<p>Uh, another question… How do you do chi-square?</p>
<p>Chi square formula:</p>
<p>Xsub2=E(observed-expected)/expected</p>
<p>how long is the ap bio exam?</p>
<p>Sporozoans are often in mutalistic relationships with Plants. True or False?</p>
<p>^ True … right?</p>
<p>^ Uh, false? Sporozoans are those malaria causing protists…</p>
<p>@ DarkFlames, thank you for the chi-square explanation.</p>
<p>^ @ darkflames, that was the most helpful thing posted on this thread (at least for me, lol) thank you</p>
<p>now for a question</p>
<p>describe negative and positive feedback and provide examples of each in nature</p>
<p>Negative feedback: Most human body are negative feedbacks. Like glucose level’s up, triggers insulin production, decrease glucose level.</p>
<p>Positive feedback: global warming, maybe? People burn fossil fuel to cool their buildings down in the summer, which increase the temperature more, then people burn more fuels.</p>
<p>What is the purpose of casparian strip?</p>
<p>To ensure that water that reaches the endodermis flows through the cells instead of in between or though the cell walls. That way the endoderm cells can regulate the flow of water into the vascular cylinder.</p>
<p>Someone explain gametogenesis to me plz.</p>
<p>" What is the purpose of casparian strip?"</p>
<p>To regulate what enters the vascular cylinder (stele) and thus the xylem and phloem, from the roots. It makes sure that water and important ions like K+ (used to regulate the opening and closing of stomata) enter the plant through endodermal cells, and that unimportant ions like Na+ stay out. </p>
<p>New Question: Explain the function of a nephron and how it works.</p>
<p>Explain the function of a nephron and how it works.</p>
<p>There are millions of nephrons in a chordate kidney. The nephron begins with a bulb shaped structure that consists of a glomerulus and Bowman’s capsule. Wastes passively diffuse from the glomerulus through the Bowman’s capsule by means of a beating motion. These fluids then travel through the convoluted tubule, where the concentration of solutes of the fluid is continuously varied, and then to the collecting duct where ADH functions in the reabsorption of water to prevent water loss. The fluid then drains into the renal pelvis.</p>
<p>Question: Explain the fast and slow blocks to polyspermy.</p>
<p>Yeah… never in my ap bio career have I heard that before.</p>
<p>It’s actually a significant topic and has been asked on the AP exam before…a large portion in Campbell’s is devoted to it.</p>
<p>can you reword your question? I have no idea what you mean; is it about sporogensis?</p>
<p>Polyspermy occurs if multiple sperm fertilize one egg. This would be bad because then a polploid zygote would form and die. There are many ways to avoid this.</p>
<p>Fast blocks include:</p>
<p>Electrical: In some nonmammals, the egg has a negative charge but becomes positive upon fertilization. Another sperm cannot successfully penetrate the (+) charged egg. </p>
<p>Slow blocks include:</p>
<p>Cortical reaction: The zona pellucida (outer membrane) of the secondary oocyte hardens thatnks to a protein secretion of the sperm, not allowing any other sperm to penetrate.</p>
<p>DISCLAIMER: Yes, I did look part of this up, but in essence it’s hard more because prep books don’t seem to refer to the slow and fast blocks. Barron’s and Cliff’s I know for sure go over the cortical reaction, which I bet more people know, but never explains it as a “slow block.” I don’t think this will matter too much though on the test. DataBox, do you know how this concept was tested on the AP before?</p>
<p>New Question: What are the three main germ layers in animals? What are the fates of each in terms of development?</p>
<p>A large portion in Cambell? It’s only about 2 pages out of the 1200+ in Campbell… and it’s a chapter that we never even went over in class :/</p>
<p>
</p>
<p>Ectoderm: Upper-most layer; fated to produce nervous system/skin
Mesoderm: Middle layer (in some species, mesoglea, a glue like substance, takes its place); fated to produce blood/bones
Endoderm: fated to produce viscera (guts) and lining of the digestive system</p>
<p>Explain how B cells and T cells respond to a pathogen.</p>
<p>Layers in blastrula: Ectoderm- skin, eyes, nerve system; Mesoderm- pretty much everything inside (bones and muscles, etc); Endoderm- linings of digestive and respiratory tract, liver, gall bladder…</p>
<p>Can someone give me a summary of how muscle works?</p>