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  • General

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  • 植物进化

    Fossilized fern leaves showing patterns, indicating ancient plant life from millions of years ago.

    Which moved onto land first, plants or animals?
    ::哪些先移到陆地, 植物还是动物?

    This fossilized may be millions of years old. Over 200 million years ago, the first evidence of ferns related to several modern families appeared. The "great fern radiation" occurred in the late-Cretaceous, which ended 65 million years ago, when many modern families of ferns first appeared. And if were the first on land, would many have starved?
    ::这种化石化可能已经存在数百万年了。 超过2亿年前,出现了与几个现代家庭有关的出生物的第一批证据。 “大产物辐射”发生在6500万年前结束的后冷战时期,当时许多现代产物家庭首次出现。 如果在陆地上是第一个,许多人会饿死吗?

    Evolution of Plants
    ::工厂的演变

    As shown in Figure , plants are thought to have evolved from an green . Later, they evolved important adaptations for land, including , seeds , and flowers . Each of these major adaptations made plants better suited for life on dry land and much more successful.
    ::如图所示,植物被认为从绿色演变而来。后来,植物对土地,包括种子和鲜花等,产生了重要的适应性变化。 每一次重大调整都使植物更适合干地上的生活,并且更加成功。

    The evolution of plants from aquatic algae to vascular and seed plants.

    From a simple, green alga ancestor that lived in the water, plants eventually evolved several major adaptations for life on land.
    ::植物最终演变出几大适应陆地生命的适应方法。

    The Earliest Plants
    ::最贵的植物

    The earliest plants were probably similar to the stonewort , an aquatic algae pictured in Figure . Unlike most modern plants, stoneworts have stalks rather than stiff , and they have hair-like structures called rhizoids instead of . On the other hand, stoneworts have distinct male and female reproductive structures, which is a plant characteristic. For to occur, need at least a thin film of moisture to swim to eggs . In all these ways, the first plants may have resembled stoneworts.
    ::最早的植物可能与图中描绘的水藻石织物相似。与大多数现代植物不同,石织物有尾巴而不是僵硬的,它们有发型相似的结构,称为犀牛而不是。另一方面,石织物有不同的男性和女性生殖结构,这是植物的特征。要发生这种情况,至少需要一根水分薄膜才能游到蛋中。在所有这些方面,第一批植物可能都与石织物相似。

    Aquatic algae resembling early plants, showcasing modern stoneworts and Charophyta types.

    Modern stoneworts may be similar to the earliest plants. Shown is a field of modern stoneworts (right), and an example from the Charophyta, a division of green algae that includes the closest relatives of the earliest plants (left).
    ::现代石织物可能与最早的植物类似。 显示是现代石织(右)的一块领域,也是来自沙罗菲塔(Charophyta)的一个例子,沙罗菲塔(Charophyta)是绿色藻类的分割,包括最早植物(左)的近亲。

    Life on Land
    ::生命在陆地上的生命

    By the time the earliest plants evolved, animals were already the dominant organisms in the ocean. Plants were also constrained to the upper layer of that received enough sunlight for . Therefore, plants never became dominant organisms. But when plants moved onto land, everything was wide open. Why was the land devoid of other life? Without plants growing on land, there was nothing for other organisms to feed on. Land could not be colonized by other organisms until land plants became established.
    ::当最早的植物进化时,动物已经是海洋中的主要有机体。植物还被限制在得到足够阳光的上层。因此,植物从未成为主要有机体。但是当植物移到陆地时,一切都是开阔的。为什么这片土地没有其他生命?没有植物生长在陆地上,其他生物就无从养活。在陆地植物建立之前,土地不能被其他生物所殖民。

    Plants may have colonized the land as early as 700 million years ago. The oldest of land plants date back about 470 million years. The first land plants probably resembled modern plants called liverworts , like the one shown in Figure .
    ::早在7亿年前,植物可能就已经将这片土地殖民化了。 最古老的陆地植物可追溯到大约4.7亿年前。 第一批陆地植物可能类似于现代植物,称为肝脏,如图所示。

    Close-up of green liverworts, early land plants critical for colonization of terrestrial environments.

    The first land plants may have been similar to liverworts like this one.
    ::第一批陆地植物 可能和这个一样 类似于肝脏

    Colonization of the land was a huge step in plant evolution. Until then, virtually all life had evolved in the ocean. Dry land was a very different kind of place. The biggest problem was the dryness. Simply absorbing enough water to stay alive was a huge challenge. It kept early plants small and low to the ground. Water was also needed for , so sperm could swim to eggs. In addition, temperatures on land were extreme and always changing. Sunlight was also strong and dangerous. It put land organisms at high risk of .
    ::土地的殖民化是植物进化的一个巨大步骤,在此之前,几乎所有生命都在海洋中演变,旱地是一个完全不同的地方,最大的问题是干燥。仅仅吸收足够的水来维持生命是一个巨大的挑战。它使早期的植物小而低地生长。水也是需要的,因此精子可以游到卵中。此外,陆地上的温度是极端的,而且总是在变化。阳光也非常强烈,而且非常危险。它使陆地生物处于高度危险之中。

