A-Level Biology Examination 2025

Strategies for securing an A* in A Level biology

1. Targeted Revision
   • Use the official CIE syllabus to ensure all learning objectives are covered.
   • Create summary sheets or mind maps for key topics like genetics, photosynthesis, respiration, enzyme action, and practical techniques.
2. Examiner Report Analysis
   • Go through past examiner reports to understand common mistakes and what examiners look for.
   • Discuss model answers from top scorers to highlight the level of detail expected.
3. Past Paper Practice
   • Answer as many past papers timed under exam conditions.
   • Self-mark using CIE mark schemes and adjust answers accordingly.
   • Paper 4. 9700/42 (Structured Questions) Preparation
   • This paper requires strong application of knowledge. Key strategies:
   • Mastering Command Words
     • Learn to answer questions based on keywords like “describe,” “explain,” “compare,” and “evaluate.”
     • Provide a glossary of command words with sample answers.
   • Topic-Specific Drills
     • Focus on high-weightage topics like molecular biology, biotechnology, and homeostasis.
     • Undertake quick-fire Q&A sessions to improve recall.
   • Writing Concise and Clear Answers
     • Write to the point, avoiding unnecessary details.
     • Practice using key terms correctly as expected by CIE.
   • Application and Data-Based Questions

1. Paper 5.9700/52 (Practical) Preparation

This paper assesses experimental design, analysis, and evaluation. Key strategies:

1. Hands-on Practical Experience
   • Conduct frequent lab sessions focusing on microscopy, enzyme reactions, osmosis, and ecological sampling.
   • Practice writing precise observations and conclusions based on experimental data.
2. Graph and Data Interpretation
   • Teach students how to analyze trends, identify anomalies, and suggest improvements.
   • Practice plotting graphs with correct scales, axes labels, and trend lines.
3. Experimental Design Questions
   • Focus on variables, control experiments, and method precision.
   • Use real past practical apers

1. Final Revision Plan

• March – Early April: Intensive revision and concept clarification.
• Mid-April – May: Exam-focused practice with full papers under timed conditions.
• Final 2 weeks: Error correction, last-minute topic refreshers, and confidence-building.

 and ……….A* will be yours.

Go for it! You can do it!

Top 100 concepts for A Level Biology

1. Inheritance: The transmission of characteristics from one generation to successive generations of living organism. Two aspects of inheritance are Heredity and Variation. Heredity refers to the tendency of organisms to resemble their parents by the transfer of traits(parent) from one generation (offspring) to another.Variation refers to the differences between offsprings and their parents, between offsprings and among the members of the same species.
2. Factors(genes) are the units of heredity and they may have two or more different forms called Alleles. Alleles can be dominant, recessive, or co-dominant.

     Mendelian genetics explains dominant and recessive traits using

Punnett squares.

  If tall (T) is dominant and short (t) is recessive, crossing Tt x Tt results in a 3:1 ratio of   tall to short.

• 3.Types of Variation and Natural Selection
• Variation refers to the differences between offsprings and their parents, between offsprings and among the members of the same species.

Variations can be:

• Inheritable (Genetic) variations (caused due to changes in the genetic material Mutations and recombination (during meiosis),
• Environmental Variations (caused due to climate, diet) are not inherit

4. Natural selection:

Natural selection —is the process by which individuals with a particular set of alleles survive better and reproduce than those with other alleles; over time and many generations, the advantageous alleles become more frequent in the population. Natural selection acts on variation and leads to evolution.

Survival of the fittest – individuals with advantageous traits reproduce more successfully.

The peppered moth evolved darker coloring during the Industrial Revolution due to better camouflage on soot-covered trees.

• 5. Evolution

Evolution is the change in the characteristics of a population or a species over time. Evolution is the long-term change in allele frequency over generations due to:

• Natural selection,
• Genetic drift,
• Mutation,
• Gene flow (migration).

