admin@kcseforecast.com

+2541026301456

KCSE 2022 BIOLOGY PAPER 1 REVISION

Part of the ovule that forms a zygote after fertilization

  • Embryo sac

Part of the ovule that forms testa after fertilization

  • is the integument, which is the outer layer of the ovule

The hormone responsible for deep voice in humans

  • testosterone
  • It is produced in the testes in males and in smaller amounts in the ovaries in females. Testosterone is responsible for the development of male secondary sexual characteristics such as facial hair, a deeper voice, and increased muscle mass.

Differentiate between a population and a community as used in ecology

  • A population is a group of individuals of the same species living in a specific area
  • A community is a group of populations of different species living and interacting in a specific area

Negative effects of using herbicides on human health

  1. Cancer: Many herbicides contain carcinogenic chemicals, which can increase the risk of certain types of cancer, such as leukaemia, lymphoma, and non-Hodgkin's lymphoma.
  2. Neurological problems: Some herbicides can disrupt the normal functioning of the nervous system, leading to symptoms such as tremors, dizziness, confusion, and memory loss.
  3. Birth defects: Exposure to certain herbicides during pregnancy can lead to birth defects, including abnormal brain development, abnormal growth of the heart, and limb abnormalities.
  4. Reproductive problems: Herbicides can also affect fertility and sexual development in both men and women. In men, herbicide exposure has been linked to decreased sperm count and motility, and in women, it has been linked to decreased fertility and menstrual abnormalities.
  5. Allergic reactions: Some people may have allergic reactions to herbicides, including rashes, hives, and respiratory problems.
  6. Environmental contamination: The use of herbicides can also have negative impacts on the environment, including contaminating soil and water sources and killing beneficial insects and wildlife.

Two ways in which energy is lost from one trophic level to the next in a food chain

  1. Metabolic processes: Energy is lost during the process of metabolism, which is the chemical reaction that occurs in an organism's body to maintain life. This includes processes such as respiration, which converts energy stored in food into ATP (adenosine triphosphate), the energy currency of the cell.
  2. Excretion: Energy is also lost when organisms excrete waste products, such as faeces or urine. These waste products contain energy that was not fully utilized by the organism, and as they are released into the environment, this energy is not available to be passed on to the next trophic level.

Two reasons why anaerobic respiration yields less energy than aerobic respiration

  1. The efficiency of energy production: Anaerobic respiration only produces a small amount of ATP, the primary energy molecule in cells, compared to aerobic respiration. This is because anaerobic respiration only utilizes the first stage of cellular respiration, called glycolysis, which generates just two ATP molecules. In contrast, aerobic respiration generates a much larger amount of ATP through the complete process of cellular respiration, which includes glycolysis and the Krebs cycle.
  2. Energy yield from glucose: Anaerobic respiration only converts a small fraction of the energy stored in glucose into ATP. In glycolysis, only about 5% of the energy stored in glucose is used to produce ATP. In aerobic respiration, the energy yield is much higher, with about 30% of the energy stored in glucose being converted into ATP. This is because aerobic respiration is able to fully break down glucose into water and carbon dioxide, releasing the maximum amount of energy possible. Overall, these factors contribute to the lower energy yield of anaerobic respiration compared to aerobic respiration.

 

Why is fat not an efficient substrate

Fat is not an efficient substrate for energy production because it requires more oxygen to be metabolized compared to carbohydrates. This means that the body must work harder to break down and use fat as fuel, making it a less efficient source of energy. Additionally, fat stores in the body are typically larger and more abundant than carbohydrate stores, so it takes longer for the body to access and use fat as fuel.

 

 

Explain why protozoans do not require an elaborate system of gaseous exchange

Protozoans are single-celled organisms that are capable of obtaining oxygen and eliminating carbon dioxide through diffusion across their cell membranes. They do not have specialized respiratory organs or a circulatory system to transport oxygen and other gases throughout their bodies, as multicellular organisms do.

Because protozoans are so small and have a high surface-to-volume ratio, oxygen and other gases can easily diffuse across their cell membranes to reach all parts of their cells. They do not need an elaborate system of gaseous exchange because they can rely on simple diffusion to meet their oxygen needs.

Additionally, protozoans are often found in aquatic environments where oxygen is more readily available, further reducing the need for specialized gaseous exchange mechanisms. Overall, the simplicity and effectiveness of diffusion allow protozoans to survive and thrive without the need for an elaborate system of gaseous exchange.

State the causative agent of trichomoniasis

  • The causative agent of trichomoniasis is the parasite Trichomonas vaginalis.

