Habitat fragmentation: the same loss, cut two ways
"Habitat fragmentation: the same loss, cut two ways" is a free, interactive Class 12 Biology simulation for NEET, built on the NCERT section "The evil quartet" in Biodiversity and Conservation. Cutting roads through a forest: the same total area lost as many small fragments wipes out large-territory and migratory species first. NEET has asked about this idea 5 times in 10 years of papers.
From the lesson The evil quartet in Biodiversity and Conservation. Change the values and watch what happens.
What it shows
NCERT §13.1.4
Cutting roads through a forest: the same total area lost as many small fragments wipes out large-territory and migratory species first.
Controls
3 to try
- Dragdraw roads/clearings across a 20×20-cell forest grid
- Toggleclear a block vs cut thin strips (same cells lost)
- Readoutlargest fragment size vs each species' minimum territory (tiger, hornbill, deer, frog; illustrative values)
Try this
Lose exactly 25% of the forest cells but keep the tiger: the largest remaining fragment must stay above its territory size.
Common mistake
Naming over-exploitation as the chief cause of extinction; habitat loss and fragmentation is the most important of the evil quartet.
In NEET
10 years of papers
Asked 5 times in 10 years of NEET.
See the past questions: Biodiversity Loss, Biodiversity and Conservation (chapter)
The idea behind it
NCERT §13.1.4
- Today's accelerated extinctions are largely caused by humans. The four major causes are nicknamed 'The Evil Quartet'.
- Habitat loss and fragmentation is the most important cause. Tropical rain forests, which once covered over 14 per cent of the land surface of the Earth, now cover no more than 6 per cent; 1000 more hectares are lost in the time it takes to read this chapter.
- The Amazon rain forest, called the 'lungs of the planet' and home to probably millions of species, is being cleared to grow soya beans or to make grassland for beef cattle. Pollution also degrades many habitats.
- When large habitats are broken into small fragments, mammals and birds that need large territories, and animals with migratory habits, are badly hit and their populations decline.
- Over-exploitation: when 'need' turns to 'greed', species are harvested to extinction. Steller's sea cow and the passenger pigeon were lost this way in the last 500 years, and many marine fish populations are over-harvested today.
- Alien species invasions: introduced species can turn invasive. After the Nile perch was introduced into Lake Victoria in east Africa, over 200 species of cichlid fish, an ecologically unique group, eventually went extinct.
- In India, the invasive weeds carrot grass (Parthenium), Lantana and water hyacinth (Eichhornia) damage the environment, and the illegally introduced African catfish Clarias gariepinus threatens native catfishes in our rivers.
- Co-extinctions: when a species dies out, species bound to it in an obligatory way die too. A host fish takes its unique parasites with it, and in a coevolved plant-pollinator mutualism the loss of one leads to the loss of the other.
Questions
4 answers
- What does the "Habitat fragmentation: the same loss, cut two ways" simulation show?
- Cutting roads through a forest: the same total area lost as many small fragments wipes out large-territory and migratory species first.
- What mistake does the "Habitat fragmentation: the same loss, cut two ways" simulation fix?
- A common mistake it clears up: naming over-exploitation as the chief cause of extinction; habitat loss and fragmentation is the most important of the evil quartet.
- Has NEET asked about this idea?
- Yes. NEET has asked about this idea 5 times in 10 years of papers.
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "The evil quartet" in Biodiversity and Conservation (Class 12 Biology).
Embed this simulation
Free, with a link back
Teaching this idea? Put the simulation on your own page or LMS with this code.