Explanation

The dermis is the layer of skin beneath the epidermis, and it contains:

• Blood vessels (which supply oxygen and nutrients to the skin)
• Nerve endings (which transmit sensory information)
• Hair follicles (which produce hair)
• Sebaceous glands (which produce oil)
• Sweat glands (which produce sweat)
• Collagen and elastin fibers (which provide structure and elasticity)

A layer of dead cells is actually a characteristic of the epidermis, the outermost layer of skin, where dead skin cells are constantly shed and replaced by new ones.

So, the correct answer is A layer of dead cells!

Explanation

• Coronaviruses get their name from the crown-like shape of the viral particles, which have a distinctive "corona" or halo of protein spikes on their surface.
• These spikes give the virus its characteristic appearance under an electron microscope, resembling a crown or a halo.
• This is why the name "coronavirus" was chosen, as it reflects the virus's unique morphology.

Explanation

The epididymis is a tube-like structure located behind each testicle where sperm cells are stored, matured, and nourished before being transported to the vas deferens and eventually ejaculated.

Explanation

• Flukes (trematodes) and tapeworms (cestodes) are both types of parasitic flatworms (Platyhelminthes).
• They have a well-developed reproductive system, which allows them to produce large numbers of eggs and reproduce effectively in their host organisms.

Explanation

• Down's syndrome, also known as Trisomy 21, is a genetic disorder caused by the presence of an extra copy of chromosome 21.
• This occurs due to a process called nondisjunction, where the chromosomes fail to separate properly during cell division (meiosis), resulting in an extra copy of chromosome 21 being inherited.

Explanation

• The phrase "above board" is an idiomatic expression that means to be honest, transparent, and ethical in one's dealings, especially in business or financial matters.
• It implies that all actions and decisions are open and fair, with no hidden agendas or secrets.

Explanation

• Cytotoxic T cells are a type of T lymphocyte that plays a crucial role in eliminating infected cells or tumor cells from the body.
• They recognize and bind to specific antigens presented on the surface of infected cells or tumor cells, and then release cytotoxins, such as granzymes and perforin, which form pores in the plasma membrane of the target cell, leading to cell lysis and death.

Explanation

• Fishes are the first formed Chordates, which is a phylum of animals that includes vertebrates (animals with backbones) and some invertebrates (animals without backbones).
• Chordates are characterized by the presence of a notochord (a flexible, rod-like structure that provides support and stiffness) at some stage in their development.

Explanation

• The Genetic Balance Theory, also known as the "genic balance theory", was proposed by American geneticist Thomas Hunt Morgan to explain the complex mechanism of sex determination in Drosophila (fruit flies).
• According to this theory, the sex of an individual is determined by the balance of genetic factors, rather than by a single gene or chromosome.

Explanation

• A J-shaped growth curve is a characteristic of exponential growth, where the population grows rapidly and unchecked, with no limits or restrictions.
• This type of growth occurs when a population has unlimited resources, such as food, water, and space, and is able to grow at its maximum rate, known as its biotic potential.