Welcome to Dr. Mitra's Biology Webpage!

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Practice what you learn!

AP Biology

A copy of the syllabus for this course can be found here.

Here is a link to ALL the PowerPoint presentations for this textbook. Here is another webpage with the PowerPoints.

All the chapter notes can be found here.

The animation on diffusion and osmosis that we viewed in class on Thursday can be found here.

The animation that showed the internal structure of a cell can be found here.

The animation that shows how enzymes work can be found here.

Here is video of the lac operon.   And the trp operon.

This is the animation on chromatin structure that we looked at in class.

Here is a link to an animation that explains DNA Transcription.  We watched it in class.

This is the video on histone deacetylation and its role in gene regulation.

This video explains RNA interference or RNAi.

Here is a good explanation of the importance of transposons in the human genome.

And there's got to be some comedy in here somewhere, right?  Check out the Transposon Song -- I kid you not!!  It's pretty awful .....in a wonderful kind of way!!

Here is a link to the online simulation that explains gel electrophoresis and restriction enzymes.  It's fun! 

Here is a link to a web page called the Dolan DNA Learning Center.  It has animations on gel electrophoresis, restriction enzymes, PCR, DNA sequencing, how alu jumps, and more.  You should check it out.

Here is the Lick Your Rats activity!

The most challenging material in the evolution unit are the Hardy-Weinberg problems.  Here is a tutorial on YouTube that explains it all!

I graded the Hardy Weinberg problems that were in the Lab 8 packet and there was one mistake that many of you made.  I want to clear up this misunderstanding. It involves problems where you are given information about the dominant phenotype.

Suppose a problem says:
In rabbits, black fur is dominant and white fur is recessive.  In a population of 100 rabbits, 64% show the dominant phenotype of black fur.  What percentage will be BB, Bb and bb?

First, the question tells us about phenotypes.  Since we cannot distinguish a homozygous dominant from a heterozyote, we can't do much with that information.  But, we can assume that the other 36% of the population shows the recessive phenotype since 64% and 36% must equal 100% of the population.  Since the recessive phenotype is represented by q², we now know that q² = 0.36.  By taking the square root, we determine that q = 0.6.  By subtraction, we find that p = 0.4.
Now we can determine the frequency or percentage of all three genotypes.
p² = 0.16  and is the percentage for BB;

2pq = 2 ( 0.6 )( 0.4 ) = 0.48 and is the percentage for Bb;

q² = 0.36 and is the percentage for bb.


Chapter 35 Plant Structure and Function

Here are definitions and descriptions of the most common cell types found in the plant body.

Study Guide  Plant Cell Types 

Chapter 35, Figure 35.9,  pages 718 – 719

Parenchyma
The most common cell type in the plant body.  The can be filled with chloroplasts or starch grains.  They have only a thin primary cell wall so these cells can be induced to divide again.

Collenchyma
Plant cells with irregularly thickened primary cell walls.  Used to strengthen stems and leaves of non-woody plants.

Sclerenchyma
Both types of sclerenchyma have thickened secondary cell walls that are strengthened with lignin.  Since these cells have secondary cell walls, their size and shape is fixed; they will never divide again.

Sclereids
Small roundish cells with very thick cell walls.  Found in nut shells and in pear fruit.

Fibers
Long, slender, tapered cells that occur in bundles.  They help strengthen stems.  Found in hemp and flax fibers.

Xylem
Xylem conducts water through the plant body.  It is dead at functional maturity.  It contains two main cell types.

Tracheids
Long, slender, tapered cells, similar in size and shape to fiber cells, but these cells conduct water.  The only type of xylem found in gymnosperms.

Vessel elements
Short, wide xylem cells found in angiosperms.  They form vessels.  Because they're wider than tracheids, they do a better job of transporting water.

Phloem
Phloem conducts sugars through the plant body.  It is alive at functional maturity because it takes energy (ATP) to load sugar against the concentration gradient into these cells.  It contains two main cell types.

Sieve tube members
These cells are arranged end to end, forming sieve tubes.  They lack a nucleus and most organelles.  They transport sugars!

Companion cells
They cells are located next to sieve tubes.  They regulate the flow of sugar in the phloem.  They do not transport sugars themselves.

The Nervous System - Chapter 48

Here is a link to a pencast that covers section 48.2 and 48.3.  It describes how the resting potential of a neuron is generated, how an action potential in generated, and how it is propagated down the axon.

Here is a link to an online animation that explains action potentials.

On Friday, March 25, we will be taking a quiz on Chap 48 Nervous System.  Everyone will be required to take it.  The study guide is as follows:
Make sure you know the structure of a neuron, Fib 48.5 page 1014
Make sure you understand how an action potential is generated.  Fig 48.11 explains how the levels of Ca and K ions sets up the resting potential of a cell - page 1017.  Figs 48.12 and 48.13 explain how action potentials work.  I have also posted a link on my web page that explains it all.  And a pencast. If you don't want to listen to my voice, you could google the topic and seen what comes up.  I would recommend on YouTube going to Kahn Academy action potential, or any topic in from these chapters.  His little talks are great.
Make sure you understand how the synaptic cleft works Fig 48.17.
Look at the table of neurotransmitters and make sure you can recognize them  pg 1024
Make sure you know the parts of the central nervous system and the periperal nervous system, pgs 1026 and 1027
And very briefly, the parts of the brain.  The brainstem controls "primitive" functions while the cerebrum controls our higher ordered thinking.
The quiz will be just like last time, 10 multiple choice questions, 1 point each.

 

College Biology (Sophomore)

Welcome to College Prep Biology for sophomores!  A copy of the course syllabus can be found here. 

We will be taking our next test on Wednesday.  It will cover cell structure, organelles, comparing prokaryotic and eukaryotic cells, as well as comparing plant and animals cells.  Here is a link to the cell review game that we viewed in class today.

It will also cover transport in and out of cells.  That includes simple diffusion, facilitated diffusion, active transport, phagocytosis, pinocytosis, and exocytosis.

Here are links to the cell labeling activities we did in class.  An animal cell, a plant cell, and another animal cell.  This is a link to the animation of transport across membranes.

Junior/Senior Biology

Welcome to College Biology for Juniors and Seniors.  A copy of the course syllabus can be found here.

We will be taking our next test on Wednesday as well.  It will cover cells, organelles, and transport.  We looked at a great review page yesterday.  Here is a link to it.  Links to the review pages we viewed today are posted above on my sophomore page.

STUDY!!   You can do well if you invest the effort!

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