide?

• Search for the seven features of life (as explained above) in the sample.
• A very thin section of the sample can be observed for signs of life, the presence of cells under a microscope. With the help of advanced microscopes, even the physiological and biochemical processes inside the cell can be appreciated.  
• You can tamper physically with the sample to observe for any response. It might not be moving but if you break it, for instance, it might change its appearance (e.g., color or texture) over a period of time.
• You can add some chemicals (for example, water, any acid or base) externally on it to see for any response.