Category: Uncategorized

 

Main Idea Practice Answers

Main Idea Exercise 1 1.b; 2.b Exercise 2 1. Across the country, many states have abolished the policy of “social promotion,” even though there is no hard evidence that making children repeat a grade has a positive effect. 2. In 1932, Wallace H. Carothers developed nylon, the first synthetic fiber, which had a dramatic effect on world events. Exercise 3 1. No nicknames for soldiers of previous generations have earned the popularity of the term GI. 2. Since her death, Frida Kahlo’s reputation has overtaken her husband’s. Exercise 4 1. King Leopold of Belgium exploited the Congo for personal gain and all but ruined the country. 2. The invention of the CAT scan was as important a discovery as the development of X-Rays. Inference Exercises Exercise 1 1. Abraham Lincoln Clue: He steered the country through civil war. Explanation: Lots of people have big Adam’s apples, but America has had only one civil war. 2. Tina Turner Clue: She ruled the stage but Ike ruled the roost. Explanation: There were many popular women singers in the sixties but only one was linked to a domineering husband named Ike. Exercise 2 Answers may vary. 1. Inference: The puppy may well have been abused by its former owners. 2. Inference: The students are going to take advantage of the substitute teacher. Exercise 3 1. b; 2. a Exercise 4 1. a; 2. b Exercise 5 Answers will vary. 1. Richard the Lionhearted was not so pure of heart as some movies suggest. 2. Her romantic attachment to Clyde Barrow led Bonnie Parker into a life of crime.

 

Introduction
Transpiration is the process through  which water is lost from a plant by evaporation. Water is taken into a plant through roots and root hairs by osmosis, and it exits the plant through ting openings on the underside of leaves known as stomata. Oxygen and carbon dioxide are exchanged through the stomata. Transpiration is also the major mechanism that powers the movement of water throughout a plant. This transportation of water through the plant is due to water potential. Water potential is the potential energy created by the water molecules within the plant stem. Water always flows from areas of high water potential to areas of low water potential. Gravity, pressure, and solute concentration are all factors determining water potential in a plant.

There are three main kinds of cells in plants. the most abundant is parenchyma cells. These cells are mainly unspecialized and make up the mesophyll layer in leaves. Most parenchyma cells store food such as starch to be used later in the plant. Sclerenchyma cells are lignified and dead at maturity. These cells make up fibers and have thick secondary cell walls. They serve as support in plants. Collenchyma cells can be found in young stems and leaves. They are living at maturity and have thick primary cell walls.  There are also three types of tissues found in plants — xylem, phloem, and epidermal. The epidermal cells make up the outermost layer of cells on a plant and function in protecting the plant. Xylem is the water conducting tissue of the plant, while phloem is the food conducting plant tissue.

 

In this experiment, four bean plants will be used to test transpiration rates under different environmental conditions. The conditions included a normal room setting, exposure to a fan, heat lamp, and moist environment ( air misted and plant covered with plastic bag). Data will be obtained from each setting to determine if the various conditions affected the rate of water loss from leaves.

Hypothesis
Under the setting in which the plant is prayed with water and then covered in a plastic bag to create a moist environment, there will be the lowest rate of transpiration.

Materials
9A
Materials used for part A included a graduated cylinder, parafilm, distilled water, bean plant, scalpel, watch, fan, heat lamp, spray bottle, plastic bag to cover plant, and a metric scale.
9B
Materials needed for part B included a microtome, single edge razor blade, paraffin, 50% ethanol, toluidine blue stain, distilled water, 50% glycerine, microscope slide, petri dishes, and compound microscope.

 

Methods
9A
First make a potometer by filling the graduated cylinder with water and covering it securely with parafilm. Poke a hole in the parafilm. Remove the root from the rest of the plant and insert the plant into the parafilm hole so that the end of the stem is below the water level in the graduated cylinder. Record the initial water level in the potometer. Weigh the potometer with the plant and record the initial mass.  Expose this plant to one of the four conditions (misted plant), and take readings of the potometer mass every 10 minutes for a total of 30 minutes. Record this data in your data table.

