Plants are living entities, they are highly organized systems, they have cells and DNA, they use energy to grow and reproduce, and they can react to their environment. Plants are highly organized systems; they can be broken down into two main systems, the roots and the shoots. However, within the two main systems, there are multiple subsystems and processes. They all work together to help the plant gain and use energy so that they can grow and reproduce.

One of things that plants need to gain and use energy is water. The main way that plants attain water is through the root system.
Root System

The main purposes of roots are to stabilize the plant in the soil while also absorbing water and nutrients and absorb them from the soil and then begin to travel them up to disperse to the rest of the plant. Plants can also act as storage sites for food reserves. Water doesn't come to roots nearly as much as roots must come to water. Roots constantly have to grow to adapt to new water supplies. This constant need for water helps with the process of photosynthesis. Each plant has its own root system. We saw evidence of these roots systems through the various plants we saw in lab. These systems include either a taproots system or a fibrous root system that serves its own individual purpose.

A
taproot system can be described as a large central root with numerous smaller lateral roots extending from that (ex: carrot). This large central root provides a strong anchor for the plant in the soil. Sometimes it is also used for food storage including a buildup of starch and water storage. The smaller, lateral roots serve as the main source to the central root for water and nutrients. Sections of this taproot system can create a new plant.

A
fibrous root system consists of many roots that are all the same size; it has no predominant root. This root system has a large surface area to volume ratio (meaning that there is more area of the root touching the soil then there is actual volume of the root) making it effective in gathering nutrients. It also helps to anchor the plant and prevent soil erosion. Both of these systems have a threadlike extension (elongated cells) of their roots called root hairs.

The vascular bundles consist of the xylem and phloem and run throughout the plant as the transport system. They carry water to the leaves and carry sugar from photosynthesis throughout the plant. Vascular bundles refers to collections of tubes through which fluid materials move from one part of the plant to another. In lab we saw evidence of these vascular bundles when we witnessed the red dye from the bottom of the celery stalk travel all the way to the top of the stalk. This happened through these vascular bundles.

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Within a plant there are two main vascular tissues: the xylem and the phloem. The
xylem is a principal vascular tissue within the plant. It transports water and helps to dissolves inorganic nutrients. The xylen is the tissue through which water and dissolved minierals flow in vascular plants. Xylem cells are stacked together to form a pipeline/tube throughout the plant from the root to the tips of all the leaves. The xylem is also involved in a process known as transpiration, serving as a tube to carry the water up the plant out the stomata. A xylem consists of vessel elements and tracheids which are two types of fluid conducting cells. These cells die off before the point of maturity. The tubes are essentially just strands of empty cells that have been cleared out. The walls of these cells are strengthened with cellulose and lignin that enables the load-bearing capacity.

Transpiration is the process that results once the water has evaporated from the plant and there is open space within the leaf. This space then creates a type of "suction" that is then filled by more water until it reaches the xylem. Once the water has reached the xylem the process of cohesion of hydrogen bonds between water molecules allows water to be transported, against gravity, up the plant. Also at work is the role of adhesion of the water molecules to the sides of the xylem helping with the transpiration stream of water.

The second main vascular tissue is called the phloem. Its primary purpose is in creating pressure flow.
Phloem cells are laid out end to end in the plant to create a tube that transfers the product of photosynthesis (glucose or sugar) and some hormones throughout the plant. When photosynthesis occurs it creates sugar that is then loaded into the phloem, which then transports that sugar to the fruits, stems, and roots when it is stored. Phloem contains a sieve element who's job is to do the actual nutrient conducting. It doesn't die at maturity but it loses it's cell nucleus including all DNA. Every sieve element has an associating with a companion cell that retain its DNA and does all the housekeeping needs. The nucleus is removed to make extra space for the rapid flow of food through it.
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Plants make their own energy through the process of photosynthesis which takes place in the shoot system.
The Shoot System
The shoot system is the part of the plant that we see above the ground. The shoot system is composed of many parts – the reproductive shoot (flower), the terminal bud, the node, the leaf, and the stem.
A plant grows tall because of the terminal bud. Located at the tip of the plant, the terminal bud has developing leaves and a compact series of nodes. It’s basically two or more tiny little leaves (the number depends on the plant) closed up like a little bud, as the plant grows, the bud opens up and the leaves begin to grow.

