🌿 NEET 2025 ORGANISMS & POPULATION 🌿
Complete Guide to Population Interactions & Attributes
💎 3 GOLDEN FACTS (NEET 2015-24)
87%
Questions from Population Interactions
4x
More questions on Mutualism than Parasitism
7
Direct questions on Population Growth since 2018
⚖️ POPULATION INTERACTIONS COMPARISON
| Interaction | Species A | Species B | Examples | NEET Frequency |
|---|---|---|---|---|
| Mutualism | + (Benefits) | + (Benefits) | Lichens, Mycorrhizae | 3 Q/yr |
| Competition | - (Harmed) | - (Harmed) | Barnacles, Trees | 2 Q/yr |
| Predation | + (Benefits) | - (Harmed) | Tiger-Deer, Insect-Plants | 2 Q/yr |
| Parasitism | + (Benefits) | - (Harmed) | Tapeworm, Cuscuta | 1 Q/yr |
🌍 Organisms & Environment
Major Abiotic Factors:
- Temperature: Affects enzyme activity and metabolism
- Water: Critical for survival (adaptations in xerophytes/hydrophytes)
- Light: Photoperiodism in plants, vision in animals
- Soil: pH, composition affects species distribution
Organism Adaptations:
Behavioral:
- Hibernation (bears)
- Migration (birds)
- Nocturnal activity
Physiological:
- Countercurrent mechanism (aquatic mammals)
- CAM pathway (xerophytes)
- Antifreeze proteins (Arctic fish)
Morphological:
- Thick cuticle (cacti)
- Webbed feet (ducks)
- Streamlined body (fish)
🧠 ADAPTATIONS Mnemonic
"BPM": Behavioral, Physiological, Morphological
Remember all adaptation types with this simple trick
🤝 Population Interactions
Types of Interactions:
Mutualism (+/+)
- Definition: Both species benefit
- Examples:
- Lichens (algae + fungus)
- Mycorrhizae (plants + fungi)
- Rhizobium-legume root nodules
- NEET Focus: Obligate vs facultative mutualism
Competition (-/-)
- Definition: Both species are harmed
- Types:
- Intraspecific (same species)
- Interspecific (different species)
- Examples: Barnacles competing for space
- Gause's Principle: Competitive exclusion
Predation (+/-)
- Definition: Predator benefits, prey is harmed
- Examples:
- Carnivores (tiger-deer)
- Herbivores (cow-grass)
- Insectivorous plants (Venus flytrap)
- Importance: Controls population, maintains balance
Parasitism (+/-)
- Definition: Parasite benefits, host is harmed
- Types:
- Ectoparasites (ticks, lice)
- Endoparasites (tapeworm)
- Brood parasitism (cuckoo)
- Examples: Cuscuta (dodder plant), Plasmodium
🎯 PYQ Highlights:
NEET 2022: Example of mutualism? Answer: Lichens
NEET 2020: Gause's principle explains? Answer: Competitive exclusion
NEET 2018: Cuscuta shows which interaction? Answer: Parasitism
📊 Population Attributes
Key Attributes:
Birth Rate (Natality)
- Number of births per 1000 individuals per year
- Crude birth rate vs specific birth rate
- Factors: Age structure, fertility, mating systems
Death Rate (Mortality)
- Number of deaths per 1000 individuals per year
- Type I, II, III survivorship curves
- Factors: Predation, disease, environmental stress
Age Distribution:
Pre-reproductive: 0-14 years (future growth potential)
Reproductive: 15-44 years (current breeding population)
Post-reproductive: 45+ years (declining population)
🧠 POPULATION Mnemonic
"BDA": Birth rate, Death rate, Age structure
Remember the three key population attributes for NEET
📈 Population Growth Models
Growth Patterns:
Exponential Growth (J-shaped)
- Occurs in unlimited resources
- Formula: dN/dt = rN
- r = intrinsic rate of increase
- Example: Bacteria in culture
Logistic Growth (S-shaped)
- Occurs in limited resources
- Formula: dN/dt = rN[(K-N)/K]
- K = carrying capacity
- Example: Most natural populations
Population Growth Factors:
Density-dependent:
- Competition
- Predation
- Disease
Density-independent:
- Climate
- Natural disasters
- Pollution
🎯 PYQ Highlights:
NEET 2021: Formula for logistic growth? Answer: dN/dt = rN[(K-N)/K]
NEET 2019: What does 'K' represent? Answer: Carrying capacity
NEET 2017: Example of J-shaped growth? Answer: Bacterial culture
Growth Curve Mnemonic:
"JESUS": J-shaped (Exponential), S-shaped (Logistic)
📈 NEET 2025 Predictions
High Probability Topics (90% chance):
- Population interaction symbols (+/+, +/- etc.)
- Comparison of exponential vs logistic growth
- Age pyramid interpretations
- Examples of mutualism and parasitism
Dark Horse Candidates (Surprise Elements):
- Gause's competitive exclusion principle
- Calculations of birth/death rates
- Brood parasitism examples
- Density-dependent vs independent factors
💡 NEET 2025 Master Strategy
- ✅ Memorize all population interactions with examples
- ✅ Practice drawing and interpreting growth curves
- ✅ Solve all PYQs on age pyramids (2015-2024)
- ✅ Create comparison charts for different interactions
With these strategies, you'll dominate the 5-7 marks from Organisms & Population section in NEET 2025! 🌱👥
🚨 NEET GENETICS ALERT!
Pedigree Analysis asked every year since 2015 - Master it now!
