12.12 原生植物类原生植物的复制 -- -- 先进
Section outline
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A carpet of . How?
::地毯,怎样?Given proper growth conditions, this algae can reproduce very quickly. allows for large numbers of offspring. But algae can also reproduce sexually.
::在适当的生长条件下,这种藻类可以很快繁殖,可以让大量后代繁殖。但是藻类也可以在性方面繁殖。Reproduction of Plant-like Protists
::类似植物的原生人的复制Life Cycle Overview
::生命周期概览Division Chlorophyta, Phylum Rhodophyta, and Phylum Heterokontophyta are the three main algal groups. They all have complex alternations of generations in their life cycles. In general there is an asexual phase where the seaweed's are diploid and a sexual phase where the cells are haploid . During the sexual phase, the alga is in the gametophyte phase , so called because they produce male and female gametes . The body type is called the gametophyte .
::叶绿素类、 叶绿素类、 叶绿素类、 叶绿素类、 叶绿素类、 叶绿素类、 叶绿素类是三大主要藻类组。 它们在其生命周期中各代人之间有着复杂的交替关系。 一般来说, 海藻是一种性相交的阶段, 其中海藻是低脂的, 细胞是低脂的。 在性阶段, 藻类处于游戏植物阶段, 之所以叫它, 是因为它们产生了男性和女性的游戏。 身体类型被称为“ 游戏植物类 ” 。During the asexual phase, the alga produces spores, and is in the sporophyte phase . The body form in the asexual phase is called the sporophyte . Asexual reproduction may also involve splitting (fission) or fragmentation of algae.
::在无性阶段,藻类产生螺旋,处于麻黄素阶段,性阶段的身体形式被称为,性生殖还可能涉及藻类分裂(分裂)或分裂。Asexual reproduction is advantageous in that it allows large numbers of offspring, but less is possible. allows more variation but is more costly because of the waste of gametes that fail to mate, among other things. Often there is no strict alternation between the sporophyte and gametophyte phases.
::性生殖是有利的,因为它允许大量后代,但可能性更小。 它允许更多的变异,但成本更高,因为浪费了无法交配的调子。 除其他外,它通常不会在花生植物和草药阶段之间发生严格的交替。Life Cycles of Algae: Zygotic Meiosis (A), Gametic Meiosis (B), and Sporic Meiosis (C). In life cycle A (left), diploid (2n) zygotes result from fertilization and then undergo meiosis to produce haploid gametes (+ or -). The gametes undergo mitosis and produce many additional copies of themselves. How are life cycles B and C different from life cycle A?
Some undergo an alternation of generations , including , foraminifera, and many algae. Alternation of generations is a reproductive cycle of plants, , and some protists in which a sexual reproductive phase alternates with an asexual reproductive phase. Alternation of generations occurs in almost all marine algae. In most red algae, many green algae, and a few brown algae, the phases are free-living.
::一些藻类的代代相传,包括有孔虫和许多藻类。 代代相传是植物的生殖循环,有些原生者将性生殖阶段与性生殖阶段交替。 代代相传几乎发生在所有海洋藻类中。 在大多数红藻类、许多绿藻类和少数棕藻类中,代代相传是免费的。The unicellular algae Chlamydomonas , shown in Figure , go through alternation of generations. Chlamydomonas cells are haploid, which means they have only one copy of their in their . The haploid algae divide by binary fission , or by multiple fissions, to produce offspring that are identical to the parent cell . During multiple fission, a single cell divides to produce more than two identical daughter cells .
::图中显示的非冰藻藻类衣拉米多莫纳,经过几代人的交替。 衣拉米多莫纳细胞是杂交的, 这意味着它们只有一份它们的细胞。 用二进制裂变或多种裂变来产生与母细胞相同的后代。 在多重裂变中,一个单细胞分离产生两个以上的相同女儿细胞。When conditions get tough for Chlamydomonas algae, they reproduce sexually to form a zygote ; two haploid cells come together and their and nuclei fuse to form a diploid zygote. The zygote has a tough outer coat that protects the cell from harsh conditions. When conditions improve, the cell within the zygote divides by to produce four haploid daughter cells. These daughter cells will grow into mature Chlamydomonas cells. For some of protists the daughter cells remain attached to form a filament, and in other cases the cells form a .
::当奇拉米多莫纳藻类的条件变得困难时,它们会以性繁殖方式形成一个zygote;两个杂交细胞聚集在一起,它们和核素引信形成一个diploid zygote; zygote有一个坚硬的外衣保护细胞免受严酷条件的伤害; 当条件改善时, zygote内的细胞会分裂成四个杂交女儿细胞; 这些女儿细胞会发展成成熟的克拉米多莫纳细胞; 对于一些原生者来说, 女儿细胞仍然附着在形成一个丝状体上, 而在另一些情况下, 细胞会形成一个。Scanning Electron Microscope (SEM) image of Chlamydomonas algae. Summary
::摘要-
In general there is an asexual phase where the algae cells are diploid (sporophyte phase) and a sexual phase where the cells are haploid (gametophyte phase).
::一般而言,存在一种无性阶段,即藻类细胞是低脂的(SPorophite section)和性阶段,即细胞是低脂的(gametophite section)。 -
Asexual reproduction is advantageous in that it allows for large numbers of offspring, but less genetic variation is possible. Sexual reproduction allows more variation but is more costly because of the waste of gametes that fail to mate.
::性生殖是有利的,因为它允许大量后代生育,但遗传变异的可能性较小。 性生殖允许更多的变异,但成本更高,因为浪费了无法交配的调子。 -
Some protists undergo an alternation of generations, including slime molds, foraminifera, and many marine algae.
::一些原生生物代代相传,包括粘泥模型、有孔虫和许多海洋藻类。
Review
::回顾-
What does it mean for an organism to undergo alternation of generations?
::生物体代代相传意味着什么? -
Describe the sexual and asexual phases of algae reproduction.
::描述藻类繁殖的性与非性阶段。 -
Why do
Chlamydomonas
algae reproduce sexually?
::为什么衣拉米多莫纳藻类会性繁殖? -
What are the advantages and disadvantages of producing asexually?
::无性生产的利弊何在?
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In general there is an asexual phase where the algae cells are diploid (sporophyte phase) and a sexual phase where the cells are haploid (gametophyte phase).