The node is the point on the stem where the leaves are attached.
Leaves are part of the plant most responsible for photosynthesis. Although green stems can also perform photosynthesis, leaves increase the surface area of the plant, therefore capturing more solar energy for photosynthesis. Leaves are composed of many complex parts. The petiole is the stalk part of the leaf; it joins the blade to the node on the stem. The blade is the flat green part of the leaf. On the outside of the blade is the dermal tissue system. The dermal tissue is like our skin; it's the outer protective covering that "forms the first line of defense against physical damage and pathogenic organisms. In nonwoody plants, the dermal tissue usually consists of a single layer of tightly packed cells called the epidermis" (Campbell 717). The cuticle is also part of the epidermis that exists on leaves and most stems; it's a waxy coating that helps prevent water loss and is an important adaptation to living on land. On the bottom of the blade, the epidermal tissue is interrupted by the stomata (singular, stoma). A stoma is a pore with two guard cells on either side of the opening. The guard cells control the opening and the closing of the pore. The opening and closing regulates the "CO2 exchange between the surrounding air and the photosynthetic cells inside the leaf" (Campbell 724). In addition to regulating the CO2 exchange, the stoma (and guard cells) are a key part of cellular respiration. On the inside of the inside of the leaf, under the dermal tissue, is the ground tissue and vascular tissue. "Tissues that are neither dermal nor vascular are part of the ground tissue system. Ground tissue that is internal to the vascular tissue is called pith, and ground tissue that is external to the vascular tissue is called cortex" (Campbell 717). Within the ground tissue are theparenchyma cells.
The parenchyma cells are responsible for most of the metabolic functions of the plant. They synthesize and store various organic productions. However, one of the most important functions of the parenchyma cells is photosynthesis.

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The stem is an organ consisting of alternating systems of nodes and internodes. Inside the stem are the vascular tissues xylemand phloem. Together, the xylem and phloem make up vascular bundles. Vascular bundles not only exist in the stem and root system, but also within the veins of the leaves.

The cells inside of the leaves are highly organized also.
Cell Function

Cells are the smallest unit of life that contains DNA. In order to survive it needs matter and energy because it is a highly complex and organized living system. Plant cells occur in groups. Groups of cells make up tissues. Collections of tissues make up an organ. Groups of organs make up an organ system. Collective organ systems make up an organism. Mass bodies of organisms form a population. Different populations that come together forms a community. A community makes up an ecosystem. Thus an ecosystem makes up a biosphere. Eukaryotic (non-bacterial cells) contain organelles (“tiny organs”). Every cell has a specific job and thus they become organized “bodies” together

3 Unique Structures & Roles:
1.) Cell Wall – limits water uptake, maintain cell membrane shape, protect from outside influences.
2.) Central Vacuoles – cell metabolism, pH balance, digestion, water maintenance
3.) Chloroplasts - photosynthesis

We saw the greatest evidence of plant cells and their 3 unique structures within the lab looking at the elodea plants. When we looked at the elodea plant cells under the microscope we could see clearly the cell wall, cell membrane, and the central vacuole.


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Cell walls are almost always present in plant cells. In general, it protects plants from harmful outside influences. They help limit the amount of water being absorbed into the cell. The cell wall is located on the outside of the cell membrane with a rigid outside covering. Cell walls give strength to the plant and provide plant cells with structure while limiting flexibility. Cell walls are composed of a type of carbohydrate called cellulose. Cellulose acts as a fibrous mesh in the cell wall adding solidarity. Cell walls help limit the water being taken in.

Cell membrane (aka: plasma membrane) It is semi-permeable (see osmosis below for more details), and allows water and lipid substances to pass through but does not allow for larger charged substances. As a membrane it encloses the fluid cell contents of the cell. Cell membranes are the essential way for plants to get water. It can only cause harm in cases of extreme solute imbalance which results in water flowing out of the cells that can penetrate cell dehydration. The membrane can push up against the cell wall with some force setting up a pressure that keeps more water from entering.