9B
In this part of the experiment, a cross-section of a leaf will be observed. Cut the stem of a non-woody plant about 5mm longer than the depth of the microtome. Hold the stem vertically in the microtome and pour melted paraffin around it. Allow the paraffin to cool and harden around the stem. Use a razor blade to cut off the excess stem above the paraffin. Slightly turn the microtome to expose a thin layer of the stem. Slice several thin layers of the stem from the microtome and place these slices in a petri dish containing 50% ethanol for 5 minutes. Move the slices to another petri dish containing toluidine blue stain for  1-2 minutes. Rinse the slices and then mount each section on a microscope slide in a drop of 50% glycerine. Add a cover slip and observe under a compound microscope. Draw the stem cross-section.

 

Calculating Leaf Surface Area

 

Data 9A

Transpiration Rate

 

Transpiration Rate

Data 9A

Leaf Cross Section

 

Questions

1. Calculate the average rate of water loss per minute for each of the following treatments:
Room:    0 ml/min
Fan:        .53 ml/min
Light:      .367 ml/min
Mist:       .23 ml/min

2.

4. A plant with its stomata closed prevents water that is needed by the plant from escaping.

5. Some plants, such as CAM plants, have adaptations to prevent water loss. These plants have their stomata closed during the day (hottest part of the day when water loss would be greatest) and their stomata open during the night when its cooler to carry out photosynthetic reactions. This reduces water loss from leaves.

Error Analysis
During this experiment, there were many complications that arose. When using potometers, sealing the potometers was difficult affecting  the rate of water loss. By changing the procedure and massing the graduated cylinders at timed intervals, more accurate data was obtained.

Conclusion
Although the misted plant did have a low rate of water loss, it was not the lowest transpiration rate observed.  The lowest transpiration rate came from the plant at room temperature, the control plant. The plants exposed  to the heat lamp and fan showed the highest rate of water loss as expected.

* Art work from Lab Bench    Http://www.biology.com

 

 

Introduction

Most of the water a plant absorbs is not used for a plant’s daily functioning. It is instead lost through transpiration, the evaporation of water through the leaf surface and stomata, and through guttation, which is the loss of water from the vascular tissues in the margins of leaves.

There are three levels of transport in plants: uptake and release of water and solutes by individual cells, short distance cell to cell transport at tissue and organ levels, and long distance transport of sap by xylem and phloem at the whole plant level. The transport of water is controlled by water potential. Water will always move from an area of high water potential to an area with low water potential. This water potential is affected by pressure, gravity, and solute concentration.

Water moves into the plant through osmosis and creates a hydrostatic root pressure that forces the water upward for a short distance, however, the main force in moving water is the upward pull due to transpiration. This pull is increased by water’s natural properties such as adhesion and cohesion. Transpiration decreases the water potential in the stele causing water to move in and pull upward into the leaves and other areas of low water potential. Pressure begins to build in the leaves, so to prevent downward movement, guttation occurs. Guttation occurs through leaf openings on the leaf margins called hydrathodes. Loss of water through transpiration can be facilitated by the opening and closing of the stomata depending on environmental conditions.

There are three types of cells in plants: parenchyma, sclerenchyma, and collenchyma. Parenchyma cells are the most abundant and are not specialized. They are found in the mesophyll of leaves, the flesh of fruits, the pith of stems, and the root and stem cortex. Sclerenchyma are elongated cells that make up fibers. They have thick secondary walls and the protoplasts often die as they grow older. They are used for support and are found in vascular tissue. Collenchyma cells are living at maturity and have a thickened secondary wall.

 

Hypothesis

 

In Lab 9A, all of the plants in this experiment will lose water through transpiration, but those affected by the heat sink and the fan will lose a larger amount of water due to the environmental conditions. This transpiration will pull water from the potometer into the plant. The structure and cell types of a stem cross-section can be observed under a microscope.

 

Materials

 

Exercise 9A: Transpiration

The materials needed for this exercise were a pan of water, timer, a beaker containing water (heat sink), scissors, 1-mL pipette, a plant cutting, ring stand, clamps, clear plastic tubing, petroleum jelly, a fan, lamp, spray bottle, a scale, calculator, and a plastic bag.

Exercise 9B: Structure of the Stem

The materials needed for this exercise were a nut-and-bolt microtome, single-edge razor blade, plant stems, paraffin, 50% ethanol, distilled water, 50% glycerin, toluidine blue O stain, a microscope slide and cover slip, pencil, paper, and a light microscope.

