Theoretical Question - Plants Without Animal life

[Segnosaur]

I was out camping this past weekend, seeing all the trees around, and a thought crossed my mind....

What would happen if all animal life (including insects, reptiles, mammals, etc) vanished, leaving only plant life, bacteria, fungi and perhaps protozoa?

I know some plants are controlled by animals, either through grazing, or in other ways (e.g. grubs eating roots of grass plants, catepillers eating leaves of trees). In the short term, what would happen to the various mixtures of plants? Would we end up with a different 'mixture'? (Perhaps we'd get a higher proportion of 'low-growing' plants, since they are the ones that are most affected by 'grazers'.)

And how would the balance be altered without animals to produce the carbon dioxide that plants use? (I would assume that the certain types of bacteria would probably generate the necessary CO2)

In the long run, I would assume that some species would evolve to take the place of what we consider "animals" (mobile creatures able to feed on/digest other material). But what would be the basis for those new species? Would certain groups of plants evolve into the niche currently held by animals? Or would certain bacteria/protozoa evolve into that role?

Anyone have any ideas? (No real right or wrong answer here...)

[~enigma~]

I was out camping this past weekend, seeing all the trees around, and a thought crossed my mind....

What would happen if all animal life (including insects, reptiles, mammals, etc) vanished, leaving only plant life, bacteria, fungi and perhaps protozoa?

I know some plants are controlled by animals, either through grazing, or in other ways (e.g. grubs eating roots of grass plants, catepillers eating leaves of trees). In the short term, what would happen to the various mixtures of plants? Would we end up with a different 'mixture'? (Perhaps we'd get a higher proportion of 'low-growing' plants, since they are the ones that are most affected by 'grazers'.)

And how would the balance be altered without animals to produce the carbon dioxide that plants use? (I would assume that the certain types of bacteria would probably generate the necessary CO2)

In the long run, I would assume that some species would evolve to take the place of what we consider "animals" (mobile creatures able to feed on/digest other material). But what would be the basis for those new species? Would certain groups of plants evolve into the niche currently held by animals? Or would certain bacteria/protozoa evolve into that role?

Anyone have any ideas? (No real right or wrong answer here...)
Didn't plants grow on dry land before animal life was on dry land?

[Segnosaur]

Didn't plants grow on dry land before animal life was on dry land?

Yes, I believe so.

It began with plants, followed by invertebrates, then others.

But my question assumes that our post-animal world already has the same plant species that we currently have.

[makaya325]

Without animal life, i am guessing that Plants would actually grow larger.

[~enigma~]

Yes, I believe so.

It began with plants, followed by invertebrates, then others.

But my question assumes that our post-animal world already has the same plant species that we currently have.
Then why would you expect plants that were aided by animals to continue living without them?

[gtc]

Then why would you expect plants that were aided by animals to continue living without them?

He's not.

He is saying:

Assume all animals etc die out today. What happens next.

[BenBurch]

Well, there would be no source of CO2 other than the weathering of rock and fires.

This would eventually limit plant growth and also cool the planet.

Nutrient would not go back into the soils and soil would not be replaced without the actions of worms and insects.

The planet would become a near ice ball pretty fast with maybe some plant life left in the tropics for a few million years. And what there would be would be self-pollinating or wind pollinated. Flowering plants depending on animal symbionts for pollination would be gone pretty fast.

[~enigma~]

He's not.

He is saying:

Assume all animals etc die out today. What happens next.
And I said why would you expect plants that were helped by animals to live. Is that wrong?

[gtc]

I apologise, I thought you were saying that he had said that he assumed those plants would live.

Ignore my post.

[Tumbleweed]

Well, there would be no source of CO2 other than the weathering of rock and fires.

This would eventually limit plant growth and also cool the planet.

Nutrient would not go back into the soils and soil would not be replaced without the actions of worms and insects.

The planet would become a near ice ball pretty fast with maybe some plant life left in the tropics for a few million years. And what there would be would be self-pollinating or wind pollinated. Flowering plants depending on animal symbionts for pollination would be gone pretty fast.

