Answer: Option (1)
Explanation:
The extinction event played an important role in the creation of new diverse life forms on earth. After an extinction event, both globally and locally, more than 75% of animal species gets vanish and the only those highly resistant life supporting organisms survive and with due course of time, they undergoes evolution, thereby bringing changes to the existing life forms. This is how they initiates and helps in the increasing species diversity.
Thus, the correct answer is option (1).
The lac operon, which stands for Lactose operon is known as an inducible system. It is the an operon required for the transport and metabolism of lactose some enteric bacteria (Echerichia coli for example). The Lac operon is only activated in the presence of a key molecule. The key molecule is lactose.
From the given options the following best describes the Lac operon:
D. The repressor is freed from the operator when lactose is present.
The answers are "water and mineral ions" and "amino acids and sucrose" respectively.
For the xylem, it usually transports water and mineral ions that are absorbed from the root hair cells up to the leaves, where photosynthesis take place. Water is one of the necessary substance for photosynthesis to take place, while different mineral ions can help the plant by for example Magnesium ions can help produce chloroplast.
While phloem transports amino acid and sucrose from the location of production (eg. Leaves by photosynthesis) to the place where it is used or stored. Plant needs these substances to generate energy for activities such as growth by for example cellular respiration. This process is called translocation.
Both of these tubes help transport substances in the plant, in order to keep the plant alive.