ALGAE

Concepts/Ideas/Notes:

1. algae are classified based on color, food storage substances, and the composition of the cell wall

Definitions:

1. Algae – eukaryotic, plant-like, autotrophic, organisms
2. Pyrenoids – organelles that synthesizes and stores starch
3. Phytoplankton – photosynthetic microorganisms
4. Plankton – aquatic, unicellular algae
5. Unicellular Gametangia – single-celled gamete holders
6. Holdfast – “root” or basal part of a multicellular alga that attaches itself to a solid object
7. Stipe – supporting stalk of kelp
8. Blade – the broad, expanded part of a leaf; the lamina
9. Air Bladders – gas filled bladders on seaweed that allow the leaf blades to float
10. Phycobilins – accessory pigments that absorb violet, blue, and green light that penetrates deeper in the ocean.
11. Carageenan – a sticky, polysaccharide used in cosmetics.
12. Valves – silicon containing, highly ornamented half-walls of a diatom that fits together

a.       Centric Diatoms – have circular or triangular valves and are most abundant in marine waters

b.   Pennate Diatoms - have rectangular valves and are most abundant in freshwater ponds and lakes.  Some pinnate diatoms move about by secreting threads which attach to the water’s surface and contract allowing the organism to move.

12. Diatomaceous Earth – sediment layer made from the discarded silicon shells of diatoms
13. Sulcus – a flagella that fits into the vertical groove of a dinoflagellate
14. Girdle – flagella that fits into the horizontal groove of a dinflagellate
15. Bioluminescence – the ability to produce light biologically
16. Red Tide – discolorations of sections of the ocean caused by the population explosion of dinoflagellates (algae bloom) which can be toxic.
17. Algae Bloom – huge population explosion of algae in an area
18. Zoospore – flagellated, haploid, asexually produce spore
19. Asexual Reproduction – reproduction that occurs without meiosis, ploidy reduction, and fertilization.  Asexual reproduction is the primary form of reproduction for single celled organisms such as protests and bacteria.  Some of the advantages of asexual reproduction are that it allows for faster population growth, uses less energy, organisms can reproduce without a partner in situations where the population density is low, and offspring are typically genetically similar to their parent which may be beneficial if the genotype is well-suited to a stable environment.
20. Hapteron – A disklike holdfast on the stem of certain algae.
21. Conjugation – sexual reproduction whereby one (+) gamete moves to the other (-) through a conjugation tube between adjacent filaments producing diploid zygote.
22. Gametangia (gametangium ) – modified cells that produce and hold gametes.
1. antheridium – male unicellular gametangium produce sperm
2. oogonium – female unicellular gametangium produce egg
23. Alternation of generation life cycle – requires that diploid cells divide by meiosis to create haploid cells. Haploid cells then fuse to recreate the diploid number and a new organism. Alternation of generations refers to the occurrence in the plant life cycle of both a multicellular diploid organism and a multicellular haploid organism, each giving rise to the other.
24. Aquaculture – farming the ocean
25. Furrowing – the pinching of the plasma membrane inward from the margins of the cell that occurs when algal cells divide.
26. Carpogonium – female sex organ of red algae
27. Stigma – the red pigment “eyespot”
28. Rhodopsin – visual pigment that is ubiquitous in multicellular animals
29. Isogamy – type of sexual reproduction in which the gametes are alike in size
30. Oogamy – sexual reproduction in which one gametes (the egg) is large and non-motile, and the other gamete (sperm) is smaller and motile.
31. Anisogamy – the condition of having unequal or dissimilar motile gametes.  Usually the male is smaller.
32. Plurilocular Gametangia – multicellular reproductive structures of brown algae

Structure:

1. Thallus – a type of body that is undifferentiated into root, stem, or leaf.  Can be unicellular, colonial, filamentous, or thalloid.
1. colonial algae – groups of independent cells that move and function as a unit.  Certain cells become specialized for certain functions.
2. filamentous algae – consists of cells in a linear arrangement with structures that anchor them to the ocean floor.
3. thalloid algae – organisms in which cells divide in many directions to create a body that is multicellular and often modified into root-like, stem-like, and leaf-like parts.  An example is kelp.

