2.1 The diagram below shows part of the human brain - NSC Life Sciences - Question 2 - 2022 - Paper 1

Part D has the following functions:

1. It is responsible for higher thought processes, including intelligence and memory.
2. It controls all voluntary actions of the body.

The hormone secreted by gland C that affects long bones is Growth Hormone (GH).

The hormone that acts on mammary glands in the breasts is Prolactin.

The hypothalamus plays a crucial role in thermoregulation by receiving input about body temperature and activating mechanisms to either conserve or dissipate heat. This includes triggering sweat production to cool down the body or inducing shivering to generate heat when it's cold.

Part B sends impulses to the following effectors:

1. Breathing muscles
2. Diaphragm

Part A is the Vas deferens.

One function of part B is sperm storage.

After a vasectomy, the semen will not contain sperm because the vas deferens is cut and tied, preventing sperm transport. However, it will still contain other secretions from the accessory glands like seminal fluid and prostate fluid.

If part C is located inside the body and fails to descend, it can lead to higher temperatures within the testicular area which may inhibit proper sperm production and development. This can result in potential infertility as the required conditions for sperm maturation are not met.

Spermatogenesis is the process where diploid germinal epithelial cells in the seminiferous tubules undergo meiosis to form haploid sperm cells. This involves several stages:

1. Mitosis of spermatogonia to produce spermatocytes.
2. Meiosis, resulting in secondary spermatocytes which further develop into spermatids.
3. Spermiogenesis, where spermatids mature into functional sperm.

In ovoviviparous organisms, the developing embryo is protected within the egg, which is retained within the mother's body. The egg provides essential nutrients through the yolk, while structures like the amniotic fluid cushion the embryo, aiding in protection against physical shock and dehydration.

Average urine volume at 15:00 = 71.53 ml/h Average urine volume at 03:00 = 34.72 ml/h Difference = 71.53 - 34.72 = 36.81 ml/h.

High levels of ADH at 03:00 increase the permeability of the renal tubules, allowing for more water reabsorption. This leads to less urine production during the night hours.

One advantage of the high ADH levels at 03:00 is that it prevents excessive water loss during the night, ensuring that the body remains hydrated and maintains homeostasis.

In patients whose renal tubules are impermeable to water, high ADH levels are expected to remain because the body attempts to compensate for the lack of water reabsorption by retaining ADH production to maintain fluid balance.

Two alkaloids found in plants are:

1. Caffeine
2. Nicotine

Caffeine production acts as a defense mechanism in plants as follows:

1. The bitter taste deters herbivores from feeding on them.
2. Caffeine has toxic effects on certain fungi, preventing them from affecting the plant's health.

One other plant defense mechanism is the production of thorns, which help deter herbivores from consuming the plant.