ALGAEBy Erica Gonzales

What are algae?

Protists that use photosynthesis

Classified by their pigments: Purple, Rusty-red, Olive-brown, Yellow, Golden Brown

Both unicellular and multicellular

Phytoplankton Major producer of

nutrients and oxygen in the world

Classified into 3 phyla: Euglenoids Diatoms Dinoflagellates

Look like plants No roots, stem or

leaves Large and Green

Unicellular Algae Multicellular Algae

Characteristics

• Euglenoids• Diatoms• Dinoflagellates

Unicellular Algae

Euglenoids

Unicellular aquatic protists Plant AND animal

characteristics Made of cellulose; no cell

wall Have flagella to move

towards light or food Have a flexible pellicle

around cell membrane

Notice that there are similarities between the Euglenoid and a plant cell

Parts of a Euglenoid

Characteristics

Contain chlorophyll

Conduct photosynthesis

Autotrophic

Can eat food when light is not available

Ingest food like protozoa

Heterotrophic

Plant-Like Animal-Like

Diatoms

Unicellular photosynthetic organisms

Have shells composed of silica

Abundant in fresh and saltwater ecosystems

Box-shaped Contain chlorophyll and

carotenoids (a pigment) for golden color

Diatom Shells

Each species of diatoms has its own unique shape, differently patterned with grooves and pores.

Food

Use sunlight for food (photosynthesis) Food is stored as oils, not starch Gives them an oily taste to fish that eat

them Oil allows them to float near water’s

surface for sunlight

Reproduction

Two halves of the box split

Each pieces produces a bottom half to fit inside it

Half of offspring are smaller than parents

Stops when diatoms are ¼ original size

Then switches to sexual reproduction

Produce gametes (egg or sperm)

Fuse to form zygotes Zygote fully develops

and divides asexually for a while

Asexually Sexually

Diatom Reproduction

Death

Shells sink to ocean floor at death

Million-year-old diatom deposits have been found

Used for tooth or metal polishes

Dinoflagellates

Have cell walls made of thick cellulose plates

Contain chlorophyll, carotenoids & red pigments

2 flagella in grooves right angles to each other

Live in freshwater, but mostly saltwater Can live symbiotically with jellyfish,

mollusks and coral Some species emit light

Toxic Dinoflagellates

Several species produce toxins One species Pfiesteria piscicida can

cause massive fish kills Gonyaulax catanella produces extremely

lethal nerve toxins A very numerous population of these cause

a red tide Inhabited by 40 to 60 million dinoflagellates

per liter of seawater Can make humans ill

Red Tides

The yellow and orange spots in the water are red tides, areas so densely infested by toxic dino-flagellates.

• Red Algae• Brown Algae• Green Algae

Multicellular Algae

Red Algae

Multicellular marine seaweeds Thallus – body of a seaweed: lacks

roots, stem and leaves Uses structure called holdfasts to

attach to rocks Found in tropical waters or in cold

waters on rocky coastlines

Pigments

Contain Chlorophyll and phycobilins – photosynthetic pigments that absorb green, violet, and blue light (the only lights that penetrate water past 100 meters)

Allows algae to deeper than most seaweeds

Brown Algae

Live in salt water along rocky coasts in cooler areas

Contain chlorophyll and fucoxanthin

Fucoxanthin – yellowish-brown carotenoid (a pigment) that gives them their brown color

Most species have air bladders Keep them floating near

the surface for sunlight

Kelp

Largest and most complex brown algae

Thallus (body) is divided into holdfast, stripe and blade

Holdfasts anchor them to rocks or ocean floor

May grow to 60 meters long

Some giant kelps form underwater forests Many organisms live in

them

Green Algae

Most diverse algae; over 7000 species

Have many pigments that give yellow-green color Main one is

chlorophyll Live in: freshwater,

saltwater, moist soil, tree trunks, even the fur of sloths

Colony: group of cells that lives together in close association

Different Types of Green Algae

Unicellular

Multicellular

Colonies

Volvox Colony

Composed of hundreds of cells with flagella in one layer to form a hollow ball Cells are connected by strands of

cytoplasm Flagella face outwards and beat in unison

to spin the colony in the water Smaller balls, “daughter colonies” form

inside the hollow space Wall of larger colony eventually breaks

to release the daughter colonies

Reproduction

Reproduce sexually AND asexually Fragmentation – (asexual

reproduction) an individual breaks up into pieces and each piece grows into a new individual Some species use this method of asexual

reproduction Alternate from producing sexually and

asexually throughout lifecycle Produce gametes for sexual reproduction Produce spores for asexual reproduction

Alternation of Generations

Pattern of alternating between existing as a haploid and diploid organism, creating 2 different generations

Gametophyte – haploid form of organism; produces gametes They fuse to form a zygote

Sporophyte – diploid form of organism, also zygote of previous generation; produces spores Cells undergo meiosis and eventually become

haploid spores that can become gametophyte

Throughout their lives, green algae switch from being a diploid to a haploid.

Life Cycle of Green Algae