Evidence for Evolution includes:

• Palaeontological evidences (Fossils)
• Biochemical evidences (similarity in bio-molecules such as DNA ,Amino acids and Proteins)
• Anatomical evidences (Comparative anatomy)

Darwin’s finches show Adaptive radiation – different beak shapes evolved for different food sources on the Galápagos Islands. This is an example for Divergent Evolution.

• 6. Gene Technology (Genetic Engineering)

Genetic engineering involves manipulation of the genetic material (DNA) of an organism by adding, deleting or replacing genes. The newly formed DNA is called Recombinant DNA. Therefore, it is also called Recombinant DNA Technology. The technique involves many steps such as  

• Isolating desired gene,
• Inserting into vector (plasmid/virus),
• Transferring to host organism.

Genetically modified organisms are called Transgenics  or  GM(Genetically modified organisms)  It is used in the production of GM crops, Humulin (Human insulin) and gene therapy.
Eg: Insulin for diabetics is produced using genetically modified E. coli bacteria with the human insulin gene.

7. Cloning

Cloning creates genetically identical copies of gene/cell/organisms.

Types:

• Natural cloning: e.g. Asexual reproduction by means vegetative propagules such as buds/suckers/runners in plants.

• Artificial cloning:
  • In animals (e.g., Dolly the sheep),
  • In plants (micro-propagation using Plant tissue culture).

Applications of Cloning include the conservation of desirable traits.

Eg:
Horticulture companies clone disease-resistant plants through tissue culture to maintain consistency and increase supply.

• 8. Stem Cells

Stem cells are undifferentiated cells with the potential to become various cell types.

• Embryonic stem cells: Pluripotent.
• Adult stem cells: Multipotent (e.g., bone marrow → blood cells).

Used in regenerative medicine and treatment of degenerative diseases.

Eg: Leukaemia patients can receive bone marrow transplants (rich in stem cells) to regenerate blood cells after chemotherapy.

9. Hormonal Coordination

Hormones are chemical messengers produced by endocrine glands, transported in the blood to target organs. They act slower but last longer than nervous responses. Key hormones include insulin, glucagon, adrenaline, ADH, and thyroxine.

Adrenaline prepares the body for ‘fight or flight’ in emergencies, increasing heart rate and blood flow to muscles.

• 10. Control of Blood Glucose

Maintaining blood glucose concentration is crucial for metabolic stability. Insulin lowers it by stimulating glucose uptake and glycogenesis, while glucagon raises it by promoting glycogenolysis and gluconeogenesis. Negative feedback maintains balance.

 

In Type 1 diabetes, insulin production is deficient, requiring insulin injections to regulate blood sugar.

• 11. Excretion

Excretion is the removal of metabolic waste, including carbon dioxide (lungs), urea (kidneys), and salts/water (skin, kidneys). The liver plays a key role in de-amination to produce urea.

Metabolic wastes such as Urea are removed by dialysis in patients with renal failure, replacing kidney function.

1. 11. Control of Heart Rate

Heart rate is regulated by the medulla oblongata and the autonomic nervous system. Sympathetic nerves increase heart rate, while parasympathetic nerves decrease it. Receptors in the aorta and carotid arteries detect CO₂ and pH changes.

During exercise, increased CO₂ triggers faster heart rate to deliver more oxygen and remove waste.

 12. Photosynthesis:

Photosynthesis is the process by which green plants convert light energy into chemical energy, using carbon dioxide and water. It occurs in chloroplasts and involves light-dependent and light-independent (Calvin cycle) reactions.

 

Plants like maize and sugarcane use photosynthesis to produce glucose, which is stored and used for energy.

13. Respiration

Respiration is the breakdown of glucose to release energy. It can be aerobic (with oxygen) or anaerobic (without oxygen). The energy released is used to produce ATP.

 

During intense exercise, human muscles switch to anaerobic respiration, producing lactic acid.

 

13. Enzymes

Enzymes are modified protein as biological catalysts that speed up metabolic reactions without being consumed. They are affected by temperature, pH, and substrate concentration.

