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  • General

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  • 种子植物演变

    A vibrant sunflower stands tall against a blue sky, surrounded by more sunflowers in a field.

    Why are they called sunflowers?
    ::为什么他们叫向日葵?

    When the plant is in the bud stage, the flower tends to track the movement of the sun across the horizon, hence the name sunflower. Flowering plants were the last group of plants to evolve. The flower contains both the male and female reproductive structures, and these plants have become tremendously successful. But these plants could not have evolved without the prior evolution of the seed . So what exactly is a seed?
    ::当植物处于萌芽阶段时,花朵往往会跟踪太阳在地平线上的移动,因此就叫向日葵。花朵是最后一批进化的植物。花朵包含男性和女性的生殖结构,这些植物已经非常成功。但是这些植物没有种子的进化是不可能进化的。究竟什么是种子呢?

    Seed Plants Emerge
    ::新兴种子植物

    For , early still needed moisture. had to swim from male to female reproductive organs for . Spores also needed some to grow and often to disperse as well. Of course, dryness and other harsh conditions made it very difficult for tiny new offspring plants to survive. With the evolution of seeds in vascular plants, all that changed. evolved a number of adaptations that made it possible to reproduce without water. As a result, seed plants were wildly successful. They exploded into virtually all of Earth’s habitats .
    ::早期仍需要水分,因为必须从男性到女性的生殖器官。 Spories也需要某些植物来生长,而且往往也需要驱散。 当然,干燥和其他恶劣条件使得小小的后代植物很难生存下来。 随着血管植物种子的进化,所有这些变化都发生了变化。 进化出了一系列适应方法,使得在没有水的情况下进行繁殖成为可能。 结果,种子植物非常成功。 它们爆发到几乎所有的地球栖息地。

    Why are seeds so adaptive on land? A seed contains an embryo and a food supply enclosed within a tough coating. An embryo is a zygote that has already started to develop and grow. Early growth and of a plant embryo in a seed is called germination . The seed protects and nourishes the embryo and gives it a huge head start in the “race” of life. Many seeds can wait to germinate until conditions are favorable for growth. This increases the offspring’s chance of surviving even more.
    ::种子为什么如此适应土地? 种子含有胚胎,食物供应也包含在坚硬的涂料中。 胚胎是一种已经开始发育和生长的zygote。 种子的早期生长和种子中的植物胚胎被称为发芽。 种子保护和养育胚胎,使其在生命的“种族”中有一个巨大的开端。 许多种子可以等待发芽,直到生长的条件有利。 这增加了后代存活的机会。

    Other reproductive adaptations that evolved in seed plants include ovules , pollen , pollen tubes, and pollination by .
    ::在种子植物中演化的其他生殖适应包括、花粉、花粉管和授粉。

    • An ovule is a female reproductive structure in seed plants that contains a tiny female gametophyte . The gametophyte produces an egg . After the egg is fertilized by sperm, the ovule develops into a seed.
      ::在种子植物中,卵子是一种女性生殖结构。种子植物中含有一个很小的雌性植物。该植物产生一个蛋。在卵子受精之后,卵子会发展成一个种子。
    • A grain of pollen is a tiny male gametophyte enclosed in a tough capsule (see Figure ). It carries sperm to an ovule while preventing it from drying out. Pollen grains can’t swim, but they are very light, so the wind can carry them. Therefore, they can travel through air instead of water.
      ::一粒花粉是一个小小的雄性游戏植物,它被困在一个坚硬的胶囊里(见图 ) 。 它将精子带入卵巢,同时防止它干涸。 花粉粒不会游泳,但很轻,因此风能携带它们。 因此,它们可以通过空气而不是水而行走。
    • Wind-blown pollen might land anywhere and be wasted. Another adaptation solved this problem. Plants evolved traits that attract specific animal pollinators . Like the bee in Figure , a pollinator picks up pollen on its body and carries it directly to another plant of the same . This greatly increases the chance that fertilization will occur.
      ::风花粉可能会在任何地方落地并被浪费掉。 另一项适应性调整解决了这个问题。 植物会演变成吸引特定动物授粉者的特点。 像图中的蜜蜂一样, 授粉者会在其身体上采集花粉, 并将花粉直接运到另一植物。 这大大增加了施肥的机会。
    • Pollen also evolved the ability to grow a tube, called a pollen tube , through which sperm could be transferred directly from the pollen grain to the egg. This allowed sperm to reach an egg without swimming through a film of water. It finally freed up plants from depending on moisture to reproduce.
      ::花粉还进化了种一个管子的能力,叫做花粉管,通过它精子可以直接从花粉粒粒中传到蛋中。这使得精子可以在不通过水膜游泳的情况下到达卵子。它最终使植物摆脱了依赖水分的繁殖。

    Magnified pollen grains alongside a bee covered in yellow pollen on flowers.

    Individual grains of pollen may have prickly surfaces that help them stick to pollinators such as bees. What other animals pollinate plants?
    ::个别的花粉颗粒可能有刺痛的表面,有助于它们坚持使用蜜蜂等授粉器。 还有什么其他动物授粉植物?

    Seed Plants Diverge
    ::种子植物

    The first seed plants formed seeds in cones. Cones are made up of overlapping scales, which are modified leaves (see Figure ). Male cones contain pollen, and female cones contain eggs. Seeds also develop in female cones. Modern seed plants that produce seeds in cones are called gymnosperms .
    ::最早的种子植物在锥体中形成种子。锥体由相互重叠的天平组成,这些天平是经过修改的叶子(见图 ) 。 雄锥体含有花粉,而雌锥体含有蛋。 种子也在雌锥体中发展。 生产锥体种子的现代种子植物被称为体操。

    Images of gymnosperm cones showing seeds attached to overlapping scales.

    Gymnosperms produce seeds in cones (left). Each scale has a seed attached (right).
    ::Gymnosperms 以圆锥(左)种种籽,各等级各附一个种籽。

    Later, seed plants called evolved. They produce flowers , which consist of both male and female reproductive structures. The female reproductive structure in a flower includes an organ called an ovary . Eggs form in ovules inside ovaries, which also enclose and protect developing seeds after fertilization occurs. In many species of flowering plants, ovaries develop into fruits , which attract animals that disperse the seeds.
    ::后来,种子植物被称作进化植物,它们生产鲜花,由男女生殖结构组成;花中的女性生殖结构包括一种叫做卵巢的器官;卵巢中的卵卵蛋形成卵巢,卵巢中还含有并保护在施肥后生长的种子;在许多种类的开花植物中,卵巢发展成水果,吸引驱散种子的动物。

    Summary
    ::摘要

    • The evolution of seeds and pollen allowed plants to reproduce on land without moisture.
      ::种子和花粉的进化使得植物能够在没有水分的土地上繁殖。
    • Flowering plants evolved flowers with ovaries that formed fruits. They have been the most successful plants of all.
      ::鲜花植物进化出花朵,卵巢形成水果,它们是最成功的植物。

    Review
    ::回顾

    1. What is a seed?
      ::什么是种子?
    2. Describe cones.
      ::描述锥形。
    3. Compare and contrast gymnosperms and angiosperms, and give an example of each.
      ::比较和对比体操和血管, 并举个例子。
    4. Which major plant adaptation—vascular tissues or seeds—do you think was more important in the evolution of plants? Choose one of the two adaptations, and write a logical argument to support your choice.
      ::你认为哪一种主要植物适应——血管组织或种子——在植物的进化中更重要吗?选择两种适应方法之一,并写一个逻辑论点来支持你的选择。