    Vascular Plants Evolve
    ::蒸发

    Plants evolved a number of adaptations that helped them cope with these problems on dry land. One of the earliest and most important was the evolution of vascular tissues. Vascular tissues form a plant’s “plumbing system.” They carry water and minerals from soil to leaves for photosynthesis. They also carry food (sugar dissolved in water) from photosynthetic to other cells in the plant for growth or storage. The evolution of vascular tissues revolutionized the plant . The tissues allowed plants to grow large and endure periods of drought in harsh land environments. Early probably resembled the fern shown in Figure .
    ::植物在干地上发展了有助于它们应付这些问题的若干适应措施,其中最早和最重要的之一是血管组织的演变。血管组织形成植物的“管道系统 ” 。 它们把水和矿物质从土壤运到光合作用叶子。 它们也把食物(在水中溶解)从光合体运到植物中的其他细胞,以供生长或储存。血管组织的演变使植物发生革命。 组织允许植物在严酷的陆地环境中长成大片和持续干旱时期。 早期可能与图所示的胎儿相似。

    Close-up of green fern-like plant with small yellow structures, representing early vascular plants.

    Early vascular plants may have looked like this modern fern.
    ::早期血管植物 可能长得像这个现代动物

    In addition to vascular tissues, these early plants evolved other adaptations to life on land, including lignin , leaves, roots, and a change in their .
    ::除了血管组织之外,这些早期的植物还发展了适应陆上生活的其他适应方法,包括木乃伊、叶子、根部和它们的改变。

    • Lignin is a tough molecule that is hydrophobic (“water fearing”). It adds support to vascular tissues in stems. It also waterproofs the tissues so they don’t leak, which makes them more efficient at transporting fluids. Because most other organisms cannot break down lignin, it helps protect plants from herbivores and parasites .
      ::Lignin是一种强固分子,它具有水分恐惧性(“水恐惧 ” ) 。 它增加了对导血管组织根部的支持。 它还为组织防水,防止其漏水,从而使它们更高效地运送液体。 由于大多数其他生物无法分解液,它有助于保护植物免受草药和寄生虫的侵袭。
    • Leaves are rich in that function as solar collectors and food factories. The first leaves were very small, but leaves became larger over time.
      ::叶子作为太阳能收集器和食品工厂的作用丰富。 第一批叶子很小,但随着时间推移叶子变大。
    • Roots are vascular organs that can penetrate soil and even rock. They absorb water and minerals from soil and carry them to leaves. They also anchor a plant in the soil. Roots evolved from rhizoids, which had used for absorption .
      ::根是能够穿透土壤甚至岩石的血管器官,它们吸收土壤中的水和矿物,并将水和矿物运到树叶上,它们还将植物固定在土壤中,根由用于吸收的犀牛衍生而来。
    • Land plants evolved a dominant diploid sporophyte generation. This was adaptive because diploid individuals are less likely to suffer harmful effects of mutations. They have two copies of each gene , so if a mutation occurs in one gene, they have a backup copy. This is extremely important on land, where there’s a lot of solar radiation.
      ::陆地植物演变成一种主要的低水分螺旋藻一代。 这是适应性的,因为低水分个体不太可能受到突变的有害影响。 它们拥有每个基因的两份副本,因此如果突变发生在一个基因中,它们就有一份备份副本。 这在陆地上非常重要,因为那里有大量太阳辐射。

    With all these advantages, it’s easy to see why vascular plants spread quickly and widely on land. Many nonvascular plants went extinct as vascular plants became more numerous. Vascular plants are now the dominant land plants on Earth.
    ::有了所有这些优势,人们就很容易理解为什么血管植物在陆地上迅速和广泛扩散。 许多非血管植物随着血管植物的增多而灭绝。 血管植物现在是地球上占主导地位的陆地植物。

       

     

    Summary
    ::摘要

    • The earliest plants are thought to have evolved in the ocean from a green alga ancestor.
      ::最早的植物被认为 已经从绿色的海藻祖先 进化到海洋中
    • Plants were among the earliest organisms to leave the water and colonize land.
      ::植物是最早离开水和殖民土地的生物。
    • The evolution of vascular tissues allowed plants to grow larger and thrive on land.
      ::血管组织的演变使植物得以生长壮大,在陆地上蓬勃发展。

    Review
    ::回顾

    1. What were the first plants to evolve?
      ::最先进化的植物是什么?
    2. What are vascular tissues of a plant? What is their function?
      ::植物的血管组织是什么?
    3. Explain why life on land was difficult for early plants.
      ::解释为什么早期植物很难在陆地上生活。
    4. Why did plants need to become established on land before animals could colonize the land?
      ::为什么植物需要建在陆地上, 动物才能殖民土地?