Chapter 38 - Mastering Biology

True or false? The endosperm in a seed develops into the embryo. True False

False (The endosperm in a seed is not the embryo, but the food supply for the embryo.)

Which part of a plant attracts pollinators? Stamen Carpel Sepal Petals

Petals (The petals of a plant serve to attract pollinators.)

Which of the following statements about seed formation in a flowering plant is true? The swellings that develop into cotyledons are located at the end of the embryo on top of the row of single cells. The basal cell formed from mitosis of the zygote divides to form a globular mass that is the route for nutrient transfer to the developing embryo. The terminal cell formed from mitosis of the zygote divides to form a row of single cells that eventually forms the embryo. Hypocotyls are the seed leaves of the embryonic plant.

The swellings that develop into cotyledons are located at the end of the embryo on top of the row of single cells. (The swellings that develop into cotyledons do indeed grow on top of the row of single cells produced by the basal cell.)

The diagram below illustrates the alternation of generations that is characteristic of the angiosperm life cycle. Label structures and processes (using white labels), indicate whether different structures are haploid or diploid (using pink labels), and indicate the types of cell division that occur at different points in the life cycle (using blue labels). Drag the labels to their appropriate locations on the diagram of the angiosperm life cycle. Labels can be used once or more than once. Use only white labels for white targets, pink labels for pink targets, and blue labels for blue targets.

a. meiosis b.haploid c.mitosis d.gametophyte e. pollination f.meiosis g.haploid h.mitosis i.gametophyte j.fertilization k. zygote l. diploid m. sporophyte (The alternation of generations refers to the alternation between the diploid sporophyte and the haploid gametophytes in plants. In angiosperms, meiosis occurs in floral structures of the larger, diploid sporophyte, producing haploid microspores in the anthers and haploid megaspores in the ovaries. These microspores and megaspores divide by mitosis and form the haploid male and female gametophytes, respectively. Pollination occurs when the male gametophyte, contained in a pollen grain, is transferred to the stigma of a flower. Sperm travels to the female gametophyte, where fertilization (fusion of sperm and egg) forms a diploid zygote. The zygote develops into an embryo and eventually an adult sporophyte. The cycle repeats, each time allowing for the production and development of new individuals.)

Many aspects of the angiosperm life cycle make flowering plants particularly well-suited to life on land. In fact, angiosperms are the most diverse and widespread of all plants. Which six of the following statements reflect angiosperm adaptations to life on land? Fertilization in angiosperms is dependent on the presence of water. Flowers attract animal pollinators carrying pollen from other plants of the same species. Seeds enable plant embryos to be dispersed long distances from the parent plant via wind or animals. Spores contain a supply of stored food, enabling the embryo to remain dormant until conditions are suitable for germination. In angiosperms, a gametophyte protects a dependent sporophyte from desiccation. Seeds protect and nourish plant embryos, and fruits protect the seeds. Floral parts of the sporophyte protect the reduced female gametophyte from drying out and from UV radiation. In many angiosperms, the male gametophyte contained in a pollen grain can be transported many miles away by wind or animal pollinators. Fruits aid in the dispersal of seeds by wind or by animals that carry or eat the fruits.

In many angiosperms, the male gametophyte contained in a pollen grain can be transported many miles away by wind or animal pollinators. Fruits aid in the dispersal of seeds by wind or by animals that carry or eat the fruits. Floral parts of the sporophyte protect the reduced female gametophyte from drying out and from UV radiation. Seeds enable plant embryos to be dispersed long distances from the parent plant via wind or animals. Seeds protect and nourish plant embryos, and fruits protect the seeds. Flowers attract animal pollinators carrying pollen from other plants of the same species (As plants evolved and populated terrestrial environments, one challenge that had to be dealt with was the absence of water. Angiosperms have met this challenge, in part, with adaptations that enable them to reproduce without water. The following table lists some differences between nonvascular plants, such as mosses, and angiosperms. Note how the angiosperm adaptations enable them to reproduce in dry terrestrial environments.)

Which structure formed by the male gametophyte allows sperm to reach the ovary of a flowering plant? Micropyle Stigma Pollen tube Anther

Pollen tube (The pollen tube is formed after a pollen grain is transferred to a receptive stigma and germinates, forming a tube that grows down through the style to the ovary of a flowering plant.)

Which process involves the transfer of pollen grains from an anther to a stigma? Germination Fertilization Pollination Gametogenesis

Pollination (Pollination is the transfer of pollen grains from an anther to a stigma.)

How is fertilization in flowering plants different from fertilization in other plant groups? One sperm nucleus fuses with the egg to form a diploid zygote, whereas the other sperm nucleus fuses with two polar nuclei to form a cell that develops into endosperm. Two sperm nuclei fuse with a polar nucleus to form a diploid zygote. One sperm nucleus fuses with the egg to form a diploid zygote, whereas the other sperm nucleus fuses with a polar nucleus to form a diploid cell that forms a nutrient-rich tissue. One sperm nucleus fuses with the egg to form a diploid zygote.

One sperm nucleus fuses with the egg to form a diploid zygote, whereas the other sperm nucleus fuses with two polar nuclei to form a cell that develops into endosperm. (Angiosperms are unusual in that one sperm nucleus fuses with the egg and one sperm nucleus fuses with two polar nuclei to form a triploid cell that develops into a nutrient-rich tissue that nourishes the growing embryo.)

You have learned that the fusion of egg and sperm produces a zygote. But how does the sperm reach the egg, and how does the zygote develop into a seed, which eventually germinates and grows into a mature sporophyte? In this activity, you will demonstrate your understanding of double fertilization and seed development in angiosperms. Drag the statements to their appropriate locations on the flowchart of pollination, fertilization, and seed development.

Pollen grain lands on stigma---> a) pollen tube grows down the style b) generative cell divides, forming two sperm c) two sperm are discharged to them female gametophyte d) sperm fuse with the egg and two polar nuclei e) zygote forms and divides into a terminal cell and a basal cell f) cells of embryo differentiate into three tissue types---> seed dries out and becomes dormant. (((((During pollination, a pollen grain is transferred from an anther to a stigma. Once the pollen grain lands on a suitable stigma, it germinates and forms a pollen tube, a structure that grows down through the style to the ovary. Once in the pollen tube, the generative cell from the pollen grain divides by mitosis, forming two sperm. The sperm travel down the pollen tube and are discharged into the female gametophyte. In a process called double fertilization, one sperm fertilizes the egg, forming the zygote; the other sperm fuses with two polar nuclei in the female gametophyte, forming a triploid (3n) nucleus. The zygote develops into the plant embryo, and the triploid nucleus divides and gives rise to the endosperm. Double fertilization prevents the waste of the plant's resources by ensuring that the nutrient-rich endosperm only develops if the egg is fertilized. After double fertilization, the ovule starts to develop into a seed containing the plant embryo. As the embryo develops, the three tissue systems are established, and the cotyledons (seed leaves) form. The seeds of many species dry out as they mature. These dry seeds lie dormant until suitable germination conditions occur.)))))

Which term describes the male gametophytes of flowering plants? Microsporocytes Micropyle Pollen grains Megaspores

Pollen grains (Pollen grains are the male gametophytes of flowering plants; they contain a generative cell that develops into sperm.)