Page 118 - Ultimate Visual Dictionary (DK)

PLANTS

Algae and seaweeds BROWN SEAWEED
Channelled wrack
(Pelvetia canaliculata)
Receptacle
(fertile tip
ALGAE ARE NOT TRUE PLANTS. They form a diverse group of frond)
of plantlike organisms that belong to the kingdom Protista.
Like plants, algae possess the green pigment chlorophyll Thallus
(plant
and make their own food by photosynthesis (see pp. 138-139).
body)
Many algae also possess other pigments by which they can be
classified; for example, the brown pigment fucoxanthin is Apical
found in the brown algae. Some of the 10 phyla of algae are notch
exclusively unicellular (single-celled); others also contain Margin of
lamina (blade) Hapteron (holdfast)
aggregates of cells in filaments or colonies. Three phyla— rolled inward to
the Chlorophyta (green algae), Rhodophyta (red algae), form channel BROWN SEAWEED
Spiral wrack
and Phaeophyta (brown algae)—contain larger, multicellular, (Fucus spiralis)
thalloid (flat), marine organisms commonly known as seaweeds. Apical notch
Most algae can reproduce sexually. For Conceptacle
EXAMPLES OF ALGAE (chamber)
example, in the brown seaweed
Reproductive Receptacle
chamber Fucus vesiculosus, gametes
(sex cells) are produced in (fertile tip Thallus
Cap conceptacles (chambers) in of frond) (plant
Sterile whorl body)
the receptacles (fertile tips
Lamina
of fronds); after their release
Cell wall (blade)
into the sea, antherozoids
Stalk
(male gametes) and oospheres Smooth margin
(female gametes) fuse; the
Rhizoid Midrib Hapteron (holdfast)
resulting zygote settles on a rock
GREEN ALGA and develops into a new seaweed. Apical notch
Acetabularia sp.
Coenobium
Flagellum
Eyespot Contractile (colony of cells) Spine
vacuole
Receptacle
Daughter
Cytoplasm Cytoplasm (fertile tip
coenobium
of frond)
Nucleus
Cell Girdle Vacuole
wall Chloroplast Gelatinous
sheath Plastid Conceptacle
Pyrenoid Nucleus (photosynthetic (chamber)
(small protein
Starch organelle) containing
grain body) Biflagellate cell reproductive
GREEN ALGA GREEN ALGA DIATOM Lamina Midrib structures)
Chlamydomonas sp. Volvox sp. Thalassiosira sp. (blade)
BROWN SEAWEED RECEPTACLE
Oarweed Spiral wrack
(Laminaria digitata) Thallus (plant body) (Fucus spiralis)

Lamina (blade)
palmately
divided