PHYLUM CHLOROPHYTA

• comprise the green algae and land plants

• common synapomorphies

  • cell walls containing cellulose

  • chloroplasts containing chlorophylls a and b

  • food stored in the form of starch

  • typically have mitochondria with flat cristae

Kingdom Viridiplantae

what are the two lineage subgroups of Viridiplantae

two lineage subgroups

• Chlorophyta (cholorobiont clade)

• Streptophyta (Streptobiont clade)

  • Charophyta

  • Embryophyta

what are the differences between the Chlorobionts and Streptibionts in terms of mitosis

chlorobionts: generally with centrioles (centric) and closed (the nuclear envelope remains intact)

streptobionts: no centrioles (acentric) and open (the nuclear envelope breaks down)

what are the differences between the Chlorobionts and Streptibionts in terms of cytokinesis

Chlorobionts: Phycoplast

Streptobionts: Phragmoplast

what are the differences between the Chlorobionts and Streptibionts in terms of flagellar insertion

Chlorobionts: at the apex of motile cells

Streptobionts: subapical on motile cells

set of microtubules arranged parallel to the plane of cell division

Phycoplast

microtubules arranged perpendicular to the plant of division

Phragmoplasts: (charophyceae)

nuclear envelope remains intact (Ulvophyceans)

Closed mitosis

nuclear envelope breaks down early in mitosis (Charophyceans and in higher plants)

open mitosis

• includes most of the green algae

• may grow as colonies, unicells, filaments, and larger seaweeds

• occur in almost all types of water and often are dominants in freshwater environments

• some are terrestrial species

Phylum Chlorophyta

Ulva (sea lettuce)

describe the sexual and asexual reproduction of ulva (sea lettuce)

• flat expanded sheet

• asexual reproduction

  • biflagellated zoospores

• sexual reproduction

  • isogamous

  • alternation of diploid and haploid isomorphic generation

Chlamydomonas (sea cockroach)

• motile unicellular algae; oval in shape

• cell wall of glycoprotein and non cellulosic polysaccharides

• with prominent cup or bowl shaped chlroplast

• pyrenoid contain starch sheath

• 2 anterior flagella (whiplash; 9+2 arrangment)

Chlamydomonas (sea cockroach)

• composed of numerous flagellate cells similar to Chlamydomonas, up to 50,000 in total

  • haploid adult cells

volvox

• cells are embedded in the surface of a hollow sphere or coenobium containing an extracellular matrix made of gelatinous glycoprotein

• occurs by repeated mitotic division of one of the cells (zooids) to form a hollow sphere of cells, with flagellated ends of the cells inside

• The sphere then turns itself inside out to form a daughter colony similar to the parent colony

• Several daughter colonies are formed inside the parent colony before they escape by rupture of the parent

Volvox: asexual reproduction

Describe the sexual reproduction of volvox

• some of zooids differentiate into macro gametes or microgametes

• Macrogametes are fewer and larger and are loaded with food for nourishment of the young organisms

• microgametes, by repeated division, form flagellated sperm that leave the mother organisms and swim about to find a mature ovum

• After fertilization, the zygote secretes a hard, spiny, protective shell around itself

• When released by the breaking up of a parent, a zygote remains dormant during the winter

• Within its shell the zygote undergoes repeated division, producing a small organisms that breaks out in the spring

Composed of 8, 16, or sometimes 32 cells, held together at their bases surrounded by mucilage

Pandorina

Composed of 16 or 32 spherical biflagellate cells loosely aggregated into a globular shape within a mucilage envelope

Eudorina

• members are organized as coenobium colonies and occur in quite or slow moving waters

Pediastrum

What is the family of pediastrum?

Family Hydrodictyaceae

• free floating with two to 128 polygonal cells

• Cells are arranged in a stelate plate, one cell in thickness

• Each cell has a single parietal plate like chloroplant

Pediastrum

What is the life cycle of Pediastrum

Haplontic life cycle

Describe the asexual reproduction of Pediastrum

• a parent colony produces a number of biflagellate zoospores kept within a vesicle

• Aggregation and arrangement of motile spherical spores transform into “butterfly-shaped cells”

• The cells organize into a new complete daughter colony drifting and floating along water current

Describe the sexual reproduction of Pediastrum

• the cell forms two bi-flagellate gametes (isogamy)

• The gametes fuse into a zygote and develop further through the asexual lifecycle as described above

Oedogonium

• filamentous; cells uninucleate

• Sexual reproduction: oogamous; with flagellated zoospores

Oedogonium

Oedogonium is an unbranded filaments with only certain cells that can divide. Those that do divide have stacks of old cell walls called?

Apical caps (at the cell apex)