Plant Diversity I: Mosses and ferns (non vascular and seedless vascular plants)

Question 1

What are five features of all plants that separate them from algae and reflect their adaptation to life on land?

Answer 1

1. Protection of gametes, zygotes, and spores: Plants have gametangia (archegonia in females, antheridia in males) and sporangia that protect reproductive cells.
   
   2. Multicellular, dependent embryos: Embryos develop within the parent plant for protection and nourishment (“embryophytes”).
   3. Protected spores: Spore walls contain sporopollenin to prevent drying.
   4. Apical meristems: Localized regions of growth allow plants to grow toward resources above and below ground.
   5. Alternation of generations: Plants have distinct multicellular haploid (gametophyte) and diploid (sporophyte) phases.

Question 2

What are the characteristics of nonvascular plants (e.g., mosses), and what is unique about their life cycle?

Answer 2

1. Characteristics:
   ○ No vascular tissue (rely on diffusion and osmosis).
   ○ Dominant gametophyte generation.
   ○ Require water for reproduction (sperm are flagellated).
2. Life cycle:

Flashcard Explanation: Moss Life Cycle
Side 1: Key Steps in the Moss Life Cycle
Question: How does the moss life cycle progress, including the roles of gametophytes and sporophytes?

Side 2: The Moss Life Cycle

1. Spores (Haploid, n):

Spores are produced in the sporangium (capsule) of the sporophyte via meiosis.
Spores are dispersed into the environment and germinate in suitable moist conditions.
2. Protonema Formation (Haploid, n):

Spores germinate into a filamentous structure called the protonema, which grows through mitosis.
Buds form on the protonema, developing into male and female gametophytes.
3. Gametophytes (Haploid, n):

The gametophyte is the dominant, leafy stage of the moss.
Male gametophytes produce sperm in structures called antheridia.
Female gametophytes produce eggs in structures called archegonia.
4. Fertilization (Diploid, 2n):

Water is required for sperm to swim to the egg inside the archegonium.
Sperm fertilizes the egg, forming a zygote (2n).
5. Sporophyte Development (Diploid, 2n):

The zygote develops into a sporophyte, which grows out of the female gametophyte and remains attached to it for nutrients.

Inside the sporangium, meiosis produces haploid (n) spores.
Spores are released and the cycle begins again.
Key Terms to Remember:

Haploid Gametophyte: Dominant stage; produces gametes (sperm and egg).
Diploid Sporophyte: Attached to the gametophyte; produces spores via meiosis.
Water-Dependent Fertilization: Sperm swim to egg in moist environments.
This alternation of generations allows mosses to reproduce and thrive in moist environments!

Question 3

What is the ecological importance of mosses

Answer 3

1. Colonize and stabilize bare soil and rocks.
   
   2. Retain nitrogen in the ecosystem.
   3. Peat mosses (Sphagnum) store large amounts of carbon and help regulate atmospheric CO₂ levels.
   4. Important in water retention and preventing soil erosion.

Question 4

What are the characteristics of seedless vascular plants (e.g., ferns)?

Answer 4

1. Vascular tissue: Xylem transports water; phloem transports sugars.
   
   2. Dominant sporophyte generation.
   3. True roots, stems, and leaves.
   4. Reproduce via spores, not seeds.
   5. Gametophyte phase is independent but small.

Question 5

What is the ecological importance of seedless vascular plants?

Answer 5

1. Contributed to the formation of the first forests (Devonian and Carboniferous periods).
   
   2. Removed CO₂ from the atmosphere, potentially contributing to global cooling.
2. Modern descendants play roles in nutrient cycling and as habitat for other organisms.