Week 5: Chapters 25 & 26

what is the importance of Archaeplastida?

critical role in agriculture, transformers of the atmosphere, terraformers (alters earth’s surface), serve as a habitat for organisms

what are the functions of archaeplastida in the ecosystem?

major primary producers, key role in the carbon cycle, loss of plants/trees (increased CO2 in the atmosphere), evapotranspiration by plants is important in climate regulation

what is evapotranspiration?

water molecules stick to each other, forming a chain that can flow up the plant

what is ethnobotany?

the study of regional plants and their usage in local cultures

what are the five major intervals in the history of plants?

origin of land plants, silurian-devonian explosion, carboniferous period, diversification of gymnosperms, and diversification of angiosperms

what are land plants NOT?

protists

what are charophytes?

a group of green algae that have a lot of similar characteristics to land plants

what are the two major groups of green algae?

chlorophytes and charophytes

how are green algae similar to plants?

they both contain chlorophyll A & B, carotenoids, starch for storage and cellulose in cell walls

what do charophytes and land plants have in common?

cell plate division along phragmoplasts, possess plasmodesmata, apical growth, ~420 million years old

what are phycoplasts?

microtubule structures in chlorophytes that aid in the organization of cell wall (run perpendicular to the spindle or parallel to the cell wall)

what are phragmoplasts?

an assembly of microtubules and other associated molecules that guide the formation of the cell plate & help deliver vesicles containing cell wall components (run parallel to the spindle or perpendicular to the cell plate)

what are plasmodesmata?

narrow channels connecting the plant cells

characteristics of non-vascular plants

first embryophytes, still need water (swimming gametes, no vascular tissue), gametophyte is the dominant stage, three divisions are marchantiophyta (liverworts), bryophyta (true mosses), anthoceraphyta (hornworts)

characteristics of vascular seedless plants

paraphyletic group, possess lignin, possess vascular tissues (xylem & phloem), flagellated sperm, sporophyte dominant

major groups are lycophytes and monilophytes

characteristics of gymnosperms (spermatophytes)

possess “naked seeds” - ovule exposed on scale at pollination, five extant divisions containing 700 species (pinophyta, cupressophyta, cycadophyta, gnetophyta, ginkgophyta), no flowers or fruit

characteristics of angiosperms

about 250,000 species, major modifications include modified pollen, ovary, and flowers (co-evolution between plants and animals)

angiosperm lineages

basal angiosperms (amborella, water lilies, magnoliids, star anise), monocots (grasses, lilies, orchids, palms, bamboo), dicots (200,000+ species)

what are some major plant adaptations for terrestrial life?

protection from desiccation (water loss), UV protection, vertical growth, vascular tissue, reproductive adaptations

what is the role of the cuticle in preventing water loss?

it is a waxy layer that prevents water loss from stems and leaves

what is the role of the stoma (stomata) in preventing water loss?

they have pores that allow gas exchange in photosynthetic tissues

how can plants reduce damage from UV rays?

they contain protective flavonoids and other pigments that are developed to prevent photodynamic damage from UV-B radiation

some plants produce antioxidants and have mechanisms to repair DNA damage

some have reduced surface area

what is lignin?

a complex polymer within the cell walls of xylem cells that is impermeable to water and provide strength and rigidity

what is the importance of vascular tissue for plants?

it is critical for providing water and nutrients and for supporting the stem (taller plants get more light)

what is the probable sequence of development for vascular tissue?

simple water-conducting cells → first vascular tissue → tracheids → vessel elements

what is sporopollenin?

complex organic molecules related to carotenoids that are resistant to chemical and biological degradation, found in spores of non-vascular and vascular components and in walls of pollen-seeded plants and within spores of certain charophytes

where did early land plants house gametes?

in gametangia

how are plant embryos protected?

multicellular embryos remain attached and are nourished by the parent plant (embryophyta)

what is the set up of plant life cycles?

all plants have alternation of generations with increasing complexity (diploid stage became the dominant portion, gametophytes became limited in size, sporophyte became nutritionally independent)

what is the important of heterospory?

protection for gametes, prevents self-fertilization, improves the spread of microspores, larger megaspores contain more nutrients

characteristics of seeds of seed plants

seed replaces spore for dispersal, spores are tough but small, seeds are multicellular and much more complex (protection and food supply provided)

characteristics of flowering plants

angiosperms (most diverse group of plants), major innovations (flowers, double fertilization, fruit)

what is pollination?

the transfer of pollen from the male structure to the female structure

how are gymnosperms pollinated?

by the wind

how are angiosperms pollinated?

by the wind and pollinators (insects, birds, and mammals, flowers facilitate directed pollination)

what is coevolution?

two or more interacting species have reciprocal evolutionary changes (plants and animals, plants and pollinators)

what is fruit?

a ripened ovary, important for seed dispersal, can be fleshy or dry, vary in dispersal methods (wind dispersed, “clinging” fruit, edible fruit)

what is angiosperm radiation?

adaptive radiation, 3 key adaptations are vessel elements, flowers, and fruit