 

Amylase breaks down starch into sugars in the human mouth and small intestine.

15. Replication:

DNA replication is the process by which two identical copies of DNA are formed from a mother DNA.

 

When skin cells divide to repair a wound, they replicate their DNA to maintain genetic consistency.

1. 16. Protein Synthesis

 

Protein synthesis involves transcription (DNA to mRNA) and translation (mRNA to protein). Ribosomes read codons on mRNA to assemble amino acids into polypeptides.

 

Insulin is a protein hormone synthesized by pancreatic beta cells using this process.

1. 17. Mitosis

Mitosis is a type of cell division that results in two genetically identical daughter cells. It is essential for growth, repair, and asexual reproduction.

 

Human skin and hair cells undergo mitosis continuously to replace old cells.

1. 18.Meiosis

 

Meiosis is a reduction division that produces four genetically different haploid cells (gametes), increasing genetic variation in sexually reproducing organisms.

 

Meiosis occurs in human ovaries and testes to produce eggs and sperm(Gametogenesis).

• Genetic Mutations

 

19.Mutations are sudden heritable changes in the DNA sequence. They can be neutral, beneficial, or harmful and are a source of genetic variation.

 

Sickle cell anemia is caused by a point mutation in the gene for hemoglobin.

• 20. Transport in Plants

 

Plants transport water, minerals, and sugars through xylem and phloem. Xylem transports water via transpiration pull; phloem uses translocation for sugars.

 

Tall trees like redwoods rely on xylem to move water from roots to leaves.

• 21. Transport in Animals

 

The circulatory system in animals transports oxygen, nutrients, hormones, and waste. It includes the heart, blood vessels, and blood. Humans have a double circulatory system.

 

Red blood cells transport oxygen from the lungs to body tissues via hemoglobin.

• 22.Homeostasis

 

Homeostasis is the maintenance of a stable internal environment within an organism, despite external changes. It involves sensors, effectors, and negative feedback mechanisms.

 

The human body maintains a constant internal temperature of about 37°C through sweating or shivering.

• 23.Osmoregulation

Osmoregulation is controlled by the hormone ADH which increases water reabsorption in response to dehydration.

 

In a dehydrated person, more ADH is released, leading to the production of concentrated urine.

• 24.Nervous System

The nervous system consists of the brain, spinal cord, and peripheral nerves. It uses electrical impulses to enable rapid responses to stimuli via reflex arcs and voluntary actions.

 

Touching a hot object triggers an immediate withdrawal reflex via the spinal cord.

• 25.Synapses and Neurotransmitters

 

Synapses are junctions between neurons where neurotransmitters transmit signals across gaps. They ensure unidirectional impulse flow and allow integration of signals.

Neurotransmitters Serotonin and dopamine are neurotransmitters involved in mood regulation and motivation.

 

Cones allow color vision in bright light, while rods are more sensitive to dim light.

• 26. Drugs and the Nervous System

 

Drugs affect neurotransmission. Stimulants increase transmission (e.g. caffeine), while depressants slow it down (e.g. alcohol). Some mimic or block neurotransmitters.

 

Morphine blocks pain by mimicking endorphins and binding to pain receptors.

• 27. Reproduction in Humans

 

Human reproduction involves gamete formation, fertilization, development of the embryo, and birth. Hormones regulate ovulation and menstrual cycle.

 

The placenta facilitates nutrient and gas exchange between mother and fetus during pregnancy.

• 28. Reproduction in Plants

 

Plants reproduce sexually via pollination, fertilization, and seed dispersal. Wind- and insect-pollinated flowers have distinct structural adaptations.

 

Sunflowers rely on bees for pollination, while grasses use wind to transfer pollen.

• 29.Growth

 

Growth is an irreversible increase in size and mass. It involves division, enlargement and differentiation of cells.

30. Development

Development includes all changes from a zygote to a mature organism, controlled by hormones and genes.

