Diversity In Living Organisms Class 8th Science Term 3 Tamilnadu Board Solution

Class 8th Science Term 3 Tamilnadu Board Solution

Evaluation
Question 1.

Match the following.

a) Endoplasmic Reticulum __ sweat gland

b) Glandular Epithelium __ streamlined body

c) Retina __ porter

d) Kidney __ cone cells

e) Fish __ nephron


Answer:



Question 2.

Muscle fibres are branched in (cardiac/ skeletal) muscle.


Answer:

Muscle fibres are branched in cardiac muscle.

The diagram of cardiac muscle is shown below:



Such type of branched arrangement helps the cells to communicate with each other. They form a giant network. They are connected to one another at ends by intercalated discs.



Question 3.

Bone and cartilage are types of (nerves/ connective) tissues.


Answer:

Bone and cartilage are types of connective tissues.

Bone and cartilage are considered as connective tissue because they connect different tissues and organs and provide support to other structures of the body.



Question 4.

Ciliated epithelium is found in (trachea / oesophagus)


Answer:

Ciliated epithelium is found in trachea.

ciliated epithelium is a type of epithelium which contains hair like structures known as cilia which move in a manner to transport particles. This type of epithelium is present in trachea which acts as a barrier to pathogen thus preventing infections and tissue injury. It also moistens and protects the airways.


The diagram is shown below:




Question 5.

Choose the correct answer:

i) Assertion: The image falls on Fovea

ii) Reasoning: Because of refraction of light by vitreous humors

a. A is correct B is wrong

b. B is correct A is wrong

c. B explains A

d. A explains B.


Answer:

c. B explains A

Explanation: human eyes project light to produce sharp images. Light rays from distant object are focussed on retina through cornea, aqueous humor, the lens and then to vitreous humor. The light rays show the phenomenon of refraction due to change in the refractive index of the different mediums. This is how light is focused on retina reaching fovea which have highest density of cone cells.



Question 6.

Complete the table by filling the functions.



Answer:


The diagrams are shown below:






Question 7.

i) Identify part A and part B.

ii) How does part A differ from part B?



Answer:

A. wings of birds

B. wings of bats


i) The diagram is labelled as:




ii) The wings of birds and bats are analogous structures that mean they have same functions and different origin i.e. separate evolutionary origin. These structural changes are result of convergent evolution.



Question 8.

Our kidneys help our body to lead a healthy life - How?


Answer:

1. Living with a healthy body is the best road to live happy, to feel better, and to look better.

2. Different organs and organ systems works in a coordinated manner to achieve this goal. Kidneys are one such organ which helps our body to lead a healthy life.


3. The kidneys are the filtering organs of blood. The kidneys shed waste products from metabolism of wastes such as urea, uric acid crystals, and creatinine by secreting urine. Urine may also contain trace amount of sulfate and phenol waste and excess sodium, potassium, and chloride ions.


4. The kidneys play major role in maintaining homeostasis by regulating the concentration and volume of body fluids. For example, the amount of H+ and HCO3- secreted by the kidneys controls the body's pH. They also regulate the blood pressure of an organism by secreting hormones.



Question 9.

Can you name and describe the muscle which is present only in our heart and works throughout our life?


Answer:

Cardiac muscles are the muscles of heart which works in a regulated manner throughout our life.

Description:



STRUCTURE OF CARDIAC MUSCLE


1. Cardiac muscle, synonym for heart muscle, is the layer of muscle tissue present between the endocardium and epicardium. These inner and outer layers of the heart, respectively, surround the cardiac muscle tissue and separate it from the blood and other organs.


2. Cardiac muscle is made from sheets of cardiac muscle cells. These cells, unlike skeletal muscle cells, are typically unicellular connected to one another through special intercalated discs. These specialized cell junction and the arrangement of muscle cells enable cardiac muscle to contract quickly and repeatedly, forcing blood throughout the body.


3. Cardiac muscles are composed of tubular cardiomyocytes, or cardiac muscle cells. The cardiomyocytes are composed of tubular myofibrils, which are repeating sections of sarcomeres.


4. Intercalated disks transmit electrical action potentials between sarcomeres.



Question 10.

Identify the odd item from column A and write it under column B. Write the common features of the other two items in column.



In Column A, 3 terms are given of which 2 belong to one group and 1 remains odd. Identify the odd item and write it under Column B. Write the common features of the other two under Column C.


Answer:



Question 11.

Copy the diagram of the human eye. Label the following parts:

a. The transparent part of the sclera.

b. The spot on the retina where cones are most abundant.