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25.3B: Liverworts and Hornworts - Biology


Liverworts and hornworts are both bryophytes, but aspects of their structures and development are different.

Learning Objectives

  • Describe the distinguishing traits of hornworts and liverworts

Key Points

  • The leaves of liverworts are lobate green structures similar to the lobes of the liver, while hornworts have narrow, pipe-like structures.
  • The gametophyte stage is the dominant stage in both liverworts and hornworts; however, liverwort sporophytes do not contain stomata, while hornwort sporophytes do.
  • The life cycle of liverworts and hornworts follows alternation of generations: spores germinate into gametophytes, the zygote develops into a sporophyte that releases spores, and then spores produce new gametophytes.
  • Liverworts develop short, small sporophytes, whereas hornworts develop long, slender sporophytes.
  • To aid in spore dispersal, liverworts utilize elaters, whereas hornworts utilize pseudoelaters.
  • Liverworts and hornworts can reproduce asexually through the fragmentation of leaves into gemmae that disperse and develop into gametophytes.

Key Terms

  • alternation of generation: the life cycle of plants with a multicellular sporophyte, which is diploid, that alternates with a multicellular gametophyte, which is haploid
  • pseudoelater: single-celled structure that aids in spore dispersal
  • gemmae: small, intact, complete pieces of plant that are produced in a cup on the surface of the thallus and develop into gametophytes through asexual reproduction

Liverworts

Liverworts (Hepaticophyta) are viewed as the plants most closely related to the ancestor that moved to land. Liverworts have colonized every terrestrial habitat on earth and diversified to more than 7000 existing species. Liverwort gametophytes (the dominant stage of the life cycle) form lobate green structures. The shape of these leaves are similar to the lobes of the liver; hence, providing the origin of the name given to the phylum. Openings that allow the movement of gases may be observed in liverworts. However, these are not stomata because they do not actively open and close. The plant takes up water over its entire surface and has no cuticle to prevent desiccation.

The liverwort’s life cycle begins with the release of haploid spores from the sporangium that developed on the sporophyte. Spores disseminated by wind or water germinate into flattened thalli gametophytes attached to the substrate by thin, single-celled filaments. Male and female gametangia develop on separate, individual plants. Once released, male gametes swim with the aid of their flagella to the female gametangium (the archegonium), and fertilization ensues. The zygote grows into a small sporophyte still attached to the parent gametophyte and develops spore-producing cells and elaters. The spore-producing cells undergo meiosis to form spores, which disperse (with the help of elaters), giving rise to new gametophytes. Thus, the life cycle of liverworts follows the pattern of alternation of generations.

Liverwort plants can also reproduce asexually by the breaking of branches or the spreading of leaf fragments called gemmae. In this latter type of reproduction, the gemmae (small, intact, complete pieces of plant that are produced in a cup on the surface of the thallus ) are splashed out of the cup by raindrops. The gemmae then land nearby and develop into gametophytes.

Hornworts

The hornworts (Anthocerotophyta) belong to the broad bryophyte group that have colonized a variety of habitats on land, although they are never far from a source of moisture. The short, blue-green gametophyte is the dominant phase of the lifecycle of a hornwort. The narrow, pipe-like sporophyte is the defining characteristic of the group. The sporophytes emerge from the parent gametophyte and continue to grow throughout the life of the plant. Stomata appear in the hornworts and are abundant on the sporophyte. Photosynthetic cells in the thallus contain a single chloroplast. Meristem cells at the base of the plant keep dividing and adding to its height. Many hornworts establish symbiotic relationships with cyanobacteria that fix nitrogen from the environment.

The life cycle of hornworts also follows the general pattern of alternation of generations and has a similar life cycle to liverworts. The gametophytes grow as flat thalli on the soil with embedded gametangia. Flagellated sperm swim to the archegonia and fertilize eggs. However, unlike liverworts, the zygote develops into a long and slender sporophyte that eventually splits open, releasing spores. Additionally, thin cells called pseudoelaters surround the spores and help propel them further in the environment. Unlike the elaters observed in liverworts, the hornwort pseudoelaters are single-celled structures. The haploid spores germinate and produce the next generation of gametophytes. Like liverworts, some hornworts may also produce asexually through fragmentation.


Bryophyta: Features, Classification and Economic Importance

The division Bryophyta (Gr. bryon=moss) includes over 25000 species of non-vascular embryophytes such as mosses, liverworts and hornworts.