31. Metamorphosis:

A tadpole develops into a frog through a process called metamorphosis.

• 32. Population Dynamics

Population dynamics study changes in population size due to birth rates, death rates, immigration, and emigration. Limiting factors include food, disease, and space.

Rabbit populations in Australia exploded without predators, then declined due to disease introduction.

Blood group is an example of genetic variation, while sun-tanned skin is due to environmental variation.

1. 33. Monohybrid and Dihybrid Crosses

 

Monohybrid crosses involve one gene; dihybrid crosses involve two genes. These crosses predict offspring genotype and phenotype ratios.

 

A dihybrid cross between RrYy x RrYy yields a 9:3:3:1 phenotypic ratio.

• 34.Sex Determination

 

Sex determination in humans is controlled by XX (female) and XY (male) chromosomes. The father’s sperm determines the child’s sex.

 

A child inheriting an X from the father will be female (XX), and a Y will make the child male (XY).

 

• 35.Selective Breeding

Selective breeding involves choosing parents with desired traits to produce offspring with those traits.

Cows are selectively bred for high milk yield, and crops for pest resistance.

Evolution is the gradual change in organisms over time. Speciation occurs when populations become reproductively isolated and form new species.

 

Darwin’s finches evolved different beak shapes on the Galápagos Islands due to ecological isolation.

• Water Transport in Plants
  Water transport in plants occurs primarily through xylem vessels, moving from roots to leaves due to capillary action, root pressure, and the evaporative pull from transpiration.
   It is crucial for nutrient transport, photosynthesis, and maintaining cell turgor, affecting plant growth and productivity.

• Transpiration
   Transpiration is the process by which water evaporates from the plant’s leaves, creating a negative pressure that helps draw more water upward from the roots.
   It aids in nutrient transport, regulates temperature, and maintains water balance within the plant.

• Transpiration pull:

The physiological process in plants where in a pulling force(-ve pressure) is produced inside the xylem tissue. This force helps in the upward movement of water through the xylem vessels into the leaves. This process leads to the loss of water in the form of vapours through leaves are observed.

• Plasmodesmata:

Cytoplasmic strands extended between adjacent cells through the pits which connects their cytoplasms together as a multinucleate mass referred to as Symplast. Water flows from the cytoplasms of adjacent cells. This is called the Symplast pathway. Here the moving water can use the simplast pathway to pass through the plasma membrane along the water potential gradient. It is by going down the water potential gradient water reach the xylem vessel

• Ethanol fermentation in rice:

Rice is moistly cultivated as wet crop and sometimes they remain immersed in water for long periods. Some varieties of rice plants respond to this situation of over flooding by ethanol fermentation and grow upwards. In this process the starch in the submerged cells is anaerobically converted into ethanol.

52. Cohesion-Tension Theory
 This theory explains how water moves through plants via the cohesive properties of water molecules and the tension created by transpiration.
 It is essential for understanding how plants can transport water against gravity, making it fundamental for plant biology.

53. Xerophytes and Hydrophytes
 Xerophytes are plants adapted to arid environments, while hydrophytes thrive in aquatic environments. They have special adaptations for water conservation or absorption.
 Understanding these adaptations is crucial for ecology, conservation, and agriculture in varying climates.

54. Mass Transport in Animals
 The movement of substances (such as gases, nutrients, and waste) throughout an organism via the circulatory system, primarily facilitated by the blood.
 Vital for maintaining homeostasis, delivering oxygen and nutrients, and removing metabolic waste.

55. Haemoglobin
 A protein in red blood cells that binds oxygen for transport from the lungs to tissues and assists in carbon dioxide transport back to the lungs.
 Central to respiratory physiology, essential for effective oxygen delivery and cellular respiration.

56. Tissue Fluid Formation
 Tissue fluid (or interstitial fluid) is formed when blood plasma exits capillaries, providing a medium for nutrient and waste exchange between cells and blood.
 Important for maintaining tissue health and facilitating cellular processes.

