Topic 13: Evolution of Land Plants Flashcards

• since colonizing land, plants have diversified into roughly how many living species

  250,000
• land plants are part of what super group

  archaeplastida
• how did land plants evolve

  descendants of protists that underwent primary endosymbiosis of cyanobacteria to form chloroplasts
• many characteristics of land plants also appear in a variety of what

  protist clades, mostly algae
• what characteristics do land plants share with algae (5)

  -multicellular, photosynthetic, photoautotrophic eukaryotes-cell walls made of cellulose-have chloroplasts with chlorophyll a and b-store photosynthetic sugars like starch in the plastids-alteration of generations in plants
• what was used to identify charophytes as the closest living relatives of land plants

  comparisons of nuclear and chloroplast DNA
• what is the closest living relative to land plants

  Zygnema charophyte
• land plants are not descended from what

  charophytes, but they share a common ancestor
• are charophytes uni or multi cellular

  multicellular
• many charophytes inhibit shallow freshwaters subject to what

  occasional drying
• what are three key traits land plants share only with charophytes

  -rings of cellulose-synthesizing proteins anchored in the plasma membrane-homologous structure of flagellated sperm-phragmoplast formation during cell division
• what do cellulose synthesizing proteins do

  -synthesize cellulose microfibrils that provide structural rigidity to the cell wall
• cellulose deposition in cell walls is very similar in what to organisms


  charophytes and land plants
• the sperm of basal land plants resemble the sperm of what

  charophytes
• not all plant sperm is what

  flagellated
• phragmoplast formatin durng cell division helps construct what

  cell wall plate that fuses with the original cell wall, separating the two daughter cells
• what are plants defined as

  embryophytes, plants with embryos.
• Movement onto land by charophyte ancestors provided what (5)


  -Decreased competition (spacious habitats). −Increased photosynthesis (bright sunlight, unfiltered by water and phytoplankton algae). −An atmosphere with plentiful CO 2. −Soils rich in mineral nutrients. −At first, relatively few herbivores or pathogens.
• Living on land presented what challenges (2)

  −Scarcity of water (desiccation). -The lack of structural support to support upright growth.
• what permitted colonization of land by early land plants

  accumulation of traits that facilitated survival on land
• what adaptation enabled colonization of land plants (4)

  -sporopollenin-adaptation for water conservation-lignified vascular tissue for internal transport-functional compartmentalization in terrestrial plants
• what do charophyte zygotes secrete

  Durable polymer called sporopollenin in the cell wall
• what are sporopollenins

  complex, chemically inert biological polymers, which are resistant to degradation by enzymes and inorganic chemicals.
• what is the purpose of sporopollenin in charophyte zygotes

  protects charophyte zygotes from desiccation, UV light, and physical stresses.
• where do many charophytes live

  in ephemeral ponds that dry up
• other than charophytes, where else is sporopollenin found

  in the cell walls of spores and pollen of plants
• how did land plants adapt to conserve water (2)

  -waxy cuticle covering the epidermis: waterproofing, protection from microbial attack-stomata: pores in the epidermis of leaves and other photosynthetic organs
• how did stomata

  -allow gas exchange between air and leaf interior-sites for water to exit via evaporation-stomata can close pores: minimize water loss in dry conditions
• how does lignified vascular tissue for internal transport assist land plants to adapt to terrain

  provides:-rigidity supporting vertical growth-water transport that allows plants to grow in dry environments
• What are xylem and phloem?

  Xylem: complex vascular tissue through which most of the water and minerals of a plant are conductedPhloem: food-conducting tissue in the stem (living cells)
• dead cell walls act as what in plants

  microscopic water pipes
• how did functional compartmentalization assist in the adaptation for plants to be on land (2)

  -search for water and minerals underground (roots)-search for light & gases aboveground (shoots)
• What is lignin?

  a complex organic polymer deposited in the cell walls of many plants, making them rigid and woody.
• what enables growth towards higher concentrations of resources.

  − Elongation and branching maximizes root and shoot exposure to environmental resources.
• what are the characteristics what separate land plants from charophytes (5)

  -alteration of generations-multicellular dependent embryos-walled spores produces in sporangia-multicellular gametangia-apical meristems
• the lifecycle of land plants alternates between what two multicellular generations

  -sporophyte-gametophyte
• what is a sporophyte

  the fusion of gametes (fertilization) gives rise to diploid sporophyte which produces haploid spores by meiosis
• what is the sporophyte specialized for

  dispersal
• what is the gametophyte specialized for

  fertilization
• what is a gametophyte

  haploid and produces haploid gametes by mitosis