Multicellular algae are classified as plants even though they lack specialized tissues. They are divided into three groups - green, brown, and red algae - based on their structure, pigments, food storage, and cell walls. Algae have complex life cycles that involve alternating between sexual reproduction through fertilization and asexual reproduction via spores, with phases that are either haploid or diploid.

1. Plant-like protists

2. Core concepts
• Multicellular algae are photosynthetic
organisms that are classified under Kingdom
Plantae, yet are simple in that they have an
undifferentiated plant body that lacks
specialized conductive tissue

3. • The multicellular algae consists of three
groups: the green algae (Chlorophyta),
the brown (Phaeophyta) and the red
algae (Rhodophyta). This classification is
based mainly on their structure,
photosynthetic pigments, food storage
product and cell wall composition.

4. Algae have complex life cycles that
involve alternation of
generations, where they
reproduce sexually by
fertilization and asexually by the
production of spores.

5. Keywords
• accessory pigment solitary colonial
• Filamentous thallus blade
• bladder stipe holdfast
• alternation of generations gametophyte
• Sporophyte haploid (N) diploid (2N)
• Zygote gamete isogamy
• Anisogamy heterogamy egg
• sperm