Ss2 Second Term Biology Exam Questions And Answers
SS2 Second Term Biology Exam Questions and Answers
When preparing for SS2 (Senior Secondary 2) second term biology exams, it is beneficial to review key topics and practice potential exam questions. Below, I have compiled some possible exam questions along with their answers. These questions cover a range of biology topics typically included in the SS2 curriculum.
Questions and Answers
1. What are the processes involved in photosynthesis?
Answer:
Photosynthesis is a process used by plants, algae, and some bacteria to convert light energy into chemical energy stored in glucose. The main processes involved include:
- Light-dependent reactions: These take place in the thylakoid membranes of the chloroplasts where sunlight is absorbed by chlorophyll, splitting water molecules (H_2O) into oxygen (O_2), hydrogen ions, and electrons. This process generates ATP and NADPH.
- Light-independent reactions (Calvin Cycle): Occurring in the stroma of chloroplasts, these reactions use ATP and NADPH produced in the light-dependent reactions to fix carbon dioxide (CO_2) into organic molecules like glucose.
2. Explain the structure and function of the cell membrane.
Answer:
The cell membrane, also known as the plasma membrane, is a complex structure that defines the boundary of the cell. Its key characteristics include:
- Phospholipid Bilayer: Two layers of phospholipids with hydrophilic heads facing outward and hydrophobic tails facing inward. This arrangement provides a semi-permeable barrier.
- Proteins: Embedded in the bilayer to facilitate the transport of molecules and ions, serve as receptors, or act as enzymes.
- Carbohydrates: Often attached to proteins or lipids on the extracellular side, contributing to cell recognition and signaling.
Functions of the cell membrane include:
- Selective Permeability: Controls the entry and exit of substances, allowing the cell to maintain homeostasis.
- Protection and Support: Protects the cell and provides structural support.
- Communication: Contains receptors for signal transduction.
3. Describe the various types of symbiotic relationships in ecosystems.
Answer:
Symbiotic relationships are interactions between different species living closely together. The primary types are:
- Mutualism: Both species benefit. Example: Bees and flowering plants – bees get nectar, and plants get pollinated.
- Commensalism: One species benefits, the other is unaffected. Example: Barnacles on whales – barnacles gain mobility to access food, but whales are unaffected.
- Parasitism: One species benefits at the expense of the other. Example: Tapeworms in humans – tapeworms absorb nutrients, harming the host.
4. What is the role of enzymes in biological reactions?
Answer:
Enzymes are biological catalysts that speed up chemical reactions in cells without being consumed. Their roles include:
- Lowering Activation Energy: Enzymes decrease the energy required to start a reaction, making it proceed faster.
- Specificity: Each enzyme is specific to a particular substrate due to the shape of its active site.
- Regulation: They play a crucial role in controlling metabolic pathways, by being regulated through inhibitors or activators.
5. How does the human circulatory system function?
Answer:
The human circulatory system consists of the heart, blood, and blood vessels, working to transport oxygen, nutrients, hormones, and waste products throughout the body. Key components include:
- Heart: A muscular organ that pumps blood. It has four chambers: two atria and two ventricles.
- Blood Vessels: Include arteries (carry blood away from the heart), veins (return blood to the heart), and capillaries (exchange of substances with tissues).
- Blood: Composed of red blood cells (carry oxygen), white blood cells (immune response), platelets (clotting), and plasma (liquid containing nutrients and hormones).
The circulatory system operates through two primary circuits:
- Systemic Circulation: Delivers oxygenated blood from the heart to the body.
- Pulmonary Circulation: Carries deoxygenated blood from the heart to the lungs for oxygenation.
6. Discuss the structure and function of DNA.
Answer:
DNA (Deoxyribonucleic Acid) is the hereditary material in almost all organisms. Its structure is a double helix, composed of nucleotides. Each nucleotide has a sugar (deoxyribose), a phosphate group, and a nitrogenous base (Adenine, Thymine, Cytosine, or Guanine).
- Base Pairing: Adenine pairs with Thymine, and Cytosine pairs with Guanine through hydrogen bonds.
- Function: DNA stores genetic information and instructions for protein synthesis. It replicates to pass genetic information to new cells and organisms during reproduction.
7. What are the phases of mitosis in eukaryotic cells?
Answer:
Mitosis is a type of cell division resulting in two identical daughter cells, maintaining the diploid chromosome number. The phases include:
- Prophase: Chromosomes condense and become visible, the nuclear membrane disintegrates, and the spindle apparatus forms.
- Metaphase: Chromosomes line up along the equatorial plate.
- Anaphase: Sister chromatids are pulled apart to opposite ends of the cell.
- Telophase: Chromatids reach the poles, nuclear membranes re-form, and the chromosomes decondense.
- Cytokinesis: The cytoplasm divides, resulting in two daughter cells.
8. Explain the importance of biodiversity in ecosystems.
Answer:
Biodiversity refers to the variety of life in an ecosystem. It is crucial due to:
- Ecosystem Services: Biodiversity contributes to services like pollination, climate regulation, and water purification.
- Resilience: Diverse ecosystems are more resilient to environmental changes and disturbances.
- Genetic Variation: A wide range of species increases genetic diversity, essential for adaptation and evolution.
- Cultural and Economic Value: Biodiversity supports recreation, tourism, and resources like medicines and food.
9. What is the nitrogen cycle, and why is it important?
Answer:
The nitrogen cycle is the series of processes through which nitrogen is converted into multiple chemical forms as it circulates among the atmosphere, terrestrial, and marine ecosystems. Critical steps include:
- Nitrogen Fixation: Conversion of nitrogen gas (N_2) from the atmosphere into ammonia (NH_3) by bacteria or through industrial processes.
- Nitrification: Conversion of ammonia to nitrite (NO_2^-) and then to nitrate (NO_3^-) by soil bacteria.
- Assimilation: Uptake of ammonia, nitrite, or nitrate by plants to synthesize proteins and nucleic acids.
- Ammonification: Decomposition of organic nitrogen back to ammonia by decomposers.
- Denitrification: Conversion of nitrate back to nitrogen gas by bacteria, returning it to the atmosphere.
Importance:
- Essential for Life: Nitrogen is a fundamental component of amino acids and nucleic acids, critical to all living organisms.
- Soil Fertility: The availability of nitrogen affects plant growth, impacting agriculture and ecosystem productivity.
10. Describe the adaptations of xerophytes to survive in arid environments.
Answer:
Xerophytes are plants adapted to survive in environments with minimal water. Their adaptations include:
- Thick Cuticle: Reduces water loss by transpiration.
- Reduced Leaf Surface Area: Minimizes water loss by having small or spine-like leaves.
- CAM Photosynthesis: Reverses normal stomatal opening patterns to nighttime, reducing water loss.
- Deep or Extensive Root Systems: Maximizes water uptake from soil.
- Water Storage Tissues: Stores excess water in stems or leaves (e.g., cacti).
These adaptations are crucial for xerophytes to conserve water and thrive in drought-prone areas.
By studying these topics and practicing similar questions, students can enhance their understanding and be better prepared for their biology exams. If you need more information on a specific topic or additional questions, feel free to ask! @LectureNotes