[BOTLEC] M4 - Plant Diversity and Evolution

• Are algae plants?

  No, they are photosynthetic protists.
• What are the closest living relatives of plants?

  The closest living relatives of plants are the green algae known as charophytes, specifically the groups Zygnema & Coleochaete.
• What are the characteristics shared between plants and charophytes?

  1.) Rings of cellulose-synthesizing protists

  2.) Streptophytes

  3.) Formation of phragmoplast
• What is the phragmoplast?

  It is where the cell plate develops.
• What are streptophytes?

  They are the structure of flagellated sperm.
• What are the benefits that encouraged plants to move to land?

  Living on land provided benefits such as increased sunlight, more CO2, and access to nutrient-rich soil.
• What are the challenges that plants faced during their move to land?

  Water scarcity & lack of structural support for gravity
• How did plants address the challenge of water scarcity?

  They developed roots and later xylem & phloem in order to facilitate the transfer of H2O and nutrients.
• How did plants address the challenge of gravity?

  They developed leaves and stems which allowed them to support themselves.
• What is sporopollenin?

  It is a layer of durable polymer that prevents exposed zygotes in charophytes, plant spore walls and pollen from drying out.
• The boundary dividing plants and algae is still under debate. How do we differentiate plants from algae?

  Plants are embryophytes, they possess a sterile jacket of cells called an embryo.
• What is the earliest diverging group of algae?

  Red algae such as the seaweed served in restaurants.
• What are chlorophytes?

  They are green algae, charophytes are a part of this.
• What are the 5 key traits unique to most plants?

  1.) Alternation of generations

  2.) Multicellular, dependent embryos

  3.) Walled spores produced in sporangia

  4.) Multicellular gametangia

  5.) Apical meristems
• What is alternation of generations?

  These are life cycles that include both multicellular haploid (gametophytes) and diploid (sporophytes) organisms.
• What is the meaning of multicellular dependent embryos?

  Embryos rely on parent plant for protection and nutrition.
• What is the meaning of walled spores produced in sporangia?

  Sporopollenin found in sporangia strengthens spore walls.
• What are multicellular gametangia?

  Plant gametes are produced in archegonia (female) and antheridia (male) gametangia.
• What are apical meristems?

   Specialized root and shoot growths allow plants to obtain essential nutrients both above and below ground.
• What are the other key traits of plants?

  Cuticle - to prevent dehydration

  Stomata - gas exchange

  Mycorrhizae associations w/ fungi - provides plants with extra nutrients
• What are the two main classes of plants?

  Nonvascular Plants (Bryophytes) and Vascular Plants
• What are the phyla under Bryophytes? Give their common names as well


  Hepatophyta (Liverworts), Bryophyta (Mosses), Anthocerophyta (Hornworts)
• What are the 3 subclasses of vascular plants?

  Seedless vascular plants, Gymnosperms (non-flowering seed plants), Angiosperms (Flowering plants)
• What are the phyla under seedless vascular plants? Give their common names.

  Lycophyta (Lycophytes - Club Mosses) & Monilophyta (Monilophytes - Ferns )
• What are the phyla under Gymnosperms? Give their common names.

  Ginkgophyta (Ginkgo), Cycadophyta (Cycads), Gentophyta (Gnetophytes), Coniferophyta (Conifers)
• What is the phyla under Angiosperms? Give its common name.

  Anthophyta (Flowering plants)
• Nonvascular plants lack vascular tissues, what do they have to replace them?

  Hydroids and testoids.
• Which lineages are the earliest to diverge from the common ancestor of land plants?

  Hepatophyta, Bryophyta, and Anthocerophyta
• What do you call organisms that are grouped based on key biological features?

  A grade.
• True or False: Seedless vascular plants form clades.

  False. They can be divided into clades but do not form a clade themselves.
• What does thalloid mean?

  It describes a plant body that is not separated into roots, leaves and stems.
• Why are the organisms in Phylum Hepatophyta called liverworts?

  Thalloid liverworts were thought to help treat liver diseases.
• Describe the characteristics of Phylum Bryophyta (Mosses).

  They mainly consist of green gametophytes and elongated sporophytes that turn tan when ready to release spores.
• Describe the characteristics of Phylum Anthocerophyta (Hornworts)

  Hornwort sporophytes lack seta and only have one sporangium that splits open starting at the tip of the “horn”. Their symbiotic relationship with nitrogen-fixing bacteria allow them to quickly colonize moist soil.
• True or False: In all bryophytes, sporophyte and gametophytes are co-dominant.

  False. Gametophytes are larger and longer-living than sporophytes.
• What is a bryophyte gametophyte made of?

  It consists of a protonema and 1 or more gamete-producing gametophores.
• What is a protonema?

  It is a green, branched, single-cell-thick structure that increases the surface area for water absorption.
• How are gametophores formed?

  They are formed when protonemata grow "buds" with apical meristems.
• Why aren't mosses tall in height like other plants?

  They can only form moss carpets because their lack of vascular tissues constrains the height of gametophytes.
• What are rhizoids and how do they help bryophytes?

  They are filaments of cells and help anchor the bryophytes' gametophytes to substrate. They are not composed of tissues and lack specialized conducting cells.