View previous topic | View next topic

Tropical Forests

Page 2 of 4
Goto page Previous  1, 2, 3, 4  Next

Curious Danny
194176.  Mon Jul 23, 2007 2:06 pm Reply with quote

Spell check doesn't work on forum posts

 
smiley_face
194177.  Mon Jul 23, 2007 2:07 pm Reply with quote

Proof reading does though. :-P

 
Curious Danny
194178.  Mon Jul 23, 2007 2:08 pm Reply with quote

ha ha ha

 
smiley_face
194179.  Mon Jul 23, 2007 2:09 pm Reply with quote

Do I sense a small element of sarcasm there?

 
Curious Danny
194180.  Mon Jul 23, 2007 2:10 pm Reply with quote

Alarm! Alarm!

Minus 10 points for an obvious answer

 
Flash
194182.  Mon Jul 23, 2007 2:19 pm Reply with quote

We haven't discussed this for a while, but it used to be forum etiquette not to make an issue of spelling mistakes and typos because a) it's discourteous and b) it's beside the point - we're interested in what's being said, not how it's spelt. Personally, I think that was a good approach to take.

 
smiley_face
194187.  Mon Jul 23, 2007 2:45 pm Reply with quote

Also, spelling errors can throw up new things. For example, I never would have known that bontany is the study of bridges. I'm sure there are other examples of spelling errors causing me to learn new things, but I'll be damned if I can think of any at the moment!

 
dr.bob
194347.  Tue Jul 24, 2007 3:58 am Reply with quote

Curious Danny wrote:
You take things far too seriously, Dr. Bob.


Really? I was just questioning some of your statements. Generally this website works by people asserting various statements and backing them up with documentary evidence to show that they're not just making it up. I the absence of any references, I was simply questioning whether what you said was true or made up.

Curious Danny wrote:
Ever heard of desertification? No plants leads to scorched, cracked earth (just ask the Ethiopians).


That's certainly true if you consider desertification at one of the hottest points on the planet. Deserts in Antarctica aren't quite so scorched or cracked.

Even in Ethiopia, there is plenty of water. Check out http://www.selamta.net/lakes.htm for a list of some Ethiopian lakes.

Curious Danny wrote:
The CO2 level in the atmosphere was much higher and the poles were ice-free and barren.


Ice free and barren they may have been, but how hot were they? Scotland is currently ice free, but I'd hardly call it scorched. Certainly not this summer :(

Curious Danny wrote:
No plants also mean stronger winds as there is no resistance from trees.


That's a good point, although winds are also slowed down by land masses such as mountains. This is why there are stronger winds in the Southern Hemisphere, where it's mostly ocean, than in the Northern Hemisphere.

Curious Danny wrote:
Rain in deserts evaporates almost immediately and is not soaked into the soil.


There would be no soil since soil is composed of organic matter. It would just be covered in sand.

Curious Danny wrote:
Eons ago, vast deserts also never saw rain or rivers.


Prove it.

Curious Danny wrote:
Ever see a river in the Sahara that stayed wet all the time?


Me personally, no. But then I wasn't around during the interglacial periods 240,000, 350,000, and 420,000 years ago when Lake Megafezzan was reaching sizes between 76,250 and 150,000 km2 (http://uk.geocities.com/morris.drake@btinternet.com/megafezzan.htm)

Curious Danny wrote:
To my knowledge, palaeobontany also shows the earliest plants developing on the edge of ancient seas.


If you can produce some reference to back that up, I'd be interested in reading them.

Curious Danny wrote:
I also think smiley_face is wrong. Plants and animals are found in ever concievable habitat on Earth.


As has been discussed elsewhere on this site, all life on this planet appears to require liquid water to survive. Areas of the planet where there is no liquid water show no signs of life. Since these areas have not yet been conquered by life, then I think smiley_face is right: life still has a way to go before it's finished covering the globe.

 
Curious Danny
194579.  Tue Jul 24, 2007 11:36 am Reply with quote

My whole point was animals couldn't leave the ocean behind until their was a fertile environment on land (courtesy of plants).

The poles were a lot warmer and ice free. All of the nutrients in the current polar ecosystem come from icecaps. In complete opposition to land ecosystems, polar oceans are more diverse than tropical ones. It's not a question of temperature, it is how much water there is.

Eons ago, the land was covered by vast deserts and the middle of such deserts never see rainfall. The triassic period was blighted by lack of water and deserts as rain clouds never made it far inland. Rivers were only found on sea edges.

The sahara is a modern comparision. The fact it used to be so lush is a good example of how much an enviroment can change over time

Plant history here: http://www.xs4all.nl/~steurh/eng/old1.html
http://www.newscientist.com/article/mg17924132.500-earliest-plants-found.html

Point is, plant evolved from algae type creatures. In the desert enviroment of eons ago, the best place to find them was by the sea.

 
dr.bob
194699.  Wed Jul 25, 2007 4:03 am Reply with quote

(Apologies in advance for the length of this post)

Curious Danny wrote:
My whole point was animals couldn't leave the ocean behind until their was a fertile environment on land (courtesy of plants).


They certainly couldn't have left the ocean behind permanently before plants had colonised the land because there would have been nothing to eat. Although it's conceivable that they might have left the ocean briefly to avoid predators or suchlike even before plants colonised the land.

My whole point is that you seem to be peddling the idea that all the land was hot, deserty, and covered in volcanoes until life arrived and everything was lush, green, and lovely. This is the kind of simplified model that is taught at school. The reality usually turns out to be rather more interesting.

Curious Danny wrote:
The poles were a lot warmer and ice free.


