Which of the below mentioned regions exhibit less seasonal variations? (a) Tropics (b) Temperates (c) Alpines

NCERT Exemplar · Q18

Q. Which of the below mentioned regions exhibit less seasonal variations?

(a) Tropics

(b) Temperates

(d) Both

(a) & (b)

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Concept understanding — Species Richness Estimation

Let’s begin with something you already know from everyday life.

Imagine you walk into a large, busy market. You see different kinds of shops: a fruit seller, a tailor, a tea stall, a bookshop, a mobile repair kiosk. Now, if someone asks you, “How many types of shops are there in this market?” you would count the distinct categories — fruit, tailoring, tea, books, mobile repair — and say “five types.” That count of distinct types is, in a very rough sense, what ecologists call species richness.

Now take that same market and imagine it’s a forest. Instead of shops, you have different kinds of trees, birds, insects, and fungi. The number of different species present in a given area — say, a national park or a pond — is its species richness. It is the simplest and most fundamental measure of biodiversity: just a count of how many distinct species live there.

Note

Species richness does not tell you how many individuals of each species exist. A forest could have 10 species of trees, with 1,000 individuals of one species and just 2 of another — the richness is still 10. It is a qualitative count, not a quantitative one.

Why does this matter? Because species richness is the first thing ecologists want to know when they study an ecosystem. A forest with 50 tree species is generally considered more biodiverse — and often more stable — than one with only 5. Governments and conservation agencies use species richness to decide which areas to protect. If a wetland has very high richness of bird species, it might be declared a bird sanctuary.

But here is the practical problem: you cannot count every single species in a large area. It is impossible to walk every square metre of a rainforest and list every beetle, moss, and frog. So ecologists use estimation — they sample a small part of the area, count the species they find there, and then use statistical methods to estimate the total richness for the whole area. That is what species richness estimation means: using data from a sample to make an educated guess about the total number of species present.

The NCERT textbook (Class 12 Biology, Chapter 15 – Biodiversity and Conservation) introduces this idea when it talks about how biodiversity is measured. It states that species richness is one of the three key components of biodiversity (the others being species evenness and genetic diversity). The textbook emphasises that tropical regions like the Amazon rainforest have much higher species richness than temperate regions — for example, a single hectare in the Amazon may contain more species of trees than the entire United Kingdom. …

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The Tropics exhibit less seasonal variation than Temperate or Alpine regions, making option (A) the correct choice.

The question asks about seasonal variation — that is, how much the climate, temperature, and day length change over the course of a year. This is a core concept in ecology and biogeography, and the NCERT textbook for Class 12 Biology (Chapter 13, Biodiversity and Conservation) discusses it while explaining why tropical regions have such high biodiversity.

Let’s think about what “seasonal variation” means. In temperate regions (like much of Europe, North America, and northern Asia), the year is sharply divided into warm summers and cold winters. Day length changes dramatically — long days in summer, short days in winter. This forces plants and animals to adapt to a wide range of conditions. Alpine regions (high mountain zones) also experience extreme seasonal shifts, with long, harsh winters and short growing seasons.

Now contrast this with the tropics — the belt around the equator, roughly between the Tropic of Cancer and the Tropic of Capricorn. Here, the sun is nearly overhead throughout the year. Temperature remains high and fairly constant, with little difference between the warmest and coolest months. Day length also varies very little — roughly 12 hours of daylight every day, all year. Rainfall may show some seasonality (wet and dry seasons), but the overall climate is much more stable.

Note

The NCERT textbook states that tropical environments, unlike temperate ones, are “less seasonal, relatively more constant and predictable.” This stability is one reason why tropical forests can support such an enormous number of species — organisms don’t need to invest energy in surviving extreme cold or long periods of darkness. …

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Q.Which of the below mentioned regions exhibit less seasonal variations?

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