Year 9 Biology Promotional Exam Study Guide

📚 BIOLOGICAL MOLECULES & NUTRITION

Key Definitions

• Balanced Diet: A diet containing all main nutrients in correct amounts and proportions to maintain good health
• Malnutrition: Result of not eating a balanced diet - wrong amounts, incorrect proportions, or lacking key nutrients
• Monosaccharide: Simple sugar (e.g., glucose)
• Disaccharide: Two simple sugars joined (e.g., maltose)
• Polysaccharide: Many simple sugars joined (e.g., starch, glycogen, cellulose)

The Big Three Organic Molecules

1. CARBOHYDRATES 🍞
   • Made of carbon, hydrogen, oxygen
   • Function: Energy source
   • Examples: Glucose → Maltose → Starch/Glycogen/Cellulose
2. PROTEINS 🥩
   • Made of amino acids (20 different types)
   • Function: Growth, repair, enzymes
   • Structure: Amino acids → Polypeptide chains → Proteins
3. LIPIDS 🧈
   • Made of glycerol + 3 fatty acids = Triglyceride
   • Function: Energy storage, insulation, cell membranes
   • Types: Fats (solid) vs Oils (liquid)

Food Tests (Remember Colors!)

Malnutrition Effects

• Obesity: Too much food
• Coronary Heart Disease: Too much saturated fat → cholesterol buildup
• Starvation: Too little food
• Kwashiorkor: Protein deficiency in children (edema, skin problems)

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🌱 GROWTH & DEVELOPMENT

Key Definitions

• Growth: Increase in size and mass
• Development: Changes in complexity and function over time
• Embryo: Early stage of organism development

Growth Process

1. Single cell → Cell division → Embryo → Baby → Adult
2. Cells contain protein (need protein for growth)
3. Energy needed for cell division
4. Growth continues until 18-20 years old

Development Stages

• 0-1 year: Infant
• 2-4 years: Toddler
• 4-11 years: Child
• 12-17 years: Adolescent
• 18+ years: Adult

Exercise Benefits

• Uses energy (prevents fat storage)
• Strengthens heart and muscles
• Improves mental health

Smoking Dangers

• Nicotine: Addictive, damages blood vessels, heart disease
• Tar: Causes cancer (lung, throat, etc.)
• Carbon Monoxide: Reduces oxygen transport, less energy
• Particulates: Damage alveoli, breathing problems

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🌍 ECOLOGY & ENVIRONMENT

Key Definitions

• Ecosystem: Community of organisms + their physical environment
• Biodiversity: Variety of species in an ecosystem
• Habitat: Place where organism lives
• Population: All organisms of same species in an area
• Community: All populations in an area

Ecological Hierarchy

Individual → Population → Community → Ecosystem

Abiotic vs Biotic Factors

Abiotic (Non-living):

• Light intensity
• Temperature
• Moisture
• Soil pH
• Mineral content

Biotic (Living):

• Food availability
• Predators
• Pathogens
• Competition

Food Chains & Energy Transfer

Trophic Levels:

1. Producers (plants/algae) - make own food
2. Primary consumers (herbivores)
3. Secondary consumers (carnivores)
4. Tertiary consumers (apex predators)
5. Decomposers (bacteria/fungi)

Energy Transfer Rules:

• Only 10% energy passes to next level
• 90% lost as heat, movement, waste
• Explains why food chains are short

Cycles in Nature

Carbon Cycle:

• CO₂ removed by photosynthesis
• CO₂ added by respiration, combustion, decomposition

Nitrogen Cycle:

• N₂ gas → Nitrates (by bacteria/lightning)
• Plants absorb nitrates
• Decomposers break down proteins → ammonia → nitrates

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🏭 HUMAN ENVIRONMENTAL IMPACT

Air Pollution

Sulfur Dioxide:

• Source: Burning fossil fuels
• Effects: Acid rain, kills aquatic life, corrodes buildings

Carbon Monoxide:

• Source: Incomplete combustion
• Effects: Binds to hemoglobin, reduces oxygen transport

Greenhouse Effect

Greenhouse Gases: CO₂, methane, water vapor, nitrous oxide, CFCs Effects: Global warming, climate change, rising sea levels, habitat loss

Water Pollution

Sewage:

• Bacteria use oxygen for decomposition
• Algae bloom blocks sunlight
• Result: Oxygen depletion, fish death

Eutrophication:

• Fertilizers → algae bloom → oxygen depletion

Deforestation Effects

• Soil erosion (no root structure)
• Leaching of nutrients
• Disrupted water/carbon cycles
• Loss of biodiversity
• Climate change

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🦠 ENVIRONMENTAL PROBLEMS

Invasive Species

Definition: Non-native organisms that disrupt ecosystems Characteristics: Rapid reproduction, high dispersal, no natural predators Examples: Zebra mussel, Cane toad, Kudzu

Bioaccumulation

Definition: Build-up of toxic substances in organisms Process: Toxins absorbed faster than eliminated Examples: DDT, mercury, lead Effects: Biomagnification up food chain

Ozone Depletion

Cause: CFCs destroy ozone molecules Effects: Increased UV radiation, skin cancer, cataracts

Desertification

Definition: Fertile land becomes desert Causes: Overgrazing, deforestation, poor farming Effects: Loss of biodiversity, food insecurity

Bush Burning

Causes: Hunting, farming, construction, accidents Effects: Destroys soil organic matter, erosion, extinctions

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🌾 RESOURCES FROM LIVING THINGS

Plant Resources

Food Crops: Vegetables, fruits, grains, tubers Cash Crops: Cotton, oil palm, cocoa, coffee Others: Medicinal plants, timber, ornamental plants

Animal Resources

Food: Meat, eggs, dairy products Materials: Hide, skin, bones, horns, feathers Services: Beasts of burden, pets, manure

Economic Importance

• Food security
• Raw materials for industry
• Employment opportunities
• Income generation
• Tourism (zoos, parks)

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🧬 DNA STRUCTURE (Extended)

DNA Basics

• Full name: Deoxyribonucleic acid
• Structure: Double helix (two strands)
• Function: Contains genetic instructions

Nucleotide Components

1. Phosphate group
2. Deoxyribose sugar
3. Nitrogenous base (A, T, G, C)

Base Pairing Rules

• Adenine (A) pairs with Thymine (T)
• Guanine (G) pairs with Cytosine (C)

DNA Structure

• Phosphate + sugar = backbone
• Base pairs = rungs of ladder
• Hydrogen bonds hold strands together

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🎯 EXAM SUCCESS TIPS

Remember for Food Tests

Always state BOTH starting color AND positive result color!

Energy Transfer

10% rule: Only 10% energy transfers between trophic levels

Cycles

Carbon cycle: Photosynthesis removes CO₂, respiration adds CO₂ Nitrogen cycle: Bacteria convert N₂ to nitrates for plants

Environmental Impact

Human activities → pollution → ecosystem damage → need for conservation

Key Processes

• Photosynthesis: CO₂ + H₂O → glucose + O₂
• Respiration: glucose + O₂ → CO₂ + H₂O + energy

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Good luck with your promotional exam! Remember to read questions carefully and use specific scientific terminology in your answers.