Question

WHAT IF? Suggest a possible reason why species in the green algal lineage may have been more likely to colonize land than species in the red algal lineage.

Short answer

The presence of flagellar structure in gametic cells of green algae members and some radiation blocking chemicals in their body parts (zygote coat, cytoplasm, and cell wall) favors their colonization in terrestrial habitats. Red algal lineage lacks these features, and so they colonize aquatic habitats.

Step-by-step solution

Evolution and lineage

In biology, evolution is explained as the phenomenon through which the life form originated billions of years ago, modified and diversified into different groups inhabiting today’s world. The sequence of life forms that shows the evolutionary relationships between ancestors and descendants is denoted as lineage.

Difference between algal groups

The algae are diverse and have several parameters for classification; some are classified based on pigmentation, while some are classified based on body structure (unicellular or multicellular). In terms of pigmentation, algae are of three different types.

Green algal lineage and red algal lineage and their colonization

Life originated earlier in the aquatic environment and slowly evolved to survive on land. In order to colonize land, organisms require several characteristics and adaptation to withstand the harsh terrestrial conditions (such as higher temperature and shortage of water).

Organisms of the green algal lineage are more likely to colonize terrestrial habitats because of the presence of flagellated gametes (facilitated fertilization independently of water) and chemical compounds that block harsh solar radiations within the cell wall, zygote coat, and cytoplasm.

The lineage of the red algal group does not have flagellated gametes and is thus dependent on the motion of water for fertilization. This lineage also lacks radiation blocking chemicals, which makes their body unfavorable for surviving the harsh terrestrial conditions.