A
central vacuole is an organelle surrounded by a thin coat of cytosol. A central vacuole is capable of taking up more than 90% of cell volume. Central vacuoles are mainly holds water. The central vacuole contains nutrients water, waste products, and hydrogen ions pumped in to maintain a near-neutral pH level. Central vacuole is the place to store nutrients, retention of waste products or degrades them with digestive enzymes. The central vacuole when filled also helps cells stay rigid. We saw the impact of the central vacuole as providing structure when we added salt water to the elodea plant and the vacuole emptied of water causing the cell the "shrink".

Plants are green primarily due to the pigment chlorophyll which is located inside
chloroplasts. Chloroplasts, the tiny organelles are the sites of photosynthesis (when sunlight is captured and coverts carbon dioxide into food, specifically glucose that functions as the plant’s food source) with the help of carbon dioxide, water, and a few minerals. As a result, oxygen is left over. (See below for more details on photosynthesis). Chloroplasts are a special type of plastid. Chloroplasts have special pigments which makes the human eye see green because that is the only color not absorbed when light reflects off of them. Chloroplast have their own DNA. The stacks of these "pancake-like" disks are called thylakoids and stacks of thylakoids are called grana.


The
nucleus is the site of the plant cell’s DNA (complete specifications for a protein) and is the control center of the cell. The outer boundary of the nucleus is a concentric double membrane called the nuclear envelope. Compounds pass into and out of the nucleus through nuclear pores. Inside the nucleus it the nucleolus which specializes in the production of RNA (material that makes up ribosomes).


Cell Diagram
Cell Diagram


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Plants gain energy through the process of photosynthesis. Within the process of photosynthesis, there are many sub-processes that need to take place in order for photosynthesis to work, such as diffusion, cellular respiration, and active transport.
Processes

Photosynthesis - 6H2O +6CO2 à C6H12O6 +6O2

Photosynthesis consists of two different parts. The Light Reaction is the photo part. Next is the Calvin Cycle which is the synthesis part. In order for photosynthesis to take place carbon dioxide gas is needed, enzymes to break and rearrange chemical bonds, ATP a molecule that stores and releases chemical energy. NAD+, NADP+ and FADH used to escort electrons and protons around cells to make energy and of course sunlight. Photosynthesis allows for carbon dioxide to come in and oxygen to come out.

In the Light Reaction (photo part) the conversion of solar energy to ATP and NADPH is taken place. The energy emitted from the sun is used to excite chlorophyll which splits water (H20) into hydrogen and oxygen and stores solar energy in ATP and NADPH which is necessary later.
Inside the thylakoid membrane there are stacks of chloroplasts. First the sunlight strikes chlorophyll which gets the electrons excited. The water molecules split apart (H+ and O) consequently the H electrons go to chlorophyll. The oxygen gas is then released from chloroplast. Electrons are then passed around a series of proteins which is referred to as the electron transport chain. Meanwhile, energy is being stored in ATP and NADPH (chemical energy). [2H20 + 4H+ + O2]

On the other hand, the Calvin Cycle (synthesis part) reaction is independent from the light reaction. The use of CO2, H+ and energy is combined together to make sugar. Using the energy made in the Light Reactions, the hydrogen atoms (H+) from the water split (in the light reaction) combine with CO2 taken in from the stomata to make glucose (C 6H12O6). [4H+ + CO2 + CH20(Glucose) = H2O
Consequently, glucose is transported and made available to every cell of the plant to help with flower production, seed production, growth and cell maintenance. Glucose provides both matter and energy to the plant. Matter in terms of carbon, hydrogen, and oxygen that build the cells. Including the SPONCH Café = (Sulfur, Phosphorus, Oxygen, Nitrogen, Carbon, Hydrogen, Calcium, Iron) Also, energy in the forms of chemical bonds that store energy. ATP is the plant conversion from solar energy into chemical energy.


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Plants need water, carbon dioxide and light for the process of photosynthesis. Plants acquire carbon dioxide through stomata in leaves. The stomata stays open during the daytime for carbon dioxide to enter and for oxygen and water to come out. But remains closed at night. Plants get maximum sunlight on leaves with high SA to V ratio because more cells are being exposed to the light. Plants accumulate water with the help of the vascular tisue existing in both the roots and the shoots. Most photosynthesis takes place in the several layers of mesophyll cells.

