The definition of life is an organism that is capable of reproduction. Spiders are alive because they can produce offspring. A web is something the spider secretes, and so it is not alive because it can't reproduce itself.

Biologists have a hard time deciding if viruses are alive, for example, because viruses have to infect a host organism in order to reproduce - therefore, they don't neatly fit into our definition of life because they don't appear to be alive or inanimate objects!

Spiders are living creatures, but their webs are not. The way biologists define life relies on whether the life form can reproduce itself if left on its own.

For instance, a single bacterial cell can divide into two identical cells that have the same parts as the original cell, and can reach the same size as the original cell. Therefore, bacterial cells are living things. Along the same line of logic, rocks are not alive because a rock cannot produce other rocks that are identical to it - it can only give chips of itself. Spiders can mate with other spiders and produce more spiders, while webs themselves cannot make more webs, so spiders are alive but their webs are not.

Spiders are living, but their webs are not. This is because a spider is an animal that contains living tissue, while its web is a string of protein filaments that attach between locations.

Spiders are living and quite advanced organisms. They metabolize food (other insects), respond to their environment, and reproduce. All of these things indicate that they are living. Spider webs are not living. Spider webs are made up of a protein molecule that the spider makes and then secretes called spider silk protein. Spider silk.