Biology · Ecosystems · NEET
No. It is usually upright but not always. In a grassland, there are many grass plants at the base, fewer herbivores above them, and very few top carnivores at the apex, so it is upright. But in a single big tree ecosystem, the pyramid of number is inverted because one tree (the producer) supports many insects, and those insects support even more small birds. So the pyramid of number can be either upright or inverted depending on the ecosystem. Only the pyramid of energy is always upright.
Because number depends on the size and count of organisms, not on their biomass. In a tree ecosystem, there is just one tree at the base but hundreds of insects feeding on it, and even more small birds feeding on those insects. So the count increases as you go up the pyramid. When the base has fewer organisms than the levels above it, the pyramid becomes inverted. This is the classic NCERT example: one tree at the bottom is narrow, insects and birds above are wide.
It is upright. This is a very common NEET point. In a grassland, the producers (grass) are the largest in number, herbivores (deer, rabbits) are fewer, and top carnivores (snakes, hawks) are the fewest. So the base is broad and the apex is narrow, which is an upright pyramid. NEET repeatedly gives 'Pyramid of numbers in grassland is upright' as a correct statement, so remember it.
In an upright pyramid, the number of organisms is highest at the producer level (base) and decreases at each higher trophic level, giving a broad base and narrow top. In an inverted pyramid, the base (producers) has the fewest organisms and the number increases upward, giving a narrow base and broad top. Grassland gives an upright pyramid; a single big tree with insects and birds gives an inverted pyramid.
NCERT uses two examples. For upright, it points to normal ecosystems where producers outnumber herbivores and herbivores outnumber carnivores. For inverted, it asks you to count insects feeding on a big tree, then the small birds eating the insects, then larger birds eating the smaller ones. Since one tree supports many insects and many birds, the shape comes out inverted.
Which of the following ecological pyramids is generally inverted?
Which of the following statements is not correct?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Yes. It is inverted when one large producer supports many small consumers, like a single tree supporting many insects and then many birds. In that case the base has fewer organisms than the higher levels, so the pyramid is upside down.
A single big tree ecosystem. One tree at the base, many insects feeding on it, and even more small birds feeding on the insects. This is the NCERT example.
Yes, a pond or aquatic pyramid of number is generally upright because tiny phytoplankton producers are extremely large in count compared with the consumers above them. The inversion in aquatic systems is famous for biomass, not for number.
The base represents the producers, which are the first trophic level. The apex represents the top-level (tertiary) consumer. This is true for all ecological pyramids.
Because energy is always lost as heat at each step when it flows from one trophic level to the next, so a higher level can never hold more energy than the level below it. Number and biomass do not follow this rule strictly, so they can invert.