Bryophytes are small plants (2cm to 60cm) that grow in moist shady places. They don’t attain great heights because of absence of roots, vascular tissues, mechanical tissues and cuticle. They are terrestrial but require external water to complete their life cycle.

Hence, they are called “Amphibians of plant kingdom”.

The fossil record indicates that bryophytes evolved on earth about 395 – 430 million years ago (i.e. during Silurian period of Paleozoic era). The study of bryophytes is called bryology. Hedwig is called ‘Father of Bryology’. Shiv Ram Kashyap is the ‘Father of Indian Bryology’.

Salient features of Bryophytes:

1. Bryophytes grow in damp and shady places.

2. They follow heterologous haplodiplobiontic type of life cycle.

3. The dominant plant body is gametophyte on which sporophyte is semiparasitic for its nutrition.

4. The thalloid gametophyte differentiated in to rhizoids, axis (stem) and leaves.

5. Vascular tissues (xylem and phloem) absent.

6. The gametophyte bears multi-cellular and jacketed sex organs (antheridia and archegonia).

7. Sexual reproduction is oogamous type.

8. Multi-cellular embryo develops inside archegonium.

9. Sporophyte differentiated into foot, seta and capsule.

10. Capsule produces haploid meiospores of similar types (homosporous).

11. Spore germinates into juvenile gametophyte called protonema.

12. Progressive sterilization of sporogenous tissue noticed from lower to higher bryophytes.

13. Bryophytes are classified under three classes: Hepaticae (Liverworts), Anthocerotae (Hornworts) and Musci (Mosses).

Classification of Bryophytes:

According to the latest recommendations of ICBN (International Code of Botanical Nomenclature), bryophytes have been divided into three classes.

1. Hepaticae ( Hepaticopsida = Liverworts)

2. Anthocerotae (Anthocertopsida= Hornworts)

Class 1. Hepaticae or Hepaticopsida:

1. Gametophytic plant body is either thalloid or foliose. If foliose, the lateral appendages (leaves) are without mid-rib. Always dorsiventral.

3. Each cell in the thallus contains many chloroplasts the chloroplasts are without pyrenoi.

4. Sex organs are embedded in the dorsal surface.

5. Sporophyte may be simple (e.g., Riccia) having only a capsule, or differentiated into root, seta and capsule (e.g., Marchantia, Pallia and Porella etc.)

6. Capsule lacks columella.

Class 2. Anthocerotae or Anthocerotopsid:

1. Gametophytic plant body is simple, thalloid thallus dorsiventra without air cambers, shows no internal differentiation of tissues.

2. Scales are absent in the thallus.

3. Each cell of the thallus possesses a single large chloroplast with a pyrenoid.

4. Sporophyte is cylindrical only partly dependent upon gametophyte for its nourishment. It is differentiated into bulbous foot and cylindrical capsule. Seta is meristematic.

5. Endothecium forms the sterile central column (i.e., columella) in the capsule (i.e. columella is present). 6. It has only one order-Anthocerotales.

Class 3. Musci or Bryopsida:

1. Gametophyte is differentiated into prostrate protonema and an erect gametophores

2. Gametophore is foliose, differentiated into an axis (=stem) and lateral appendages like leaves but without midrib.

3. Rhizoids multi-cellular with oblique septa.

4. Elaters are absent in the capsule of sporangium.

5. The sex organs are produced in separate branches immersed in a group of leaves.

6. It has only three orders:

Economic importance of Bryophytes:

1. Protection from soil erosion:

Bryophytes, especially mosses, form dense mats over the soil and prevent soil erosion by running water.

Mosses are an important link in plant succession on rocky areas. They take part in binding soil in rock crevices formed by lichens. Growth of Sphagnum ultimately fills ponds and lakes with soil.

Sphagnum can retain 18-26 times more water than its weight. Hence, used by gardeners to protect desiccation of the seedling during transportation and used as nursery beds.

It is a dark spongy fossilized matter of Sphagnum. Peat is dried and cut as cakes for use as fuel. Peat used as good manure. It overcomes soil alkalinity and increases its water retention as well as aeration. On distillation and fermentation yield many chemicals.

Mosses are good source of animal food in rocky and snow-clad areas.

Decoction of Polytrichum commune is used to remove kidney and gall bladder stones. Decoction prepared by boiling Sphagnum in water for treatment of eye diseases. Marchantia polymorpha has been used to cure pulmonary tuberculosis.

