The correct answer is:
D. It attracts a metal striker, which then hits the bell.
The function of an electromagnet in an electric doorbell is it attracts a metal striker, which then hits the bell.
Answer:
Density, dispersion, growth
Explanation
Population refers to the total number of all members of a species occupying a particular area or habitat at a given time. Populations are not static but change in size, structure and organization. Some of the characteristics of population are:
- Density which refers to the number of members of a species per unit area or volume.
- Dispersion refers to the spread and distribution of individuals of a species within a habitat.
- Growth is the rate of increase or decrease in the number of individuals in a population which is balanced by birth rate and death rate.
The issues that affect population include competition, predation, emigration, diseases and parasites.
A team of scientists is working to formulate a drug that can treat children who are diagnosed with gigantism. Gigantism is caused by the excess production of growth hormone by the pituitary gland present in the fore-brain. Growth hormone in turn signals the liver to produce a second harmone, Insulin-like Growth Factor-1 (IGF-1). The growth hormone and IGF-1 together tell the cells in the muscles, bones and skin to increase their number. Hence the possible effect of the administered drug will be to decreases the secretion of substances from the pituitary gland that cause growth.
Answer:
Some mutations don't have any noticeable effect on the phenotype of an organism.
Explanation:
This can happen in many situations: perhaps the mutation occurs in a stretch of DNA with no function, or perhaps the mutation occurs in a protein-coding region, but ends up not affecting the amino acid sequence of the protein.