Wiki.Answers sucks. Their answers are invalid because they let illogical people answer them.
Many celled organisms are referred to as multicellular organisms. In order for single cells to form into multicellualr organisms, they must identify and attach themselves to other cells.
O2
Cells make up all organisms, from single-celled to multi-cellular organisms. The order of complexity in a multi-cellular organism is, in order, cell, tissue, organ, system, organism.
Unicellular organisms usually come from Protista kingdom, but in order for them to reproduce and survive there is a nucleus of course. im not aware of any exceptions though. Well if i could answer ur question i'd say animalia , without being 100% correct. animals have red blood cells! (anucleated cells!)
The parts of the single-celled algae that are responsible for capturing energy are chloroplasts. Chloroplasts have to be there in order for cells to capture energy.
The simplest example would be of single celled animals. A single celled animal that reproduces by fission need only consume and convert sufficient resources to divide, producing two animals of similar size. A single celled organism that reproduces by budding requires fewer resources yet as it is producing a much smaller version of itself. The same single celled animal must, in order to reproduce sexually, find another animal of the same type, both must have sufficient resources to pair, exchange genetic material and then at least one of them must acquire the energy to divide, producing new organisms. Even at the single celled level it is easy to see the time differential between asexual and sexual reproduction.
Technically, a virus is not considered to be alive, therefore is not an organism at all. A virus does not have a conventional membrane, unless, as with HIV, it takes some from a host cell in order to mask its presence to other cells.
They have to in order for their bodies to survive
Euglenoids and male sperm are both single-celled organisms. In order for Euglenoids and sperm to move, they both use a flagella. A flagella is a microscopic whip-like appendage that enables single-celled organisms to swim.
Amoeba, being single celled organisms, undergo a process known as Mitosis in order to grow and reproduce. Mitosis is a division of a cell in which the DNA recombines to increase genetic diversity.
Water, Food and Sunlight.
Homeostasis is the steady internal state all organisms must maintain in order to survive.