Bryophytes arc used as packing material for fragile goods, glass wares etc. Some bryophytes act as indicator plants. For example, Tortell tortusa grow well on soil rich in lime.


Photo_1_bryophytes_1.jpg

Bryophytes also play a very important role in the environment: they colonize sterile soils, absorb nutrients and water and release them slowly back into the ecosystem, contributing to the formation of soil for new plants to grow on.

Still, there is much to learn about bryophytes, especially in the tropics where there are less abundant and therefore less studied. There is a growing interest in boosting the study of bryophytes in the tropics, to discover more about their evolution, and their role in the biodiversity of the region.

“Each species has its role in nature,” Villareal adds, “and each new species demonstrates that biodiversity needs attention, we need to know how many species we have to know their ecological function.”


Liverworts and Hornworts, - Structure, life cycle NEET Notes | EduRev

Hepaticopsida (Liver Worts)

Hepaticopsida

  • All the bryophytes included in this class have shape like liver, so they are known as liverworts.
  • Plant body of this group is like thallus. Rhizoids and scales are present on thallus. Rhizoids are unicellular and unbranched. Scales are multicellular.
  • The sporophyte of Liverworts is completely dependent on gametophyte i.e. it is dependent on gametophyte for food, water and habitat.
  • The sporophyte of Liverworts is made up of foot, seta and capsule. (Except Riccia sporophyte is made up of only capsule).
  • In this class formation of spores and nurse cells takes place by the cells of endothecium. Cells of amphithecium form only wall of sporophyte.
    Amphithecium = Wall of sporophyte
    Endothecium = sporogenous cells = spore mother cells + nurse cells
  • Elaters are present in sporophyte of some members of liverworts. (eg. Marchantia - In Marchantia nurse cells are modified into elaters). Elaters are hygroscopic and they help in dispersal of spores.
    Example: Riccia, Marchantia, Cryptothallus, Riella, Pellia, Porella.

Note : In Bryophytes, sporophyte of Riccia is the simplest.

Anthocerotopsida (Hornworts)

Anthocerotopsida

  • The plant body of this group is also thallus like. Scales are absent but rhizoids are present on thallus. Rhizoids are unicellular and unbranched.
  • The sporophyte of Hornworts is divided into foot and capsule.
  • The sporophyte of Hornworts is not completely dependent on its gametophyte i.e. it is semi-parasite because its sporophyte is photosynthetic therefore it can manufacture its own food. So it does not depend on gametophyte for food, it depends only for water and habitat.
  • In Hornworts, wall of sporophyte and spores are formed by cells of amphithecium. Cells of endothecium formed only elaters.
    Amphithecium = Wall of sporophyte and Spores
    Endothecium = Elaters
  • In hornworts spore forming cells and elaters forming cells are separate, so elaters are known as pseudoelaters.
    Pseudoelaters are structurally and functionally similar to true elaters.
  • In Hornworts on the basal part of sporophyte, a special, type of meristem is present. Due to the activeness of this meristem, the sporophyte grows rapidly. It grows like the horn of animals.
    Example: Notothylus, Anthoceros

Anthoceros have some Algae like characters such as:

  • Archegonia is jacketless.
  • In each cell of Anthoceros, only one chloroplast is present which is a character of green algae. In the cells of higher plants, many chloroplast are present.
  • Pyrenoides (starch storing granules) are present in the chloroplast of Anthoceros, which is an algal character.
  • Anthoceros shows ancestral characters which prove that bryophytes have originated from green algae.

Note: Due to these reasons, Anthoceros are also termed as synthetic-archegoniatae.

Bryopsida or Musci (Mosses)

Bryopsida

  • All the Mosses are included in this class. The plant body of mosses is made up of stem, leaves and rhizoids.
  • The Rhizoids present in the plants of this class are multi-cellular and branched. These rhizoids have oblique septa.

Note: The presence of leaves in gametophyte is one of the unique character of Moss. In plant kingdom not a single gametophyte has leaves.


Hornwort

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Hornwort, (division Anthocerotophyta), also called horned liverwort, any of about 300 species of small nonvascular plants. Hornworts usually grow on damp soils or on rocks in tropical and warm temperate regions. The largest genus, Anthoceros, has a worldwide distribution. Dendroceros and Megaceros are mainly tropical genera. Hornworts have an ancient lineage and are thought to be some of the earliest plants to have evolved on land.

