Section – C (5 Marks Each)

Question 27: (a) Why is there a difference in the rate of breathing between aquatic organisms and terrestrial organisms? Explain.

Answer:

One full breath consists of a single inhale and exhalation of air. The number of times a full breath is taken in a minute is hence the measure of breathing rate. The rate at which aquatic and terrestrial organisms breathe varies. This is because dissolved water, which is found in the gills of aquatic species like fish, provides them with oxygen. And we know that there is less dissolved oxygen in water than there is in air when it comes to oxygen in its undissolved state.

To fulfill their respiratory needs, they consequently breathe quickly. To keep up with the body’s need for oxygen, they breathe more quickly than humans do. Swimming over a river causes swimmers to breathe more quickly, as can be observed. Consequently, the rates at which aquatic and terrestrial creatures breathe vary.

(b) Draw a diagram of the human respiratory system and label – pharynx, trachea, lungs, diaphragm and alveolar sac on it.

Answer:

The human respiratory system can be shown as:

OR

(a)   Name the organs that form the excretory system in human beings.

Answer:

Human excretory system consists of following organs:

1. Two kidneys: One on each side of the spine, near the liver. The kidneys are a vital organ found in pairs in the human body. The kidney aids in blood cleansing.

2. The urinary bladder: This structure resembles a sac and holds urine until it is out. Urine is sent to it through ureters that are attached to each kidney independently.

3. Urethra: This structure, which resembles a tube, emerges from the bladder. In males, it is longer, whereas in females, it is shorter. It is a typical route for both urine and sperm in males.

(b) Describe in brief how urine is produced in the human body.

Answer:

Chemical waste products produced by our bodies include uric acid and urea. The kidneys remove these waste products from the circulation. Thus, the kidney functions only as a blood filter. It has nephrons, which are the basic kidney structures that aid in the filtering of blood.

The renal tubule and Bowman’s capsule make up its two components. The cup-shaped Bowman’s capsule contains the Glomerulus, a coiled blood capillary tube that aids in blood filtration. The renal tubule receives the filtrate.

However, as the first filtrate travels through the renal tubule, some of the substances such as glucose, amino acids, and salts are more frequently absorbed together with an immense quantity of water in the capillaries surrounding the tubule. The remaining liquid travels to the bladder through the collecting duct to be stored. Urine travels down the urethra and exits the body when the bladder is full.

Also Read: Urine Formation

Question 28: (a) What is the law of dominance of traits? Explain with an example.

Answer:

Gregor Mendel, who discovered the fundamental principles of heredity, established the Law of Dominance. According to this, “only one form of trait appears in the next generation when parents with pure, contrasting traits are crossed together.” An organism’s appearance of a trait is typically caused by two alleles, of which the dominant allele manifests its effects more strongly than the recessive one. In other words, in heterozygous individuals, the dominant allele suppresses the recessive allele.

Consider the plant’s height; ‘T’ indicates tallness, whereas ‘t’ indicates dwarfism.

In the pea plant, the allele “T” is dominant over the allele “t.”

Consider a plant that has genotype Tt crossed with Tt and exhibits “tall” phenotypic traits.

Below is a diagram of a Punnett square representation of the cross.

In the above cross, the genotypic ratio is 1:2:1, meaning that one plant appears tall due to two dominant alleles, two plants have one dominant and one recessive allele, and one plant appears dwarf due to two recessive alleles. With a 3:1 phenotypic ratio, three plants appear to be tall and one is dwarfed.

(b) Why are the traits acquired during the lifetime of an individual not inherited? Explain.

Answer:

The characteristics that an individual acquires throughout their lifetime are known as acquired traits. Changes in lifestyle, injuries, loss of blood components, and food intake are the causes of acquired attributes. In contrast, hereditary traits are those that are determined by genetics. These are traits, like eye color or bone structure, that parents pass on to their children. However, every mutation—a change in the gene sequence—is also transmitted to the DNA sequence, which is the source of heredity. However, because these modifications occur in somatic cells, which are non-reproductive tissues, they cannot be passed on to the following generation, making acquired features not inherited. Therefore, characteristics that a person acquires over their lifetime are not inherited.

CBSE class 10 previous year question papers helps you to understand the level of questions asked in the previous exams, along with the changes in pattern. Practicing the biology class 10 previous year question papers enhances time-management skills while appearing in the board examination. It makes you understand the importance of different topics that have been asked previously.

CBSE Class 10 pyq Biology will boost your confidence level to appear in the examination with proper knowledge of different topics that are going to be asked. It enhances the understanding of the topic and acts as a checkpoint to see the level of preparation that you have done. CBSE biology previous year question paper 2020 is available here.