new aim: how is all life united? chapter 1 - introduction: the scientific study of life topic 8...

NEW AIM: How is all life united?

Chapter 1 - Introduction: The Scientific Study of Life

Topic 8Scientific Inquiry and Skills

Chapter 1 - Introduction: The Scientific Study of Life AIM: What is Science?

The process we use to know something

What is Science ?


We use the scientific method

How do we do science?


Fig. 1.3A


A conclusion you make based on observations

Inference

AIM: How is all life united?


Let’s do an experimental design questionThings to keep in mind:

1. Question in bullets should be answered in bullets and you should only be answering what the bullet asks.

2. A hypothesis is NOT and IF/THEN. It is a statement that answers your question like: The plants getting fertilizer will grow taller. NOT if the plants get fertilizer then they will grow taller.

3. The independent variable is the one you alter (it starts with the letter “I”. It is not fertilizer, it is the AMOUNT OF fertilizer. – goes on x axis of graph

4. The dependent variable is what you measure…height, mass, color, etc… - goes on y axis of graph

5. Make sure you use a placebo (sugar pill) if you are treating HUMAN subject only.



Let’s do an experimental design questionThings to keep in mind:

6. If they are asking what is wrong with an experiment…

Always look for sample size, for a control group, and look if it was repeatable.

7. If they ask how to make the experiment more valid

Increase sample size, repeat experiment



Laboratory skills

There are 1000 micrometers (um) in 1 mm

How many micrometers in 2.3 mm? 2300um

Chapter 4 - A Tour of the Cell

AIM: The practical microscope…

Field of view with mm ruler

Estimate the field of view at 1.5mm and estimate that 3 organisms fit across it. Therefore the organism is around 0.5mm or 500um.

Laboratory skills

What is the width of this organism?



Field of view with mm ruler

Estimate the field of view at 1.5mm and estimate that 4 cells fit across it. Therefore the organism is around 1.5/4 or 0.375mm or 375um.

Laboratory skills

What is the width of this cell?


AIM: The practical microscope… Laboratory skills

Remember that as magnification increases, FOV decreases

Low Power High Power



Remember that magnification is ocular times objective lens and know the parts.



Under the microscope, the object you are looking at will be rotated by 180 degrees…



Measuring Liquid Volume:

Use a graduated cylinder and read the bottom of the meniscus.

Fig. 12.10

Gel Electrophoresis

This technique allows one to not only indirectly view the DNA, but also to separate and view the DNA fragments.

Chapter 12 - DNA Technology and the Human Genome

AIM: What are some other tools of DNA technology?

Laboratory skills

Fig. 12.10

Gel Electrophoresis



Gel (like jell-o)

The gel is made of either agarose or polyacrylamide. It has tiny, microscopic pores that DNA can fit through.

Fig. 12.10

Gel Electrophoresis



The DNA sample is loaded in the wells at the top of the gel. One sample per well.

Gel (like jell-o)

Fig. 12.10

Gel Electrophoresis



Electricity is then run through the gel. Why do you think the negative end is on the sample side and the positive end is on the other end of the gel?

Electricity (electrons flow from top of gel by the samples to the bottom of the gel)

DNA is negative because the phosphates are negative. The negative electrons moving down push (repel) the DNA down with them.

Gel Electrophoresis



Which will move faster through the micro-porous gel, the longer DNA fragments or the shorter DNA fragments?

The small fragments (fewer nucleotides) will move more easily through the gel and hence go faster than the large ones. Therefore, gel electrophoresis separates DNA fragments by SIZE.

Fig. 12.10

Gel Electrophoresis



This is all great, but we still can’t physically see the DNA…

Fig. 12.10

Gel Electrophoresis



The gel is soaked with a a compound called ethidium bromide, which sticks to DNA and lights up when you hit the gel with UV light…

Restriction enzymes

1. molecular DNA scissors (enzymes that cut DNA)


How can we use bacteria to manipulate DNA and protein?

2. Different restriction enzymes cut different sequences of DNA.

3. Scientists have isolated hundreds of different restriction enzymes from many different bacteria – EcoRI, BamHI, NcoI, etc…

Fig. 12.4

Restriction enzymes



Ex. The restriction enzyme EcoRI cuts at GAATTC

Restriction enzymes



Ex. EcoRI

EcoRI



Draw what the gel would look like for the restriction digest of the criminal and the suspect.

Section of the DNA from the crime scene

Section of the same DNA segment from the suspect.

Different people have different restriction sites in their DNA due to mutations (see left).

Fig. 12.11Acriminal suspect

Suspect’s DNA fingerprint

Criminal’sDNA fingerprint



Suspect did not do it!!

Can also be used to detect disease, determine paternity, or analyze general genetic relatedness as more closely related individuals will have more similar band patterns (similar size fragments).



Review:



1. Digest DNA with restriction enzymes2. Run restriction fragments on a gel (gel electrophoresis) – shorter ones go further3. Compare fragments

Relationships and BiodiversityState Lab

Remember Paper chromatography?

- Analytical technique for separating and identifying mixtures based on their attraction to the paper or the solvent running up the paper

Laboratory skills


How does Paper chromatography work?

The solvent (water in this case) will wick (travel) up the paper. The solvent will eventually make its way to the sample absorbed on the paper (which must be above the water level).

The molecules in the sample will have different attractions for the paper and the solvent (water):

If the affinity is high for the solvent, the molecule will move quickly up the paper with the solvent. If the molecule has a high affinity for the paper, it will stick to the paper and resist movement and only move slowly up the paper thereby separating the different molecules.


Station 4 - Paper Chromatography to Separate Plant Pigments

2. Draw a line 2 cm from the bottom of each of the four chromatography papers. Use a pencil to label the top edge of the chromatography paper either Bc (Botanus curus), X, Y, or Z (look at Figure 2 in the lab manual).

1. Take four strips of chromatography paper and try to straighten them the best you can by curling them in the opposite direction and putting a slight crease down the center (see example setup on the bench).


Station 4 - Paper Chromatography to Separate Plant Pigments

4. Place two drops of plant extract from Botanus curus just above the pencil line as shown in Figure 2.

3. Add about 1cm of water to each beaker.

5. Place the paper into the water and allow the water to move up the paper. Repeat steps 4 and 5 for the other samples.

Pigment Sample MUST BE above the water level or the pigment will just diffuse into the water!!!!!!



Dichotomous keys



Four State Labs

new aim: how is all life united? chapter 1 - introduction: the scientific study of life topic 8...

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