57. Lymphatic System
 A part of the circulatory and immune systems that helps maintain fluid balance and transport lymph, which contains white blood cells.
 Crucial for immune responses and the removal of excess tissue fluid, preventing edema.

58. Pathogens and Disease
 Pathogens (bacteria, viruses, fungi, and parasites) can cause diseases in hosts, leading to a variety of symptoms and health issues.
 Understanding pathogens is critical for disease prevention, public health, and medical research.

59. Immune Response
 The body’s defense mechanism against pathogens, involving both innate (immediate) and adaptive (specific) responses.
 Essential for health as it protects against infections and diseases.

60. Vaccination
 The introduction of a small, safe amount of a pathogen or its components into the body to stimulate an immune response.
 Key tool in disease prevention, helping control and eradicate infectious diseases.

61. Monoclonal Antibodies
 Lab-produced antibodies that are identical and specific to a particular antigen, used for diagnostics and treatments.
 Important in targeted therapies, especially in cancer treatment and disease diagnostics.

62. HIV and AIDS
 HIV (Human Immunodeficiency Virus) attacks the immune system, leading to AIDS (Acquired Immunodeficiency Syndrome), where the body can no longer fight infections.
 Understanding HIV/AIDS is crucial for prevention, treatment strategies, and addressing global health issues.

63. Antibiotics and Resistance
 Antibiotics are substances that kill or inhibit bacteria, but misuse can lead to antibiotic resistance, where bacteria evolve to survive treatment.
 Critical for public health, it highlights the need for responsible use of antibiotics to combat resistant strains.

64. Cell Cycle and Mitosis
 The cell cycle consists of stages that lead to cell division (mitosis), during which one cell divides into two identical daughter cells.
 Fundamental for growth, repair, and reproduction of organisms, and understanding cancer development.

65. Meiosis and Genetic Variation
 Meiosis is a type of cell division that reduces the chromosome number by half, resulting in four gametes, each genetically distinct from the parent cell. It includes two rounds of division and introduces genetic variation through processes like crossing over and independent assortment.
Meiosis is crucial for sexual reproduction and ensures genetic diversity in populations, which is important for evolution and adaptation.

66. Stem Cells
 Stem cells are undifferentiated cells capable of giving rise to various cell types. They can be classified into embryonic stem cells and adult stem cells.
Stem cells hold potential for regenerative medicine, allowing for the development of therapies for diseases such as diabetes, Parkinson’s, and injuries by regenerating damaged tissues.

67. Totipotency and Pluripotency
 Totipotent cells can differentiate into any cell type, including extra embryonic tissues (like the placenta). Pluripotent cells can develop into nearly all cell types but cannot form whole organisms.
 Understanding these concepts is essential in developmental biology and therapeutic applications, as they delineate the potential of stem cells in research and medicine.

68. Gene Therapy
 Gene therapy involves altering or manipulating genes to treat or prevent disease, often by inserting therapeutic genes into a patient’s cells.
 This approach holds promise for treating genetic disorders, some cancers, and viral infections, providing a potentially permanent solution rather than symptom management.

69. Epigenetics
 Epigenetics studies heritable changes in gene expression that do not involve changes to the underlying DNA sequence, often influenced by environmental factors.

 Understanding epigenetics is critical for insights into development, responses to environmental stressors, and diseases such as cancer.

70. Apoptosis
 Apoptosis is programmed cell death, a crucial mechanism for maintaining homeostasis and development by eliminating unnecessary or damaged cells.
 It plays a vital role in preventing cancer by removing malfunctioning cells and is important in shaping tissues during development.

71. Plant Hormones and Growth
 Plant hormones (or phytohormones) are chemical substances that regulate plant growth and development, including auxins, gibberellins, cytokinin, and abscisic acid. Understanding plant hormones is essential for agriculture and horticulture, allowing for improved crop yields and health.

