What is crossing over in meiosis?

Legumes, a type of plant, require rhizobia, a type of soil bacteria, to survive since these organisms fix nitrogen during photosynthesis. rhizobia use the legumes for food. what would most likely happen to the legume population if rhizobia suddenly became extinct?

Consider the classification levels of a human. eukarya ,animalia ,chordata ,mammalia ,primates, hominidae ,homo ,sapiens .which is the most specific taxonomic level in the classification system above? a sapiens b homo c hominidae d primates

Tides that occur during the new and full moons