General Biology Flashcards

Which of the following is a primary function of Luteinizing Hormone (LH) in males?

Answer: Stimulation of Leydig cells to produce testosterone

In males, Luteinizing Hormone (LH) acts on the Leydig cells within the testes, stimulating them to produce testosterone. Testosterone is crucial for spermatogenesis and the development of male secondary sexual characteristics. Follicle-stimulating hormone (FSH), not LH, primarily acts on Sertoli cells.

A biologist observes a mule, which is the offspring of a male donkey and a female horse. The mule is healthy and strong but is sterile. This is an example of which type of reproductive isolating mechanism?

Answer: Hybrid sterility

Hybrid sterility is a post-zygotic isolating mechanism where the hybrid offspring of two different species is viable but unable to produce functional gametes, and is therefore sterile. A mule is a classic example of hybrid sterility. Hybrid inviability means the hybrid zygote fails to develop or dies before birth. Hybrid breakdown refers to when F1 hybrids are fertile, but their F2 offspring are inviable or sterile. Gametic isolation is a pre-zygotic barrier where gametes from different species are incompatible.

Which of the following conditions is NOT an assumption for a population to be in Hardy-Weinberg equilibrium?

Answer: Small population size

The Hardy-Weinberg principle assumes a very large, ideally infinite, population size to negate the effects of genetic drift. A small population size allows for random fluctuations in allele frequencies (genetic drift), which violates the equilibrium. The other assumptions are no mutation, no gene flow, random mating, and no natural selection.

In the process of eutrophication, what is the direct cause of the depletion of dissolved oxygen in the water, leading to the creation of a 'dead zone'?

Answer: The decomposition of dead algae by aerobic bacteria.

Eutrophication begins with nutrient enrichment, leading to a massive algal bloom. When these algae die, they sink and are decomposed by aerobic bacteria. This decomposition process consumes large amounts of dissolved oxygen from the water, leading to hypoxic or anoxic conditions that kill fish and other aquatic life.

At the neuromuscular junction, the arrival of an action potential at the motor neuron's terminal button triggers the release of which neurotransmitter into the synaptic cleft?

Answer: Acetylcholine

Acetylcholine (ACh) is the primary neurotransmitter used at the neuromuscular junction. Its release from the motor neuron and subsequent binding to receptors on the muscle fiber's motor end plate initiates the process of muscle contraction.

A patient suffers an injury that severs a structure connecting a muscle to a bone. Which of the following has most likely been damaged?

Answer: A tendon

Tendons are tough, fibrous connective tissues that attach muscles to bones, transmitting the force of muscle contraction to facilitate movement. Ligaments, by contrast, connect bone to bone to stabilize joints. Cartilage is a flexible connective tissue found in joints and other areas, while a fascicle is a bundle of muscle fibers.