Biology Test 368

The correct answer is Cells of Leydig.

Cells of Leydig secrete androgen hormones in human beings.

Cells of Leydig constitute the endocrine tissue of the testes.

Androgens are a group of male sex hormones.

Statement I describes the corpus callosum, a structure in the brain. The corpus callosum is a large bundle of nerve fibers that connects the two cerebral hemispheres, allowing for communication between them. This statement is correct.

Statement II mentions the brain stem and lists its components as the medulla oblongata, pons, and cerebrum. The error here is in including the cerebrum as part of the brain stem. In actuality, the brain stem consists of the medulla oblongata, the pons, and the midbrain, not the cerebrum. The cerebrum is part of the forebrain and is responsible for higher cognitive functions such as thinking, perceiving, planning, and understanding language. Therefore, Statement II is incorrect.

Corpus luteum of the ovary secretes progesterone, and relaxin. Prolactin is secreted by anterior lobe of pituitary gland. Aldosterone is a principal mineralocorticoid secreted by the adrenal cortex and testosterone is secreted by the Leydig's cells in the testes.

The species-area relationship explains how species richness increases with habitat area, but it is not a cause of species loss. The main causes of species loss include habitat loss, over-exploitation, and biological invasions.

The hormone responsible for converting glucose into glycogen is produced by the pancreas.

This process is vital for regulating blood sugar levels. Here are some key points:

• The pancreas secretes insulin, a hormone that facilitates the uptake of glucose by cells.
• Once inside the liver, glucose is transformed into glycogen for storage.
• When blood sugar levels drop, glycogen can be converted back into glucose, ensuring a steady energy supply.

In summary, the pancreas plays a crucial role in managing energy by producing insulin, which helps maintain healthy blood sugar levels.

The correct answer is B: Thyroid.

- The thyroid gland plays a crucial role in regulating the basal metabolic rate (BMR) in body cells.

- Thyroid hormones, such as thyroxine (T4) and triiodothyronine (T3), control metabolism by influencing the body's energy production and consumption.

- These hormones affect how quickly cells use energy and produce proteins, impacting the body's overall metabolic rate.

- An imbalance in thyroid hormone levels can lead to either an increased (hyperthyroidism) or decreased (hypothyroidism) metabolic rate.

Global water cycle consists of evaporation from water bodies (oceans, rivers, lakes etc.) and precipitation of water in the form of rain, snow and hail. Hence, water circulates between hydrosphere and atmosphere. It does not involve living organisms.

Gause's 'Competitive Exclusion Principle' states that two closely related species competing for the same resources cannot co-exist indefinitely and the competitively inferior one will be eliminated eventaully. Thus, statement I is correct.

Statement II is incorrect as in general, herbivores and plants appear to be more adversely affected by competition than carnivores.

To match List I with List II correctly, we start by identifying the function of each brain region described in List I and match these descriptions to the corresponding functions stated in List II:

• Pons: The pons is part of the brainstem located between the midbrain and the medulla oblongata. It principally acts as a bridge connecting various parts of the brain, and it is also involved in controlling essential functions like sleep and respiration.
• Hypothalamus: The hypothalamus is a small portion at the base of the brain that plays a crucial role in hormone release and regulation of essential bodily functions, including temperature control, thirst, hunger, sleep, mood, and sexual behavior. It contains several neurosecretory cells that produce hormones.
• Medulla: The medulla oblongata, also part of the brainstem, primarily controls autonomic functions such as breathing, heart rate, and digestion (including gastric secretions).
• Cerebellum: The cerebellum is located at the back of the brain and is responsible for controlling motor skills, balance, coordination, and posture. It helps refine the movements dictated by the motor cortex.

Now, let's match these descriptions to those listed in List II:

A. Pons should match with "Connects different regions of the brain." - this corresponds to III.

B. Hypothalamus should match with "Neurosecretory cells." - this corresponds to IV.

C. Medulla should match with "Controls respiration and gastric secretions." - this corresponds to II.

D. Cerebellum should match with "Provides additional space for Neurons, regulates posture and balance." - this corresponds to I.

When we look at the given options:

Option A: A-II, B-III, C-I, D-IV (wrong)

Option B: A-III, B-IV, C-II, D-I (correct)

Option C: A-I, B-III, C-II, D-IV (wrong)

Option D: A-II, B-I, C-III, D-IV (wrong)

The correct answer is Option B: A-III, B-IV, C-II, D-I.

Darwin during his famous voyage, observed that finches from various islands of Galapagos had beaks of different sizes and shapes. He observed that this was due to adaptation to different available food types. He concluded that the ancestral finches on reaching different islands occupied all empty ecological niches in absence of competition and evolved into different species. This provides evidences for origin of species by natural selection.