Don't volcanoes put out LOTS of CO2? And unless you stipulate that humans get to go on, their global warming co2 goes bye bye along with their respiratory co2. So there would be somewhat less c02 so there would less systemic plant growth. I suspect there would be a big extinction event among the plants existing symbiotically with animals, for example those that require insects for pollination but eventually the Earth would go back to being what it was like before there were animals - at least on land. But then how did/ would they decay without bacteria? Fire only that accomplishes the same thing only quicker? Oops I checked you said bacteria are okay

[Doghouse Reilly]

As BenBurch touched on, a huge number of plant species rely on pollination by insects to reproduce. So all of these species would go extinct.
That alone would cause a massive re-configuration of the "plant landscape" so to speak.

[Doghouse Reilly]

On a related note, all fruiting and flowering trees would go extinct, or become unrecognizable. They only exist because some species like to eat the fruit they produce, or are attracted to the flowers.

Edited to add: there may be some types of flowers that wind pollinate exclusively, but most are there to attract insects, birds, or animals of some kind.

The more I think about pollinators, fruit, flowers, etc, the more I think that this "no animal and insect thing" is much bigger than you might think. The symbiotic relationship between animals and plants is staggering.

[Tumbleweed]

But them if many plants also go extinct, the ones that don't will then have plenty of CO2 to thrive, getting even lusher , especially with no predators around, so lowering CO2 somewhat wouldn't matter- okay that's shaky logic. And oxygen levels would rise due to the lack of animals consuming it for metabolism. Plants would continue to break down water, and there would be no animals to reassemble it using the Carbon Cycle, but uncontrolled fires and bacteria would easily take or maintain their place in that regard, just as in their CO2 replacement
So then a postulation comes to mind - or is it a conjecture: If humans weren't around, would CO2 levels stay the same due to the onset of uncontrolled burning in forests? I say no because all that wood is going to decay, if not burn, despite our beimg around so our absence would make no difference. And a lot of it is being burned now by humans, so increased nature burning would only offset none of it now being burned by humans

[Tumbleweed]

On a related note, all fruiting and flowering trees would go extinct, or become unrecognizable. They only exist because some species like to eat the fruit they produce, or are attracted to the flowers.

Edited to add: there may be some types of flowers that wind pollinate exclusively, but most are there to attract insects, birds, or animals of some kind.

The more I think about pollinators, fruit, flowers, etc, the more I think that this "no animal and insect thing" is much bigger than you might think. The symbiotic relationship between animals and plants is staggering.
Well, there is some pollination of fruit trees and the like by wind. Just a lot less than with insects

[Tumbleweed]

But then the forests would all come back due to man not chopping them down and then-- aw Jeez, to many tangents and variables - and just before bed!

[rjh01]

The amount of CO2 may drop as the number and size of plants increase. However this will reach a new equilibrium, when the amount of plants die and decay or burn equal the amount of plant growth. The only carbon going out of the system would be if plants are buried without releasing their stored carbon.

Visit the world 100 years after animals go and you will see a vast difference in plant life alone.

[Thabiguy]

I will try to address the part of the OP that hasn't been addressed yet.

In the long run, I would assume that some species would evolve to take the place of what we consider "animals" (mobile creatures able to feed on/digest other material). But what would be the basis for those new species? Would certain groups of plants evolve into the niche currently held by animals? Or would certain bacteria/protozoa evolve into that role?

Of course, it's impossible to give authoritative answers here, so let me just offer some guesses.

I wouldn't expect bacteria to beat other lifeforms to spawning new "animals". The eukaryotes that you allowed to survive, with their mitochondria and superior energy management, would have clear advantages in that regard.

Of the eukaryotes you allowed, modern plants would be the least likely origin of the new "animals". They are quite specialized doing what they do, and they would have a very long evolutionary way to go - and little pressure to do so. Unicellular organisms with primitive lifestyle and not so much specialization are in a much better position to adapt.

