BIO 123 Lecture Notes - Lecture 11: Null Hypothesis, Soil Health, Invertebrate

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orangeeel486

17 Nov 2016

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P-value tells us the percent chance of our null hypothesis being true. *if percent chance of our null hypothesis being true is small enough, we can accept our alternate hypothesis. Percent chance needs to be below 5% There for you can accept your alternate hypothesis. If p-value is less than . 05, we can say the data is significant. Run anova test on data to prove significance. Leaf litter moisture levels of different environments does not have an effect on species diversity (h") of invertebrates found there. Leaf litter moisture levels of different environments does have an effect on species diversity (h") of invertebrates found there. The anova test showed that there was as a significant difference in invertebrate diversity between the three moisture levels. (p=. 00058, table 1) Give a brief description of what your table is, what it is showing. Table legend at the top of table.

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Introduction: A Chi-square test is used to compare observed data with expected data according to a hypothesis. For instance, if you were crossbreeding 2 heterozygous pea plants, you would expect to see a 3:1 phenotypic ratio in the offspring. In this case, if you were to breed 400 pea plants, you would expect to see 300 plants showing the dominant trait and 100 showing the recessive trait. But what happens if you observe only 260 plants with the dominant trait and 140 plants with the recessive trait? Does this mean something is wrong with Mendelian genetics or is this difference in expected results just due to chance (random sampling error)? These are the questions that can be answered using Chi-square statistics. The results of this statistical test is used to either reject or accept (fail to reject) the null hypothesis. The null hypothesis states there is no significant difference between the observed results and the expected results. This means that if the null hypothesis is accepted, the difference in observed and expected results was just a matter of chance and so the observed results basically "fit" with what was expected. Degrees of freedom (df) = number of independent outcomes (Y) being compared less 1 df = Y-1 At the 95% confidence interval we are 95% confident that there is a significant difference between the observed and expected results, therefore rejecting the null hypothesis. Probability Value - Is the decimal value determined from the X2 table and is the probability of accepting the null hypothesis. A 0.05 probability value equates to a 95% confidence interval.

The Chi-squared test formula is: Example: If we cross two pea plants that are heterozygous yellow pods, we would expect a 3:1 phenotypic ratio. So let's say we actually did the cross and got 280 plants with green pods and 120 plants with yellow pods. Question: Is this a 3:1 phenotypic ratio? This is the value of Chi-squared Test. We have a total of 400 plants and we expect a 300 green:100 yellow phenotypic ratio If the calculated Chi-squared value is less than the critical value listed in the Chi-squared table, then we accept the null hypothesis. This means that there is no significant difference between the observed and the expected values. Our degrees of freedom (df) = 2 outcomes - 1, or df = 1. Now we go the X2 table below and using the df = 1 and probability value of 0.05, our critical value is 3.84. Since our calculated X2 value is 5.33, and is larger than the critical value, we reject the null hypothesis and can say (at 95% confidence) that there is a significant difference between our observed and expected values.

The parent generation is yellowed podded and green podded pea plants. You cross a yellow podded pea plant with a green podded pea plant and you get 100% yellow podded plants in the F1 Generation (Phenotypic ratio 4 : 0, yellow to green). What will be the expected phenotypic ratio when you allow the F1 generation to reproduce?

Fill out the Punnett square.

If we actually did the cross and got 1150 yellow and 350 green. Would this be a consistent with what was expected?

Learning Outcomes Questions

1. Why would you run a Chi-squared test?

To determine if our data is consistent with expected results.
		a To determine if our data is consistent with expected results. b To determine if our data exactly matches the expected results.
		c To determine the expected results.
	d	To compare the phenotypic ratios to the genotypic ratios.

2. Determine the degrees of Freedom of the phenotypic ratio for this genetic cross.

a. 1

b. 2

c. 3

d. 4

e. 5

3. Using the data given, what is the result of your Chi-squared analysis? x2= ___.

	a.	2.22
	b	2.71
	c	4.36
	d	187.78
	e	448.27

4. Using the results of your Chi-squared analysis, do we fail to reject or reject the null hypothesis?

a.		Fail to reject the null
b.		Reject the null
c.		It cannot be determined from the data given

silversalmon27

Asexual reproduction: the first step to extinction
When species become asexual they could be taking the first stepto
extinction, say researchers who have been studying the geneticstructure
of Penicillium marneffei, an asexual fungus only found in parts ofsouthÂ
east Asia. Their research found that although P. marneffei sporeswere
able to spread over large distances on currents of air, they werenot able
to âinvadeâ the new environments in which they landed.
âWe believe the failure of P. marneffei to adapt to newenvironments is
because the fungus has largely dispensed with sexualreproduction.
Without sex, you will not have the mixing of genes it causes,something
all organisms need in order to be able to adapt to newenvironmentsâ, said
a member of the research team. Evolutionary theory predicts thatwhile
asexual organisms can initially prosper and out-compete theirsexual
cousins, they pay a price for being unable to adapt throughthe
recombination of genes caused by sexual reproduction.
DNA typing was used to show that different clones of the fungusare
found in different environments, and the researchers believe thatthe
adaptation of the fungus to these environments is limiting theirability to
adapt to other areas. They believe this is why P. marneffei isonly
endemic to a relatively small area of south-east Asia. Even thoughthe
6_________________________________________________________________
fungus makes spores which can spread over very large distances,the
researchers found that all the samples from any given locationwere
genetically very similar. This led them to the conclusion that thefungus
becomes highly adapted to its local environment, making ithighly
successful there, but stopping it spreading to other areas.
âBy being asexual, P. marneffei is not only limiting its ability toadapt, it
may be at risk of becoming extinct. If it is unable to adapt tonew
environments, it will be unable to adapt to changes in itscurrent
environment. While becoming asexual may provide short term
advantages to a species, in the long term, they are likely to endup in
evolutionâs ultimate dustbin â extinctionâ, concluded a member ofthe
research team

