Common Ancestor of Plants: Evolution Theory Explained

[Spirit]

Hello,

According to the evolution theory:

Does plants, all plants, have a common ancestor? As Well: Do they have some common ancestors with animals? [i mean beside the single-cell first creature may be ..etc]

Please excuse my english amd modest knowledge about the topic.
-Spirit

 

[TRCSF]

Yes, all plants have a common ancestor and it's shared with animals (along with everything else).

Now they wouldn't have been the first single celled organisms, but they would have been single celled eukaryotes. The important change occurred with the ability to use photosynthesis, perhaps with the incorporation of chloroplasts in a manner similar to how eukaryotes incorporated mitochondria.

 

[Phobos]

This phylogenetic tree shows the relationships (plants and animals in the upper right side).
http://en.wikipedia.org/wiki/Image:PhylogeneticTree.jpg

 

[Spirit]

Thanks for your replies TRCSF and Phobos,

I am wondering if it found a species between the 'stable plants' and the common ancestors who were able to move [or at leasat not fixing themsleves to a fixed position]

:)

 

[Ouabache]

Not sure if I understand your comment. Are you wondering if species have been found that fall somewhere between two distinct and well defined branches on the phylogenetic tree? When you say "were able to move" do you mean to a different position on the tree?

If this is the meaning of your comment, I would say yes there have been species that may fall between two branches, but for one reason or another, they resulted in a dead end. One major influencing factor could have been, change in climate. As the evolutionary process is an extended experiment, lots of variations have occured. But only those with some selective advantage, survived and propagated to future generations.

As far as moving to a different position on the tree, that would be very difficult. A distinct species is placed somewhere on this tree due to its relationship with those that came before it (evolutionarily speaking). Those occurring further down a branch, gain in complexity.
In order for that same species to move or occur at another position, it would need to have evolved independently along another branch on the tree. The probability of that happening is infinitesimally small. So small, for all intents and purposes, it probably won't happen.

 

[Moonbear]

I am wondering if it found a species between the 'stable plants' and the common ancestors who were able to move [or at leasat not fixing themsleves to a fixed position]

:)

Do you mean something like the Euglena that are flagellated, photosynthetic organisms? It has both chlorophyll and motility, if that's what you're asking. (Some cool pictures of Euglena are here: http://www.btinternet.com/~stephen.durr/euglena.html) Other algae would fall into this description as well.

There are also animals that are not motile, such as sponges, so motility is not something that characterizes plants from animals, if that's the source of confusion.

 

[Ouabache]

Movement of plants from a fixed position is interesting. I hadn't thought about motility. There are also other ways plants (or their parts) have evolved to move.

For instance, when seeds of a maple tree fall, they spin like little helicoptors and carry their seed a considerable distance from the mother plant, and increase their chances of finding a suitable place to grow. Other plants have evolved a feathery appendage that faciliates wind dissemination (e.g. dandelion Taraxacum officinale and milkweed Asclepias sariaca). When animals ingest fruits they carry them some distance and drop the seeds (and some fertilizer) allowing the next generation to grow somewhere else. When a coconut from the palm tree, falls to the ground, some will roll into the sea. They will float and remain viable until reaching the shores of another place, germinate and grow many miles from its mother plant.

Also, in the ocean, while some do anchor themselves, many alga are free floating and move around with the ebb and flow of the tides.

 

[misskitty]

Just to make sure I read carefully; humans and plants have a common ancestor.

~Kitty

 

[Ouabache]

Yup, see Phobos' link to diagram of a phylogenetic tree, it indicates organisms that were ciliate-like and slimemold-like; predated and evolved to the common ancestor of not only plants and animals, but also of the fungi.

 

[misskitty]

After how many divisions did the cells begin to differential themselves as distinctly human or plant?

~Kitty

 

[Ouabache]

That's an unanswerable question.. No one was around to record how many divisions occurred before these organisms began to differentiate as distinctly animal or plant.

 

[Phobos]

Agree. Consider this...
First prokaryotes (cellular organisms) formed about 3.5 to 3.8 billion years ago.
First eukaryotes (cells with a definite nucleus like plants and animals have) formed about 1.8 to 2 billion years ago...which was about the same time photosynthetic plants (algae) first appeared.
First animals formed about 0.6 to 0.7 billion years ago.

That's a lot of generations in between.

 

[Monique]

Just to make sure I read carefully; humans and plants have a common ancestor.

~Kitty

Yes, we share many genes and mechanisms.

 

[selfAdjoint]

Just to make sure I read carefully; humans and plants have a common ancestor.

~Kitty

Yes, we share many genes and mechanisms.

I believe I read somewhere that there is a 25% overlap between the genomes of humans and oak trees.

 

[Monique]

I believe I read somewhere that there is a 25% overlap between the genomes of humans and oak trees.

I was trying to find a source for such homology figures earlier, but couldn't find one.
*edit* the following free paper describes the collection of orthologous genes (homologous genes descended from a common ancestor) http://www.pubmedcentral.gov/picrender.fcgi?artid=222959&blobtype=pdf Arabidopsis thaliana would be a plant often used as a model organism.

There was a comment in Nature that critized the publication of the human genome: "We note, however, that the papers analysing the data of the human genome substantially lack comparisons to the Arabidopsis genome." http://www.ncbi.nlm.nih.gov/entrez/..._uids=11268174&query_hl=6&itool=pubmed_docsum