Role of hair-like structures in the fallopian tube

  • Hair-like structures, known as cilia, play a vital role in the fallopian tube by helping to move the egg along the tube towards the uterus. The cilia line the inner surface of the fallopian tube and move in coordinated waves, creating a current that pushes the egg towards the uterus. This movement helps to ensure that the egg is properly positioned for fertilization by sperm.
  • Additionally, the cilia also help to remove any debris or mucus that may block the path of the egg, ensuring that the egg has a clear passage to the uterus.
  • Overall, the cilia in the fallopian tube play an essential role in the reproductive process by helping to transport the egg to the uterus and maintaining a healthy environment for fertilization to occur.

Role of hair-like structures in the nasal lining

  • Firstly, cilia help to filter the air we breathe by trapping and removing dirt, dust, and other debris that may enter the nasal cavity. This helps to prevent these particles from entering the lungs, which could cause irritation and inflammation.

Name the agent of pollination in maize plant

  • The agent of pollination in maize plants is typically wind.

Explain the role of the antidiuretic hormone when the human blood water level is below normal

  • The antidiuretic hormone, also known as vasopressin, plays a crucial role in maintaining normal blood water levels in the body.
  • When blood water levels are low, the body's thirst mechanism is activated, causing an increase in the secretion of antidiuretic hormone. This hormone acts on the kidneys by stimulating the reabsorption of water from the renal tubules back into the bloodstream. This helps to conserve water in the body and increase blood volume, bringing it back to normal levels.

Explain the effects of carboxyhaemoglobin in the human body

  • In severe cases, carboxyhemoglobin can lead to unconsciousness and death. This is because the binding of CO to haemoglobin reduces the amount of oxygen that is delivered to the body's cells and tissues. This can lead to hypoxia, which is a lack of oxygen in the body's tissues. Hypoxia can cause damage to the body's cells and organs and can ultimately lead to death.

Two reasons why humans are not used as specimens for genetic studies

  • Ethical considerations: Using humans as specimens for genetic studies raises significant ethical concerns, as it involves manipulating or altering an individual's genetic makeup. This can have unintended consequences and may be seen as a violation of the individual's autonomy and dignity.
  • Legal restrictions: There are also various laws and regulations in place that prohibit the use of humans as specimens for genetic studies. These laws are in place to protect the rights and interests of individuals and ensure that they are not subjected to unnecessary harm or exploitation.

Two environmental conditions that may lead to the formation of carboxyhaemoglobin the body

  1. High levels of carbon monoxide in the air: Carbon monoxide is a toxic gas that is produced when fuels such as gasoline, wood, or coal are burned. It is colourless, tasteless, and odourless, making it difficult to detect. When inhaled, it competes with oxygen for binding sites on the haemoglobin molecule, resulting in the formation of carboxyhemoglobin.
  2. Poor air quality in enclosed spaces: Carboxyhemoglobin can also form in poorly ventilated spaces where there is a high concentration of carbon monoxide. This can occur in poorly maintained buildings, cars, or boats where there are faulty heating systems or appliances. It is important to ensure that these spaces are well-ventilated to prevent the formation of carboxyhemoglobin.

Significance of human lungs being elastic

  • The elasticity of the human lungs is crucial for the proper functioning of the respiratory system. When we inhale, the elasticity of the lungs allows them to expand and fill with air, while the elasticity of the bronchial tubes allows them to stretch and accommodate the incoming air. When we exhale, the elasticity of the lungs allows them to contract and push the air out, while the elasticity of the bronchial tubes allows them to return to their normal size.
  • This elasticity is essential for maintaining proper ventilation and oxygenation of the body. Without it, the lungs would be unable to expand and contract properly, resulting in impaired breathing and reduced oxygen delivery to the body's tissues.
  • In addition, the elasticity of the lungs helps to maintain the proper pressure gradient between the inside and outside of the lungs. This helps to prevent the collapse of the alveoli (small air sacs in the lungs) and ensures that the airways remain open and unobstructed.

Significance of pleural fluid in the lungs

  • Pleural fluid is a clear, sticky liquid that surrounds the lungs and helps to lubricate and protect them. It is produced by the pleural membranes, which are thin layers of tissue that line the chest cavity and enclose the lungs.
  • There are several functions of pleural fluid in the lungs. It helps to reduce friction between the lungs and the chest wall during breathing, allowing the lungs to move smoothly and easily. It also helps to maintain the proper shape and position of the lungs, keeping them from collapsing or becoming distorted.
  • In addition, pleural fluid has several important immune functions. It contains white blood cells and antibodies that help to protect the lungs from infection and inflammation. It also helps to remove debris and other foreign substances from the lungs, keeping them clean and healthy.
  • However, an excess of pleural fluid can also be a sign of a serious medical condition. This is known as pleural effusion, and it can be caused by a variety of factors, including infections, heart failure, cancer, and other diseases. Pleural effusion can cause shortness of breath, chest pain, and other symptoms, and it may need to be treated with medications or other therapies.
  • Overall, pleural fluid is an essential component of the respiratory system, playing a vital role in protecting and supporting the lungs. It is important to monitor and maintain the proper balance of pleural fluid in the body to ensure optimal respiratory health.