Plants (3) - Bryophytes flashcards

All 50 cards

1. Card 1

   Define bryophytes and explain the primary reason for their limited size and preference for moist environments.

   Bryophytes are nonvascular land plants, meaning they lack specialized tissues like xylem for water transport. This absence, along with their inability to produce lignin, restricts their height to only a few centimeters and necessitates moist environments for survival and reproduction.

2. Card 2

   How do rhizoids in bryophytes differ from true roots found in vascular plants?

   Rhizoids in bryophytes serve primarily to anchor the plant to the soil but do not absorb water or nutrients. In contrast, true roots in vascular plants contain xylem and phloem, allowing them to efficiently absorb and transport water and nutrients throughout the plant.

3. Card 3

   Explain the significance of the gametophyte being the dominant, visible plant in bryophytes.

   The dominant, visible plant in bryophytes is the haploid gametophyte, which is responsible for photosynthesis and overall plant structure. The sporophyte, which produces spores, is typically smaller, short-lived, and nutritionally dependent on the gametophyte for its development and survival.

4. Card 4

   In what specific way does the reproductive strategy of bryophytes necessitate the presence of moisture?

   Bryophytes require moisture for sperm transfer during reproduction. Sperm produced in the antheridia are flagellated and must swim through a film of water to reach the egg located within the archegonium, enabling fertilization.

5. Card 5

   Distinguish between thalloid liverworts and leafy liverworts based on their gametophyte structure.

   Thalloid liverworts have a gametophyte composed of a flattened, irregular body of green tissue called a thallus, which does not form distinct leaves or stems. Leafy liverworts, however, have a gametophyte that consists of an axis with leaf-like structures, typically one cell thick.

6. Card 6

   Describe the role of gemma cups and gemmae in Marchantia.

   Gemma cups are structures found on the thallus of Marchantia that produce gemmae. Gemmae are small, disc-shaped multicellular bodies that are dispersed by raindrops and can develop into new, genetically identical gametophytes, facilitating asexual reproduction.

7. Card 7

   How does the sporophyte of Marchantia obtain its nutrition, and what structures comprise it?

   The sporophyte of Marchantia is nutritionally dependent on the gametophyte, anchoring to it via a foot. The mature sporophyte consists of three main structures: the foot, which attaches it to the gametophyte; the seta, a stalk that elongates; and the capsule (sporangium), where spores are produced by meiosis.

8. Card 8

   What is the primary function of the capsule (sporangium) in a bryophyte sporophyte?

   The primary function of the capsule (sporangium) in a bryophyte sporophyte is to produce spores through the process of meiosis. These spores are then dispersed, and under suitable conditions, they can germinate and develop into new haploid gametophytes.

9. Card 9

   Explain why bryophytes are considered 'low growing' and cannot achieve the height of vascular plants.

   Bryophytes are low growing because they lack lignin, a rigid polymer that provides structural support in vascular plants, and specialized vascular tissues (xylem) for efficient water transport. Without these, they cannot support tall structures or move water against gravity over significant distances.

10. Card 10

    What does it mean for Marchantia to be 'dioecious,' and how does this impact its reproduction?

    Marchantia is dioecious, meaning it has separate male and female plants. This implies that for sexual reproduction to occur, sperm from a male plant must be transferred to an egg on a female plant, often facilitated by external agents like raindrops splashing sperm.

11. Card 11

    How do antheridia and archegonia contribute to sexual reproduction in Marchantia?

    Antheridia are male gametangia that produce sperm, located on male gametophores. Archegonia are female gametangia that produce eggs, each within a venter on female gametophores. Sperm from antheridia fertilize eggs in archegonia, leading to zygote formation.

12. Card 12

    What is the role of the gametophore in Marchantia?

    The gametophore in Marchantia is a stalk-like structure that elevates the gametangia (antheridia or archegonia) above the thallus. This elevation can aid in the dispersal of sperm (from male gametophores) or the reception of sperm (by female gametophores).

13. Card 13

    Why is the development of an embryo into a diploid sporophyte considered an important step in the bryophyte life cycle?

    The development of an embryo into a diploid sporophyte is crucial because it represents the diploid phase of the life cycle, formed after fertilization. The sporophyte then undergoes meiosis to produce haploid spores, which are essential for the dispersal and continuation of the species.

14. Card 14

    Compare the function of rhizoids in bryophytes with the function of roots in vascular plants, highlighting a key difference.

    Rhizoids in bryophytes primarily anchor the plant to the substrate but do not play a significant role in water or nutrient absorption. In contrast, roots in vascular plants are specialized organs equipped with xylem and phloem for efficient absorption and transport of water and nutrients.

15. Card 15

    Describe the process of fertilization in Marchantia, including the role of water.

    In Marchantia, fertilization occurs when raindrops splash sperm from the antheridia on male gametophores to the female gametophores. The sperm then swim through a film of water to reach the egg inside the archegonium, leading to the formation of a zygote.

16. Card 16

    What is a thallus, and in which type of liverwort is it a prominent feature?

