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Direct Hit

Theme A - Unity & diversity

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Page Facing Up

Theme B - Form & Function

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Pill

Theme C - Interaction &  Interdependence

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Keycap Digit One

Theme D - Continuity & Change

🌟 Fun Fact: Every cell in your body has about 2 meters of DNA. If you uncoiled all the DNA in your body and lined it up, it would reach from the Earth to the Sun and back about 600 times!

<ul>
	<li>Species Specificity: Members of a species typically have the same number of chromosomes. Why?
	<ul>
		<li>The Big Reason: Sexual reproduction! 🌸❤️🌼</li>
	</ul>
	</li>
	<li>What happens during sexual reproduction:
	<ul>
		<li>Gametes (like sperm and eggs in humans) are produced by males and females. These have half the normal chromosome number, known as the haploid number (23 in humans).</li>
		<li>Formation of gametes is through meiosis &ndash; a process that halves the chromosome number.</li>
		<li>A male and female gamete fuse to form a zygote &ndash; this has the full, or diploid, number of chromosomes (46 in humans).</li>
	</ul>
	</li>
	<li>🌍 Real-World Example: Think of a puzzle. If you mix pieces from two completely different puzzles, you won&rsquo;t get a complete picture. Similarly, if two different species mate, the resulting offspring, with mismatched chromosome numbers, would be like a jumbled puzzle &ndash; which leads to problems.</li>
</ul>

<ul>
	<li>In a diploid nucleus, chromosomes come in pairs, carrying the same sequence of genes - these pairs are homologous chromosomes.</li>
	<li>During meiosis, these buddies pair up, ensuring they go to separate daughter cells &ndash; halving the chromosome number.</li>
	<li>Problem Alert 🚨: If organisms with different chromosome numbers mate, their offspring will face meiosis issues. Some chromosomes won&#39;t find their pair (homologous partner). Hence, resulting cells aren&rsquo;t viable and offspring are typically infertile.</li>
</ul>

<ul>
	<li>DNA Content Estimation: Use a stain that binds to DNA and measure how much light it absorbs.</li>
	<li>Q&amp;A Time
	<ul>
		<li>Comparing DNA content of bog mosses: Look for variations in the DNA estimates across species.</li>
		<li>Why do six species have the same chromosome number?: Shared ancestry? Environmental conditions?</li>
		<li>What&#39;s up with S. arcticum and S. olafii?
		<ul>
			<li>They might&#39;ve arisen when meiosis went on vacation in one of their ancestors.</li>
			<li>Deduce their chromosome count based on the given DNA content and comparison with other species.</li>
			<li>Downside of Extra DNA: More energy to maintain and replicate? Increased vulnerability to mutations?</li>
		</ul>
		</li>
		<li>Odd Chromosome Numbers in Mosses: Unlike most plants and animals, mosses can have an odd number of chromosomes. Mosses have certain mechanisms, perhaps related to their life cycle, that allow for this odd number without causing viability issues.</li>
	</ul>
	</li>
</ul>

🌟 Note to Self: Always remember, while having more DNA might sound like an advantage (more data = better, right?), nature always has a balance. Too much can be just as problematic as too little!

&nbsp;

Happy Studying! 🌺📚🔬

Chromosome Count's Role In Species Fertility And Diversity

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Higher Level

Biology HL

Theme A - Unity & diversity

Chromosome Count's Role In Species Fertility And Diversity

Table of content

Chromosome numbers - why so consistent?

Unlock the Full Content!

Theme A - Unity & diversity

Chromosome Count's Role In Species Fertility And Diversity

Table of content

Chromosome numbers - why so consistent?

Unlock the Full Content!