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Please Help me with these two questions.
1.Early botanists admired ferns but found their life cycle perplexing. In the 1700s, they learned to propagate them by sowing what appeared to be tiny dustlike "seeds" from the undersides of fronds. Despite many attepts, the scientists could not find the pollen source, which they assumed must stimulate the "seeds" to develop.
Imagine you could write to one of these botanists. Compose a note that would clear up their confusion.
2.Today, the tallest bryophytes reach a maximum height of 20 centimeters (8 inches) or so. So far as we know from fossils, there were no giants among their ancestors. Lignin and vascular tissue first evolved in relatives of club moss, and some extinct species stoode 40 meters (130 feet) high. Among modern seed plants, Sequoia (a gymnosperm and Eucalyptus (an angiosperm) can be more than 100 meters (330 feet) high.
Explain why evolution of vascular tissues and lignin would have allowed such a dramatic increase in plant height. How might being tall give one plant species a competitive advantage over another?
You could find that answer if you typed life cycle of ferns in google, it'd be easier than asking some questions straight out of a book.
As for the second part though, because the lignin is what gives the cell walls of the plants their rigidity, thus causing them to be able to hold more weight on itself. And if you can't figure it out, taller plants have more access to sunlight, therefore outcompeting other plants for valuble resources.
They need a nutrient source, they also need a media to grow in, either organic or inorganic. It would also greatly help if this didn't allow sunlight to penetrate towards the roots.
The life cycle of a fern is beautiful and complex, but with a little study, you can understand it. Start with number 1 below, the spore. This is like the seed of a flowering plant, in that it is the way the fern reproduces and spreads. A spore, however, is different in that it is a single cell that has only one copy of each chromosome (haploid), and a seed is multicellular and has two (diploid). The spore develops into a plant called a gametophyte that can produce both sperm and eggs. These unite in the processes called fertilization, producing a "baby" fern called a zygote, which now has two copies of each chromosome (it is diploid). By normal cell division, this grows into the fern as we know it, the green leafy plant on the forest floor. The fern produces the spore (still diploid), and the cycle continues.
Read more: http://www.davidlnelson.md/Cazadero/Fern_Life_cycle.htm
8 posts • Page 1 of 1
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