Ernst Haeckel was a very versatile and complete biologist,equally at home with imaginative leaps of conceptualization,serious natural history in the wild, and meticulous experimentationin embryology. His work shaped the developmentof a holistic evolutionary perspective that brought ecology,ontogeny, phylogeny, and biogeography together into a unifiedexplanation of the patterns of diversity seen in the livingworld. He, along with Darwin and Mendel, was perhaps oneof the three most consequential biologists of the nineteenth century,in many ways the golden age of biology.

In many ecosystems, apex consumers (top predators) play acrucial role in food web dynamics. Their top-down impactsare known to spread downwards through the food webs ina cascading fashion. Trophic cascades manifest when toppredators are excluded from an ecosystem or introduced intoa system lacking them. Two such case studies are describedhere. Trophic cascades are generally more pronounced in theaquatic than in the terrestrial ecosystems, which in turn isrelated to the differences in the average body sizes of herbivoresrelative to the plant resources they feed upon andin the structure of their food webs. Scientists express concernthat human activities have been leading to planet-widetrophic downgrading (loss of apex consumers) which couldaffect vital ecological processes of the biosphere.

In the presently available literature, one finds distinct resultsfor the electric field at the surface of a charged conductingsphere. In most textbooks, only a simple model is presentedin which the electric field leaps from zero (inside the sphere)to a maximum value (just outside the sphere), as follows fromGauss’s law. For points exactly at the surface, the charge surroundedby the Gaussian surface becomes ambiguous, andthis law is inconclusive. In this paper, by treating the sphericalsurface as a series of rings, it is shown that that field evaluatesto half the discontinuity mentioned above, a result whichagrees with more elaborate microscopic models.

In this article, I discuss the life cycle of cumulus clouds. Theevents of birth, growth and demise of clouds are discussedin terms of microphysical processes that underlie them. Myhope is that the next time you raise your eyes to the sky andsee a cloud, it will present itself to your mind’s eye as morethan a ‘white fluffy thing’.

In this article, I will describe how a simple, curiosity-basedexperiment to understand how ants are smart enough to choosethe shortest path led the exploration of self-organization andswarm-intelligence and resulted in major applications in computerscience and optimization algorithms. The focus willbe on curiosity, simplicity, interdisciplinarity, and being unmindfulof immediate applications.

The article demonstrates the condensation of water vapourunder pressure and at room temperature, using a disposablesyringe and an ambient light source. The small amount oftrapped water vapour inside a syringe along with the air iscompressedmanually to one-sixth of its original volume. Thecompressedwater vapour inside the syringe can be easily seenin the form of a white condensate on the inner side of thetransparent, circular wall of the syringe. The condensatecloud can be observed in the atmosphere by releasing it in theopen air while holding the syringe in front of a light sourceover a dark background. This model can be used as an analogousexperiment while explaining the concept of condensationof gases under pressure – from school to postgraduatestudents.

In this article, we report some experimental results on the behaviourof the flame of a candle kept at the bottom of a glasstube, which is open at the top and closed at the bottom. Thus,the supply of oxygen for the continuous burning of the flameis possible only from the top open end of the tube. We findthat the candle burns steadily below a critical tube height.Above this height, the flame oscillates in size, and a further increasein tube height leads to the flame extinguishing quickly.