1 there are many external factors that impact how well a...

There are many external factors that impact how well a plant grows, including the type of soil, the amount of water, and the amount of nutrients and minerals. a. How would a scientist determine how factors impact plant growth under field conditions when there are many variables (e.g., temperature, soil type, water, nutrients) affecting growth? b. Design an experiment to test the effects of one external factor on plant growth. Formulate a hypothesis, identify your independent, dependent, and control variables, and outline what data you will collect to answer your hypothesis. 2) Genetically engineered plants are used today to grow more drought- or pest-resistant crops. While this practice increases yield and reduces cost, it also reduces genetic variety. Explain why this is problematic. 3) Why would commercial nurseries routinely pump carbon dioxide into their greenhouses?

Transcript

00:01 So we're looking at the factors that might influence how a plant grows.

00:05 So first of all, how would we assess which factors impact plant growth under field conditions when there are many variables? so they're going to have to collect a lot of data.

00:19 So you would collect data and you would have to collect data on the variables, so all of the variables.

00:35 And collect data on the outcome, the plant group.

00:39 And then you would have to analyze this with statistics.

00:45 And this is not ideal, but under field conditions, this is the best you're really going to get, because you cannot control the variables.

00:55 So it's not ideal.

00:57 But if we look at b, we're going to design an experiment to focus on a single factor.

01:02 So now we're going into experimental conditions.

01:05 So, we need to ask a question.

01:09 My hypothesis might be, more water means more growth, probably up to a point beyond which it's too much.

01:19 So, our hypothesis is, more water means more growth.

01:26 How would we test this experimentally? well, we need an independent, a dependent, and the control variables.

01:33 So the independent variable is what we change.

01:42 The dependent is what we measure.

01:44 So when you ask a question, in this case, does more water mean more growth, you're asking, does my independence affect my dependence? so here, the independent is the amount of water.

01:59 So it's what we change.

02:00 And the dependent is going to be the growth.

02:03 Whichever factor you choose here, it's going to be your independent, and the dependent will always be the growth, because that's what we're testing.

02:11 The control variables are everything else.

02:18 So going back to those field conditions, maybe there's a hot, humid day, and there's a lot of winds, and it's moving the soil around, and when you look at the plant growth, you don't know which factor is really changing it.

02:33 But here, you can narrow it down, keep everything the same except for one factor and then any change in the dependent variable, you know it was because of that one factor.

02:45 So the soil type, the plant type, the temperature, the nutrients, all of those will be control variables.

02:51 So to collect the data to answer this, we have to measure the growth of the plant and we're going to analyze how it is affected by the amount of water they get...

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