Traditionally, hornworts have been classified as bryophytes, together with mosses (division Bryophyta) and liverworts (division Marchantiophyta). In some classification systems, hornworts have been grouped as horned liverworts in the subclass Anthocerotidae (class Hepaticae), class Anthocerotopsida, order Anthocerotales. However, molecular evidence suggests that hornworts have an evolutionary history distinct from both mosses and liverworts, and the plants are now placed in their own taxonomic division, Anthocerotophyta. The classification of the group remains controversial, and the number of hornwort families, genera, and species is under revision.

The plants’ gametophytes (sexual generation) are typically flattened, irregularly lobulated (thallose) structures that are usually less than 2 cm (0.8–1.6 inches) in diameter. The sporophyte, or asexual generation, forms a tapered cylinder. The sporophyte is dependent on the attached gametophyte for nutrients and water. Most sporophytes grow to up to 5 cm (2 inches). The thallus, or flat, gametophyte, usually lacks a midrib. The sexual organs are sunk into the upper surface of the thallus. Rhizoids (rootlike structures) on the undersurface anchor the plant. Cavities in the thallus sometimes contain colonies of the blue-green alga Nostoc.

Hornworts differ from other bryophytes in having a region of continuous growth at the base of the sporophyte, and a large irregular foot. The stalk that attaches the foot to the spore-bearing capsule in liverworts is absent in hornworts.

Hornworts reproduce sexually by means of waterborne sperm, which travel from the male sex organ (antheridium) to the female sex organ (archegonium). A fertilized egg in a female sex organ develops into an elongate sporangium, which splits lengthwise as it grows, releasing the spores that have developed within it. Elaters (elongated cells that aid in spore dispersal) are usually irregular and multicellular.

This article was most recently revised and updated by Melissa Petruzzello, Assistant Editor.


Hornworts

Figure 4. Hornworts grow a tall and slender sporophyte. (credit: modification of work by Jason Hollinger)

The hornworts (Anthocerotophyta) belong to the broad bryophyte group. They have colonized a variety of habitats on land, although they are never far from a source of moisture. The short, blue-green gametophyte is the dominant phase of the lifecycle of a hornwort. The narrow, pipe-like sporophyte is the defining characteristic of the group. The sporophytes emerge from the parent gametophyte and continue to grow throughout the life of the plant (Figure 4).

Stomata appear in the hornworts and are abundant on the sporophyte. Photosynthetic cells in the thallus contain a single chloroplast. Meristem cells at the base of the plant keep dividing and adding to its height. Many hornworts establish symbiotic relationships with cyanobacteria that fix nitrogen from the environment.

The lifecycle of hornworts (Figure 5) follows the general pattern of alternation of generations. The gametophytes grow as flat thalli on the soil with embedded gametangia. Flagellated sperm swim to the archegonia and fertilize eggs. The zygote develops into a long and slender sporophyte that eventually splits open, releasing spores. Thin cells called pseudoelaters surround the spores and help propel them further in the environment. Unlike the elaters observed in horsetails, the hornwort pseudoelaters are single-celled structures. The haploid spores germinate and give rise to the next generation of gametophyte.

Figure 5. The alternation of generation in hornworts is shown. (credit: modification of work by “Smith609”/Wikimedia Commons based on original work by Mariana Ruiz Villareal)


Liverworts and Hornworts

Liverworts and hornworts are both bryophytes, but aspects of their structures and development are different.

Learning Objectives

Describe the distinguishing traits of hornworts and liverworts

Key Takeaways

Key Points

  • The leaves of liverworts are lobate green structures similar to the lobes of the liver, while hornworts have narrow, pipe-like structures.
  • The gametophyte stage is the dominant stage in both liverworts and hornworts however, liverwort sporophytes do not contain stomata, while hornwort sporophytes do.
  • The life cycle of liverworts and hornworts follows alternation of generations: spores germinate into gametophytes, the zygote develops into a sporophyte that releases spores, and then spores produce new gametophytes.
  • Liverworts develop short, small sporophytes, whereas hornworts develop long, slender sporophytes.
  • To aid in spore dispersal, liverworts utilize elaters, whereas hornworts utilize pseudoelaters.
  • Liverworts and hornworts can reproduce asexually through the fragmentation of leaves into gemmae that disperse and develop into gametophytes.