Methods

Exercise 9A: Transpiration

The tip of the pipette was placed in the plastic tubing and they were submerged in a tray of water. Water was drawn into the pipette and tubing until no bubbles were left. The plant stem was cut underwater and inserted into the plastic tubing. Petroleum jelly was immediately placed around the tube edging to form an airtight seal around the stem. The tubing was bent into a “U” shape and two clamps were used on the ring stand to hold the potometer in place. The potometer was allowed to equilibrate for ten minutes.

The plant was exposed to a fan, which was placed one meter away and set on low speed. The time zero reading was recorded and then it was continually recorded every three minutes for 30 minutes. After the experiment, all the leaves were cut off the plant and massed by cutting a one cm2 box and massing it.

Exercise 9B: Structure of the Stem

A nut-and-bolt microtome was obtained and a small cup was formed by unscrewing the bolt. The stem was placed in the microtome and melted paraffin was poured around the stem. The paraffin was allowed to dry and the excess stem was cut off. The bolt was twisted just a little and then cut with the blade. The slice was placed in the 50% ethanol. The slices were left in the ethanol for five minutes. Using the forceps, the slices were moved to a dish of the toluidine blue O stain and left for one minute. The sections were rinsed in distilled water. The section was mounted on the slide with a drop of 50% glycerin. A cover slip was placed over the slide. The cross section was observed under a light microscope and drawn.

 

Results

Table 9.1: Individual Potometer Readings

 

Time (min)	Beginning (0)	3	6	9	12	15	18	21	24	27	30
Reading (mL)	.02	.03	.04	.05	.06	.07	.09	.10	.11	.13	.13

 

Class Potometer Readings

 

Time (min)	Beginning (0)	3	6	9	12	15	18	21	24	27	30
Room	.53	.54	.55	.56	.57	.58	.59	.60	.61	.62	.63
Mist	.34	.36	.38	.40	.42	.43	.43	.44	.45	.45	.46
Light	.67	.68	.69	.70	.71	.72	.73	.74	.75	.77	.79
Fan	.02	.03	.04	.05	.06	.07	.09	.10	.11	.13	.13

 

Mass of leaves = 1.1 g
Leaf Surface Area = 0.0044 m2

 

Table 9.2: Individual Water Loss in mL/m2

 

Time Interval (minutes)
	0-3	3-6	6-9	9-12	12-15	15-18	18-21	21-24	24-27	27-30
Water Loss (mL)	.01	.01	.01	.01	.01	.02	.01	.01	.01	0
Water Loss per m2	2.27	2.27	2.27	2.27	2.27	4.55	2.27	2.27	2.27	0

 

 

 

Table 9.3: Class Average Cumulative Water Loss in mL/m2

 

	Time (minutes)
Treatment	0	3	6	9	12	15	18	21	24	27	30
Room	0	5	5	5	5	5	5	5	5	5	5
Light	0	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	4	4
Fan	0	2.27	2.27	2.27	2.27	2.27	4.55	2.27	2.27	2.27	0
Mist	0	4.17	4.17	4.17	4.17	2.08	0	2.08	2.08	0	2.08

 

 

Analysis of Results

Calculate the average rate of water loss per minute for each of the treatments:
Room: 1.67 mL/m2
Fan: 0.76 mL/m2
Light: 0.93 mL/m2
Mist: 0.83 mL/m2

 

Explain why each of the conditions cause an increase or decrease in transpiration compared with the control.

 

 

How did each condition affect the gradient of the water potential from stem to leaf in the experimental plant?

 

The light and the fan decreased the water potential in the leaves and water moved up the stem by transpiration pull. The room temperature had little or no effect on the water potential. The mist increased the water potential of the air causing less transpiration to occur from the leaves.

 

What is the advantage to a plant of closed stomata where water is in short supply? What are the disadvantages?

 

The closing of the stomata would prevent transpiration of water and minimize this loss if water was in short supply. It is a conservational adaptation. However, closing stomata prevents the exchange of gases in plants and limits their carbon supplies.

 

Describe several adaptations that enable plants to reduce water loss from their leaves. Include both structural and psychological adaptations.

 

Plants that are adapted to drier climates are called xerophytes. Some of these plants have adapted small, thick leaves with a reduced surface area. They may also have a thickened cuticle to protect themselves from the environment. The stomata may be sunken into pits. Some xerophytes shed their leaves during the driest seasons and others can store water such as cacti. CAM plants uptake CO2 at night and change it into crassulacean acid that can be broken down during the day for sugars. These plants can close their stomata during the day.

