Nonvascular Plants
Nonvascular plants (informally called bryophytes) generally live very close to the ground, sprawling out rather than growing upward. This growth form is due to their thin body parts and lack of vascular structures that would support upward growth. Three phyla of bryophytes exist today: liverworts, hornworts, and mosses.
Part A – Bryophyte structure
Label the structures on this diagram of a moss.
Drag the labels onto the diagram below. Not all labels will be used.
In the life cycle of bryophytes, gametophytes are the dominant stage and are generally larger than sporophytes. The sporophytes of mosses are made up of a foot, a seta, and a sporangium. The foot is embedded in the gametophyte and absorbs nutrients from it. The seta, or stalk, transports the nutrients to the sporangium, which produces spores.
Rhizoids, which resemble the roots of vascular plants, anchor the gametophytes to a substrate. Rhizoids are not vascular structures.
Part B – Life cycle of mosses
Arrange the events in the life cycle of mosses in the flowchart below.
Start the life cycle with the mature sporophyte stage in target 1. Not all labels will be used.
Part B – Life cycle of mosses
Arrange the events in the life cycle of mosses in the flowchart below.
Start the life cycle with the mature sporophyte stage in target 1. Not all labels will be used.
Which of these characteristics is shared by algae and seed plants?
chloroplasts.
Both algae and seed plants have cells with chloroplasts.
Angiosperms are most closely related to _____.
gymnosperms.
The branching pattern of the phylogenetic tree in the activity indicates that angiosperms are most closely related to gymnosperms.
Which of these was the dominant plant group at the time that dinosaurs were the dominant animals?
gymnosperms.
Both gymnosperms and dinosaurs were dominant during the Mesozoic.
This is an image of a(n) _____.
charophycean.
Charophyceans are the green algae most closely related to plants.
Plants evolved from green algae approximately _____ million years ago.
475.
Plants evolved from green algae about 475 million years ago.
_____ are an example of seedless vascular plants.
Ferns.
Ferns are seedless vascular plants.
The living plants that are most similar to the first plants to bear gametangia are the _____.
bryophytes.
Bryophytes, such as mosses, are the extant plants that are most similar to the first plants to bear gametangia.
The closest algal relatives of land plants are _____.
charophytes.
These green algae and plants share many homologous features.
Which of the following traits was most important in enabling the first plants to move onto land?
the development of sporopollenin to prevent the desiccation of zygotes.
Without sporopollenin, plant reproduction on land would have been much more difficult. This was one of the first problems that had to be solved in order for plants to take advantage of the habitats available on land.
The diploid generation of the plant life cycle always _____.
produces spores.
The diploid generation of the plant life cycle always produces spores.
According to the fossil record, plants colonized terrestrial habitats _____.
in conjunction with fungi that helped provide them with nutrients from the soil.
The most direct ancestors of land plants were probably _____.
green algae.
About 450 million years ago, the terrestrial landscape on Earth would have _____.
had non-vascular green plants similar to liverworts forming green mats on rock.
What evidence do paleobotanists look for that indicates the movement of plants from water to land?
waxy cuticle to decrease evaporation from leaves.
Spores and seeds have basically the same function-dispersal-but are vastly different because _____.
spores are unicellular; seeds are not.
Retaining the zygote on the living gametophyte of land plants _____.
allows it to be nourished by the parent plant.
The structural integrity of bacteria is to peptidoglycan as the structural integrity of plant spores is to _____.
sporopollenin
A student encounters a pondweed which appears to be a charophyte (stonewort). Which of the following features would help the student determine whether the sample comes from a charophyte or from some other type of green alga?
1. molecular structure of enzymes inside the chloroplasts
2. structure of sperm cells
3. presence of phragmoplasts
4. rings of cellulose-synthesizing complexes
2, 3, and 4.
Which of these represents the sporophyte generation of the moss life cycle?
E
In moss, _____ produce sperm.
antheridia.
Moss antheridia, found on the tops of male gametophytes, produce sperm.
The sperm produced by mosses require _____ to reach an archegonium.
Moisture.
Moss sperm swim to archegonia.
In mosses gametes are produced by _____; in ferns gametes are produced by _____.
mitosis … mitosis.
In both, gametes are produced by haploid gametophytes.
Which statement is true for all sexually reproducing plants and animals?
The process of meiosis produces haploid cells.
The products of meiosis contain one complete set of chromosomes.
Which structures are haploid? Select all that apply.
Egg, Spores, Gametophyte.
Spores, which are haploid, grow by mitosis to become haploid gametophytes. The gametophyte produces eggs by mitosis; eggs are also haploid.
Consider the characteristics of moss and fern life cycles.
Which of the following sets of statements is true?
n mosses, the gametophyte is the dominant stage of the life cycle; in ferns, the sporophyte is the dominant stage of the life cycle. In both mosses and ferns, moisture is required for sperm to reach the egg.
The gametophyte is the dominant stage of the life cycle in mosses; the sporophyte develops on the body of a gametophyte, where it lives for a briefer time than the gametophyte’s life span. In ferns, the sporophyte is dominant; the gametophyte is tiny and short-lived. Both mosses and ferns have swimming sperm that require moisture to reach an egg.
Stomata _____.
open to allow gas exchange and close to decrease water loss.
Liverworts, hornworts, and mosses are grouped together as the Bryophytes. Besides not having vascular tissue, what do they all have in common?
They require water for reproduction.
Most moss gametophytes do not have a cuticle and are 1-2 cells thick. What does this imply about moss gametophytes and their structure?
They can easily lose water to, and absorb water from, the atmosphere.
How are the bryophytes and seedless vascular plants alike?
In both groups, sperm swim from antheridia to archegonia.
The leaflike appendages of moss gametophytes may be one to two cell layers thick. Consequently, which of the following is LEAST likely to be found associated with such appendages?
stomata.
Most bryophytes, such as mosses, differ from all other plants in that they _____.
lack true leaves and roots.
The bryophytes generally lack true leaves and roots, which all other plants have.
What evolutionary development allowed plants to grow tall?
lignified vascular tissue.
The polymer lignin strengthens the xylem and phloem, giving the plant more support and allowing it to grow taller.
Which of the following is not evidence that charophytes are the closest algal relatives of plants?
the presence of chloroplasts.
In plants, which of the following are produced by meiosis?
haploid spores
Which of these facts provides the best support for the hypothesis that plants evolved from green algae?
The chloroplasts of plants and green algae all have both chlorophyll a and b.
Of the three choices, this statement does provide the best support for the hypothesis that plants evolved from green algae. In addition to green algae and plants, euglenids and a few dinoflagellates have chlorophyll a and b. The very best evidence for the hypothesis is the derived traits shared by charophytes (a taxon of green algae) and plants.
Select the correct statement about the life cycle of a fern.
Plant gametophytes are haploid multicellular bodies.
Plant gametophytes vary in size, but they are haploid and multicellular in all plant life cycles. Look for plant gametophytes in the basic sexual life cycle of plants and in the life cycles of nonvascular and seedless vascular plants.
Select the correct statement contrasting gametophytes and sporophytes.
Sporophytes are diploid, whereas gametophytes are haploid.
Look at the basic sexual life cycle of plants and the life cycles of nonvascular and seedless vascular plants.
Select the correct statement contrasting gametophytes and sporophytes.
x

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