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Page Facing Up

Theme B - Form & Function

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Direct Hit

Theme A - Unity & diversity

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Pill

Theme C - Interaction &  Interdependence

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Keycap Digit One

Theme D - Continuity & Change

<ul>
	<li>Definition: Saprotrophs are organisms that feed on dead or decaying organic matter.</li>
	<li>Process
	<ul>
		<li>Secrete digestive enzymes onto the dead stuff.</li>
		<li>Digest it externally.</li>
		<li>Absorb the digested nutrients.</li>
	</ul>
	</li>
	<li>Alias: Known as &quot;decomposers&quot;.</li>
	<li>Significance: They recycle nutrients! By breaking down dead matter, they release elements like nitrogen back into the ecosystem.
	<ul>
		<li>Real-world example: Think of fungi in a forest. Dead trees and leaves? No problem! Fungi secrete enzymes, decompose them, and turn them into nutritious soil. Nature&#39;s cleanup crew! 🌳🍂➡️🍄➡️🌱</li>
	</ul>
	</li>
</ul>

<ul>
	<li>
	Trophic Levels (TL): It&rsquo;s like the food chain&rsquo;s floor number!

	<ul>
		<li>Producers (e.g., plants): TL 1</li>
		<li>Primary consumers (e.g., herbivores): TL 2</li>
		<li>... and it keeps going up!</li>
	</ul>
	</li>
	<li>
	Why not whole numbers? Some animals dine at multiple levels (buffet style 🍽️). So, their TL is an average.
	</li>
	<li>
	Over-fishing crisis: We&#39;re catching too many high TL fish, which are typically long-lived. So, we&#39;re left with more fish that are from the lower TL.

	<ul>
		<li>Catchy phrase: &ldquo;fishing down marine food webs&rdquo;.</li>
	</ul>
	</li>
	<li>
	Real-world context: Imagine a restaurant that used to serve mostly steak (high TL), but as steaks become rarer, they serve more salads (low TL).
	</li>
</ul>

<ul>
	<li>
	How to find a fish&#39;s TL post-capture?

	<ul>
		<li>Look at its diet! If it eats plants, it&#39;s lower. Eats other fish? Higher. Uses its TL as a hint.</li>
	</ul>
	</li>
	<li>
	Marine vs. Freshwater fisheries since 1970:

	<ul>
		<li>Compare data on average TL of fish caught from both sources over the years.</li>
	</ul>
	</li>
	<li>
	Why would a fish&#39;s mean TL increase with age?

	<ul>
		<li>As fish grow, they might switch from eating smaller prey to larger ones, climbing the food chain ladder.</li>
	</ul>
	</li>
	<li>
	Age change of captured fish?

	<ul>
		<li>If we&#39;re catching more lower TL fish, they&#39;re probably younger on average than the big, old high TL fish.</li>
	</ul>
	</li>
	<li>
	Pros of catching &amp; eating lower TL fish:

	<ul>
		<li>Sustainability: Lower TL fish often reproduce faster and in greater numbers.</li>
		<li>Energy Efficiency: Remember the 10% rule? Eating lower on the food chain uses less energy overall.
		<ul>
			<li>Real-world example: Imagine 10,000 units of plankton. They can directly feed 1,000 small fish (TL2), but only 100 bigger fish (TL3) that eat the small fish. By eating lower, we get more food with the same energy!</li>
		</ul>
		</li>
	</ul>
	</li>
</ul>

<ul>
	<li>Saprotrophs are nature&rsquo;s recyclers. 🔄</li>
	<li>Trophic Levels are the ecosystem&#39;s stair steps. 📶</li>
	<li>Over-fishing higher TL fish means our catches are getting &quot;younger&quot; and lower on the food chain. 🎣</li>
</ul>

Now, go ace that exam, and maybe give the big fish a break next time you&#39;re out fishing! 🐠📘✨

Unlocking Secrets Saprotrophic Nutrition & Marine Food Webs

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Higher Level

Biology HL

Theme B - Form & Function

Unlocking Secrets Saprotrophic Nutrition & Marine Food Webs

Table of content

Saprotrophic nutrition in fungi & bacteria 🍄

Fishing down marine food webs 🐟

Unlock the Full Content!

Theme B - Form & Function

Unlocking Secrets Saprotrophic Nutrition & Marine Food Webs

Table of content

Saprotrophic nutrition in fungi & bacteria 🍄

Fishing down marine food webs 🐟

Unlock the Full Content!