BiologyChapter 14: Evolution
Natural Selection and Fitness
Fitness here means relative reproductive success, not gym fitness.
Learning objectives
- Explain natural selection and fitness in clear biological language.
- Distinguish 1. three graphs from 2. artificial.
- Use the key terms to answer a short Federal Board exam question.
Definition
Fitness here means relative reproductive success, not gym fitness. Types named: directional (one extreme), stabilising (middle), disruptive (both extremes). Sexual selection: mate choice, peacocks named. Artificial selection: humans pick (cows, cabbage) — farm history, not a GMO protocol. Selection needs heritable variation; without genes, the trait dies with the body. Natural selection is the differential survival and reproduction of individuals with heritable traits suited to their environment. It is not goal-directed and does not produce perfection.
Important terms
- NATURAL SELECTION AND FITNESS
- Fitness here means relative reproductive success, not gym fitness.
- 1. THREE GRAPHS
- Directional: bigger beaks after a drought (school).
- 2. ARTIFICIAL
- Same genetics, human choice.
Relationship
- fitness = offspring that survive to breed
Overview
Who leaves more young:
Three Graphs
Directional: bigger beaks after a drought (school). Stabilising: human birth mass tale. Disruptive: two food types, two bill sizes. Draw a shifted histogram in words.
Examples Peppered moth named as a colour tale · Industrial melanism as history · Not a how-to to stain moths
Artificial
Same genetics, human choice. Broccoli and kale from Brassica named. Faster than wild selection. Inbreeding risk named. Not a CRISPR farm.
Examples Dairy cows · Dogs · No gene-edit steps
WHAT — NATURAL SELECTION AND FITNESS
Fitness here means relative reproductive success, not gym fitness. Types named: directional (one extreme), stabilising (middle), disruptive (both extremes). Sexual selection: mate choice, peacocks named. Artificial selection: humans pick (cows, cabbage) — farm history, not a GMO protocol. Selection needs heritable variation; without genes, the trait dies with the body. Natural selection is the differential survival and reproduction of individuals with heritable traits suited to their environment. It is not goal-directed and does not produce perfection.
WHY — Why this topic matters
NATURAL SELECTION AND FITNESS is an independent FBISE learning unit because students must connect its structures and processes with their biological functions and examples.
HOW — How it works
THREE GRAPHS: Directional: bigger beaks after a drought (school). Stabilising: human birth mass tale. Disruptive: two food types, two bill sizes. Draw a shifted histogram in words. Examples: Peppered moth named as a colour tale; Industrial melanism as history; Not a how-to to stain moths. ARTIFICIAL: Same genetics, human choice. Broccoli and kale from Brassica named. Faster than wild selection. Inbreeding risk named. Not a CRISPR farm. Examples: Dairy cows; Dogs; No gene-edit steps. Worked directional: Environment favours one extreme. That extreme breeds more. The population mean moves that way.
Worked example
- Worked directional:
- Environment favours one extreme.
- That extreme breeds more.
- The population mean moves that way.
In simple words
Selection as an idea. No breeding-lab protocol.
Key points
- fitness = offspring that survive to breed
- three graph types
- mean moves or not
- human pickers
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Natural Selection and Fitness
Sticky Notes · Quick Revision
Core Idea
- Fitness here means relative reproductive success, not gym fitness. Types named: directional (one extreme), stabilising (middle), disruptive (both extremes). Sexual selection: mate choice, peacocks named. Artificial selection: humans pick (cows, cabbage) — farm history, not a GMO protocol. Selection needs heritable variation; without genes, the trait dies with the body. Natural selection is the differential survival and reproduction of individuals with heritable traits suited to their environment. It is not goal-directed and does not produce perfection.
1. THREE GRAPHS
- Directional: bigger beaks after a drought (school). Stabilising: human birth mass tale. Disruptive: two food types, two bill sizes. Draw a shifted histogram in words.
2. ARTIFICIAL
- Same genetics, human choice. Broccoli and kale from Brassica named. Faster than wild selection. Inbreeding risk named. Not a CRISPR farm.
Exam Example
- Worked directional:
- Environment favours one extreme.
- That extreme breeds more.
- The population mean moves that way.
Common Misconception
- Do not treat 1. THREE GRAPHS and 2. ARTIFICIAL as the same idea; each explains a different part of the topic.
FBISE Exam Check
- Define natural selection and fitness, explain the two key parts, and use the correct biological terms.
- Exam reminder: Worked directional: Environment favours one extreme. That extreme breeds more. The population mean moves that way.
60-second revision
- Fitness here means relative reproductive success, not gym fitness.
- 1. THREE GRAPHS: Directional: bigger beaks after a drought (school).
- 2. ARTIFICIAL: Same genetics, human choice.
- Exam reminder: Worked directional: Environment favours one extreme. That extreme breeds more. The population mean moves that way.
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