    A thallus is a flattened, irregular body of green tissue that constitutes the gametophyte without forming distinct leaves or stems. It is a prominent feature of thalloid liverworts, such as Marchantia.

17. Card 17

    Why are bryophytes considered nonvascular, and what are the implications of this characteristic?

    Bryophytes are nonvascular because they lack specialized conductive tissues like xylem and phloem for transporting water and nutrients. This limitation restricts their size, necessitates moist habitats, and means they cannot grow tall or efficiently distribute resources over long distances.

18. Card 18

    How does the diploid sporophyte of a liverwort like Marchantia relate genetically and physically to its gametophyte?

    The diploid sporophyte of Marchantia is genetically distinct from the gametophyte, resulting from the fusion of gametes. Physically, it remains attached to and nutritionally dependent on the haploid gametophyte throughout its development.

19. Card 19

    Identify the three main groups within bryophytes and their approximate species numbers.

    The three main groups within bryophytes are Liverworts (approximately 9,000 species), Mosses (approximately 13,000 species), and Hornworts (approximately 225 species).

20. Card 20

    What is the primary difference in structural complexity between Marchantia's thallus and the 'leaves' of leafy liverworts?

    Marchantia's thallus is a relatively thick, flattened body of green tissue, typically about 20 cells thick. In contrast, the 'leaves' of leafy liverworts are much simpler, generally consisting of only one cell thick, arranged along an axis.

21. Card 21

    Explain how the absence of lignin impacts the growth and structural integrity of bryophytes.

    The absence of lignin in bryophytes means they lack the rigid structural support found in vascular plants. This prevents them from growing tall, as they cannot maintain upright structures against gravity, and further limits their ability to transport water efficiently over distance.

22. Card 22

    Why is the term 'true roots' not applicable to the rhizoids of bryophytes?

    The term 'true roots' is not applicable to bryophyte rhizoids because true roots in vascular plants contain specialized vascular tissues (xylem and phloem) for water and nutrient absorption and transport. Rhizoids, on the other hand, primarily function as anchors and lack these vascular tissues.

23. Card 23

    What is the significance of meiosis occurring in the capsule of the sporophyte?

    Meiosis occurring in the capsule of the sporophyte is significant because it reduces the chromosome number from diploid (2n) to haploid (n), producing genetically diverse spores. These haploid spores are the first stage of the new gametophyte generation, ensuring genetic variation and dispersal.

24. Card 24

    How do the male and female gametophores of Marchantia differ in appearance and function?

    Male gametophores in Marchantia have a disc-shaped upper surface where antheridia produce sperm. Female gametophores have a palm-tree-like or umbrella-shaped upper surface that supports archegonia, each containing an egg, ready for fertilization.

25. Card 25

    In what specific environmental conditions would you most likely find bryophytes, and why?

    You would most likely find bryophytes in moist, shaded environments such as forest floors, rocks near streams, or damp walls. This is because their nonvascular nature and reliance on water for sperm transfer necessitate a consistent supply of moisture for survival and reproduction.

26. Card 26

    Define 'gametophore' in the context of bryophytes.

    A gametophore is a stalk that supports several gametangia. In Marchantia, male gametophores bear antheridia on their upper surface, while female gametophores support archegonia.

27. Card 27

    How does asexual reproduction occur in Marchantia?

    Asexual reproduction in Marchantia occurs through gemma cups located on the thallus. These gemma cups produce gemmae, which are small, disc-shaped structures capable of developing into new gametophytes for vegetative reproduction.

28. Card 28

    Explain the role of the protonemata in the moss life cycle.

    The protonemata is a filamentous, green, haploid structure that germinates from a dispersed spore. It resembles algae and serves as an initial growth phase, from which buds can form to develop into new, upright, leafy gametophytes.

29. Card 29

    Distinguish between the sporophyte structure of Marchantia and mosses.

    In Marchantia, the mature sporophyte consists of a foot, seta, and capsule. In mosses, the sporophyte also has a foot, seta, and capsule, but it additionally features an operculum (a lid) and a peristome (tooth-like structures) that regulate spore release.

30. Card 30

    Why is moisture essential for sperm transfer in bryophytes like mosses?

    Moisture is crucial for sperm transfer in mosses because the sperm are flagellated and must swim to reach the egg within the archegonium. Raindrops splash sperm from male to female plants, allowing them to move through a film of water to achieve fertilization.

31. Card 31

    What is the function of the peristome in a moss sporophyte?

    The peristome is a ring of tooth-like structures located below the operculum of a moss capsule. Its function is to regulate the release of spores over time, often by responding to changes in humidity, ensuring gradual dispersal rather than a single burst.

32. Card 32

    How does the sporophyte of hornworts differ structurally from that of mosses?

    The sporophyte of hornworts is unique because it is often long and horn-like, lacking a distinct seta, and grows from a basal meristem. In contrast, a moss sporophyte has a prominent seta that elevates the capsule, which contains an operculum and peristome.

33. Card 33

    In what way is the hornwort sporophyte considered photosynthetic?

    The hornwort sporophyte is photosynthetic because it is green and persistent, meaning it can produce its own food. Unlike the sporophytes of Marchantia and mosses, which are largely dependent on the gametophyte, the hornwort sporophyte contributes to its own nutrition.

34. Card 34

    Explain the nutritional relationship between the sporophyte and gametophyte in Marchantia.

    In Marchantia, the sporophyte is nutritionally dependent on the gametophyte. The foot of the sporophyte anchors it to the gametophyte tissue, through which it absorbs nutrients necessary for its development and spore production.

35. Card 35

    What is the significance of the zygote developing into an embryo in the moss life cycle?

    The zygote developing into an embryo signifies the beginning of the diploid sporophyte generation. This embryo then matures into the young sporophyte, which remains attached to and dependent on the haploid gametophyte, marking the transition between generations.

36. Card 36

    Describe the process of fertilization in Marchantia.

    Fertilization in Marchantia occurs when sperm, splashed by raindrops from male plants, swim to the egg located within the archegonium on female plants. This union of sperm and egg forms a diploid zygote, initiating the sporophyte generation.

37. Card 37

    What is the role of the costa in moss leaves?

    The costa is a central vein found in the leaves of mosses. While mosses lack lignin and xylem, the costa provides some structural support to the often several-cells-thick leaf and may aid in water conduction, though it is not a true vascular tissue.

38. Card 38

    Why are mosses considered to lack true vascular tissue?

    Mosses lack true vascular tissue because they do not possess lignin and xylem. These are the key components of vascular tissue responsible for efficient water and nutrient transport over long distances in more complex plants. Instead, mosses rely on simpler conduction mechanisms and absorption directly from their environment.

39. Card 39

    How does spore dispersal differ between Marchantia and mosses?

    In Marchantia, spores are produced in the capsule and released, though specific mechanisms for regulated dispersal are not detailed. In mosses, spore dispersal is more regulated by the operculum, which acts as a lid, and the peristome, which controls the gradual release of spores over time.

40. Card 40

    What is the ploidy level of the visible green plant in mosses, and why is this significant?

    The visible green plant in mosses is the haploid gametophyte. This is significant because it represents the dominant generation in the moss life cycle, responsible for photosynthesis and sexual reproduction, contrasting with vascular plants where the sporophyte is dominant.

41. Card 41

    Define 'operculum' in the context of moss sporophytes.

    The operculum is a lid that covers the spore-releasing opening of the capsule in a moss sporophyte. Its removal is a crucial step in the process of spore dispersal, often preceding the action of the peristome.

42. Card 42

    What is the primary function of rhizoids in mosses?

    The primary function of rhizoids in mosses is to anchor the plant to its substrate. Unlike true roots, rhizoids are not specialized for significant water or nutrient absorption, which mosses typically absorb directly through their surface.

43. Card 43

    How does the growth pattern of the hornwort sporophyte contribute to its persistence?

    The hornwort sporophyte grows from a basal meristem, which allows for continuous growth over an extended period. This persistent growth, combined with its photosynthetic capability, enables the sporophyte to remain active and produce spores for a longer duration.

44. Card 44

    What structures are responsible for producing sperm and eggs in mosses?

    In mosses, antheridia, located on male gametophytes, are responsible for producing sperm. Archegonia, found on female gametophytes, contain and produce eggs.

45. Card 45

    Explain the term 'thalloid body' as it applies to hornwort gametophytes.

    A 'thalloid body' refers to a flattened, undifferentiated plant body that lacks true stems, leaves, or roots. In hornworts, the gametophyte typically presents as such a thalloid structure, lying flat against the substrate.

46. Card 46

    In the moss life cycle, what event immediately follows the germination of a spore?

    In the moss life cycle, the germination of a spore immediately leads to the development of a protonemata. This filamentous, haploid structure then grows and can bud to form new gametophytes.

47. Card 47

    What is the ploidy level of the spores produced by the capsule in Marchantia and mosses, and by what process are they formed?

    The spores produced by the capsule in both Marchantia and mosses are haploid (n). They are formed through the process of meiosis, which reduces the chromosome number from the diploid (2n) sporophyte parent cell.

48. Card 48

    How does the sporophyte development in Marchantia begin after fertilization?

    After fertilization in Marchantia, the resulting zygote undergoes cell division to form an embryo. This embryo then develops into the diploid sporophyte, which remains nutritionally dependent on the gametophyte.

49. Card 49

    What is the function of the seta in the sporophyte of Marchantia and mosses?

    The seta is a stalk-like structure in the sporophyte of both Marchantia and mosses. Its function is to elongate, elevating the capsule above the gametophyte, which facilitates the dispersal of spores into the environment.

50. Card 50

    Why are hornworts considered a smaller group of bryophytes compared to mosses?

    Hornworts are considered a smaller group of bryophytes primarily due to their lower diversity compared to mosses. Mosses are described as the most diverse group of bryophytes, dominating many moist habitats, while hornworts have fewer species and unique, but less varied, sporophyte characteristics.

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