So the protozoa you allowed would be the favorite in this race - depending further on what specifically you'd allow, because "protozoa" are a vaguely defined paraphyletic group. For example, I would say that choanoflagellates are just "animals waiting to happen".

(And perhaps, with enough luck, something interesting might evolve out of some primitive fungi.)

Another question is, whether they'll manage to do that in the time they have left. Last time, it took about half a billion years to get from simple multicellular organisms to reasonable land animals. Some projections say that changes in solar energy output might make Earth uninhabitable within a billion years.

[BenBurch]

Volcanos are not a significant source in our era. 400 million years ago it was different.

[BenBurch]

The amount of CO2 may drop as the number and size of plants increase. However this will reach a new equilibrium, when the amount of plants die and decay or burn equal the amount of plant growth. The only carbon going out of the system would be if plants are buried without releasing their stored carbon.

Visit the world 100 years after animals go and you will see a vast difference in plant life alone.

Without animals to help, many plants WOULD get buried without decaying.

Animals break up the plant material into small units that the fungi and bacteria can get to.

[Segnosaur]

Then why would you expect plants that were aided by animals to continue living without them?
I wouldn't. As others have mentioned, plants that use insects as polinators, or animals to spread seeds would die (or have to go very rapid evolution, depending on HOW MUCH they rely on animals.)

Wind-assisted polinations would continue, as would non-flowiering plans.

[Segnosaur]

Of course, it's impossible to give authoritative answers here, so let me just offer some guesses.

Guesses were all that I was expecting. (Wasn't looking for definitive answers, just people's guesses.)

Of the eukaryotes you allowed, modern plants would be the least likely origin of the new "animals". They are quite specialized doing what they do, and they would have a very long evolutionary way to go - and little pressure to do so. Unicellular organisms with primitive lifestyle and not so much specialization are in a much better position to adapt.

Makes sense, and I certainly agree...

So the protozoa you allowed would be the favorite in this race - depending further on what specifically you'd allow, because "protozoa" are a vaguely defined paraphyletic group. For example, I would say that choanoflagellates are just "animals waiting to happen".

I agree again... Yes 'protozoa' is vague. But then, all of the traditional "kingdoms" (Plant, animal, fungus, bacteria, and protozoa) are vague in some way.

Another question is, whether they'll manage to do that in the time they have left. Last time, it took about half a billion years to get from simple multicellular organisms to reasonable land animals. Some projections say that changes in solar energy output might make Earth uninhabitable within a billion years.

Well, according to wikipedia, the first Eukaryotes appeared ROUGHLY 2 billion years ago. Multicelular organisms evolved about 1 billion years ago, and more 'complex' animals took a few hundred million years after that. So yeah, the timing would be very tight.

Then you have the question about whether the existance of complex plant life would be a help or hindrance to any evolution from protozoa->animal like creatures.

[Segnosaur]

Well, there would be no source of CO2 other than the weathering of rock and fires.

In the original post, I did say that bacteria might produce at least SOME of the CO2. As others have pointed out, volcanoes would contribute some as well.

Perhaps we may see a greater expansion of fungus, since I believe they're net O2 consumers/CO2 producers.

Nutrient would not go back into the soils and soil would not be replaced without the actions of worms and insects.

True, but currently many plant species are able to take hold in areas that haven't previously been affected by the action of worms and insects. (I'm thinking of moss that grows in rocks, etc.)

Perhaps we might see an initial boom of large trees (following the demise of insects capable of killing trees), then they would die off from lack of soil regeneration, replaced by low-lying moss that is capable of inhabiting 'bad' soil areas and/or rocks.

Although I have to wonder, do nitrogen-fixing plants have the same need for 'renewed' soil?