The poles have come and gone many times. I imagine they would have come and gone many times before life emerged as well, unless you have evidence to the contrary.

Curious Danny wrote:
All of the nutrients in the current polar ecosystem come from icecaps.


The key species in the Antarctic ecosystem are Antarctic krill. They derive nutrients from phytoplankton which, in turn, take their energy from the Sun. In what way does any of this "come from the icecaps"?

Curious Danny wrote:
Eons ago, the land was covered by vast deserts and the middle of such deserts never see rainfall. The triassic period was blighted by lack of water and deserts as rain clouds never made it far inland. Rivers were only found on sea edges.


What has the Triassic got to do with anything? Life began colonising the land during the Cambrian era, about 250 million years before the Triassic.
Yes, the Triassic was a very dry period with extensive desertification, but since life was a long way into the job of colonising the land by then, I fail to see what it's got to do with this discussion.

Curious Danny wrote:
The sahara is a modern comparision. The fact it used to be so lush is a good example of how much an enviroment can change over time


The sahara is an excellent comparison. Firstly it's a limited part of the entire land mass. It's a harsh desert, but land outside of the sahara exhibits a range of different conditions: wet and hot; dry and cold; wet and cold; etc.

Secondly, as you rightly point out, it has changed massively over the years. Just as the entire global ecosystem has changed. During the Cryogenian Period, long long before the first plantlife emerged on land, the planet experienced two heavy glaciations, the Sturtian and Marinoan, which were the worst ice ages known to have occurred, and may have covered the entire planet in ice. Hardly vast, scorched deserts which you seem to be implying covered the earth before life emerged from the oceans.

Curious Danny wrote:
Point is, plant evolved from algae type creatures.


Yes.

Curious Danny wrote:
In the desert enviroment of eons ago, the best place to find them was by the sea.


Except, as I hope I've shown a little of in this post, it's wrong to say that there was nothing but sahara-like hot, dry desert before life emerged onto the land. Therefore that statement has a logical fallacy.

 
Curious Danny
194779.  Wed Jul 25, 2007 6:53 am Reply with quote

The way i write posts is different. I make lots of comparisions to back up my points.

Earth before plants would have been a desert to any animal of today. If you got a man and dumped him there, he would have thought it was terrible place to be.

The enviroment became a lot wetter with plants as plants contribute to the water cycle with transpiration and, on the whole, a lot nicer.

The bit about polar ice caps comes from what i heard on an episode of blue planet. Tropical oceans are more barren than polar ones.

I used the triassic as a comparison, like the sahara. Life is nowhere near as diverse in enviroments which are very dry and very hot.

The idea i am trying to put across is that before plants came along, you either had freezing cold tundra or boiling hot deserts. Plants helped make more friendly habitats.

 
dr.bob
194803.  Wed Jul 25, 2007 7:44 am Reply with quote

Curious Danny wrote:
The way i write posts is different. I make lots of comparisions to back up my points.


Comparisons are fine if they're well founded. Comparing things happening today to an ecosystem several billion years ago might not always be possible, however.

Curious Danny wrote:
Earth before plants would have been a desert to any animal of today. If you got a man and dumped him there, he would have thought it was terrible place to be.


That's true.

Curious Danny wrote:
The enviroment became a lot wetter with plants as plants contribute to the water cycle with transpiration and, on the whole, a lot nicer.


Yet the triassic was a very dry period, as you've already pointed out. Clearly it's not as simple as "plants = wetter".

Curious Danny wrote:
The bit about polar ice caps comes from what i heard on an episode of blue planet. Tropical oceans are more barren than polar ones.


Fair enough. I was questioning your statement that "All of the nutrients in the current polar ecosystem come from icecaps" though.

Curious Danny wrote:
I used the triassic as a comparison, like the sahara. Life is nowhere near as diverse in enviroments which are very dry and very hot.


That's true enough. You have not yet demonstrated that the entire Earth did indeed resemble the sahara "eons ago", though. You have merely stated it as fact.

Curious Danny wrote:
The idea i am trying to put across is that before plants came along, you either had freezing cold tundra or boiling hot deserts. Plants helped make more friendly habitats.


Whilst I agree that plants did a lot to transform the ecosystem and make it a much nicer place for animals to be, I'm still not convinced that, before plants, you could only have one extreme climate or another. Surely there must have been points when the change between one and the other was occurring when the conditions were quite temperate. Or are you suggesting that, before life, conditions went from ice age to sahara-like heat haze in a matter of hours?

 
Curious Danny
194806.  Wed Jul 25, 2007 7:54 am Reply with quote

No! Just that ecosystems and habitats were a lot more extreme before plants colonised the land.

 
dr.bob
194808.  Wed Jul 25, 2007 7:56 am Reply with quote

More extreme, yes, but can you see that it wasn't just simply "a barren scorched desert with howling winds hostile to life" wherever you looked?

 
Curious Danny
194814.  Wed Jul 25, 2007 8:01 am Reply with quote

Curious Danny wrote:
A ridiculously long time ago, all life lived in the sea and the land was a barren scorched desert with howling winds hostile to life.
The evolution of plants started near the sea, where the oceans eroded the dry cracked land and allowed plants to take root on eroded cliffs and beaches.
The gradual spread of plants across the land allowed animal life to leave the sea for good.
Any estimates for how long it took for the whole of the barren landscape of the Earth to be covered in plants and made fertile for life?


I originally paraphrased the question like this as i wanted an answer, not more questions.

 

Page 2 of 4
Goto page Previous  1, 2, 3, 4  Next

All times are GMT - 5 Hours


Display posts from previous:   

Search Search Forums

Powered by phpBB © 2001, 2002 phpBB Group