📘 Theme 1: LIFE
1.1 Importance of Biology and Milestones
- Cell Theory: Schleiden and Schwann established that all living things are made of cells;
Virchow later added that all cells come from pre‑existing cells.
- Darwin’s Evolutionary Theory: Natural selection explains adaptation and speciation. Key
concepts: variation, struggle for existence, survival of the fittest.
- DNA Double Helix: Watson and Crick described the structure; hydrogen bonds between
base pairs (A–T, G–C) stabilize the molecule.
- Applications:
- Medicine: Vaccines, antibiotics, genetic therapies.
- Agriculture: Crop improvement, pest resistance.
- Biotechnology: Recombinant DNA, cloning.
- Environment: Conservation biology, ecosystem management.
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1.2 Science and Scientific Method
- Steps: Observation > Problem > Data > Hypothesis > Prediction > Experiment > Result.
- Controlled Experiments: Control group vs experimental group. Variables: independent,
dependent, controlled.
- Example: Testing light’s effect on plant growth. Hypothesis: “Light increases growth.”
Prediction: Plants in light will grow taller.
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1.3 Scientific Ethics
- Honesty in reporting data.
- Avoiding plagiarism.
- Respect for living organisms in experiments.
- Transparency in funding and conflicts of interest.
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1.4 Common Characteristics of Living Things
- Cellular Structure:
- Prokaryotes: No nucleus, circular DNA, 70S ribosomes.
- Eukaryotes: Nucleus, linear DNA, 80S ribosomes, membrane‑bound organelles.
- Organization: Cell > tissue > organ > system > organism.
- Nutrition:
- Autotrophs: Photosynthesis (plants), chemosynthesis (nitrifying bacteria).
- Heterotrophs: Animals, fungi.
- Mixotrophs: Euglena.
- Energy Production:
- Photosynthesis:
6CO2 + 6H2O + Light > C6H12O6 + 6O2
Occurs in chloroplasts; light reactions (ATP, NADPH) > Calvin cycle (glucose).
- Aerobic Respiration:
, C6H12O6 + 6O2 > 6CO2 + 6H2O + 36 ATP
Glycolysis > Krebs cycle > Electron transport chain.
- Fermentation:
- Lactic: Glucose > Lactic acid + 2 ATP (muscle cells, bacteria).
- Alcoholic: Glucose > Ethanol + CO2 + 2 ATP (yeast).
- Metabolism:
- Anabolism: Building molecules (protein synthesis, glycogen formation).
- Catabolism: Breaking down molecules (respiration, digestion).
- Excretion:
- Humans: Kidneys remove urea.
- Plants: Stomata release O2 and water vapor.
- Growth and Development:
- Growth: Increase in cell number/size.
- Development: Differentiation into specialized cells.
- Reproduction:
- Asexual: Binary fission, budding, spore formation.
- Sexual: Gamete fusion, genetic recombination.
- Response to Stimuli:
- Tropisms: Phototropism, geotropism.
- Nasties: Non‑directional responses (e.g., Mimosa pudica leaf folding).
- Homeostasis:
- Blood sugar regulation (insulin lowers, glucagon raises).
- Thermoregulation (sweating, shivering).
- Variation and Adaptation:
- Variation: Genetic differences (blood groups, eye color).
- Adaptation: Permanent traits aiding survival (polar bear fur, cactus spines).
- Viruses:
- Non‑cellular, require host cells to replicate.
- Contain DNA or RNA, never both.
- Examples: HIV (RNA), Adenovirus (DNA).
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1.5 Classification Approaches
- Aristotle: Classified by habitat and morphology.
- Linnaeus: Binomial nomenclature, hierarchical taxonomy (Kingdom > Phylum > Class >
Order > Family > Genus > Species).
- Modern Systematics: Based on evolutionary relationships, molecular data.
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1.6 Three Domains System
- Bacteria: Prokaryotic, peptidoglycan cell wall.
- Archaea: Prokaryotic, no peptidoglycan, extremophiles.
- Eukarya: Protists, fungi, plants, animals.
