Answer:
Organism in a lichen that provides protection - algae
Organism in a lichen that provides nutrients through photosynthesis - algae
Branched growth form of lichen - fruticose
Leafy growth form of lichen - foliose
Small and flat growth form of lichen - crustose
Explanation:
Lichens are composite organisms that are formed from symbiotic relationships between fungi and cyanobacteria/algae. The Green algae layer offers food to the fungi by photosynthesis while the latter supplies nutrients and offers protection to the algal component.
There are different types of lichen based on the growth structure:
Fruticose lichens grow upright and shrubby and posses either round or flat branches.
Foliose lichen appears like a leaf with upper and lower layers. They are usually flat or convoluted in nature.
Crustose lichens are small in appearance with flat, crusty growth on surfaces on which they grow.