You should introduce your article by very briefly explaining thepurpose of
biological reproduction and touching upon the strategies used toachieve it, then
write your account using the following list as a guide to thepoints you should
discuss in your answer:
? How does asexual reproduction differ from sexual reproduction interms of
the biological processes involved and the genetic diversity andvariation of
the DNA produced?
What are the advantages and disadvantages of asexual andsexual
reproduction?
In terms of survival and adaptation, which reproduction strategy ismore
likely to allow a species to evolve rapidly (or to become extinct)?In your
answer briefly describe the two main mechanisms used to creategenetic
variation. Also, explain the factors and pressures that are likelyto drive the
process of adaptation.

sapphireantelope107

Chose the correct answers on one through 15(plese help)

1.A research group hypothesizes that successful infection by HIVdepends upon the expression of FSH3, a human gene. They overexpressthis gene in T cells (Which HIV normally infects) so that FSH3protein levels are very high in these cells. In other T-cells, theymutate FSH3 so that none of its encoded protein is made. They thenmeasure HIV infection rate in the control, overexpression, andmutant T cells. The three cultures are otherwise grown in the sameway.

What is the independent variable(s) in this experiment? (Selectall correct answers)

		FSH3 protein levels
		The medium in which cells are grown
		The temperature at which cells are grown
		HIV resistance of cells

Question 2

Which arises from an error in a measurement or observation?

		Technical variability
		Biological variability
		Standard error
		Standard deviation

Question 3

Use the following description of an experiment to answer thenext question.

A research group hypothesizes that successful infection by HIVdepends upon the expression of FSH3, a human gene. They overexpressthis gene in T cells (Which HIV normally infects) so that FSH3protein levels are very high in these cells. In other T-cells, theymutate FSH3 so that none of its encoded protein is made. They thenmeasure HIV infection rate in the control, overexpression, andmutant T cells. The three cultures are otherwise grown in the sameway.

What is the control group(s) in this experiment? (Select allcorrect answers)

		The unaltered T cells
		The medium in which cells are grown
		The T cells in which FSH3 is mutated
		The T cells overexpressing FSH3

Question 4

How many of the following statements are true?

I. All papers have an abstract, methods, results, and discussionsection

II. The methods always follows the introduction

		0
		2
		1

Question 5

If scientific convention states that when a P value of less than0.05 is considered significant (in other words, the two groupsbeing measured are actually different), this means that: (Selectall correct answers)

		If you were to repeat the experiment 100 times, there would notbe a significant difference between the groups in 5 of theexperiments
		95% of all conclusions that state two groups are not differentbased on a 0.5% p-value threshold are false negatives
		The groups are actually not different from each other 95% of thetime
		5% of all conclusions that state two groups are different basedon a 0.5% p-value threshold are false positives

What information is typically found in the introduction sectionof a paper? (Select all that apply)

		The dependent and independent variables within the study
		Which areas of the field are not well understood and whatquestion the study addresses
		How the main question of the paper is related to other researchin the field.
		How previous work forms the basis for the current study
		The purpose of the study
		Details of the approaches used
		A summary of relevant related studies

Question 7

How can you judge for yourself whether the conclusions reachedin a paper are valid? (Select all that apply)

		Read papers of other authors studying the same question or areaof inquiry
		Determine if each hypothesis is supported by different types ofevidence/approaches.
		Consider closely whether the data actually both addresses andsupports the authorâs hypothesis.
		Examine the amount of data in the paper, and how long the paperis.
		Whether the authors find a mechanism, or exactly how on variableaffects another.
		Interpret the data for yourself without looking the discussion,then compare your interpretations to that of the authorâs.

Question 8

Where can you usually find the institutional affiliations (wherethey work) of the authors?

		Within the discussion
		In the acknowledgements section
		Below the authors list
		This is not usually included in papers

Question 9

Other than publishing primary research articles, what is themain way scientists disseminate their results?

		Lab meetings
		Personal correspondence
		Conference seminars
		Public lectures

Question 10

Use the following description of an experiment to answer thenext question.

What is the experimental group(s) in this experiment? (Selectall correct answers)

		Each group is its own control
		The T cells overexpressing FSH3
		The T cells in which FSH3 is mutated
		The unaltered T cells

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BIO 123 Lecture Notes - Lecture 11: Null Hypothesis, Soil Health, Invertebrate

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