72. Tropic movements (Tropism):

Tropic movements are directional growth movements of plants in response to directional stimuli from their environment.

They are Phototropism(light) Gravitropism(gravity), Chemotropism(chemicals),  Thigmotropism (stimulus of touch), Thermotropism(heat), and Hydrotropism(water)  Phototropism(light) and Geotropism(gravity)
 Phototropism is the growth response of plants to light, while gravitropism is their growth  response to gravity.  These mechanisms help plants orient themselves optimally in their environment for photosynthesis and structural stability.

73.Phytohornones :

Auxins, Gibberellins, and Cytokinins
 Auxins promote cell elongation, gibberellins regulate growth and development, and cytokinins promote cell division.
 These hormones are critical for plant development, influencing processes such as fruit development, seed germination, and overall growth.

74. Plant Defences against Pathogens
 Plants have various defense mechanisms against pathogens, including physical barriers (like cell walls) and biochemical responses (like producing antimicrobial compounds).  Understanding these defenses can enhance agricultural practices by improving crop resilience and reducing the need for chemical pesticides.

75. Animal Behaviour
 Animal behavior encompasses the actions and reactions of animals in response to external or internal stimuli, influenced by genetic and environmental factors. Studying animal behavior helps in understanding species interactions, ecology, and can inform conservation efforts and animal welfare practices. 

• 76. Evolutionary Biology
  
   Evolutionary biology studies the processes that drive the diversity of life on Earth, focusing on mechanisms such as natural selection, gene flow, genetic drift, and mutation.
  
   This field helps us understand the origins of species, their adaptations, and how life evolves over time, which is crucial for conservation efforts and understanding biodiversity.
  
  77. Speciation
  
   Speciation is the process by a new species is formed from a pre-existing species, by accumulation of variations often due to geographical, ecological, or behavioral barriers.
  
   Understanding speciation is key to comprehending biodiversity and evolution, and it informs conservation strategies by highlighting the importance of genetic variation and habitat preservation.
  
  78. Extinction
  
   Extinction is the end of an organism or group of organisms, typically when the last individual of a species dies. It can occur naturally or due to anthropogenic factors like habitat destruction.
  
   Studying extinction helps us understand ecological dynamics and the consequences of biodiversity loss, guiding conservation efforts and sustainable practices.
  
  79. Ecosystem Dynamics
  
   Ecosystem dynamics refers to the interactions and changes within ecosystems, including energy flow, nutrient cycling, and population dynamics.
  
   Understanding these dynamics is essential for ecosystem management and addressing environmental issues like climate change and habitat degradation.
  
  80. Conservation Biology
  
   Conservation biology is the scientific study aimed at protecting and managing biodiversity, focusing on the preservation of species, habitats, and ecosystems.
  
   This field is vital for safeguarding endangered species and restoring natural habitats, which supports ecosystem health and human well-being.
  
  81. Climate Change and Its Effects
  
   Climate change refers to long-term alterations in temperature and weather patterns, mainly caused by human activities such as burning fossil fuels.
  
   Understanding its effects is crucial for developing strategies to mitigate its impact on ecosystems, weather patterns, and species survival.
  
  82. Sustainability
  
   Sustainability refers to managing resources in a way that meets current needs without compromising the ability of future generations to meet theirs.
  
   Promoting sustainability is essential for environmental health, economic stability, and social equity, ensuring a viable planet for future generations.
  
  83. CRISPR
  
  Clustered Regularly Interspaced Short Palindromic Repeats) is a revolutionary genome-editing technology that allows scientists to modify DNA with precision, efficiency, and ease.

    It is a part of the immune system in bacteria which is being harnessed as a powerful tool for    

    genetic modification of organisms.

    Two major components of CRISPR are

1. Guide RNA (gRNA): A short synthetic RNA molecule is designed to match the target DNA sequence. It guides the Cas9 enzyme to the specific location in the genome.
   1. Cas9 Enzyme: This protein cuts both strands of the DNA at the targeted site.

