DDT is an insecticide that was used extensively in agriculture in the mid-1900s to kill many insect pests including the boll weevil (pictured below), another pest of commercial cotton, DDT was initially effective at controlling boll weevil outbreaks, but after about a decade DDT became much less effective, because many populations of boll weevil had evolved resistance to DDT. Which of the following conditions would biologists say was required for the evolution of DDT resistance in a population of boll weevils? A) Boll weevils in the population learned to adapt to the high levels of DDT in the environment. B) The boll weevil population needed to evolve DDT resistance in order to avoid extinction C) A few boll weevils in the population were resistant to DDT before it was ever used. D) Exposure to DDT caused specific, nonrandom mutations for DOT resistance within the population.

Alichen is an organism that structurally appears to be a single organism. but a lichen is actually two different organisms—a fungus and green algae—living together as one organism. the fungal partner derives its nutrition from the photosynthesizing algae. how does a lichen differ in its photosynthetic activity from elysia chlorotica, the sea slug that’s considered to be a photosynthesizing animal? a. in lichens, the fungi photosynthesize on their own, while elysia chlorotica forms a relationship with a photosynthesizing plant. b. in lichens, the relationship with the algae lasts throughout the life cycle, but in elysia chlorotica, the relationship occurs only during the immature juvenile stage of the slug’s life cycle. c. lichens can photosynthesize only because of the living algal partner, while elysia chlorotica incorporates chloroplasts from algae into its cells. d. in lichens, the association between the fungi and algae is permanent, while elysia chlorotica associates with a photosynthesizing organism only when it requires food.

What are the types of mutations, and how does each alter the encoded protein? college level answer

If a robot fixed another robot is it a engineer or doctor?