 

Why did you need to calculate leaf surface area in tabulating your results?

 

The surface area has to be calculated because this greatly affects the amount of water lost through transpiration. Smaller leaves may lose less water than the larger ones, but by calculated water loss by surface area creates comparable data that is constant and consistent.

 

Error Analysis

 

This lab had many opportunities for error. The potometer set up was a complicated procedure. If any air bubbles were present in the plastic tubing, it could cause drastic error to occur. Any miscalculations or inaccurate weighing could also account for error.

 

Discussion and Conclusion

 

Transpiration in plants is controlled by water potential. This change in water potential in leaves causes a gradient by which water can be moved upward. When the water potential of the air was increased by the mist and plastic bag, less water evaporated from the leaves, decreasing the water potential gradient between the root and stem. This decreased the transpiration pull. The fan and floodlight simulated environmental conditions such as wind, heat, and intense light. These conditions increase the amount of water transpired by plants. This in turn increased the water potential gradient causing more water to be pulled through the stem. The control plant should have had normal rates of transpiration.

The stem must have specialized cells for support and transport. The epidermis is the outermost layer of the stem. The xylem is a transport tube for water, and the phloem transports food and minerals through the plant. Parenchyma are non-specialized cells and are located in the interior. The tougher sclerenchyma and collenchyma make up the structural outer support of the epidermis and the transport tubes of phloem and xylem.

All Materials © Cmassengale

Arkansas is essentially a forest state because more than half of the state is covered with trees.  The climate and soils of Arkansas also support a great variety of trees, both conifers and deciduous.  Trees are one of Arkansas’ most important crops.  Forests are also valuable in preventing erosion, in offering parks and recreational areas, and in providing homes for wildlife.  In addition, many trees have been introduced into the state as ornamentals.

Leaf collecting is a good way to learn the trees native to your area.  Collecting leaves will also help you to learn leaf margins, shapes, and  venations and how to use different taxonomic keys to identify trees.

Materials needed:

• leaf press
• black ink pen
• pencil
• small notebook to record leaves collected
• scissors
• Elmer’s glue
• art paper, poster board, etc. for mounting
• labels
• taxonomic keys (Trees of Arkansas published by the Arkansas Forestry Commission)

Top

Directions for making a leaf press:
1. Cut 10-15 pieces of corrugated cardboard 30 cm by 50 cm in size.
2. Cut several sheets of newspaper the same size as the cardboard.
3. Lay sheets of newspaper between each cardboard layer sandwich style.
4. A piece of wood may be added to the top and bottom to better “press” the leaves flat
5. Use two stretch belts or cords to bind the press together.
6. Leave the press in an area so that air can circulate &  more quickly dry the leaves.

Top

Getting started with your collection:
1. Study the shapes, margins, venations, tips, bases, etc. in your Trees of Arkansas book.

Click here to view reference page

2. Learn to distinguish simple leaves (one blade) from compound leaves (multiple leaflets) and conifers (evergreens) from deciduous (lose leaves) trees.
3. Learn to distinguish a tree from a shrub. (Trees with a single trunk)
4. leaves attach to twigs at NODES. INTERNODES are the distance between leaves on a twig.
5. Gather your collecting materials together – press, pencil, scissors, & small notebook.
6. Always get permission before collecting leaves on someone else’s property.
7. Be sure to collect at least two of each type of leaf so both the bottom & top side of the leaf can be shown in your collection.
8. Place leaves in your press immediately after collecting them so they do not start to dry out and wrinkle.
9. Record the name of each leaf, date collected, and place collected in your notebook as you collect.
Also record tree characteristics such as shape of the crown, color and type of bark, etc.

Top

Collecting:
1. Remember to collect two of every type of leaf!
2. Carefully remove an entire leaf, not a leaflet, from the tree, and place this in your press between newspaper layers.
3. If leaves are damaged or torn, don’t use them because you will not receive credit.
4. Make sure that none of the leaf parts extend beyond the edge of the press.
5. You may also collect & press seeds and/or fruits from some trees if they fit in your press.
6. Leave the leaf in the press for 3 – 5 days depending on its thickness and moisture content.  .
7. Keep the press in an area where air is circulating (in front of a fan).