[Marduk]

there would be little change, the only effects would be on those plants which have been altered by domestification, they would die out, the majority of CO2 in the atmosphere is caused by forest fires and vulcanism, no change there, the vast majority of oxygen is generated by algae, no change there. Plants are not dependant on animal life to procreate, it may be true that some fruits are helpful to a plants propogation, but the majority of pollen is spread by wind, not insects. Youre basically asking what would happen to a form of life that existed and evolved 3000 Ma all on its own and was the only species for 2400 Ma before the first fish realised what it was missing. Well obviously, there would be no change at all, plants ruled the earth far longer than anything else did, they would be quite happy to do so again given the chance

[William Parcher]

Perhaps we might see an initial boom of large trees


Possibly not. Besides pollinating plants, animals disperse seeds. Some seeds have special features for this purpose (burdocks, etc). I believe that there are some seeds which will not germinate unless they have passed through the gut of an animal.

Plants are in competion with each other for space, light and resources, and animals take seeds to places in which they can grow. The squirrel and the acorn are an example. Squirrels bury acorns in various places and do not succeed in finding and eating all of them later. Without animals to disperse them, all acorns simply fall beneath an adult oak tree and will enter a world of limited light (shade) if they germinate there.

[Marduk]

Possibly not. Besides pollinating plants, animals disperse seeds. Some seeds have special features for this purpose (burdocks, etc). I believe that there are some seeds which will not germinate unless they have passed through the gut of an animal.

Plants are in competion with each other for space, light and resources, and animals take seeds to places in which they can grow. The squirrel and the acorn are an example. Squirrels bury acorns in various places and do not succeed in finding and eating all of them later. Without animals to disperse them, all acorns simply fall beneath an adult oak tree and will enter a world of limited light (shade) if they germinate there.

you are ignoring the obvious, the acorn has been around millions of years longer than the squirrel, this is why the uk had large oak forests until the neolithic expansion. When the oak tree has proven itself capable of being very succesful on its own you might look to the fact that an acorn is much more evolved to fall than to be carried and oak trees do not require sunlight until a long time after germination

[Segnosaur]

Possibly not. Besides pollinating plants, animals disperse seeds. Some seeds have special features for this purpose (burdocks, etc). I believe that there are some seeds which will not germinate unless they have passed through the gut of an animal.

Certainly true for some plants, not sure how wide spread that is though.

Plants are in competion with each other for space, light and resources, and animals take seeds to places in which they can grow.
Being from Canada, I'm thinking of trees like the Maple (that distributes seeds via 'whirly-birds'), and the Pine (many which have seeds which are wind-dispersed). Both have species that can spread their seeds far from the tree without animal assistance, and don't need to go through an animal's intestine to germinate.

http://en.wikipedia.org/wiki/Maple
http://en.wikipedia.org/wiki/Pine

[Thabiguy]

Then you have the question about whether the existance of complex plant life would be a help or hindrance to any evolution from protozoa->animal like creatures.

My opinion is that it may not be all that important. Last time, animals evolved in the sea, and I think it would probably happen in a similar way again: when you're a tiny creature swimming around and devouring other stuff, and there's nothing larger feeding on you, advantage goes to those that grow larger, form colonies, differentiate tissues - well, we know the drill.

Could animals evolve on land, among all the plants? We can't know, but I personally doubt that. I just don't see how a self-propelled multicellular organism could evolve outside of water bodies. Maybe that's just my limited imagination and someone else can come up with a plausible way of that happening.

But I do think the plants would accelerate the transition from water to land, by offering a hefty reward to those who can do it.

[GlennB]

Without animals to help, many plants WOULD get buried without decaying.

Animals break up the plant material into small units that the fungi and bacteria can get to.



Nutrient would not go back into the soils and soil would not be replaced without the actions of worms and insects.



Dunno if that's all true BenBurch ;)

Plastic composting bins work very nicely without a multicellular organism in sight. And dry/wet rot will decompose wood to powder in surprisingly few years with no animals around to help.
50 years is barely the blink of an eye on nature's scale.

[Tumbleweed]

Possibly not. Besides pollinating plants, animals disperse seeds. Some seeds have special features for this purpose (burdocks, etc). I believe that there are some seeds which will not germinate unless they have passed through the gut of an animal.

