L5：
讲座
1. What is the main purpose of the lecture?
To explain how biologists learned that not all mutations to a species are beneficial to the species
To explain why biologists’ views about evolutionary adaptations have recently changed
To explore the advantages and disadvantages of toxins as a defense against predators
To discuss efforts to find ways to counteract a powerful toxin
2. How is tetrodotoxin different from other animal toxins?
It is equally toxic to all animals that come into contact with it.
When heated, it can be safely consumed by people.
It is poisonous only when combined with sodium.
It is found in several different species of animal.
3. What evidence suggests that puffer fish do not make tetrodotoxin themselves?
A. They die if their nerve cells are exposed to tetrodotoxin for long periods of time.
B. They do not contain tetrodotoxin if they are raised in a controlled environment
C.The steps that are necessary to produce tetrodotoxin are biologically complex.
D.The chemicals required to synthesize tetrodotoxin are not found in ocean water
4. What type of genetic mutations occurred in the evolution of certain animals that enabled them to become immune to tetrodotoxin?
Mutations that prevent the toxin from blocking sodium ion transmissions
Mutations that help the respiratory system fight off invasion by bacteria.
Mutations that prevent the animals from producing excessive amounts of the toxin
Mutations that allow the animals to exist in bacteria-free environments
5. What is the main point the professor makes when she mentions garter snakes?
Garter snakes contain venom that is similar to the venom of scorpions.
Tetrodotoxin can be synthesized by a wide variety of species.
Resistance to tetrodofoxin has evolved in some animals that feed on animals containing the toxin.
Tetrodotoxin may have spread to newts in North America as a newts to fend off certain predators.
6. What is the professor’s opinion about the replication of evolutionary changes where the same changes occur in distinct species?
She is convinced it is more frequent than Darwin thought possible.
She doubts it will ever be conclusively found in the animal kingdom.
She thinks examples that have been put forth could simply be random occurrences
She wishes the biologists were more open to the idea that it may occur.