Rhodophyta

Red Algae:

1. chloroplasts contain chlorophyll a, d, and phycobilins
2. food reserves are stored in their chloroplasts as floridean starch, which resembles the amylopectin portion of a true starch which resembles glycogen more than starch.
3. lack flagella at all stages of their life cycle
4. have polar rings instead of centrioles.
5. have rigid inner cell wall composed of microfibrils
6. nearly always grow attached to a substrate
7. mostly multicellular
8. have carageenan

Red Algae Life Cycle:

1. haploid gametophyte phase
2. diploid phase - carposporophtye
3. another diploid phase - tetrasorophyte

Chlorophyta

Green Algae:

1. chloroplasts contain chlorophylls a and b and carotenoids
2. store food reserves in their chloroplasts as starch
3. when present, the flagella are almost always equal and whiplash type.
4. plants probably evolved from green algae
5. have cell walls of cellulose
6. both unicellular and multicellular

Phaeophyta

Brown Algae:

1. chloroplasts contain chlorophylls a and c as well as the xanthophyll fucoxanthin
2. food reserves are stored in their chloroplasts as laminarin, a polymer of glucose, and as the alcohol mannitol
3. reproductive cells are unequal, one tinsel flagellum directed forward and a trailing whiplash flagellum.
4. mostly multicelluar and the largest, most complex of marine algae with some having a vegetative body  well differentiated into a holdfast, stipe, and blade.
5. cell walls contain alginic acid which contain alginates, polysaccharides used to make gels for ice cream and other foods.

Chrysophyta

Golden-Brown Algae

1. chloroplasts contain chlorophylls a and c as well as fucoxanthin
2. chrysophytes store food in the form of oils not starch
3. mostly unicellular (diatoms)

Pyrrophyta

Fire Algae or Dinoflagellates

1. cell wall made of cellulose
2. most photosynthetic and marine
3. have two flagella that fit into a groove in the cell wall, one groove running vertically (sulcus) and the other horizontally (girdle), which causes the organism to spin like a top as it moves through the water.
4. some are bioluminescent
5. cause red tides

Eugenophyta

1. unicellular algae
2. have chlorophyll a and b and store food as starch
3. do not have cell walls
4. can be both autotrophic and heterotrophic

Comparison of Green Algae and Plants

1. both have chlorophyll a and b
2. both store food as starch
3. both have cell walls of cellulose

REPRODUCTION

Unicellular Reproduction

Asexual Reproduction:

1. haploid cells produced
2. mitotic division occurs of haploid cells and several daughter cells are produced (zoospores) within the parent.
3. daughter cells (zoospores) break out of parent and eventually grow to full size.

Sexual Reproduction

1. diploid diatom undergoes meiosis
2. gametes produced
3. plus (+) and minus (-) gametes unite
4. zygote formed  and grows into mature diploid diatom

Multicellular Reproduction

Spirogyra

Conjugation

1. Conjugation – sexual reproduction whereby one (+) gamete moves to the other (-) through a conjugation tube between adjacent filaments producing diploid zygote.
2. after fertilization zygote develops
3. zygote falls from parent
4. new organisms forms

Oedogonium

Sperm and Egg

1. specialized cells for producing gametes, antheridium (male) and the oogonium (female)
2. sperm released from antheridium and swims towards oogonium (egg)
3. fertilization occurs and zygote forms a thick-walled resting spore separate from oogonium
4. now diploid spore undergoes meiosis forming 4 haploid zoospores which settle and divides
5. one new cell becomes a holdfast the other divides forming new filament.

Ulva

Alternation of Generation – two distinct multicellular phases

1. gametophyte – haploid, gamete-producing phase
2. sporophyte – diploid, spore-producing phase, these spores are called sporangia

Alternation of Generation Cycle Illustration: