Chapter 29 Flashcards
(43 cards)
Multiple innovations have increased the tolerance of land plants to what?
low water availability
The cuticle and stomata do what?
protects land plants from water loss
Vascularization separates the mosses from the rest of the plants (True/False)
True
Origin of land plants
Green algae and land plants (collectively referred to as green plants) share a common ancestor a little over 1 BYA.
a single species of freshwater green algae rise to the entire terrestrial plant lineage. exactly what this ancestral alga was is still a mystery, but close relatives, members of the charophytes, exist in freshwater lakes today.
all plants perform photosynthesis, but all photosynthetic organisms are not plants.
What issues did plants that came on land have to overcome?
water loss
protection from the harmful effects of the sun (UV rays)
How did fungi help plants colonize land?
they made nutrients available to plants
Green algae splits into what two clades?
Chlorophytes – Never made it to land.
Charophytes – Sister clade to all land plants.
what are Streptophytes?
charophytes and all land plants
All land plants…?
Have multicellular haploid and diploid stages
Trend toward more diploid embryo protection.
Trend toward smaller haploid stage.
What were some of the plant’s adaptations to terrestrial life?
Protection from desiccation
- Waxy cuticle and stomata.
Moving water using tracheids
- Tracheophytes have tracheids.
- Xylem and phloem to conduct water and food.
Dealing with UV radiation caused mutations
- Shift to a dominant diploid generation
- Haplodiplontic life cycle.
- Multicellular haploid and diploid life stages.
- Humans are diplontic.
Haplodiplontic Life Cycle
Multicellular diploid stage – sporophyte
- Produces haploid spores by meiosis.
- Diploid spore mother cells (sporocytes) undergo meiosis in sporangia.
- Produce 4 haploid spores.
- First cells of gametophyte generation.
Multicellular haploid stage – gametophyte
- Spores divide by mitosis.
- Produces gametes by mitosis.
- Gametes fuse to form diploid zygote.
- First cell of next sporophyte generation.
literally just study slide 13
Are all land plants haplodiplointic?
yes, but the sizes of the generations vary
Moss generation sizes?
Large gametophyte.
Small, dependent sporophyte.
Angiosperm generation sizes?
Small, dependent gametophyte.
Large sporophyte
What produces the gamete in plants?
the gametophyte
Bryophytes
Closest living descendants of the first land plants
3 clades - liverworts, mosses and hornworts
Called nontracheophytes
- They lack tracheids.
- Do have other conducting cells.
Mycorrhizal associations important in enhancing water uptake
- Symbiotic relationship between fungi and plants
Simple, but highly adapted to diverse terrestrial environments. Approximately 16,000 species in 3 clades
Gametophyte – conspicuous and photosynthetic
- Sporophytes – small and dependent.
Require water for sexual reproduction so they are typically found in damp areas
Liverworts (phylum Hepaticophyta)
flattened gametophytes with liverlike lobes (Form gametangia in umbrella-shaped structures)
the gametophytes have single celled rhizoids (they function like roots in terms of aiding with absorption, but they are not organs since they are unicellular)
can reproduce asexually
80% look like mosses the other 20% look like lobed liver thingies
some of them have air chambers that have rows of photosynthetic cells, each chambers have a pore at the top facilitating gas exchange, but unlike the stomata the pores of these chambers are always open and cannot be closed.
Mosses (phylum Bryophyta)
Gametophytes consist of small, leaflike structures around a stemlike axis
No true leaves – no vascular tissue
No roots, they have rhizoids that absorb water
have stomata on the capsule portion of the sporophyte
water is passively carried up a strand of specialized cells in the center of a moss gametophyte, some of them have special food conducting cells that surround the water conducting cells
(Multicellular gametangia)
Archegonia – Female gametangia.
Antheridia – Male gametangia.
- Flagellated sperm must swim in water.
study slide 20 for the life cycle
Hornworts (phylum Anthocerotophyta)
Origin is puzzling – no fossils until Cretaceous
Sporophyte is photosynthetic
Sporophyte embedded in gametophyte tissue
Cells have a single large chloroplast
typically live in a symbiotic relationship with cyanobacteria which provide them with nitrogen
Tracheophyte Plants
These are the first plants to have vascularization. (tubes in them)
first appeared about 410 MYA
dominant sporophyte generation
Cooksonia, the first vascular land plant
- Appeared about 420 MYA.
- no competition
- Phylum Rhyniophyta.
- has a vascular system even though no roots and leaves
Only a few centimeters tall
- No roots or leaves.
- Homosporous – only 1 type of spore.
Vascular tissues
Xylem
- Conducts water and dissolved minerals upward from the roots.
Phloem
- Conducts sucrose and hormones throughout the plant.
Enable enhanced height and size in the tracheophytes
Develops in sporophyte but not gametophyte
Cuticle (waxy substance) and stomata (opens and closes but it has to be careful because as it takes in carbon dioxide it releases water) also found in land plants
Tracheophytes
Vascular plants include seven extant phyla grouped in three clades
- Lycophytes (club mosses) (THEY ARE NOT MOSSES ITS A TYPE OF VASCULAR PLANT)
- Pterophytes (ferns, whisk ferns, and horsetails)
- Seed plants
Gametophyte has been reduced in size relative to the sporophyte during the evolution of tracheophytes
Similar reduction in multicellular gametangia has occurred as well
Stems, Roots, and Leaves
Stems (evolved prior to roots)
- Early fossils reveal stems but no roots or leaves.
- Lack of roots limited early tracheophytes.
Roots (evolved at least twice)
- Provide transport and support.
- absorb water
- Lycophytes diverged before true roots appeared.
- true roots are only found in tracheophytes
Leaves (evolved more than once)
- Increase surface area for photosynthesis.
- Evolved twice.
- Euphylls (true leaves) found in ferns and seed plants. (true leaves have a vascular system)
- Lycophylls found in seed plants. (Wolf leaves have one big vein)
Seeds
Highly resistant and protect the plant embryo
Contain food supply for young plant.
Lycophytes and pterophytes do not have seeds.
