Algae An Overview

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

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.

Unicellular algae

CLASSIFICATION OF ALGAE Four types of algae Unicellular Colonial Filamentous multicellular

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

Alternation of Generations

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

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.

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

Volvox colony

Caulerpa

Codium © D. Stengel

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.)

holdfast

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.

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

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

Funguslike Protist Cellular Slime molds

Plasmodial Slime Molds

Water Molds

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.

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

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

Extreme halophytes

Hot springs

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

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

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

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

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