2006-11-20 07:36:22 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Zoology
Usually, textbooks define living things as anything that has a list of characteristics. For example, they reproduce, they metabolize, they grow, they respond to their environment....
THere isn't a single thing that you can use to define "living".
2006-11-20 07:42:50 · answer #1 · answered by hcbiochem 7 · 1⤊ 0⤋
Theme #1 - Cells All living things are composed of one or more cells. Different types of cells have different "jobs" within the organism. Each life form begins from one cell, which then will split. These cells split, and so on. After this has happened several times, differentiation is undergone, when the cells change so that they are not the same thing anymore. Then they are used to begin to put together the final organism, some cells, for example, as the eyes, some as the heart, etc. The only arguable exception to this is viruses. They are not composed of cells, but are said to be "living." Theme#2 - Organization Complex organization patterns are found in all living organisms. They arrange themselves on very small levels, grouping like things together. On larger levels, they become visible. This also has to do with differentiation, as the cells are organized in a manner that makes sense for the organism after they change to what they’ll be in the final organism. Theme#3 - Energy Use All organisms use energy. The sum of the chemical energy they use is called metabolism. This energy is used to carry out everything they do. Autotrophs (plants) use energy from the sun for photosynthesis, to make their own ‘food’ (glucose). Heterotrophs (animals and humans) must ingest food for this purpose. Theme#4 - Homeostasis All organisms have stable internal conditions which must be maintained in order to remain alive. These include temperature, water content, heartbeat, and other such things. In a way, this has to do with energy use, because a certain level of energy must be kept within the body at all times. For this, obviously, humans must then ingest food on a regular basis. Not all conditions are for the body to maintain itself; though most are. Theme#5 - Growth All organisms grow and change. Cells divide to form new, identical cells. Differentiation happens, as well, when cells mutate into other types of cells, making a more complex organism. Organisms growing, changing, and becoming more complex is called development. Single-celled organisms do grow as well, but they will only become slightly larger – this is nearly unmeasurable. Theme#6 - Reproduction All organisms reproduce in order to continue the species' life. This is combining genetic information (in sexual reproduction) or splitting into two organisms (in asexual reproduction) in order to create another of the same species. In sexual reproduction, the new organism will have some characteristics from the mother, and some from father. It may look like either of them, or it may not. In asexual reproduction, the new organism is an exact copy of the first. Sometimes, not every member of a species is able to reproduce. As long as others are (which we know they can, if they still exist today) then it does not threaten the species. (Except for mules, but don't worry about them, they are a bizarre anomoly.)
2016-03-29 02:57:44 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Living beings are the ones who are given birth by parents,who grow , reproduce ,and give birth to off springs and die in due course of time
2006-11-20 07:46:07 · answer #3 · answered by red rose 5 3 · 0⤊ 0⤋
A single or multicelled organism?
2006-11-20 07:38:15 · answer #4 · answered by johndoe48507 1 · 0⤊ 0⤋
something that can breath like people
2006-11-20 07:42:16 · answer #5 · answered by Raven 2 · 0⤊ 1⤋