Explain why domestication of plants and animals was likely one of the first areas of biology

Probably because domestication of plants and animals is as old as societies themselves. Plant domestication is basically the dawn of agriculture which stopped the nomadic way of life, while animals domestication is as old as the hunter gatherer societies when animals were used to help.

An autotrophic protist - they can perform photosynthesis and mainly consist of unicellular algae. they can be divided into number of systematic group according to the shape of their cell and the type of photosynthetic pigments they use.