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1.1 Importance of Biology and Milestones
- Cell Theory: Schleiden and Schwann established that all living things are made of cells;
Virchow later added that all cells come from pre‑existing cells.
- Darwin’s Evolutionary Theory: Natural selection explains adaptation and speciation. Key
concepts: variation, struggle for existence, survival of the fittest.
- DNA Double Helix: Watson and Crick described the structure; hydrogen bonds between
base pairs (A–T, G–C) stabilize the molecule.
- Applications:
- Medicine: Vaccines, antibiotics, genetic therapies.
- Agriculture: Crop improvement, pest resistance.
- Biotechnology: Recombinant DNA, cloning.
- Environment: Conservation biology, ecosystem management.
---
1.2 Science and Scientific Method
- Steps: Observation > Problem > Data > Hypothesis > Prediction > Experiment > Result.
- Controlled Experiments: Control group vs experimental group. Variables: independent,
dependent, controlled.
- Example: Testing light’s effect on plant growth. Hypothesis: “Light increases growth.”
Prediction: Plants in light will grow taller.
---
1.3 Scientific Ethics
- Honesty in reporting data.
- Avoiding plagiarism.
- Respect for living organisms in experiments.
- Transparency in funding and conflicts of interest.
---
1.4 Common Characteristics of Living Things
- Cellular Structure:
- Prokaryotes: No nucleus, circular DNA, 70S ribosomes.
- Eukaryotes: Nucleus, linear DNA, 80S ribosomes, membrane‑bound organelles.
- Organization: Cell > tissue > organ > system > organism.
- Nutrition:
- Autotrophs: Photosynthesis (plants), chemosynthesis (nitrifying bacteria).
- Heterotrophs: Animals, fungi.
- Mixotrophs: Euglena.
- Energy Production:
- Photosynthesis:
6CO2 + 6H2O + Light > C6H12O6 + 6O2
Occurs in chloroplasts; light reactions (ATP, NADPH) > Calvin cycle (glucose).
- Aerobic Respiration:
, C6H12O6 + 6O2 > 6CO2 + 6H2O + 36 ATP
Glycolysis > Krebs cycle > Electron transport chain.
- Fermentation:
- Lactic: Glucose > Lactic acid + 2 ATP (muscle cells, bacteria).
- Alcoholic: Glucose > Ethanol + CO2 + 2 ATP (yeast).
- Metabolism:
- Anabolism: Building molecules (protein synthesis, glycogen formation).
- Catabolism: Breaking down molecules (respiration, digestion).
- Excretion:
- Humans: Kidneys remove urea.
- Plants: Stomata release O2 and water vapor.
- Growth and Development:
- Growth: Increase in cell number/size.
- Development: Differentiation into specialized cells.
- Reproduction:
- Asexual: Binary fission, budding, spore formation.
- Sexual: Gamete fusion, genetic recombination.
- Response to Stimuli:
- Tropisms: Phototropism, geotropism.
- Nasties: Non‑directional responses (e.g., Mimosa pudica leaf folding).
- Homeostasis:
- Blood sugar regulation (insulin lowers, glucagon raises).
- Thermoregulation (sweating, shivering).
- Variation and Adaptation:
- Variation: Genetic differences (blood groups, eye color).
- Adaptation: Permanent traits aiding survival (polar bear fur, cactus spines).
- Viruses:
- Non‑cellular, require host cells to replicate.
- Contain DNA or RNA, never both.
- Examples: HIV (RNA), Adenovirus (DNA).
---
1.5 Classification Approaches
- Aristotle: Classified by habitat and morphology.
- Linnaeus: Binomial nomenclature, hierarchical taxonomy (Kingdom > Phylum > Class >
Order > Family > Genus > Species).
- Modern Systematics: Based on evolutionary relationships, molecular data.
---
1.6 Three Domains System
- Bacteria: Prokaryotic, peptidoglycan cell wall.
- Archaea: Prokaryotic, no peptidoglycan, extremophiles.
- Eukarya: Protists, fungi, plants, animals.
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