What is the function of gemmae cups? What is the difference between sexual and asexual reproduction?

Would you expect the cells in gemmae cups to divide by mitosis or meiosis? What is the function of this structure? What is the ploidy level of gemmae?

 

A single thallusCross section of

thallus with rhizoids at 100X (stained)

Air pore on upper surface of thallus at 400X (stained)

Is this stage in the development of a liverwort a gametophyte or a sporophyte? Do the cells in this thallus divide by mitosis or meiosis as it grows? What is the ploidy level (haploid or diploid) of the photosynthetic tissues seen here?

What is the function of rhizoids? How many cells thick is a thallus?

What is the function of this pore? A thallus grows from a single cell. What is the name of that cell?

 

AntheridiophoresLongitudinal section of antheridiophore at 35X

(stained)

Longitudinal section of several antheridia at 100X (stained)

If a liverwort has only antheridiophores, is it a male or female? Is this the gametophyte or a sporophyte stage of the life cycle?

What is the name of this structure? What is the function of this structure?  What type of gamete is produced by this structure?

Do cells within the antheridia divide by mitosis or meiosis? Are antheridia gametangia? 

Archegoniophores Archegoniphores

Are archegoniophores male or female structures?  Is this organism a gametophyte or a sporophyte?

What is produced inside the archegonia?

Longitudinal section of a stained  archegoniophore at 35X (stained)

Longitudinal section of archegoniophore at 100X (stained)

What is the function of this structure? What type of gamete is produced by this structure?

What is the name of the structures hanging down from the undersurface of the cap? What are the dark structures in the chambers below the cap? What is their ploidy level?

Longitudinal section of archegonia at 400X showing eggs and neck canals (stained)

Sporophytes developing from fertilized eggs in archegonia  at

400X (stained)

How are sperm transferred from the male to the female gametophyte? Describe how  fertilization occurs in liverworts. Where does it occur? When fertilization occurs here, what develops? Are archegonia gametangia? 

Is the sporophyte stage dependent on or independent of the gametophyte stage in liverworts? What does the sporophyte stage produce? What is the function of this structure?

Self quiz on life cycle stages

What is dominant generation in the life cycle of this plant? Which one is the female and which the male gametophyte? What is ploidy level of this structure?

Point to the thalli, gemmae cups, antheridiophores, and archegoniophores in the above photo.

General and Comparative Essay Questions

What event starts the sporophyte stage in the life cycle of a liverwort? Where does it occur?

What event starts the gametophyte stage in the life cycle of a liverwort? Where does it occur?

If you wanted to study meiosis in liverworts where would you look for cells that might be dividing by meiosis?

Write a short paragraph that explains alternation of generations in liverworts. A count of the number of chromosomes in a cell from the thallus of a liverwort

indicated it had 22 chromosomes. How many would you expect to find in a sperm of a liverwort? In a sporophyte? In a spore?

Phylum (=Division) Bryophyta (Mosses)

In the above photos, identify which are the gametophyte and sporophyte stages. List two adaptations to the terrestrial environment  that this plant shares with all other plants? List two adaptations lacking in this plant that are found in other plants. To what phylum does this organism belong? Which of the stages of the plant's life cycle is dominant in this organism? Does this plant have true vascular tissues?

Young Gametophyte Stages

Early protonema Later protonema Protonema with gametophyte

bud (stained)

Is this the start of the sporophyte or the gametophyte stage of the life cycle?  Are protonemal cells haploid or diploid? Protonema grow from what structure in the life cycle?

What is the ploidy level of this structure? What type of cell division would you expect to find in a growing protonema?

Are gametophyte cells haploid or diploid?

 

Mature Gametophyte Stages

What types of gametes are produced in this structure?  What is the function of the neck canal seen in central archegonium? How does fertilization occur in mosses?  This structure produces gametes through the process of: A. meiosis; B. mitosis; C. diffusion.  Which of the following best describes the reproductive organ in the slide? A. Ovary, B. Microsporangia, C. Archegonia, D. Antheridia. In this slide, would you expect to see eggs or spores and why?

Archegonia and paraphyses at 100X (stained)

Antheridium (stained)

Longitudinal section of antheridium at 35X (stained)

Moss sperm (small flagellated cells)

What type of cells are produced by the antheridium? Are these cells produced by meiosis or mitosis? In mosses, the sperms develop by (A) mitosis;

Point to an antheridium.  What is the ploidy level of cells in the antheridium? What type of gamete is produced by this structure? Which of the following best describes the reproductive organ in the slide? A. Ovary, B. Microsporangia, C. Archegonia, D. Antheridia The cells stained red in this antheridia/archegonia slide were produced by ___________ (mitosis or meiosis).

What is the ploidy level of sperm?

Describe the role of water in fertilization in the bryophytes. What is the name and  function of this structure? 

(B) meiosis; (C) fertilization; (D) double fertilization.

 Mature Sporophyte Stages

Sporophyte development from Gametophyte

Immature and mature Capsule

Sporophyte capsules

Is the sporophyte nutritionally dependent or independent of the gametophyte? Can you grow a moss sporophyte alone in the soil? Why? Is sporophyte tissue diploid or haploid? Why? Are sporophyte cells produced by mitosis or meiosis? What phase of the life cycle is indicated?

Spore are produced inside these capsules by what type of nuclear division?

 

Capsules Capsule l.s. Capsule l.s. at 35X

(stained)

What is the name of the "lid" on the capsule? What is the function of the peristome?

What does this structure contain?

WHat is the ploidy level of the chamber wall tissues? Of the chambers contents?  

What do capsules produce?  Why are these products important in the life cycle?  Are these products the result of meiosis or mitosis? What is the ploidy level of this brown cells in the chambers?

 

Cross section of moss gametophyte stem (stained) Do you see any evidence of vascular tissue in the cross section?

General and Comparative Questions

Describe the alternation of generations that occurs in the life cycle of a moss. How do spores differ from seeds? What adaptations do mosses have to a terrestrial way of life? What event starts the sporophyte stage of the life cycle of mosses?  Where does it occur? What event starts the gametophyte stage of the life cycle of mosses?  Where does it occur? Which stage in the life cycle of a moss is haploid? Sporophyte? Gametophyte? Describe the gametangia in mosses. Explain why you would not expect to find only male moss gametophytes growing in one place in the wild and female gametophytes in another, quite far from the males. A species of moss has a diploid number of chromosomes equal to 28. How many chromosomes will be found in an egg? Zygote? Spore? Photosynthetic "leaf?" Protonema? If you were to examine mosses from around the world, none would be more than a foot tall (if that). How can you explain this? Is there some limitation built into the moss body plan? Mosses tend to thrive in moist damp places and are rarely found in dry places in direct sunlight. How do you explain this?