1. Algae
An Overview

2. Characteristics
Range in size from microscopic to single celled organisms to large seaweed
Autotrophic
Form the reproductive structures – gametangia or gamete chambers
Aquatic and have flagella at some point in life
Often contain pyrenoids, organelles that synthesis and store starch

3. Algae There are seven phyla of algae
They are distinguished from each other by the type of photosynthetic pigment they contain, by their cell or body composition, and food storage substance.
Algae are not considered plants because their cell structure is different and also because algae do not have root systems.
All algae contain chlorophyll in addition to the pigments that make them look brown and red.
Algae are protists that are strict phototrophs.
1. Algae are a diverse group of protists. They range in size from microscopic Single-celled organisms to large Seaweeds that may be hundreds of feet long.
2.  Algae are AUTOTROPHIC Protists- they are called Plant-like because they perform PHOTOSYNTHESIS. Like plants, Algae contain CHLOROPHYLL and produce their own Carbohydrates giving off Oxygen as a by-product of Photosynthesis.
3. Algae are Different from Plants Because they LACK Tissue Differentiation and have No True Roots, Leaves or Stems.
4. The Reproductive Structures of Algae also Differ from those of plants; they form Gametes in Single- Celled GAMETANGIA, or Gamete Chambers.  Plants form Gametes in Multicellular Gametangia.
5. For these Reasons Algae are classified as Protists.

4. Unicellular algae

5. CLASSIFICATION OF ALGAE
Four types of algae
Unicellular
Colonial
Filamentous
multicellular

6. REPRODUCTION MOST REPRODUCE BOTH SEXUALLY AND ASEXUALLY
Most sexual reproduction is triggered by environmental stress
Asexual Reproduction
Mitosis
Sexual Reproduction
Meiosis
Zoospores
Plus and minus gametes
Zygospore

7. Alternation of Generations

8. Reproduction in Multicellular Algae
Oedogonium reproduction
Antheridium-release flagellated sperm that swim to the oogonium
Oogonium-houses the zygote which is a diploid spore
The spore undergoes meiosis and produces 4 haploid zoospores. One of the four cells becomes a rootlike holdfast the others divide and become a new filament.
oogonium

9. Chlorophyta 7000 diverse species
Biologist reason that green algae give rise to land plants.
Both green algae and land plants have chlorophyll A and B as well as carotenoids - PHOTOSYNTHESIS
Both store food as starch
Both have walls made of cellulose
Most chlorophytes are aquatic, but some green algae can live on the surface of snow, on tree trunks, in soils, or symbiotically with protozoans.
Sexual and asexual reproduction
The "green algae" is the most diverse group of algae, with more than 7000 species growing in a variety of habitats. Most are freshwater unicellular organisms. Their habitats include damp soil and within the cells of other organisms as symbionts.

10. Ulva and Enteromorpha 2 genera of marine or brackish-water green algae
flat (“Sea Lettuce”)
2 layers thick
Enteromorpha
tubular
1 layer thick
No true tissues
cells are almost exactly the same throughout the thallus

11. Volvox colony

12. Caulerpa

13. Codium
© D. Stengel

14. Phaeophyta
The 1,500 species of brown algae, Phaeophyta, are almost exclusively found in marine habitats.
The browns include the largest of the seaweeds, called kelp.
The brown algae have chlorophyll a and c, as well as carotenes and xanthophylls.
Reproduction is by alternation of generations.
Individual alga may grow to a length of 100m with a holdfast, stipe and blade
The largest of the brown algae is known as kelp. Interestingly, they are among the largest organisms on the earth. They grow very long stalks and can be thought of like the trees of the ocean. Unlike trees, however, they do not have roots to anchor them or a tough cell wall like the wood found in trunks of trees. Without those things, how is it they are capable of growing upward?
(Remind students that buoyancy is dependent upon density. Macrocystis is less dense than the surrounding water. Why? The base of each leaf blade contains gas-filled sacks.)

15. holdfast

16. Rhodophyta
The red algae contain over 4,000 species, most from marine habitats.
Their pigments include chlorophyll a and the phycobiliproteins,  red phycoerythrin and blue phycocyanin, as well as carotenes, lutein, zeaxanthin.
Porphyra, commonly know as nori, is the most widely consumed seaweed in the world! It's commonly found in Asian food.
Reproduction is usually through alternation of generations.
Cells are coated in carageenan which is used in cosmetics, gelatin capsules and some cheeses
“Red algae” are mostly multicellular organisms found in warm ocean waters. The red pigments are efficient inabsorbing light that penetrates deep waters.

17. Phylum Euglenophyta 1000 species of Euglenoids
Have both plantlike and animal-like characteristics
Fresh water

18. Other Phylum Representatives
Diatoms – used in detergents, paint removers, toothpaste
Dinoflagellates – red tides
Golden algae
Important in the formation of petroleum products

19. Funguslike Protist
Cellular Slime molds

20. Plasmodial Slime Molds

21. Water Molds

22. Have you had your algae today?
How many algae derived products are in your kitchen? Some key terms that identify algae extracts are lecithin, carrageenan, algin, agar, emulsifier, and thickening agent. Identify as many algae food products in your household as you can.

23. Unicellular algal groups
Cyanophyta (Blue-green Algae; prokaryotes)
Diatoms
Dinoflagellates
Chrysophyta
Chlorophyta (Green Algae)
Rhodophyta (Red Algae)

24. Cyanobacteria (Cyanophyta)
Only asexual reproduction
Some can fix atmospheric Nitrogen
Found in extreme habitats (e.g. hot springs)
Found in lichens
Blue-green Algae
Prokaryotic, no cell organelles
Pigments: chlorophyll a, phycoerythrin + phycocyanin
Can form blooms

25. Extreme halophytes

26. Hot springs

27. Diatom Characteristics
2 orders:
Centrales
radial symmetry
(centric diatoms)
Pennales
bilateral symmetry
(pennate diatoms)

28. Diatom Characteristics
Cell wall consists of 2 shells
Large top shell (lid)
Epitheca
Small bottom shell (box)
Hypotheca
Cell wall contains silica

29. Dinoflagellate Characteristics
Generally unicellular, may form colonies or filaments
Chlorophyll a and a range of other pigments giving lots of different colours
Numerous colourless genera (animal-like): heterotrophic!
2 flagella:
one apically inserted
one in equatorial groove

30. Dinoflagellates Harmful algal blooms
Toxic algal blooms: shellfish poisoning
Parasites: fish and copepodes
Symbionts: sponges

31. Dinoflagellates: Red Tides
often the cause of “red tides” or blooms of toxic or non-toxic cells
blooms may cause mass mortalities of marine and freshwater organisms
contain toxins that are accumulated by shellfish and cause PSP (Paralytic Shellfish Poisoning)
Some species produce small amounts of light by means of enzymes