Plants are in competition with each other for space, light and resources, and animals take seeds to places in which they can grow. The squirrel and the acorn are an example. Squirrels bury acorns in various places and do not succeed in finding and eating all of them later. Without animals to disperse them, all acorns simply fall beneath an adult oak tree and will enter a world of limited light (shade) if they germinate there.

But is an oak tree absolutely dependent on that squirrel dispersing its seeds or is that act more a matter of evolutionary efficiency? It just means a whole new ball of wax and natural selection would kick in. The oak tree is forced into having its acorns dispensed in a parallel way that allows it to still compete with its neighboring competitors for earth, wind, water and fire

[William Parcher]

Fig trees might be in trouble without fig wasps (http://en.wikipedia.org/wiki/Fig_wasp).


Fig wasps are wasps of the family Agaonidae which pollinate figs or are otherwise associated with figs, a close relationship that has been at least 80 million years in the making.

[William Parcher]

Ants protect Acacia trees (http://en.wikipedia.org/wiki/Acacia_tree) from other plants.


Some species of ants will also fight off competing plants around the acacia, cutting off the offending plant's leaves with their jaws and ultimately killing it.


More. (http://waynesword.palomar.edu/acacia.htm)

In its native habitat, colonies of stinging ants (Pseudomyrmex ferruginea) occupy the hollowed-out thorns and fiercely defend the tree against ravaging insects, browsing mammals and epiphytic vines.

[Tumbleweed]

Okay now lets toss out bacteria too! No decay sans fire to keep the carbon cycle going. It becomes a function of nature's lightning rather than animal metabolism. They would all just mope around waiting for a volcano to erupt. Danged limestone dissolving just takes too long. There would be " volcano blooms", and forest fire soot blooms where everything went lush for awhile and then died back as the CO2 became sequestered in their dead ancestors or bloated bodies. Those with the best method of getting the available co2 survive. Or maybe there would just be raging fires everywhere to make up the CO2 lost through bacterial and all other animal extinction

[ben m]

Youre basically asking what would happen to a form of life that existed and evolved 3000 Ma all on its own and was the only species for 2400 Ma before the first fish realised what it was missing. Well obviously, there would be no change at all, plants ruled the earth far longer than anything else did, they would be quite happy to do so again given the chance

Your chronology is wrong, Marduk. Identifiable multicellular plants start appearing in the fossil record around the same time as animals---in the Cambrian, 500 Mya. Then the Earth spent 350 My dominated by ferns and cycads and mosses---the first seed-bearing plants don't appear until 150 Mya.

Today, of course, we have a planet specifically covered in angiosperms and gymnosperms. Even if it were true that cycads, lichens, and worts "ruled the earth" "all on its own", this does not tell us how the angiosperm-dominated world would respond.

Of course, maybe the response is: "angiosperms die off and lichens take over again", but (a) no one would call this "obviously ... no change at all" and (b) it doesn't sound likely.

[Tumbleweed]

Volcanos are not a significant source in our era. 400 million years ago it was different.

I just googled that and found that Man is putting out 130 times more co2 than volcanoes on an annual basis. Why is that fact not thrown in the face of global warming naysayers more often?
Perhaps it is because it is the misconception that volcanoes inject more than man. I am certain I read a Charles Kurault Readers Digest article about Mt Pinatubo while staying at a lodge in Carmel, Ca. in which he stated that the volcano had put out more co2 than man had since the dawn of the Industrial Revolution.
Now I am on another google quest. Let's see Kurault/Pinatubo ought to do it. If not I''ll toss in Reader's Digest

[I Ratant]

Without animals to help, many plants WOULD get buried without decaying.

Animals break up the plant material into small units that the fungi and bacteria can get to.
.
See Darwin's treatise on the earthworm. :)

[Earthborn]

Well, there would be no source of CO2 other than the weathering of rock and fires.Plants also produce CO2.

[BenBurch]

Plants also produce CO2.

But not NET.

Almost all of the carbon that makes up the material of the plant comes from air initially.

[Tumbleweed]

Kind of off subject but here's a question on a biology test that nearly everyone got wrong (except for me of course!) in the carbohydrate (CHO) the plant produces where does the oxygen come from. Nearly everyone said from the CO2. But the O2 from the CO2 is the waste product that is released to the atmosphere. The plant splits a water molecule and then combines the pieces from two or more of them with with carbon from the CO2 ---- Soooo if you were to interrupt the process after the plant splits that water molecule, you would have oodles of hydrogen. And in fact they are already experimenting to glean hydrogen from algae http://www.sciencedaily.com/releases/2009/03/090324171556.htm

[Thabiguy]

Kind of off subject but here's a question on a biology test that nearly everyone got wrong (except for me of course!) in the carbohydrate (CHO) the plant produces where does the oxygen come from. Nearly everyone said from the CO2.

And they were right.

But the O2 from the CO2 is the waste product that is released to the atmosphere.

No, it isn't. The waste oxygen comes from the water molecule as it is split during photolysis, not from the carbon dioxide. Check your textbook.

The plant splits a water molecule and then combines the pieces from two or more of them...

... hydrogen pieces, that is ...

... with carbon from the CO2 ...

... with carbon and oxygen from CO2.

---- Soooo if you were to interrupt the process after the plant splits that water molecule, you would have oodles of hydrogen. And in fact they are already experimenting to glean hydrogen from algae http://www.sciencedaily.com/releases/2009/03/090324171556.htm

That part is correct.

[shadron]

Volcanos are not a significant source in our era. 400 million years ago it was different.

Uhhhhh, volcanoes are quite significant when there is a major caldera eruption, such as the largest Yellowstone eruption 2.1 million years ago, or Lake Toba 73,000 years ago. Their effects probably last at least 10-20 thousand years. The Siberian Traps, the largest outpouring of lava on the face of Earth known, happened 250 mya, and the Deccan Traps 67 mya, and the Paraná and Etendeka Traps in SA 46 mya. True, we in in a sort of quiet phase right now in spite of Yellowstone, Hawaii and the Atlantic Ridge, but that is likely not a permanent thing.

[shadron]

My contention about the OP is that plants will get over it. They thrived on land through the Devonian and Carboniferous periods, over 100 million years, without land animals (and by thrived, I mean THRIVED). Secondly, the largest amount of oxygen breathers and CO2 exhalers is within the groups of insects and sealife, mainly plankton. If they exist, then the land animals probably won't be missed, as far as CO2 is concerned. Historically, CO2 levels don't correlate with life at all, and have a whole lot more to do, both cause and effect, with atmospheric warming. Plants will be able to give up some of their defense mechanisms (like spines and poisons). One may even eventually develop intelligence, though we probably wouldn't recognize it.

Feed me, Seymour! FEED ME!!!!!

[shadron]

I just googled that and found that Man is putting out 130 times more co2 than volcanoes on an annual basis. Why is that fact not thrown in the face of global warming naysayers more often?
Perhaps it is because it is the misconception that volcanoes inject more than man. I am certain I read a Charles Kurault Readers Digest article about Mt Pinatubo while staying at a lodge in Carmel, Ca. in which he stated that the volcano had put out more co2 than man had since the dawn of the Industrial Revolution.
Now I am on another google quest. Let's see Kurault/Pinatubo ought to do it. If not I''ll toss in Reader's Digest

Oh, it's thrown; see this for one example:

boj9ccV9htk

[shadron]

you are ignoring the obvious, the acorn has been around millions of years longer than the squirrel, this is why the uk had large oak forests until the neolithic expansion. When the oak tree has proven itself capable of being very successful on its own you might look to the fact that an acorn is much more evolved to fall than to be carried and oak trees do not require sunlight until a long time after germination


Ummmmm... Oak trees (deciduous trees in general) were evolved during the Cretaceous. First mammals roughly during the Triassic, certainly by the Jurassic. Difference is 50-100 million years. Squirrel-surrogates certainly were waiting for Oak-surrogates to create a niche for quite a while.