Biology · Biodiversity and Conservation · NEET
It decreases. Diversity is highest at the equator (tropics) and gets lower as you go towards the North or South pole. So Colombia (near the equator) has ~1,400 bird species, New York (41 degrees N) has 105, and Greenland (71 degrees N) has only 56. Remember: away from equator = fewer species.
Latitude means how far a place is from the equator (0 degrees) towards the poles (90 degrees). The latitudinal gradient means that as latitude increases (you move away from the equator), the number of species drops. Tropics (23.5 degrees N to 23.5 degrees S) hold the most species.
Altitude means height above sea level (like going up a mountain). Just like moving towards the poles, moving up a mountain usually lowers species diversity because it gets colder, has less oxygen and harsher conditions. NEET mostly tests the latitudinal gradient with exact numbers, but the altitudinal pattern follows the same idea: higher up = fewer species.
No, do not mix them. The latitudinal gradient is about WHERE you are (distance from equator) controlling diversity. The species-area relationship (Alexander von Humboldt) is about how a bigger AREA holds more species (a rectangular hyperbola). Both are 'patterns of biodiversity' but they answer different questions.
The largely tropical Amazon rainforest in South America has the greatest biodiversity on Earth. It is home to more than 40,000 plant species, 3,000 fishes, 1,300 birds, 427 mammals, 427 amphibians, 378 reptiles and over 1,25,000 invertebrates. This is a direct result of the latitudinal gradient (Amazon sits near the equator).
Which of the following regions of the globe exhibits highest species diversity?
Arrange the following in descending order of the number of species in the Amazonian rainforest: (a) Plants, (b) Birds, (c) Fishes, (d) Invertebrates, (e) Mammals.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The two main patterns are (1) the latitudinal gradient in diversity (species diversity decreases from the equator towards the poles) and (2) the species-area relationship (species richness increases with the area of a region). The altitudinal gradient (up a mountain) follows the same downward trend as the latitudinal one.
These are the exact NEET numbers: Colombia (near the equator) has nearly 1,400 species of birds, New York (41 degrees N) has 105 species, and Greenland (71 degrees N) has only 56 species. India, mostly in tropical latitudes, has more than 1,200 bird species.
Three hypotheses: (a) Tropics had a long undisturbed evolutionary time (no frequent glaciations), giving more time for speciation; (b) Tropical environments are less seasonal, more constant and predictable, which promotes niche specialisation; (c) Tropics receive more solar energy, giving higher productivity and indirectly more diversity.
The tropics lie in the latitudinal range of 23.5 degrees N to 23.5 degrees S. With very few exceptions, this belt harbours more species than temperate or polar areas.
