BiologyChapter 14: Evolution
Speciation
A species (biological): can interbreed and make fertile young (Mayr school).
Learning objectives
- Explain speciation in clear biological language.
- Distinguish 1. allopatric from 2. isolating mechanisms.
- Use the key terms to answer a short Federal Board exam question.
Definition
A species (biological): can interbreed and make fertile young (Mayr school). Horses x donkeys = sterile mule: two species. Speciation: split into two gene pools. Allopatric: a barrier (river, island). Sympatric named (polyploidy in plants school). Reproductive isolation: prezygotic (song, season, anatomy) and postzygotic (sterile hybrid). Adaptive radiation: many species from one (finches). Speciation occurs when populations become reproductively isolated and accumulate genetic differences until they cannot produce fertile offspring together.
Formula
donkeys = sterile mule
Important terms
- SPECIATION
- A species (biological): can interbreed and make fertile young (Mayr school).
- 1. ALLOPATRIC
- Geography first.
- 2. ISOLATING MECHANISMS
- Songs, pheromones, flowers wrong season.
Overview
Split a gene pool:
Allopatric
Geography first. Mutation and selection differ on each side. When they meet later, they may not breed. Ring species named if the book likes them. Geographic barrier splits population. Each group evolves independently. Reproductive isolation develops. May not interbreed if reunited (allopatric speciation).
Examples Island finches · Isthmus named optional · Time required
Isolating Mechanisms
Songs, pheromones, flowers wrong season. Hybrid inviability. Polyploid plants can speciate in one generation (named, not a colchicine recipe). Prezygotic: prevent mating or fertilisation (different songs, seasons, anatomy). Postzygotic: zygote dies or hybrid is sterile (mule). Reproductive isolation defines species boundaries.
Examples Pre: never zygote · Post: zygote fails or sterile · No polyploid-lab how-to
WHAT — SPECIATION
A species (biological): can interbreed and make fertile young (Mayr school). Horses x donkeys = sterile mule: two species. Speciation: split into two gene pools. Allopatric: a barrier (river, island). Sympatric named (polyploidy in plants school). Reproductive isolation: prezygotic (song, season, anatomy) and postzygotic (sterile hybrid). Adaptive radiation: many species from one (finches). Speciation occurs when populations become reproductively isolated and accumulate genetic differences until they cannot produce fertile offspring together.
WHY — Why this topic matters
SPECIATION is an independent FBISE learning unit because students must connect its structures and processes with their biological functions and examples.
HOW — How it works
ALLOPATRIC: Geography first. Mutation and selection differ on each side. When they meet later, they may not breed. Ring species named if the book likes them. Geographic barrier splits population. Each group evolves independently. Reproductive isolation develops. May not interbreed if reunited (allopatric speciation). Examples: Island finches; Isthmus named optional; Time required. ISOLATING MECHANISMS: Songs, pheromones, flowers wrong season. Hybrid inviability. Polyploid plants can speciate in one generation (named, not a colchicine recipe). Prezygotic: prevent mating or fertilisation (different songs, seasons, anatomy). Postzygotic: zygote dies or hybrid is sterile (mule). Reproductive isolation defines species boundaries. Examples: Pre: never zygote; Post: zygote fails or sterile; No polyploid-lab how-to. Exam mule: Horse and donkey can mate. The mule is sterile. So they stay two species on the fertility test.
In simple words
Speciation names. No chromosome-doubling protocol.
Key points
- fertile offspring test
- barrier then isolation
- place splits
- cannot share genes
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Speciation
Sticky Notes · Quick Revision
Core Idea
- A species (biological): can interbreed and make fertile young (Mayr school). Horses x donkeys = sterile mule: two species. Speciation: split into two gene pools. Allopatric: a barrier (river, island). Sympatric named (polyploidy in plants school). Reproductive isolation: prezygotic (song, season, anatomy) and postzygotic (sterile hybrid). Adaptive radiation: many species from one (finches). Speciation occurs when populations become reproductively isolated and accumulate genetic differences until they cannot produce fertile offspring together.
1. ALLOPATRIC
- Geography first. Mutation and selection differ on each side. When they meet later, they may not breed. Ring species named if the book likes them. Geographic barrier splits population. Each group evolves independently. Reproductive isolation develops. May not interbreed if reunited (allopatric speciation).
2. ISOLATING MECHANISMS
- Songs, pheromones, flowers wrong season. Hybrid inviability. Polyploid plants can speciate in one generation (named, not a colchicine recipe). Prezygotic: prevent mating or fertilisation (different songs, seasons, anatomy). Postzygotic: zygote dies or hybrid is sterile (mule). Reproductive isolation defines species boundaries.
Exam Example
- Exam mule:
- Horse and donkey can mate.
- The mule is sterile.
- So they stay two species on the fertility test.
Common Misconception
- Do not treat 1. ALLOPATRIC and 2. ISOLATING MECHANISMS as the same idea; each explains a different part of the topic.
FBISE Exam Check
- Define speciation, explain the two key parts, and use the correct biological terms.
- Exam reminder: Exam mule: Horse and donkey can mate. The mule is sterile. So they stay two species on the fertility test.
60-second revision
- A species (biological): can interbreed and make fertile young (Mayr school).
- 1. ALLOPATRIC: Geography first.
- 2. ISOLATING MECHANISMS: Songs, pheromones, flowers wrong season.
- Exam reminder: Exam mule: Horse and donkey can mate. The mule is sterile. So they stay two species on the fertility test.
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