Biology 1A Oct 20, 1998
Lecture 14 - Bryophytes
Page Contents :
Overview of Lecture:
Life cycles in early plants.
Plants evolved from Charophycean green algae.
Evolution of the plant life cycle.
Typical moss life cycle.
Bryophytes have a dominant gametophyte and a dependent sporophyte.
Bryophyte ecology and morphology.
Liverworts, Hornworts, and Mosses.
Overview of Lab:
(A bullet indicates a handout.)
I. Life Cycles in Early Plants.
A. Plants evolved from Charophycean green algae.
II. Bryophyte Ecology and Morphology.
1. Introduction to the Charophyceae
B. Evolution of the plant life cycle
a. freshwater group of green algae
2. Traits green algae share with plants
b. Spirogyra, desmids, stomeworts, Coleochaete
a. chlorophyll a & b
3. Traits the Charophyceae share with plants
a. asymmetric sperm cell flagellae
b. retain zygote on the gametophyte
d. pattern of cell wall formation
1. Charophyceae have a haploid life cycles, while plants have a heteromorphic alternation of generations.
C. Typical moss life cycle.
2. Multicelular gametangia evolved in plants.
3. The embryo develops within the archegonium.
D. Bryophytes have a dominant gametophyte and a dependent sporophyte.
1. The meaning of "dominance"
2. The gametophyte is dominant in bryophytes
3. The sporophyte is dependent in bryophytes
a. The sporophyte develops attached to the gametophyte
4. The term "bryophyte" refers to group with this kind of life cycle.
b. Never "leaves home"; needs nutrients through foot (transfer tissue)
5. Contrast with vascular plants (in other plants, SPT dominant)
A. Where do bryophytes grow?
III. Liverworts, Hornworts, and Mosses.
1. rainforest, tundra, desert, forests
B. How are they important?
2. streams, trees, rocks, floating
1. nutrient cycling
C. Bryophyte tissues are not very complex
2. soil crusts - reducing erosion
3. insulating the permafrost
1. Characteristics like early land plants, though some now very complicated
2. Usually whole gametophyte is photosynthetic
3. Bryophytes have no root system, but rely on rhizoids
5. Thalloid or leafy
6. Asexual reproduction often important (gemmae)
A. Liverworts (Hepaticophyta)
B. Hornworts (Anthocerotophyta)
a. about 6000+ species
b. only group of plants to completely lack stomata
c. basal group of land plants, probably most like plant ancestors
a. thalloid or leafy
b. dorsiventral & usually prostrate
c. some have conducting tissue
d. oil bodies
a. usually small, simple, and short-lived
b. elaters - hygroscopic cells
C. Mosses (Bryophyta)
a. thalloid, rhizoids
b. single large chloroplast per cell
a. horn-shaped (hence name)
c. basal meristem
d. mostly sporangium, columella, splits to spread spores
a. about 10,000+ species
b. third most diverse group after flowers and ferns
c. hydroids and leptoids -- evidence of relations to vascular plants
d. mosses that aren't mosses: reindeer moss, Spanish moss, club moss
b. leafy -- leaves one or two cells thick, usually a midrib
c. Question: Are there stomata in the leaves of mosses? Why or why not?
d. radial, erect or prostrate
a. calyptra - part of old GPT
4. Sphagnum - peat moss
b. operculum - cap
c. peristome (hygroscopic) - releases spores when dry
a. highly unusual - floating aquatic moss
b. the most economically important bryophyte
antheridium embryophyte operculum
archegonium foot peristome
bryophyte gametangium protonemata
calyptra gemmae rhizoid
Charophyceae hydroids sporangium
Coleochaete hygroscopic spore
columella leafy sporopollenin
dioicous leptoids sterile jacket
dominance monoicous thalloid
dorsiventral neck canal transfer tissue
elaters oil bodies vascular plant
- What are the Chrophyceae? What characteristics of the Charophyceae make them the likely ancestors of land plants?
- How is the life cycle of bryophytes different from that of the Charophyceae?
- How are the gametangia of land plants different from those in algae?
- Diagram and explain the basic structure of both an antheridium and an archegonium. What features of these structures show an adaptation for a terrestrial environment?
- What is the difference between a monoicous gametophyte and a dioicous one?
- Why are land plants also called embryophytes? How is this an adaptation for a terrestrial existence?
- What features of the bryophyte spore make it ideal as a unit of dispersal?
- How do the gametes of bryophytes locate each other? What must be present for them to get together?
- Diagram and label the major structures of a typical bryophyte sporophyte. Which structures are haploid? Which are diploid?
- How is the life cycle of the bryophytes different from other plants?
- Which generation is dominant in bryophytes? What does it mean that one generation is "dominant" over the other?
- What is the function of transfer tissue, and where is it found?
- Where do bryophytes grow? How are they important?
- Do bryophytes have roots? How do they obtain their water and nutrients?
- How are leafy and thalloid bryophytes different from each other? Which bryophytes can be thalloid? Which may be leafy?
- What are gemmae and what is their function?
- How are liverworts different from all other plants? Name one feature of other plants that liverworts lack. Name two found only in liverworts.
- How is the sporophyte of a hornwort different from other sporophytes? (There are several ways)
- How are moss leaves different from leaves in vascular plants? (There are several ways)
- What are hydroids and leptoids? In which bryophytes are they found?
- What are protonemata?
- How is the peristome of a moss capsule similar to elaters in a liverworts? How are they different?
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