AP Biology 7.11 Variations in Populations Study Notes - New Syllabus Effective 2025
AP Biology 7.11 Variations in Populations Study Notes- New syllabus
AP Biology 7.11 Variations in Populations Study Notes- AP Biology – per latest AP Biology Syllabus.
LEARNING OBJECTIVE
Explain how the genetic diversity of a species or population affects its ability to withstand environmental pressures
Key Concepts:
- Variations in Populations
7.11.A – How Genetic Diversity Helps Populations Survive
🧠 Big Idea:
Genetic diversity = variety of genes in a species or population.
More genetic diversity means more options for survival when the environment changes. It gives nature a toolbox to work with!
🔄 Why Genetic Diversity Matters:
| Without Diversity | With Diversity |
|---|---|
| Everyone is similar ➡️ same weaknesses | Different traits ➡️ some may survive |
| One disease or change could wipe them all out | Some may resist disease or harsh climate |
| Evolution slows down | Evolution keeps working and adapting |
🌍 Environmental Pressures = Survival Test
These can be biotic (living) or abiotic (non-living) factors:
- Climate changes
- Drought or flooding
- New diseases
- Predators or competition
- Human-caused destruction (pollution, habitat loss)
If a population has low diversity, it’s like everyone has the same answers on a test – if the environment “asks” a tough question, no one may survive.
🧬 Examples:
- Cheetahs: Very low genetic variation – risky if diseases hit or climate shifts.
- Crops: Monoculture (same type of crop everywhere) can be wiped out by a single pest.
- Humans: We survive better as a species because of huge genetic variety – skin color, height, disease resistance, etc.
✅ Summary:
Genetic diversity = insurance for survival.
It helps populations:
- Stay healthy
- Adapt to change
- Avoid extinction
➡️ Evolution needs variety to work!
7.11.A.1 – How Genetic Variation Affects Population Survival
🧠 Key Idea:
The amount of genetic variation in a population directly affects how well it can survive and adapt to environmental changes.
🌿 Low Diversity = High Risk
- Populations with low genetic diversity have less flexibility when the environment changes.
- If all individuals are similar, one threat (like a disease or climate change) could wipe them out.
- Example: Cheetahs have low genetic diversity one disease could threaten the whole species.
🌍 High Diversity = More Resilience
- Genetically diverse populations are better at handling surprises drought, heat, new predators, etc.
- Why? Because some individuals probably carry helpful traits that allow them to survive and reproduce.
- More survivors = species continues.
🧪 Think of it like a team with many skills – they’re better prepared for any situation.
🔁 “Good” Alleles Can Turn “Bad” (and vice versa)
- Not all traits are always helpful.
- An allele (version of a gene) that is beneficial in one environment may become harmful in another.
- ✅ Thick fur = good in winter
- ❌ Thick fur = bad in summer
- So, natural selection constantly shifts, depending on what the environment “wants”.
🧬 Summary:
- More genetic variation = more ways to survive.
- Populations with lots of variation can adapt, evolve, and avoid extinction.
- Natural selection acts on these variations – survival of the fittest traits depends on the current environment.