Question

Give biological reasons for the following.
(i) The wall of the ventricles is thicker than the auricles.
(ii) The renal cortex has a dotted appearance.
(iii) Wooden frames of doors get jammed during monsoon season.
(iv) Throat infections can lead to ear infections.
(v) The hand automatically shows the direction to turn a cycle without thinking.

Answer 1

For, (i) - This is linked to blood flow and pumping throughout the body.
(ii) – The nephron has two parts; one being the malpighian corpuscle and the other is the renal tubule part.
(iii) - It is due to the change in atmosphere at the time of monsoon season.
(iv) - Some throat infections are very severe and painful. They can also travel to other body parts and spread infections.
(v) – It is related to previous learning experiences that are incorporated in the brain.

Complete answer:
(i) – The heart is divided into four chambers. The upper two chambers are the auricles and below two are the ventricles. Based on the side on which they are present, they are classified into right atrium and right ventricle on the right side and left atrium and left ventricle on the left side. The walls of the ventricles are thicker compared to atria because the pumping of blood out of the heart is at a greater pressure from the ventricles. And so do deal with such pressure, ventricles are made thick and muscular enough to prevent the heart from collapsing.

(ii) – There are the proximal and distal convoluted tubules due to which such a type of dotted appearance is seen. The malpighian corpuscles are a part of nephrons which lie in the kidney’s cortex. They have the appearance of dots. Therefore, the renal cortex will resemble a dot like structure.

(iii) – This happens due to the process of imbibition. The absorption of one substance is done by the other. During monsoon, there is moisture present everywhere. The wooden frames of doors absorb the moisture due to which swelling happens. And because of swelling, they get jammed.

(iv) – When the throat infection is very much advanced, it can travel to ear parts such as the middle ear and Eustachian tubes and can cause infection over there. Bacteria are responsible for such infections.

(v) – We have learnt cycling since we were small kids. We become quite acquainted with the left and right directions. Therefore we have adapted this learnt behavior and our brain has an image imprinted. The brain reflexes are very powerful. This type of situational reflex is called conditional reflex. Hence, the hand automatically shows direction to turn a cycle without thinking.

Note: (i) The circulatory system arises from the lateral plate mesoderm. The heart is about the size of your fist. It arises from the splanchnic mesoderm. It is divided into four chambers in humans. Two of them are atriums and two are ventricles.
(ii) The outer part of our kidney is called the renal cortex. An important factor called Erythropoietin is produced here.
(iii) Imbibition is a phenomena occurring due to adsorption of water by the solid colloids. This in turn increases the volume. Temperature is the most important water responsible for imbibition.
(iv) Ear and the throat are connected by a tube called the Eustachian tube. This tube is lined with mucus similar to that of nose and throat.
(v) A conditional reflex is also called acquired reflex because certain behaviors are acquired ones. Due to repetition of certain tasks it becomes a conditioned reflex because we are used to it.