Photosynthesis takes place in the shoots to produce foods: leaves and stems. Shoots are further organized into tissues. Tissues are groups of specialized cells working together. Shoots help distribute food to the whole plant. It is the site of sexual reproduction.


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http://ellerbruch.nmu.edu/classes/cs255w03/cs255students/teabbott/p4/pics/photosynthesis.jpg
D
iffusion – the movement of molecules or ions from a region of their higher concentration to a region of their lower concentration. The natural tendency for any solute is to move down its concentration gradient from higher concentration to lower.


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Osmosis- the net movement of water across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration. Why? In the case of a solute like salt, water molecules will surround and bond with the sodium and chloride ions as salt separates into a solution. These soluble are not free to pass through the membrane, the water molecules bound to them will be unable to pass through the membrane. The opposite side of the membrane will consist of more “free” water. Osmosis consists of the flow from the Xylem to the Phloam.


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Active Transport – Active transport is any time in which energy is required for movement across the plasma membrane. The cell’s solution to moving solutes against their concentration is via pumps by expending energy to move substances across the plasma membrane. The energy used often is ATP (adenosine triphosphate), the cell contains electrochemical power of charged ions to move substances across the membrane. One such is called the sodium-potassium pump that allows the cell to maintain an environment of high potassium inside the cell, and high sodium outside the cell. This results in a slow “leakage” of sodium into the cell as they follow their concentration gradient down and move in through transport proteins while potassium ions are moving out.

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When a plant is ready to take the glucose molecules it has produced out of storage and use them, the glucose molecules have to travel down to the roots. In order to do this water needs to enter the phloem to push the glucose molecules down. Water enters the phloem from the xylem through the process of osmosis.
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One of the things that plants use energy for is to reproduce.
Reproductive System

We all have a general idea of what a
flower is; the flower is not only part of the shoot system, it is also part of it’s own system, the reproduction system. Flowers are the reproductive structures of plants. A flower generally has both male and female reproductive structures in it which allows it to fertilize itself. Flowers can be broken down into 4 parts:sepals are the leaf-life structures that protect the flower before it opens (drying out is a problem). The function of the colorful petals is to announce “food here” to pollinating animals. Petals may contain special patterns to attract pollination. The shape of the petals themselves can give off pollen. The main part of the flowers’ reproductive structures are the stamens and the carpel. Stamens (male sex organ) consist of a long, slender filament that is topped with an anther. Anthers contain cells that will yield sperm-bearing pollen grains.

Pollen grains have a tough (often spiky) outer coat with three cells inside – one tube cell and one germ cell (which will later split into two sperm cells). When the pollen grain lands on the stigma, it must germinate. The pollen tube sprouts and grows down the style paving the way so that sperm cells can follow. Seed is the result of the first sperm to fertilize with the egg. The other sperm that hits the ovary makes food for the seed. The tube cell is responsible for the growth of the pollen tube (http://www.answers.com/topic/tube-cell). It is these pollen grains that will be released and then carried (via pollinating bee or bird) to the carpel of another plant (or sometimes the same plant). A carpel (female sex organ) is a composite structure composed off 3 main parts: the stigma, which is the tip end of the carpel, on which pollen grains are accepted by a sticky tip; the style, a slender tube that raises the stigma to such a tall height makes it easier to catch the pollen; and the ovary is the area in which fertilization of the female egg takes place and the early development of plant embryo will take place.

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1) Get pollen on stigma
2) Pollen has to go all the way down the style to get the egg inside the ovary.
3) Once the pollen grain lands on the stigma it must germinate.
4) The pollen tube sprouts and digests down the style to make way.
5) Fertilization with the egg occurs. Simultaneously, the fertilization of the central cell takes place to make food also known as endosperm (which is rich in nutrients and sustains the growing embryo).
6) Finally a seed is born.
7) The ovary surrounding the ovule develops into a fruit.


