Naked Science Forum

Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: katieHaylor on 22/05/2018 10:58:09

Title: What's the difference between an animal and a plant?
Post by: katieHaylor on 22/05/2018 10:58:09

Mervyn says:

The "triffids" were (fictional) plants in John Wyndham's novel: The day of the Triffids. These plants could walk around and communicate and attack people etc. Surely, anything which could do all of this would be called an animal and not a plant.

Technically, what is the definition of an animal and a plant? Also, what is the difference between the two? 


Can you help?

Title: Re: What's the difference between an animal and a plant?
Post by: Kryptid on 22/05/2018 14:43:37

The technical differences lie on the cellular and genetic level. Genetically, all plants would be more closely related to each other than they are to any animals. Plant cells have cellulose-laden cell walls, but animal cells do not. They also have chloroplasts, whereas animal cells do not (take note that some plants cannot photosynthesize, despite having chloroplasts. Those live as parasites).

More information here: http://www.sparknotes.com/biology/cellstructure/celldifferences/section1/ (http://www.sparknotes.com/biology/cellstructure/celldifferences/section1/)

The preference in modern biology is to group organisms by their phylogeny (that is, groups of organisms that are related by a common ancestor). All plants have a plant common ancestor and all animals have an animal common ancestor. As such, any plant that evolved to move and eat as the Triffids do still would not be considered an animal because it would have evolved along a different evolutionary path. It would be an example of "convergent evolution" (when unrelated organisms evolve similar traits).

Title: Re: What's the difference between an animal and a plant?
Post by: evan_au on 22/05/2018 23:03:21

Here is an attempt to describe the genetic similarities between plants, animals, fungi (and their microscopic relatives).
- The closer their branches are grouped near the center, the closer they are genetically.

The green section on the right are regarded as plants, although some would regard algae is also being plants (slightly anti-clockwise of the green section).

Seen at the Mount Annan Seedbank, in Australia.
Click on the picture to expand it, then press Ctrl+ to expand it to a readable size...