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Author | Topic: Evolution of trees | |||||||||||||||||||||||||||
pesto Member (Idle past 5618 days) Posts: 63 From: Chicago, IL Joined: |
I've been thinking about the evolution of trees and other plants, and realized something I couldn't solve.
According to a video I saw online (I no longer have a link to this video), flowering plants evolved later than reptiles, birds and mammals. In general, that would mean that all flowering species of plants would be descended from one parent species. I also saw in a natural history museum a cross-section of a tree from Hawaii. According to the museum plaque, because this "tree" lacked the characteristic rings, this suggested that it evolved from a much smaller soft bodied (or non-woody) plant. This got me thinking. There are both flowering and non-flowering ringed trees (apple trees vs. conifers). There are also flowering vs. non-flowering non-trees (marigolds vs. grasses). If ringed trees suggest common ancestry, and flowers suggest common ancestry, how do we reconcile the fact that all combinations are found when looking at flowering vs. non-flowering and tree vs. non-tree?
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Admin Director Posts: 13046 From: EvC Forum Joined: Member Rating: 2.7 |
Thread moved here from the Proposed New Topics forum.
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Coragyps Member (Idle past 765 days) Posts: 5553 From: Snyder, Texas, USA Joined: |
The trees I'm aware of that have rings 1) take several years to grow and 2) are in climates, unlike Hawaii, where the cold makes them go dormant every winter. Annual plants aren't even in the running for having rings.
Oh, and all grasses and palms are flowering plants. Grasses have fairly inconspicuous flowers, but they have 'em.
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pesto Member (Idle past 5618 days) Posts: 63 From: Chicago, IL Joined: |
Cool.
I wasn't aware that grasses were considered a flowering plant. Are conifers also considered flowering plants? What would not be considered a flowering plant? Let's replace marigolds with blackberry bushes. They are perennial, grow in temperate climates and don't have rings, as far as I know.
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bluescat48 Member (Idle past 4220 days) Posts: 2347 From: United States Joined: |
Tree is not a true scientific term. It simply implies a large plant with a woody stem. Ginkos, cycads & conifers are gynosperms. While palms are monocot angiosperms related to grasses. Most trees are dicot angiosperms
such as apples, peaches, pears & cherries related to roses, as are the bushes, strawberries, raspberries ans roses themselves. When relationship is implied, it means that there are more similarities than simply what can be seen by looking at two plant species. Internal structures, embriology etc. must also be used and now that DNA is known, the relationship of the genomes. There is no better love between 2 people than mutual respect for each other WT Young, 2002 Who gave anyone the authority to call me an authority on anything. WT Young, 1969
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Coragyps Member (Idle past 765 days) Posts: 5553 From: Snyder, Texas, USA Joined: |
Are conifers also considered flowering plants? Conifers are gymnosperms, or "naked-seeds" and are not considered "flowering" - I guess because they don't have sepals, petals, and all that. I don't know if blackberries have rings, either - thorns, yes, and woody, yes, but there my botanical knowledge of them ends. Edited by Adminnemooseus, : Fixed italics code (had been closed with a "/qs".
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Blue Jay Member (Idle past 2728 days) Posts: 2843 From: You couldn't pronounce it with your mouthparts Joined: |
Hi, Pesto.
pesto writes: I wasn't aware that grasses were considered a flowering plant. Are conifers also considered flowering plants? What would not be considered a flowering plant? I'm no botanist, but I took a couple classes on the subject not too long ago, so I'll help where I can. The term "flowering plant" refers to a single taxon of plants (i.e. they all evolved from a single common ancestor). The feature that generally unites this group is the presence of flowers and fruit, neither of which words really means what it means to the layperson. The flower is a cluster of leaves that have been modified into reproductive parts (which non-flowering plants do not have), and fruit is simply a seed with a fleshy leaf wrapped around it. The fleshy leaf (the carpal) can be the soft, juicy part of a cherry, the pea pod, the hard outer covering of an acorn, or even the "wing" of a maple seed. Conifers do not have fruits or flowers: their reproductive parts are cones, and their seeds are not enclosed in a carpal. As Bluescat explained, the word "tree" refers to a body form, not a taxonomic group. So, apple trees are more closely related to roses than they are to pine trees, and the morphological similarity between apple trunks and pine trunks is actually convergent. It results from an increase in xylem (wood) in the stem of a plant, which, if you think about it, shouldn't be too difficult for mutations to produce. Darwin loves you.
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Dr Adequate Member (Idle past 315 days) Posts: 16113 Joined: |
I wasn't aware that grasses were considered a flowering plant. Grass flowers.
Let's replace marigolds with blackberry bushes. They are perennial, grow in temperate climates and don't have rings, as far as I know. A quick look on this internet thingy reveals that broom, creosote, elderberry and juniper bushes have growth rings, so I don't see why blackberry bushes shouldn't. Edited by Dr Adequate, : No reason given. Edited by Dr Adequate, : No reason given.
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Chiroptera Inactive Member |
When I was in high school biology, we learned that an important division of land plants is tracheophytes, which are plants that have specialized tissue to form a vascular system that transports water and other stuff throughout the plant.
Among the tracheophytes are the seed-bearing plants (called the spermatophytes), which includes the conifers and the angiosperms. Among the seed-bearing plants are the angiosperms, which are the flowering plants. As far as I know, this classification reflects actual evolutionary phylogeny -- angiosperms have a common ancestor that is not the common ancestor of a non-angiosperm, and spermatophytes have a common ancestor that is not the ancestor of a non-spermatophyte. Now, the ring-producing trees, which include both a conifer like a pine and a flowering tree like an oak, together would be what is called paraphyletic group -- that is, they are not a natural evolutionary grouping in that the common ancestor of all ring-producing trees is also an ancestor of grass. Speaking personally, I find few things more awesome than contemplating this vast and majestic process of evolution, the ebb and flow of successive biotas through geological time. Creationists and others who cannot for ideological or religious reasons accept the fact of evolution miss out a great deal, and are left with a claustrophobic little universe in which nothing happens and nothing changes. -- M. Alan Kazlev
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pesto Member (Idle past 5618 days) Posts: 63 From: Chicago, IL Joined: |
General reply to all:
Would tree rings then be more a consequence of environment (i.e. the changing seasons) than the specific descent of the plant itself?
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Dr Adequate Member (Idle past 315 days) Posts: 16113 Joined: |
A quick google turns up papers (here and here for example) saying that even herbaceous (non-woody) plants can exhibit growth rings (though not all of them do).
So, yes, my guess would be that growth rings are just a side-effect of seasonal growth.
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pesto Member (Idle past 5618 days) Posts: 63 From: Chicago, IL Joined: |
Question answered. Thanks.
Blinded by science!
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