Can a plant or animal be made up of a single cell?

Question

If so, please cite some examples to prove it. Thanks! :)

Answer 1

The first definition of 'animal' given by dictionary.com states that an animal is

"any member of the kingdom Animalia, comprising multicellular organisms that have a well-defined shape and usually limited growth, can move voluntarily, actively acquire food and digest it internally, and have sensory and nervous systems that allow them to respond rapidly to stimuli: some classification schemes also include protozoa and certain other single-celled eukaryotes that have motility and animallike nutritional modes."

and for plants it states that they are

"any member of the kingdom Plantae, comprising multicellular organisms that typically produce their own food from inorganic matter by the process of photosynthesis and that have more or less rigid cell walls containing cellulose, including vascular plants, mosses, liverworts, and hornworts: some classification schemes may include fungi, algae, bacteria, blue-green algae, and certain single-celled eukaryotes that have plantlike qualities, as rigid cell walls or photosynthesis."

So, according to these definitions, yes there can be monocellular plants and animals.

However it is important to note that according to the Linnaean classification system a member of the kingdom 'animalia' is a "multicellular form with specialized eukaryotic cells; have their own means of locomotion" and a member of the kingdom plantae is a "multicellular form with specialized eukaryotic cells; do not have their own means of locomotion"

According to the Linnaean system monocellular organisms fit into one of two other kingdoms, besides Animalia and Plantae, those two kingdoms are

1. Monera - small, simple single prokaryotic cell (nucleus is not enclosed by a membrane); some form chains or mats

2. Protista - large, single eukaryotic cell (nucleus is enclosed by a membrane); some form chains or colonies

There is a fifth kingdom named Fungi which consists of multicellular filamentous form with specialized eukaryotic cells

Within the two kingdoms of Monera and Protista are several phylums many of which have plant like or animal like characteristics. This means that they have one or two things in common with plants and animals, usually digestion or photosythesis, but do not meet the full requirements for being considered a plant or an animal.

Furthermore some monocellular organisms display both animal and plant characteristics while still others show no similarity to either of the multicellular kingdoms other than the fact that they meet the scientific requirements for being concidered 'life'

An example of a single cellular organism that has both plant and animal characteristics would be certain autotrophic members of the phylum Euglenophyta which have cloroplast, and are therefore able to photosynthesise their own food but which become heterotrophic (ingests sustinance which it has not produced with its own 'body') when the light levels are insufficient for performing photosythesis.

So, according to science - no it is not possible since a plant or an animal must be multicellular.

Answer 2

I doubt one can classify single cell as either animal or plant. but amoeba is an example of single cell organism.

Answer 3

Yes both animal=amoeba Bactria Plant=phytoplankton

Answer 4

The amoeba is the only single cell animal.

Answer 5

Yes,a plant or animal can be made of single cell.for example take amoeba which is a unicellular organism.

Answer 6

There are single-celled algae, so yes to the plant part too. Don't know if a protozoan would be considered an animal, but giardia is one of these.

Answer 7

Depends on your definition of Animal and Plant.

Answer 8

An amoeba.

Answer 9

it would depend on your definition of an amoeba...if that is an animal then yes.

Answer 10

Amoeba and protazoa.