Latihan Soal Persiapan OSN IPA SMP-Biologi (Part-2)

Summary

This educational video provides a detailed and engaging explanation of various science concepts, focusing on topics relevant to the preparation for the Indonesian National Science Olympiad (OSN) in Science for Junior High School. The script covers subjects such as plant water transport, menstrual cycles, human anatomy, immune system functions, genetic inheritance, and biotechnology. Through practical examples and clear explanations, the content helps students understand complex biological and physiological processes, offering insights into everyday science and preparing them for related exams and challenges.

Takeaways

• 😀 Understanding the concept of capillarity in plants: The capillary action in plant stems is influenced by the cohesive forces between water molecules, not the adhesive forces between water and vessel walls.
• 😀 Key difference between adhesion and cohesion: Adhesion refers to the attraction between different types of molecules, while cohesion refers to the attraction between similar molecules (e.g., water molecules).
• 😀 Walang Sangit as a harmful pest: Walang Sangit (Leptokorisa acuta) attacks young rice seeds, causing them to become empty and leading to crop failure.
• 😀 Menstruation cycle breakdown: The phases of menstruation include menstruation (P), pre-ovulation (Q), ovulation (R), and post-ovulation (S), each marked by specific hormone changes.
• 😀 Role of the autonomic nervous system in bladder control: The autonomic nervous system, including the sympathetic and parasympathetic nerves, controls the bladder’s function without conscious effort.
• 😀 The function of leukocytes in the immune system: Lymphocytes produce antibodies to fight viruses and bacteria, while neutrophils are the first responders to infections.
• 😀 The impact of brain injury on vision: Damage to the occipital lobe (located at the back of the brain) can result in vision impairments.
• 😀 Urine test for chlorine: The presence of white precipitate in a urine test using AgNO3 indicates the presence of chlorine, which can lead to kidney stones if excessive.
• 😀 DNA in prokaryotic cells: Prokaryotic cells, such as bacteria, have circular (not linear) DNA that is typically single-stranded.
• 😀 Genetic inheritance and blood types: Understanding the inheritance of blood types shows how recessive and dominant genes from parents contribute to the child’s blood type, including rare cases where a child may not biologically belong to the parents due to mismatched blood types.

Q & A

What is the primary factor affecting the capillarity in plants?

The primary factor affecting capillarity in plants is the cohesion force between water molecules. This allows water to be transported upward through the plant, especially in the xylem vessels.

What is the difference between adhesion and cohesion?

Adhesion refers to the attraction between molecules of different substances, while cohesion refers to the attraction between molecules of the same substance. For example, the cohesion between water molecules allows water to travel upward in plant vessels, while adhesion helps water stick to the walls of the xylem.

Which pest damages young rice seeds, causing them to become empty and ultimately leading to crop failure?

The pest causing this damage is 'Leptokorisa akuta,' commonly known as the 'Walang Sangit,' which attacks young rice seeds, preventing them from developing and leading to empty grains.

What phase of the menstrual cycle is characterized by the thickening of the endometrium?

The thickening of the endometrium occurs during the 'pre-ovulation' phase of the menstrual cycle, often referred to as phase Q, which is marked by increased levels of Follicle Stimulating Hormone (FSH).

Which part of the brain controls vision?

The 'occipital lobe' of the brain is responsible for controlling vision, even though the eyes themselves are located at the front of the head.

Which system controls the functioning of the bladder?

The bladder is controlled by the autonomic nervous system, which operates involuntarily. The sympathetic nervous system helps the bladder expand, while the parasympathetic system causes it to contract.

Which type of leukocyte is responsible for producing antibodies to fight viruses and bacteria?

The 'lymphocytes' are responsible for producing antibodies that help fight viruses and bacteria, contributing to the immune system's defense against infections.

What genetic mutation leads to sickle cell anemia?

Sickle cell anemia is caused by a genetic mutation in the hemoglobin gene, which leads to the production of abnormal hemoglobin. This mutation is typically inherited in a recessive manner.

What genetic principle explains the inheritance of blood type in humans?

Blood type inheritance follows Mendelian genetics, with the ABO blood type system being controlled by alleles A, B, and O. Type A and B are dominant over type O, and type AB results from the combination of both A and B alleles.

What technique is used to create Golden Rice, which is genetically modified to produce vitamin A?

Golden Rice is created using 'genetic engineering,' specifically the technique of inserting genes from microorganisms into rice plants to enable them to produce beta-carotene, a precursor to vitamin A.