Top

Labeling and identifying:
1. Obtain printed labels from your teacher.
2. Use only black ink to write labels, & do not mark out or white out mistakes on the labels; rewrite them.
3. Use taxonomic keys to identify each leaf, and include both the scientific & common name of the tree on the label.
4. Determine the shape, margin, tip, base, and venation of your leaf and whether it is a simple or compound leaf; record this on your label.
5. Use you key to give a description of the tree, not the leaf.
6. Research uses for the tree, its fruit, etc. and record on your label.
7. Tell if the leaf is deciduous or coniferous.

Click here for more labels

Top

Mounting leaves: 

Paste Label Here             Pg#

LEAF COLLECTION Name Date Period Subject/Teacher

1. Use pieces of cut poster board or art paper to mount your leaves.  Make sure all sheets are uniform in size! (The size of your sheets will be determined by your largest leaf.)
2. Use Elmer’s glue to adhere two leaves to each page — one showing the upper surface of the leaf and the other showing the underside of the leaf.
3. Each page should have only one type of leaf on it.
4. Arrange the leaves so they do not overlap each other and so there is room to glue the label in the lower right hand corner.  The leaves should look nice on the page.
5. On compound leaves, mount the topside of the complete leaf and then mount the underside of a single leaflet. Make sure the leaflet comes from another leaf to receive credit!
6. Use a small amount of Elmer’s glue to adhere the completed label in the lower right hand corner of the page.
7. LET THE PAGES DRY COMPLETELY BEFORE ASSEMBLING THEM TOGETHER IN YOUR COLLECTION OR THE PAGES WILL STICK TOGETHER!!!!!
8. Once the pages are dry, lay them in the correct order (see your list of required leaves), and then number the pages in the lower right corner with black ink.
9. Make a stiff front and back cover for your collection from poster board, cardboard, wood, etc.  Include the following items on your cover:

• title
• your complete name
• date collection turned into teacher
• class period

10. Use ribbon, string, etc. to bind the pages together or assemble the collection in a scrapbook or art book.  DO NOT COVER THE LEAVES WITH PLASTIC!!!

Top

Required leaves:
1. Only native, Arkansas trees may be used.  Refer to your Trees of Arkansas book.
2. Leaves must be in perfect condition without damage or tears.
3. No more then 4 oaks are allowed in the collection.
4. No fruit trees such as apple, pear, orange, peach, etc. are allowed.
5. Place the following leaves in your collection first and in this order:

1. sweet gum
2. American sycamore
3. pine (any type)
4. flowering dogwood
5. redbud
6. ash (any type)
7. redbud
8. Eastern red cedar
9. maple
10. willow
11. pecan
12. pin oak
13. willow oak
14. water oak
15. elm (any type)

 16 – 20  Any other Native Arkansas leaves

6. The remaining leaves that you include must be trees native to Arkansas!

Top

*Pre AP Biology is required to collect 30 leaves including the 15 required.

 *Biology I is required to collect 20 leaves including the 15 required.

 

Arkansas is essentially a forest state because more than half of the state is covered with trees.  The climate and soils of Arkansas also support a great variety of trees, both conifers and deciduous.  Trees are one of Arkansas’ most important crops.  Forests are also valuable in preventing erosion, in offering parks and recreational areas, and in providing homes for wildlife.  In addition, many trees have been introduced into the state as ornamentals.

Leaf collecting is a good way to learn the trees native to your area.  Collecting leaves will also help you to learn leaf margins, shapes, and  venations and how to use different taxonomic keys to identify trees.

Materials needed:

• leaf press
• black ink pen
• pencil
• small notebook
• scissors
• Elmer’s glue
• art paper, poster board, etc. for mounting
• labels
• taxonomic keys (Trees of Arkansas published by the Arkansas Forestry Commission)

Top

Directions for making a leaf press:
1.   Cut 15 – 20 pieces of corrugated cardboard 30 cm by 50 cm in size.
2. Cut several sheets of newspaper the same size as the cardboard.
3. Lay 10 or 12 sheets of newspaper between each cardboard layer sandwich style.  These sheets will need to be changed every couple of days as they absorb moisture from your leaves; therefore, cut extra sheets.
4. Use one, preferably two, stretch belts to bind the press together.
5. Leave the press in an area so that air can circulate &  more quickly dry the leaves.

