Which of the following growth curves shows a population that is at its carrying capacity?

The correct answer is a. Nuclei. Genetic information describing the characteristics of an organism is found in the nuclei of its cells. The nucleus contains the organism's DNA, which carries the genetic information that determines its traits.

b. Membranes are structures that surround and enclose cells and organelles, but they do not contain genetic information.

c. Cilia are hair-like structures that protrude from the surface of some cells and are involved in movement, but they do not contain genetic information.

d. Ribosomes are organelles that are involved in protein synthesis, but they do not contain genetic information.

The function of a totipotent cell is to develop into any kind of cell ¹. Totipotent cells have the capacity to produce all adult cell types and can enter the germ line, contributing genetic material to succeeding generations ?. They have the ability to self-replicate, producing daughter cells that are identical to the parent ?.

The other options are incorrect because they do not accurately describe the function of a totipotent cell. Fighting infectious diseases, aiding in the maturation of sex cells, and carrying electrical impulses are not functions performed by totipotent cells.

The correct answer is d. A substance with a pH of 3 is 10 times more acidic than a substance with a pH of 4. The pH scale is a logarithmic scale, which means that each change of one pH unit represents a tenfold change in the hydrogen-ion concentration. A substance with a pH of 3 has a hydrogen-ion concentration that is 10 times greater than that of a substance with a pH of 4.

A. A substance with a pH of 3 is not two times more alkaline than a substance with a pH of 4.

B. A substance with a pH of 3 is not 10 times more alkaline than a substance with a pH of 4.

C. A substance with a pH of 3 is not two times more acidic than a substance with a pH of 4.

The correct answer is d. Carbonic acid. When blood pH rises, carbonic acid can donate H+ ions to act as a buffer and help maintain the pH within a normal range. Carbonic acid is formed when carbon dioxide dissolves in water and reacts with it.

A. Oxygen is not responsible for donating H+ ions to act as a buffer when blood pH rises.

B. Carbon monoxide is a toxic gas that does not play a role in buffering blood pH.

C. Carbon dioxide can dissolve in water to form carbonic acid, which can then donate H+ ions to act as a buffer.

The organ that filters excess solutes from the blood is the kidney ¹. The kidneys are a pair of bean-shaped organs located on either side of the spine, just below the rib cage ². They are responsible for filtering waste products and excess fluid from the blood and excreting them in the form of urine ².

The other options are not correct because they do not accurately describe the organ that filters excess solutes from the blood. The stomach, spleen, and gallbladder do not filter excess solutes from the blood.

Ovulation is the process in which an ovarian follicle matures and releases a reproductive egg. During ovulation, the egg is released from the ovary and travels down the fallopian tube where it may be fertilized by sperm.

The other options are not processes in which an ovarian follicle matures and releases a reproductive egg. Oogenesis is the process of egg cell formation, menstruation is the shedding of the uterine lining, and fertilization is the fusion of an egg and sperm to form a zygote.

When a muscle cell is stimulated by a nerve impulse, calcium ions are released from the sarcoplasmic reticulum into the cytoplasm. The calcium ions bind to the troponin complex, which is a protein that regulates the interaction between actin and myosin filaments. The binding of calcium to troponin causes a conformational change that exposes the binding sites for myosin on the actin filaments. This allows the myosin heads to attach to the actin and pull the filaments past each other, resulting in muscle contraction.

The layer of skin that lacks blood vessels is the epidermis. The epidermis is the thin outer layer of the skin and does not have any blood vessels within it. It is composed of keratinized, stratified squamous epithelium and is made of four or five layers of epithelial cells, depending on its location in the body.

The other options are not correct because they do contain blood vessels. The papillary layer is part of the dermis, which contains blood vessels. The reticular layer is also part of the dermis and contains blood vessels . The hypodermis is a layer below the dermis and also contains blood vessels.

The best reason for the prolonged preservation of the body is that it was frozen in the cold temperature of the Alps shortly after death and remained frozen until it was found. Freezing can preserve a body by slowing down or stopping the decomposition process.

The other options are not as likely to have caused prolonged preservation.

Ultraviolet rays can damage molecules rather than preserve them. Toxins in food would not necessarily kill all bacteria that could cause decomposition. Blood loss from an arrow wound would not necessarily clear all enzymes that could break down tissue.

Perforins are immune system molecules that create holes in the cell membranes of their target cells in order to destroy the cell. Perforins are proteins that are released by cytotoxic T cells and natural killer cells

They form pores in the target cell membrane, allowing water and ions to enter the cell and causing it to swell and burst.

The other options are not correct because they do not accurately describe the immune system molecules that create holes in the cell membranes of their target cells. Interferons, cytokines, and lymphotoxins do not create holes in cell membranes.