Category: Biology Second Paper Lecture Sheet

1. Bone: Bone is composed of hard cartilage and calcium.
2. Cartilage: Cartilage or soft bone is composed of soft cartilage and chondrin. It does not contain calcium.
3. Ligaments: Ligaments connect one bone to another bone. It is dense, white fibrous and elastic. It holds various organs in proper place.
4. Tendon: Tendons are located at the ends of muscles and connect bones and muscles. It is dense, strong, whitish, flexible and inelastic.
5. Joint: Two or more unstable meeting points are joints. It facilitates movement, movement, bearing and function of various organs.

1. Formation of body structure: Skeletal system forms the body structure and gives specific shape to the body.
2. Preservation: The skeletal system protects the soft organs of the body such as the heart, lungs, brain, spinal cord, etc.
3. Movement: The skeletal system controls the movement of the body through the contraction and expansion of muscles.
4. Red blood cell production: The main blood producing tissue is the red bone marrow. Red blood cells are produced from the bone marrow of the crown, sternum, thorax, vertebrae, humerus and femur. An average of 26 lakh red blood cells are produced from the bone marrow every second. Macrophages are also produced from red bone marrow.
5. Immunity: Stabilized reticuloendothelial system increases the body’s immune system.
6. Breathing and Hearing: The thorax helps in breathing and the cochlea helps in hearing.
7. Mineral salt storage: Skeletal bones store calcium, phosphorus, potassium etc. About 97% of the body’s calcium is stored in bones.
8. Accumulation of toxic elements: If the body contains toxic elements such as lead, arsenic, etc., the bones store them.
9. As a junction: Acts as a junction of muscles, ligaments and tendons.
10. Pressure and ionic balance: Maintains internal pressure and ionic balance of the body.
11. Hormonal action: Osteocalcin hormone is produced from bone cells. This hormone regulates blood sugar and fat levels.
12. Chemical energy storage: With age, the red bone marrow of the human body changes into yellow bone marrow. Adipose cells are present in pale bone marrow. Adepose cell acts as a reservoir of chemical energy.

The system made up of bone and cartilage derived from the embryonic mesoderm that forms the body structure, carries the weight of the body, attaches muscles and protects the soft parts of the body is called the skeletal system. It is made up of 206 bones. The skeletal system accounts for 15% and 10% of the total body weight of men and women respectively. Volatility density is highest at 21 years of age. The branch of biology that deals with human bones is called Human osteology.

1. As a vegetable: Malvesi plant is used as a vegetable. Radish is the main vegetable. Napa plant is used as vegetable.
2. Rope making: Mestapat and kenaf rope are made from Mestapat. Ropes are used for many purposes.
3. Yarn Making: Cotton produces superior quality yarn. Textiles are made from yarn.
4. As medicine
(i) Hibiscus rosa-sinensis juice cools the head, darkens and lengthens the hair, stops hair fall and promotes new hair growth. It is a good medicine for dysentery and hemorrhoids.
(ii) Oil of forest okra (Urena lobata) is used as medicine.
(iii) Medicines are prepared from the oil of Sida cordifolia.
(iv) Turmeric is useful in diabetes or polyuria.
5. Preparation of food: Soups and other tasty food are prepared from the plants of this tribe.
6. Making Chaat Sacks: Chaat and sacks are made from jute fibers.
7. In textile industry: The plants of this tribe are used to make coatings, toshaks, bags etc.
8. Fuel: Woody plants are used as fuel.
9. Edible oil: Edible oil is produced from cotton seeds. Jalani oil is also obtained from cotton seeds.
10. Essential Materials: Pencils, toys and agricultural implements are made from Kydia calycina and Indian tulip trees.
11. Beautifiers: Plants like jaba, sthalpadma, petari etc. are planted in the garden for beautification.

Reeds are used to make paper pulp and many other things. It grows in wetlands

This grass is called a shrub because it is made into a shrub. It grows in hilly areas.

Lemon grass is a lemon-scented grass. It is used in making perfume oil and cosmetics. It is also used in making Chinese soup.

Durbaghas is used as lawn, animal fodder and medicinal plant. It acts as an herb to stop bleeding and heal wounds.

Bamboo is a tall tree-like primitive grass. 28 species of bamboo grow in Bangladesh. Bamboo is thick, woody and tall. Its flower features, hollow center and other characteristics are grass-like. Hence it is called grass. It is used to make upholstery and furniture. Bamboo plays an immense role in our daily activities.

Molasses and sugar are obtained from sugarcane. Alcohol, vinegar, methylated spirit, country liquor etc. are produced from Chitagur or molasses by fermentation process. Paper and Pertex are made from sugarcane pulp. It provides fuel.