Top

Getting started with your collection:
1. Study the shapes, margins, venations, tips, bases, etc. in your Trees of Arkansas book.

Click here to view reference page

2. Learn to distinguish simple leaves from compound leaves and conifers from deciduous trees.
3. Learn to distinguish a tree from a shrub.
4. Gather your collecting materials together – press, pencil, scissors, & small notebook.
6. Always get permission before collecting leaves on someone else’s property.
7. Be sure to collect at least two of each type of leaf so both the bottom & top side of the leaf can be shown in your collection.
8. Place leaves in your press immediately after collecting them so they do not start to dry out and wrinkle.
9. Record the name of each leaf, date collected, and place collected in your notebook as you collect.  Also record tree characteristics such as shape of the crown, color and type of bark, etc.

Top

Collecting:
1. Remember to collect two of every type of leaf!
2. Carefully remove an entire leaf, not a leaflet, from the tree, and place this in your press between newspaper layers.
3. If leaves are damaged or torn, don’t use them because you will not receive credit.
4. Make sure that none of the leaf parts extend beyond the edge of the press.
5. You may also collect &press seeds and/or fruits from some trees if they fit in your press.
6. Leave the leaf in the press for 3 – 5 days depending on its thickness and moisture content.  Remember to change the newspaper when needed.
7. Keep the press in an area where air is circulating (in front of a fan).

Top

Labeling and identifying:
1. Obtain printed labels from your teacher.
2. Use only black ink to write labels, & do not mark out or white out mistakes on the labels; rewrite them.
3. Use taxonomic keys to identify each leaf, and include both the scientific & common name of the tree on the label.
4. Determine the shape, margin, tip, base, and venation of your leaf and whether it is a simple or compound leaf; record this on your label.
5. Use you key to give a description of the tree, not the leaf.
6. Research uses for the tree, its fruit, etc. and record on your label.
7. Tell if the leaf is deciduous or coniferous.

Top

Mounting leaves:
1. Use pieces of cut poster board or art paper to mount your leaves.  Make sure all sheets are uniform in size! (The size of your sheets will be determined by your largest leaf.)
2. Use Elmer’s glue to adhere two leaves to each page — one showing the upper surface of the leaf and the other showing the underside of the leaf.
3. Each page should have only one type of leaf on it.
4. Arrange the leaves so they do not overlap each other and so there is room to glue the label in the lower right hand corner.  The leaves should look nice on the page.
5. On compound leaves, mount the topside of the complete leaf and then mount the underside of a single leaflet. Make sure the leaflet comes from another leaf to receive credit!
6. Use a small amount of Elmer’s glue to adhere the completed label in the lower right hand corner of the page.
7. LET THE PAGES DRY COMPLETELY BEFORE ASSEMBLING THEM TOGETHER IN YOUR COLLECTION OR THE PAGES WILL STICK TOGETHER!!!!!
8. Once the pages are dry, lay them in the correct order (see your list of required leaves), and then number the pages in the lower right corner with black ink.
9. Make a stiff front and back cover for your collection from poster board, cardboard, wood, etc.  Include the following items on your cover:

• title (Tree Identification Through Leaves)
• your complete name
• date collection turned into teacher
• class period
• subject
• teacher’s name

10. Use ribbon, string, etc. to bind the pages together or assemble the collection in a scrapbook.  DO NOT COVER THE LEAVES WITH PLASTIC!!!

Top

Required leaves:
1. Only native, Arkansas trees may be used.  Refer to your Trees of Arkansas book.
2. Leaves must be in perfect condition without damage or tears.
3. No more then 4 oaks are allowed in the collection.
4. No fruit trees such as apple, pear, orange, peach, etc. are allowed.
5. Place the following leaves in your collection first and in this order:

• sweet gum
• American sycamore
• pine (any type)
• flowering dogwood
• redbud
• ash (any type)
• persimmon
• Eastern red cedar
• red or silver maple
• hickory (any type)
• pecan
• pin oak
• willow oak
• water oak
• elm (any type)

6. The remaining leaves that you include must be trees native to Arkansas!

Top

*Pre AP Biology is required to collect 30 leaves including the 15 required.

 *Biology I is required to collect 20 leaves including the 15 required.