Food Webs and Trophic Cascades

Now that we know about nutrient cycling, we are ready to look at food webs as a whole. These represent feeding relationships within a community.These relationships designate certain trophic levels, so let's learn about what these mean first, and then examine certain phenomena called trophic cascades.

Script by Ulyana Horodyskyj

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!

[David_]

What a clear and concise summation of food webs! This info should be part of the basic science program in all schools be they public or private. Many food chains are severely disrupted when large fields are used to raise one crop. This inevitably leads to the diminution of many species even to the point of extinction. Monocropping results in soil degradation and necessitates the use of many pesticides and herbicides. It also, in some cases, requires copious amounts of water for crops such as avocadoes and walnuts. Many crops such as the aforementioned, are dietary luxuries. The nutrients they may provide can be obtained from other sources.

[revolade]

wohooo science jesus uploaded a new video, keep it up dave, we need you

[patrickj]

Dave it'd be awesome if you make a video on RNA autocatalytic activity. I know you reference these articles in your debates with James Tour but I'd love to see a video where you break down the science ❤

[MACH-ftzj]

I think the role of parasites should not be underestimated. In fact it is also a significant driver of ecological interactions and energy fluxes. For a complete food web you also have to consider those, which of course makes those interactions significantly more complex

[Marcus_Tullius_Cicero]

We just learned this in Ecology class, what a timing!

[JenniferWynters-kvkm]

Great video as usual Professor Dave, this is a great explanation of food webs and trophic levels. Trophic cascades can get really interesting, especially when studying how human impact affects ecosystems for anyone who wanting to map out a food web and see these levels visually, Creately's Food Web Tool can be quite useful. It lets you easily map out the feeding relationships between different organisms, making it easier to grasp the flow of energy through the ecosystem - just thought of sharing, in case someone finds it useful in their studies.

[nirmalmishra]

If heat inherently has physical meaning when in transit, constituting its existential definition as a form of energy in motion, what does it truly mean to say that heat 'flows'? When we assert that heat is a form of energy in transit, it implies movement; however, using the term 'flow' seems to redundantly invoke the concept of movement. How can the movement of energy itself be described as 'flow' without introducing redundancy?" I created this analogy to understand what the definition is trying to say:"When we say 'heat always flows from higher to lower temperature until thermal equilibrium is reached, ' it conjures an image in my mind of an invisible 'glitter glow' dispersed in the atmosphere(massless being in motion). This 'glitter glow' represents the thermal energy, and with a temperature change, it becomes unevenly distributed. In this mental model, a chunk of the glitter glow with a relatively higher distribution moves towards a lower distribution in a flow, seeking to maintain symmetry as per the Thumb Rule of the universe. The glitter glow represents thermal energy, and when it flows, we call it heat?

[falcoperegrinus]

With the reintroduction of wolves in Yellowstone, one effect was bird abundance increased, particularly in riparian areas. The wolves reduced herbivore browsing impact on bird habitat which allowed it to rebound along with the birds that rely on that habitat.

[fnaffan]

Love it, but this would have been more useful about 2 years ago when I failed my science test!

[tracyanncunningham]

I never understood and I still cannot understand whenever I'm ask the question who is feeding at, let's say the secondary level should I list the organisms in that level or should I list the organism that feed on those of the secondary level.

[uncleanunicorn]

It's the Circle.... the Circle of Liiiife... But also, the idea of energy flow and release of trophic energy may factor into the physical forces that encourage abiogenesis on an entropic level, if you've heard the hypothesis from Harvard Scientist Jeremy England.

[ssteeeeeve]

We just cycle energy obtained from the sun around here on Earth, which was obtained from a nebula, obtained from hydrogen gas, dust, and whatever, obtained from gravitational instability, obtained from another possibly endless cycle impossible to wrap one’s mind over, and so forth.

[washno.]

Do you think you could do some videos on the most likely ways the universe will end, like the Big Crunch and Heat Death?

[kirkhamandy]

Ah yes... the best reason I know of for why the Loch Ness Monster doesn't exist 😂

[juzhang]

I wish creationists understand all this😂