Pre-Lab Discussion: The members of a species are not exactly alike. Small differences called variations exist in each member of a species. Some variations may be passed on to the offspring of an organism through reproduction. Most inherited variations are neutral; that is, they do not affect the survival of the organism. Some variations are helpful. Helpful inherited variations are called adaptations. Harmful inherited variations will cause the organism to be less well-suited to its environment.
The process by which organisms with adaptations to the environment survive is called natural selection. Natural selection tends to allow well-adapted organisms to reproduce and pass the beneficial trait to their offspring.
- After you have read through the entire handout discuss with your partners whether you think plants or animals will show a greater degree of variation. DO NOT just guess your discussion should include examples and why you think one or the other will vary more. Doing this will help you with the Framework and Logic scores on your conclusion; take notes!
- Make a rough draft of the Q, H, T, diagrams, DT; you do not need to include procedures in your rd or fd.
- the data manipulation section of the rubric will be 3x score (graph=1x & analysis questions=2x)
- Graph the number of variation measurements (hand spans or blade lengths) vs the sizes in cm. Make a bar graph for the plant leaves and hand spans it will look similar to the traits lab graphs
Question: Will there be a greater degree of variation in the leaves of a plant species or in the hand span of Humans?
Procedures Hand Span variation: make a diagram
1. Place the palm of your hand on a blank piece of paper, with your fingers spread out as much as possible. Make a mark on the paper at the top of your thumb and another mark at the top of your little finger is. Don't include fingernails.
2. Measure your hand span between the two marks with a ruler. Round off your measurement to the nearest centimeter and record the information in your data table.
3. Next, gather hand span measurements for everyone in class and put them into your data table.
Procedures leaf variation: make a diagram
- Obtain a number of leaves equal to the number of students in class.
- Measure the length of the leaf blades in centimeters. Record the measurements
- Depending on the supply of leaves you may have to share leaves between tables. Try to not measure the same leaf multiple times.
- Calculate standard deviation for each sample by finding the total average of all for both hands and leaves (separately). Next. Subtract each sample from the average and this is your “standard deviation- round to nearest whole number!)
- Did the number of hand spans measured in your class influence the shape of the graph? If you had a much larger sample of hand spans, how do you think the graph might change?
- Would any of the variations you observed in hand spans be an advantage in terms of the survival of humans? List two advantages each for larger and smaller hand spans.
- What is the most common hand span? Leaf blade length?
- What is the least common hand span? Leaf blade length?
- What are two other variations observed in Humans? Leaf blades?
- QHT are variables present in all (independent = spans and dependent = degree or # of individuals/leaves measured
- Diagrams should show how leaf and span were measured and label leaf parts
- Data tables ruled, labeled & units
- Analysis questions pretty obvious and straight forward, I fixed the line graph reference and will include a deviation from the norm piece to better determine average difference from average = deviation and average of deviation = degree of variation ie.
i. 19.6 cm is ave span and 1.8 cm is ave deviation from norm
ii. 17.2 cm is ave length and 3.8 cm is ave deviation from norm
iii. 3.8 cm of plants shows nearly twice the degree of variation.
- Observations and error
i. Plants from same tree = all genetically similar most differences might be environmental or
ii. Age leaves at bottom of the branch are younger than leaves towards the top of the branch. Age is likely to have an impact on length older being longer and vice versa
iii. Inaccurate measurements if petiole was measured by some groups and not others
iv. Hand spans (maybe) finger nails, bent fingers and asking for measurement vs. actually doing it yourself.