Rhodophyta: Red Algae

Question 1

Epiphyte

Answer 1

organism that grows on another organism

Question 2

Where are red algae found?

Answer 2

intertidal or subtidal. As deep as 120m.

Question 3

What climate is red algae are found?

Answer 3

Abundant in warm waters, but also in cool areas

Question 4

Red Algae Morphology

Answer 4

1. Unicellular
2. Filamentous (simple or branched)
3. Pseudoparenchymatous (most)
   
   • interwoven, tightly packed filaments
   • superficially resemble parenchyma but
     cell division does not occur in 3
     dimensions

Question 5

Red Algae Morphology: Cell Walls

Answer 5

1. Thick: Two Layers
2. INNER LAYER: rigid, thin, layer of
   cellulose
3. OUTER LAYER: thick mucilaginous
   layer
   
   • sulfated long chain polysaccharides
   • sulfated glucose polymers
   • Imparts slippery texture

Question 6

Mucilaginous Layer: Function?

Answer 6

1. UV protection
2. prevent dessication
3. prevent organism attaching

Question 7

Coralline red algae deposit …?

Answer 7

CaCO3 in outer cell wall layer

• branching species are upright, articulated
  (jointed) & flexible
• Encrusting species are prostrate (Growing flat)

Question 8

Coraline red algae deposit … / why?

Answer 8

1. CaCO3
2. cement and stabilize coral reefs
3. particularly common in high wave energy
   areas but found throughout a reef

Question 9

Red Algae dont have?

Answer 9

1. Flagella
2. No centrioles
3. Microtubule organizing centers are called
   polar rings
4. No grana! (thylakoids not stacked) in
   plastids

Question 10

Red Algae Plastids

Answer 10

1. Primary plastid
2. Chl a and NO Chl c !
3. Phycobilins
4. Phycobilisomes

Question 11

Centrioles

Answer 11

A centriole is a cylinder shaped cell structure found in most eukaryotic cells, though it is absent in higher plants and most fungi. The walls of each centriole are usually composed of nine triplets of microtubules (protein of the cytoskeleton).

Question 12

Phycobilins

Answer 12

1. chromophores (light-capturing molecules) found in cyanobacteria and in the primary plastids of red algae
2. Absorbs longer wavelengths of light (orange, yellow, green)
3. probably the reason some red algae can grow in very deep water

Question 13

Phycobilisomes

Answer 13

1. certain water-soluble proteins, known as phycobiliproteins. Phycobiliproteins then pass the light energy to chlorophylls for photosynthesis

Question 14

Primary Pit Connections

Answer 14

1. An area of greatly reduced thickness in the primary wall of a plant cell, often penetrated by plasmodesmata. Primary pit fields enable relatively easy transfer of materials between cells.
2. a pit connection is a hole in the septum between two algal cells, and is found only in the red algae
3. Primary pit connections developed in a small pore left during cell wall construction during cytokinesis
4. In some species gap is quickly filled by a protein core & cap layers

Question 15

Primary Pit Connections, Function?

Answer 15

1. Secondary pit connections can develop between adjacent filaments & provide physical support to the thallus
2. The pit connections are thought to function as structural reinforcement, and as avenues for cell-to-cell communication and/or symplastic transport in red algae.[citation needed] While the presence of the cap membrane could inhibit this transport between cells, the tubular plug cores may serve as a means of transport.
3. Important way pseudoparenchyma is built

Question 16

Red Algae Main Carbohydrate Reserve is? Where is it formed and stored?

Answer 16

1. Floridean Starch
   
   • glucose polymer
   • more highly branched than ‘true’ starch
     in green algae & land plants
2. Formed and stored in the cytoplasm in
   granules

Question 17

Rhodophyta: Polysiphonia

Answer 17

1. Polysiphonia are small filamentous
   plants that are epiphytic on rocks,
   concrete blocks, jetties & brown algae
2. Ring of filaments surround central
   filament to form stem-like structures
   (pseudoparenchyma)

Question 18

Polysiphonia - What is the life cycle

Answer 18

1. 3-phase life cycle
2. COMPLEX ALTERNATION OF
   GENERATION
3. One Haploid
   Two Diploid
4. Tetrasporophytes (2n)
   Gametophytes (n)
   Carposporophytes (2n)
   
   • is a heteromorphic attached to stage

Question 19

Polysiphonia: Gametophytes Male

Answer 19

1. Male gametophytes produce  
    spermatangia
    - dense clusters at apex of 'branch'
    - Each spermatangia produces one 
      spermatium

Question 20

Spermatangium

Answer 20

Spermatia are free-floating, non-motile, male gametes

Question 21

Polysiphonia: Gametophytes Female

Answer 21

1. Female gametophytes bear carpogonia
   
   • carpogonium is a single-celled female
     gamete

Question 22

Carpogonium

Answer 22

1. Trichogyne is an apical, tubular
   extension that attracts spermatia
2. Enlarged base contains nucleus

Question 23

Polysiphonia Fertilization Process

Answer 23

1. Spermatium fuses with trichogyne
2. spermatium nucleus migrates to base
   and fuses with the carpogonium nucleus
3. The zygote nucleus is copied and
   transferred to an auxiliary cell(s) - not
   released
   
   • Probably a way to increase spore
     production if fertilization rates are low
4. Diploid nuclei divide mitotically to form
   carposporophyte
   
   • carposporophyte remains attached
   • diploid carposporophyte + haploid
     pericarp = cystocarp
   • carposporangia -> 2n carpospores
     (mitosis)

Question 24

Diploid carpospores develop into……

Answer 24

free-living, multicellular tetrasporophytes

Question 25

Tetrasporophyte

Answer 25

1. 2n
2. free-living
3. Tetrasporangia
4. Meiosis -> 4 haploid tetraspores per cell

Question 26

Haploid tetraspores develop into…….

Answer 26

gasmetophytes

Question 27

Ancestral life cycle in red algae

Answer 27

1. 2-stage alternation of generation
2. Haploid gametophytes
3. After fertilization zygotes are released
   into the water and developed into diploid
   sporophytes that undergo meiosis and
   release haploid spore