  
84. Human Impact on the Environment

This term examines how human activities, such as industrialization, deforestation, and pollution, affect natural ecosystems and biodiversity.

 Understanding human impact is critical for developing policies aimed at environmental protection and sustainable practices to mitigate negative effects.

85. Behavior Ecology

 Behavioral ecology studies the ecological and evolutionary basis for animal behavior, exploring how behavior contributes to survival and reproduction.

 Understanding behavior allows insights into ecosystem dynamics and species interactions, informing conservation and management strategies.

86. Biodiversity

 Biodiversity refers to the variety of life forms within a given ecosystem, species, or area, encompassing genetic, species, and ecosystem diversity.

 High biodiversity contributes to ecosystem resilience, stability, and services, making it essential for human survival and ecological health.

87. Biomes

 Biomes are large regions characterized by distinct climate, flora, and fauna. Examples include forests, deserts, tundras, and grasslands.

 Understanding biomes is crucial for studying global ecosystems, biodiversity, and the effects of climate change on different habitats.

88. Natural Selection

 Natural selection is a process where organisms better adapted to their environment tend to survive and reproduce, leading to evolutionary changes over time.

 It is a key mechanism of evolution, explaining the adaptation of species and their survival strategies in changing environments.

89. Population Genetics

 Population genetics studies the distribution and changes in frequency of alleles within populations, using principles of Mendelian inheritance and evolutionary theory.

 This field is important for understanding genetic diversity, evolution, and the effects of selection, migration, and drift in populations.

90. Genetic Drift

 Genetic drift is a mechanism of evolution that refers to random changes in allele frequencies in a population, particularly in small populations.

 It can lead to significant evolutionary changes over time and affects biodiversity, particularly in isolated populations.

91. Microevolution
  Microevolution refers to small-scale evolutionary changes within a population, typically  

  involving changes in allelic frequencies over time.
 Understanding microevolution helps explain how populations adapt to their environments and  provides insight into the mechanisms of evolution.

92. Macroevolution
 Macroevolution encompasses large-scale evolutionary changes and patterns, including the formation of new species and the impact of mass extinctions.

 Studying macroevolution helps scientists understand the history of life on Earth and the processes that lead to biodiversity.

93. Phylogenetics
 Phylogenetics is the study of evolutionary relationships among species, often using genetic data to construct evolutionary trees (phylogenies).
 This field provides insights into the evolutionary history of organisms, helping to clarify their relationships and how they evolved over time.

94. Fossil Record
 The fossil record is the collection of all known fossils and their placement in the geological time scale, providing evidence for the history of life on Earth.

 It offers crucial insights into evolution, extinct species, and past environments, helping to validate or challenge evolutionary theories.

95. Biogeography
 Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time.
 Understanding biogeography helps explain patterns of species diversity and distribution, informing conservation efforts and ecological studies.

96. Symbiosis
 Symbiosis refers to a close, long-term interaction between two different biological species, which can be mutualistic, commensal, or parasitic.
Symbiotic relationships are vital for ecosystem functioning and species interactions, influencing evolutionary processes and biodiversity.

97. Mutualism
 Mutualism is a type of symbiosis where both species benefit from the interaction, such as pollinators and flowering plants.
 Mutualistic relationships are critical for ecosystem health, biodiversity, and the functioning of various ecological systems.

98. Parasitism
 Parasitism is a type of symbiosis where one organism (the parasite) benefits at the expense of another (the host).
Understanding parasitism is important for studying disease ecology, host-parasite dynamics, and the impacts on populations and ecosystems.

99. Commensalism
 Commensalism is a type of symbiotic relationship where one organism benefits while the other is neither helped nor harmed.
These relationships can significantly influence community structure and species interactions within ecosystems.

100. Trophic Levels
Trophic levels describe the hierarchical food/ energy positions of organisms in a food chain, indicating their roles as producers, consumers, or decomposers.
Understanding trophic levels is essential for studying energy flow and nutrient cycling in ecosystems.

