1. The Algae Study of algae= Phycology Morphology, size and shape
Eukaryotic, motile or non motile
Unicellular, filamentous, or multicellular (thallic)
Wide range of sizes and shapes
Single cell- spherical, rod, club or spindle shaped
Multicellular-branched and unbranched
Cell wall- thin and rigid but diatoms have silica in their wall making them thick and very rigid
Discrete nucleus. Other inclusions are starch grains, oil droplets and vacuoles
Algal pigments- chlorophylls, carotenoids, phycobilins

2. Vegetative structure
Relatively simple eukaryotes lacking the tissues (roots, stem, leaves) of plants
Body of a multicellular alga is called a thallus
Larger algae (sea weeds) contain branched holdfasts which anchor them to rock, stem like hollow stipes and leaf like blades.
Cells covering the thallus carry out photosynthesis
Thallus lacks conductive tissue (xylem/phloem) characteristics of vascular plants

3. Unicellular alga

4. Comparison between unicellular algal, fungal and protozoal cell

5. Habitat and Nutrition
Mostly live in aquatic environment, also thrive as terrestrial algae
Ocean, salt lake, fresh water, damp soil, rocks, stones, tree bark etc.
They are found in places where there are sufficient light, moisture and simple nutrients to sustain them
Majority are photoautotrophs, contain chlorophyll and other pigments
Algae absorb nutrients from the water over their entire surface
Red Tide/Algal Bloom

6. Figure 12.11a

7. Reproduction Both sexual and asexual
Differ from plants in having simple reproductive structures for sexual reproduction
Unicellular algae may function as gametes
Asexual reproduction carried out by producing flagellated spores and/or nonmotile spores in sporangia

8. Figure 12.12b

9. Algae
Table 12.1

10. Selected phyla of algae
Brown algae (Phaeophyta)
Red algae (Rhodophyta)
Green algae (Chlorophyta)
Diatoms (Bacillariophyta)
Dinoflagellates (dinoflagellata)

11. Phaeophyta Brown algae (kelp) Cellulose + alginic acid cell walls
Multicellular
Chlorophyll a and c, xanthophylls
Store carbohydrates
Harvested for algin
Figure 12.11b

12. Rhodophyta Red algae Cellulose cell walls Most multicellular
Chlorophyll a and d, phycobiliproteins
Store glucose polymer
Harvested for agar and carrageenan
Figure 12.11c

13. Chlorophyta Green algae Cellulose cell walls
Unicellular or multicellular
Chlorophyll a and b
Store glucose polymer
Figure 12.12a

14. Bacillariophyta Diatoms Pectin and silica cell walls Unicellular
Chlorophyll a and c, carotene, xanthophylls
Store oil
Fossilized diatoms formed oil
Produce domoic acid
Figure 12.13

15. Dinoflagellata Dinoflagellates Cellulose in plasma membrane
Unicellular
Chlorophyll a and c, carotene, xanthins
Store starch
Some are symbionts in marine animals
Neurotoxins cause paralytic shellfish poisoning
Figure 12.14

16. Biological and Economic Importance
Primary producer- they form the base of most aquatic food chains because of their photosynthetic activities
Water algae increase the O2 conc through photosynthesis, help to reduce hardness of water and removes salts
Produce undesirable taste and odor in water supplies, heavy growth (mat) prevent oxygen and light penetration into water, cause suffocation to fish and marine animals

17. Commercial products from algae
From cell wall- agar, alginic acid and carrageenan are obtained
Agar, carrageenan- polymer of galactose, used to make gel or viscous materials, as stabilizer/emulsifier in food products (icecream), as binder in toothpaste or pharmaceutical products, ulcer therapy, finishing compound in textile and paper industry, thickening agent in shaving cream, lotoin, in soap industry
agar used as solidifying agent in microbiological media. Obtained from red alga Gelidium and Gracilaria.
Alginic acid obtained from brown algae eg. Laminaria, Fucus etc. Used in icecream, cheese industry, bakery, dentistry.

18. Algae as food
Mostly red and brown algae are used as food in the Far East
Porphyra is used as food in Japan, where it is called ‘Nori’
Other red algae Chondrus, Nemalion etc are used as vegetables or in soups or prepared as sweetened jellies.
Gracilaria used in China as food
Chlorella as food/source of protein for human and domestic animal

19. Algae and Disease
Prototheca- probable pathogen of Human causes systemic or subcutaneous infections/ inflammation of joints
Parasitic on higher plants. e.g. Cephaleuros attacks leaves of tea, coffee, pepper etc. (Irish potato blight)
Toxin produced by aquatic algae which are lethal to fish and animals. e.g. dinoflagellate release neurotoxin cause death of aquatic shellfish. Domoic acid intoxication due to diatoms in shellfish, diarrhea & memory loss
Poisoning of human occurs after ingesting shilfish, scallops or mussels infected with dinoflagellate.

20. Red tide
A phenomenon known as an algal bloom- an event in which estuarine, marine, or fresh water algae accumulate rapidly in the water column and results in discoloration of the surface water
Red tides are caused by increase in nutrients that algae need, usually due to farm runoff, causing an overpopulation
Their occurrence in some locations appear to be entirely natural, a seasonal occurrence resulting from coastal upwelling, a natural result of the movement of certain ocean currents while, in others they appear to be a result of human activities
It is usually found in coastal areas
The growth of marine phytoplankton is generally limited by the availability of nitrates and phosphates, which can be abundant in agricultural run-off as well as coastal upwelling zones
Coastal water pollution produced by humans and systematic increase in sea water temperature have also been implicated as contributing factors in red tides

21. When the algae are present in high concentrations, the water appears to be discolored or murky, normally being red or green.
Some red tides are associated with the production of natural toxins, depletion of dissolved oxygen or other harmful effects, and are generally described as harmful algal blooms
The most conspicuous effects of red tides are the associated wildlife mortalities among marine and coastal species of fish, birds, marine mammals, and other organisms.
In the case of Florida red tides, these mortalities are caused by exposure to a potent neurotoxin called brevetoxin which is produced naturally by the marine algae Karenia brevis.

22. Figure: Red Tide

23. THE END