Key Terms

  • alternation of generation: the life cycle of plants with a multicellular sporophyte, which is diploid, that alternates with a multicellular gametophyte, which is haploid
  • pseudoelater: single-celled structure that aids in spore dispersal
  • gemmae: small, intact, complete pieces of plant that are produced in a cup on the surface of the thallus and develop into gametophytes through asexual reproduction

Liverworts and Hornworts

Liverworts

Liverworts (Hepaticophyta) are viewed as the plants most closely related to the ancestor that moved to land. Liverworts have colonized every terrestrial habitat on earth and diversified to more than 7000 existing species. Liverwort gametophytes (the dominant stage of the life cycle) form lobate green structures. The shape of these leaves are similar to the lobes of the liver hence, providing the origin of the name given to the phylum. Openings that allow the movement of gases may be observed in liverworts. However, these are not stomata because they do not actively open and close. The plant takes up water over its entire surface and has no cuticle to prevent desiccation.

Liverworts: A liverwort, Lunularia cruciata, displays its lobate, flat thallus. The organism in the photograph is in the dominant gametophyte stage.

The liverwort’s life cycle begins with the release of haploid spores from the sporangium that developed on the sporophyte. Spores disseminated by wind or water germinate into flattened thalli gametophytes attached to the substrate by thin, single-celled filaments. Male and female gametangia develop on separate, individual plants. Once released, male gametes swim with the aid of their flagella to the female gametangium (the archegonium), and fertilization ensues. The zygote grows into a small sporophyte still attached to the parent gametophyte and develops spore-producing cells and elaters. The spore-producing cells undergo meiosis to form spores, which disperse (with the help of elaters), giving rise to new gametophytes. Thus, the life cycle of liverworts follows the pattern of alternation of generations.

Liverwort Life Cycle: The life cycle of a typical liverwort follows the pattern of alternation of generations. Spores are released from sporophytes and form the gametophyte. Male gametes fertilize female gametes to form a zygote, which grows into a sporophyte. This sporophyte disperses spores with the help of elaters the process begins again.

Liverwort plants can also reproduce asexually by the breaking of branches or the spreading of leaf fragments called gemmae. In this latter type of reproduction, the gemmae (small, intact, complete pieces of plant that are produced in a cup on the surface of the thallus ) are splashed out of the cup by raindrops. The gemmae then land nearby and develop into gametophytes.

Hornworts

The hornworts (Anthocerotophyta) belong to the broad bryophyte group that have colonized a variety of habitats on land, although they are never far from a source of moisture. The short, blue-green gametophyte is the dominant phase of the lifecycle of a hornwort. The narrow, pipe-like sporophyte is the defining characteristic of the group. The sporophytes emerge from the parent gametophyte and continue to grow throughout the life of the plant. Stomata appear in the hornworts and are abundant on the sporophyte. Photosynthetic cells in the thallus contain a single chloroplast. Meristem cells at the base of the plant keep dividing and adding to its height. Many hornworts establish symbiotic relationships with cyanobacteria that fix nitrogen from the environment.

Hornworts: Unlike liverworts, hornworts grow a tall and slender sporophyte.

The life cycle of hornworts also follows the general pattern of alternation of generations and has a similar life cycle to liverworts. The gametophytes grow as flat thalli on the soil with embedded gametangia. Flagellated sperm swim to the archegonia and fertilize eggs. However, unlike liverworts, the zygote develops into a long and slender sporophyte that eventually splits open, releasing spores. Additionally, thin cells called pseudoelaters surround the spores and help propel them further in the environment. Unlike the elaters observed in liverworts, the hornwort pseudoelaters are single-celled structures. The haploid spores germinate and produce the next generation of gametophytes. Like liverworts, some hornworts may also produce asexually through fragmentation.

Life Cycle of Hornworts: The life cycle of hornworts is similar to that of liverworts. Both follow the pattern of alternation of generations. However, liverworts develop a small sporophyte, whereas hornworts develop a long, slender sporophyte. Liverworts also disperse their spores with the help of elaters, while hornworts utilize pseudoelaters to aid in spore dispersal.


What are Hornworts?

Hornworts are another of the groups of tiny plants that are lumped together in division Bryophyta. The scientific name for their subdivision is Anthocerophyta – a name derived from the ancient Greek words anthos (bloom or blossom) and ceros (horn). This descriptive name refers to the spore-producingorgans of the hornworts, which look like horns or antlers.

Hornworts are superficially similar to thallose liverworts, but differ in some important ways. First, they have only a single large chloroplast in each photosynthetic cell. Liverworts, mosses, and vascular plants all have multiple chloroplasts. Second, their sporophytes grow from the base, rather than the tip. Third, like mosses, they have stomata (little gas-exchanging pores) on their spore-capsules. Another common feature in hornworts is that they tend to be symbiotically associated with cyanobacteria, although some liverworts also have a primitive association of this type.

Far less is known about hornworts than liverworts or mosses. There are about 300 named hornwort species, but very few occur in boreal and temperate regions, and those that do grow primarily on muddyor silty banks and shores. Because of this combination of wet habitat, small size and short duration of sporophytes, most Canadian hornworts could be easily mistaken for a smear of algae at first glance.


VII. Photoreceptors

Hornworts harbour a unique chimeric photoreceptor called neochrome, that is composed of a red/far-red-sensing module from the phytochrome and a blue-sensing phototropin (Li et al., 2014 , 2015a , b ). Neochrome was initially discovered in ferns (Nozue et al., 1998 ) and was considered a key innovation enabling ferns to diversify in the low-light angiosperm canopies (Kawai et al., 2003 Schneider et al., 2004 ). Through transcriptome- and genome-mining, Li et al ( 2014 ) found that among land plants, neochrome is restricted to ferns and hornworts, and they demonstrated that fern neochrome sequences were phylogenetically nested within those of hornworts. Such a nested relationship suggests that the fern neochrome was horizontally acquired from hornworts. Interestingly, hornwort phototropin lacks introns, similar to neochrome but unlike all other phototropin genes that typically have > 20 introns (Li et al., 2014 , 2015b ). This implies that neochrome probably originated in hornworts, possibly through a retrotransposition event.

The function of neochrome in hornworts is unknown. In ferns, neochrome integrates red/far-red and blue light to orchestrate phototropism and chloroplast relocation. However, no phototropic response has been recorded in hornworts, and because most cells contain only a single chloroplast that occupies a large portion of the cellular space, it is unclear how directional chloroplast movement is possible or even necessary. By contrast, hornwort chloroplasts can contract and expand in response to light intensity (Burr, 1969 Li et al., 2014 ) whether this is mediated by neochrome awaits future studies.


Evolutionary History of Liverworts

Like all terrestrial plants, vascular and non-vascular, liverworts appear to have their beginnings in the Ordovician period, the second of six Paleozoic Era periods. Nearly 485 million years ago, the Cambrian period came to a close, as the Ordovician opened. At this time, shallow seas covered much of a landmass known as Gondwana, a continent composed of modern Africa, South America, India, and Antarctica. The shallow sea supposedly allowed the development of the first non-vascular plants, including descendants of liverwort.

The emergence of the embryophytes, or land plants, greatly changed the atmosphere of the early world. The atmosphere was composed heavily of carbon dioxide, and contained little oxygen. As plants like ancient liverworts began to emerge, they consumed the carbon dioxide and released oxygen. This drastic changing of global chemistry would later lead to climate change and massive extinction events. Unlike liverwort, vascular plants had a distinct advantage in transporting and holding water. However, in the 485 million years since the emergence of land plants, both types have colonized nearly every terrestrial space. Liverworts and other non-vascular plants can be found in deserts, and in cold northern latitudes as well.

Liverworts, once thought to be firmly related to the ferns, have more recently been given their own subdivision. The ferns show an opposing alternation of generations. Unlike liverworts, they show a dominate sporophyte. It is now thought that ferns are more closely related to gymnosperms (conifers) and flowering plants. Liverworts, therefore, represent an ancient and mostly unchanged division of some of the first terrestrial organisms to ever come out of the water. The argument of whether to include the liverworts within the Bryophyte (moss) grouping is an ongoing debate, but recent classifications have kept them in their own division.

1. Which of the following structures produces gametes within liverworts?
A. Spore
B. Gametophyte
C. Sporophyte

2. Why are the liverworts considered closely related to moss?
A. They aren’t closely related
B. They are both plants
C. They are both non-vascular and exhibit an alternation of generations

3. Which of the following most accurately describes the liverwort life cycle?
A. Alternation of Generations with Sporophyte dominance
B. Sexual reproduction alone
C. Asexual reproduction and Sexual reproduction through alternating generations, featuring a dominant gametophyte