Topic 9 Flashcards
What are the general characteristics of the plant kingdom?
land-dwelling (terrestrial), some have returned to aquatic (freshwater) habitats
eukaryotes
multicellular
photosynthetic (photoautotrophs)
cell walls made of cellulose
alternation of generations
What are the two main groups in the plant kingdom?
Non Vascular Plants (mosses)
Vascular Plants: seedless vascular plants (ferns), gymnosperms, angiosperms
What are the benefits of plants moving to land?
spacious
unfiltered sunlight
high levels of atmospheric CO2
rich source of mineral nutrients
relatively few herbivores and pathogens
What were the challenges for plants moving to land?
less water
need to resist gravity
reproduction
What are the synapomorphic features with charophytes?
- Rings of cellulose-synthesiezing proteins (make cellulose microfibrils of the cell wall, are linear in non-charophycean algae)
- Structure of the sperm resembles the sperm of charophytes (but only for those plants with flagellated sperm)
- Phragmoplast during cell division (microtubules, constructs cell plate between incipient cells, becomes new cell wall)
What were the evolutionary innovations that allowed plants to adapt to life on land?
sporopollenin
cuticle, pores
stomata
embryophytes
vascular tissue
roots
true leaves
How was sporopollenin an adaptation to life on land?
in charophytes: protects zygote from drying
in plants: walls of plant spores
resistant to drying and physical stresses
What were adaptations for water conservation for plants moving to land?
waxy cuticle on epidermis: waterproofing, protection from microbial attack
stomata: pores on the epidermis of leaves and other photosynthetic organs, allow gas exchange between air and leaf interior, sites for water to exit via evaporation, closed stomata minimize water loss
How were multicellular, dependent embryos an adaptation to life on land?
zygotes retained within tissues of the female parent
parent provides nutrients, embryo has specialized placental cells (transfer nutrients)
in contrast to most green algae, zygotes of land plants: begin development on the parent plant
the retention of the embryo was a key event in land plant evolution
How was lignified vascular tissue for internal support an adaptation to life on land?
contain lignin (a complex polymer), which strengthens
xylem cells carry water and minerals up from roots (dead wall act as microscopic water pipes)
phloem cells distribute organic products (living cells)
How was the compartmentalization of resources an adaptation to life on land?
most plants show structural specialization for searching for water and minerals underground (roots) and light and gases aboveground (shoots)
elongation and branching maximizes root and shoot exposure to environmental resources
What are apical meristems?
undifferentiated tissue from which new, differentiated cells arise: simple in non-vascular plants, more complex structures at tips of shoots and roots in vascular plants
cells produced by meristems differentiate into various tissues, including surface epidermis and internal tissues
How is alternation of generations an adaptation to life on land?
haploid (n) multicellular and diploid (2n) multicellular body forms alternate
What is adaptive radiation?
an adaptive radiation occurs when a single lineage produces a large number of descendant species that are adapted to a wide variety of habitats
angiosperms represent one of the greatest adaptive radiations in the history of life
What are bryophytes?
nonvascular plants
not a monophyletic group
What are the characteristics of bryophytes?
lack true vascular tissue: limits their size
most tissues only one or a few cells thick
haploid (1n) gametophytes are the most conspicuous, dominant phase of the life cycle (diploid sporophytes smaller, diploid present only part of the time)
often entire plants are either male or female (sperm swim through water film to fertilize eggs, must live in moist places, not yet full terrestrial)
What are the key concepts of how plants colonized land?
land plants evolved from green algae (specifically charophytes)
three innovations allow plants to colonize land (sporopollenin, multicellular, nourished embryo)
mosses and other nonvascular plants have life cycles dominated by gametophytes
ferns and other seedless vascular plants were the first plants to grow tall
What was the origin of vascular plants?
bryophytes probably earth’s only plants for first 100 million years
aglaophyton first plant to have sporophytes not continuously nutritionally dependent on gametophytes (a feature of vascular plants)
fossils of other simple plants from early Devonian show evidence of vascular tissue in the stem
later came leaves, and then roots
What are the characteristics of extant vascular plants?
Vascular Tissue (xylem: contains lignin, strengthening polymer, dead hollow cells act as water pipes. phloem: living cells, distribute nutrients, organic products) gave plants a competitive advantage, ability to resist gravity and grow taller
Complex multicellular roots: absorb nutrients, provide anchor
Complex multicellular leaves: photosynthetic organs
Sporophylls: modified leaves that bear sporangia (spore-producing organ)
Sporophyte dominant in life cycle: increased size, complexity and persistence, not continuously nutritionally dependent on gametophyte
What are the two phylums of seedless vascular plants?
Phylum Lycophyta (quillworts, club “mosses”, spike “mosses” (not really mosses!))
Phylum Pterophyta (ferns, horsetails, whisk ferns)
What are the characteristics of seedless vascular plants?
sporophyte: dominant form
gametophytes: tiny independent plants on or just below soil surface
flagellated sperm: must swim in a film of water to reach eggs (similar to bryophytes, seedless vascular plants most common in relatively damp habitats, still need water to reproduce)
What is Phylum Lycophyta?
microphylls (small leaves)
carboniferous period: lycophytes existed as small, herbaceous plants and as giant woody trees
giant lycophytes thrived in warm, moist swamps
became extinct when the climate became cooler and drier
smaller lycophytes survived and are represented by about 1,000 species today
What is the Phylum Pterophyta?
whisk ferns once considered “living fossil” (no roots or leaves)
horsetails (in carboniferous, horsetails grew to 15 m, often found in marshy habitats and along streams and sandy roadways)
What are true ferns?
megaphylls: large leaves with extensively branched vascular system, some tree-size
most successful of extant seedless vascular plants
produce clusters of sporangia called sori on undersides of leaves
sporangia often have spring-like devices that catapult spores from the parent plant (spores can also be carried by the wind)
What are the advantages of seeds?
seeds provide some evolutionary advantages over spores
they may remain dominant for days to years, until conditions are favorable for germination
seeds have a supply of stored food
they may be transported long distances by wind or animals
What are the key concepts of seedless vascular plants?
ferns and other seedless vascular plants were the first plants to grow tall (had well developed roots and leaves)
in contrast to bryophytes, seedless vascular plants have life cycles dominated by free-living sporophytes
a change in environment at end of carboniferous reduced moisture leading to seed plants evolving