101. Food Webs
 Food webs are complex networks of feeding relationships among various organisms in an ecosystem, illustrating how energy and nutrients flow.
Food webs provide insights into ecosystem dynamics, species interactions, and the impact of changes within ecosystems.

102. Keystone Species
 Keystone species are those that have a disproportionately large impact on their ecosystem relative to their abundance.
 Protecting keystone species is critical for maintaining ecosystem stability and biodiversity.

103. Ecological Succession
 Ecological succession is the process of change in the species structure of an ecological community over time, typically following a disturbance.
Understanding succession helps in managing ecosystems, restoring habitats, and predicting changes in biodiversity.

104. Invasive Species
 Invasive species are non-native organisms that, when introduced to a new environment, can outcompete native species and disrupt ecosystems.
Studying invasive species is crucial for biodiversity conservation and ecosystem management to mitigate their negative impacts.

# 105. Ecosystem Services
 Ecosystem services are the benefits that humans receive from ecosystems, including provisioning (food, water), regulating (climate, disease), cultural (recreation), and supporting services (nutrient cycling).

 Recognizing and valuing ecosystem services is vital for conservation efforts and sustainable resource management.

86. Farming Practices and Sustainability
 Refers to farming methods that maintain the health of the environment and society over time.
 Sustainable practices help prevent soil degradation, protect water quality, and promote biodiversity.
Example: Crop rotation, cover cropping, and reduced pesticide use.

87. Organic Farming vs Conventional Farming
 Organic farming avoids synthetic fertilizers and pesticides, emphasizing natural processes, while conventional farming often relies on these chemicals.
 The choice impacts food quality, environment, and health.
Example: Organic tomatoes grown without synthetic pesticides vs. conventionally grown tomatoes treated with chemicals.

88. Intensive Farming and Productivity
 Intensive farming maximizes crop yield through high input usage (fertilizers, pesticides, and irrigation).
 Can lead to higher outputs but may cause environmental issues like soil depletion.
Example: Factory farming of poultry or monoculture practices for crops.

89. Ethics of Genetic Engineering
 Examines the moral implications of altering an organism’s genetic material.
 Concerns include potential ecological impacts and food safety.
Example: Genetically modified organisms (GMOs) like Bt corn, which is engineered for pest resistance.

90. DNA Fingerprinting
 A technique used to identify individuals based on unique patterns in their DNA.
 Widely used in forensics, paternity tests, and genetic studies.
Example: Solving a crime by matching DNA found at a crime scene to a suspect.

91. Forensic Applications of DNA Technology
 Use of DNA analysis in legal contexts to solve crimes or resolve legal disputes.
 Provides a powerful tool for identifying suspects or victims.
Example: Using DNA evidence to exonerate an innocent person.

92. PCR (Polymerase Chain Reaction)
 A method used to amplify specific DNA sequences.
 Allows for the analysis of tiny amounts of DNA, crucial in many biological applications.
Example: Diagnosing diseases by amplifying viral DNA from a patient’s sample.

93. Gel Electrophoresis
 A technique used to separate DNA, RNA, or proteins based on their size and charge.
 Essential for analyzing genetic material and conducting research.
Example: Visualizing DNA fragments after PCR to check for successful amplification.

94. Human Genome Project
 An international scientific research project aimed at mapping all the genes in the human genome.
 Has advanced our understanding of genetics and human biology.
Example: Identification of genetic contributors to diseases like cancer.

95. Genetic Screening and Counseling
 Testing for genetic disorders and providing information on risks and implications.
 Helps individuals make informed decisions regarding health and reproduction.
Example: Screening for BRCA mutations associated with breast cancer risk.

96. Bacterial Transformation
 The process in which bacteria take up foreign DNA from their environment.
 Fundamental to genetic engineering and biotechnology.
Example: Creating genetically modified bacteria that produce insulin.