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During pollination, the pollen grains are transferred to the stigma. Once the pollen grain lands on the stigma, the tube cell creates a pollen tube that grows down the style towards the ovule. While the germ cell is traveling down the pollen tube it splits into two sperm cells through the process of mitosis. The sperm move down to the pollen tube and into the ovule. Fertilization occurs when one of the sperm cells fuses with the egg inside the ovule (http://ecmsscience.tripod.com/id45.html). The second sperm cell fuses with the central cell to make form, forming the endosperm cell. The endosperm cell forms the endosperm. Endospermis a nutrient rich tissue which provides nourishment to the developing embryo in angiosperm seeds providing an energy burst. As the embryo grows into a seed, the outer coat of the ovule forms the seed coat; a tough outer covering of a seed that encloses and protects the embryo and endosperm. Out of the embryo grow the cotyledons, the first one or two little leaves of the soon to be plant (the number of leaves depends on whether the plant is a dicot or monocot). While this is taking place the ovary that surrounds the seed is also developing into a tissue called fruit. A fruit is simply the mature ovary of a flowering plant. All angiosperms have fruit in this sense because it is essentially a flowering seed plant whose seeds are enclosed within the tissue called fruit. In lab, we looked at examples of fruits with one carpel and one seed (apricot), one carpel with many seeds (pea) and many carpels with many seeds from one receptacle (strawberry). Fruit becomes ripe because of the gaseous hormone ethylene.

In the future, seeds have the capacity to stay dormant. With the right environment: light, water and temperature it can increase the chances of germination. Freezing can be helpful in extending the life of a plant. Under the right conditions, germination occurs. The seed soaks with water which breaks down the seed coat. The endosperm used by the embryo for growth is also used. Auxin, a hormone found in roots and shoots, helps with plant growth. Phototropism is a hormone that detects light or gravitropism (gravity) and helps lengthen the cells. Hormones are essentially messengers that starts in one part of a plant and sends a message to a different part of the plant and cells talk with one another in these molecules. Auxin decreases root cell elongation. It works alonside organelles to figure out which way is down also knows as gravitropism.

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In order for plants to reproduce they must combine the sperm with the female egg. Some plants can reproduce themselves through self-pollination. However, many have to rely on the spread of pollen through wind or animal pollinators. Those plants that rely on wind for pollination grow up to be small flowers. On the other hand, plants that rely on animal pollinators spend energy to show off through their petals and scents. Scent plays in a large part by attracting a pollinators’ attention. The smell of nectar or a supposed food course (carrion) can also lure them in. Pollen contains an outer external coat that houses: 1 tube cell and 2 sperm cells.

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Once the fruit has ripened the seeds are dispersed through a variety of methods.
Seed dispersal occurs in a variety of ways. Often times an animal will eat the fruit and the seed. Later the seeds are eliminated and left on the ground. First to emerge from teh seed is the root structure or radicle, which is attached to the hypocotyl, which can be thought of as all the plant tissue below the cotyledons.

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As plants are living things, they need to be able to react to their environment.
Environmental System

All plant have chemical substances inside of them that bring about a certain response called
hormones. They are small molecules that cling to a receptor within the cell membrane of plant cells where they then send a some sort of message. Hormones serve as "chemical messengers" that originate in one part of the pant and then send a message to another part of the plant. Hormone production is a more diffuse process that in collections of cells carry out a range of different functions. There are five major hormones in plants, two of which called auxins and ethylene. Auxins are hormones that promote and regulate growth in the plant and the falling off of the leaves. They are also the hormone responsible for phototropism, or the growth of plants toward their light source. Also, auxins help differentiate between xylem and phloem tissue. Ethylene are hormones that are released by plants as a gas and affect the ripening of fruit and the promotion of the falling off of leaves. It is also responsible for slowing down of the lateral bud growth For example, if you were to place an unripe banana in a paper bag with a ripe banana the ethylene gas from the ripe banana would escape and spread to the unripe banana encouraging the production of more ethylene to create ripening. Ethylene initiates the reaction that converts the starches in plants to sugar, also known as the ripening of fruit.

Environmental factors that affect a plant are numerous. One such example is Photoperiodism which is the ability of plants to grow in accordance with the lengths of day and night. This process keys the plant on to important knowledge such as the length of day in accordance to the season. It could signal to the plant that it is time to start to produce buds or flowers and conversely if the days are shorter the plant knows to produce seeds for the winter season to allow for seasonal adaptation. (http://www.wisegeek.com/what-is-photoperiodism.htm). Another response to the environment is in response to sunlight.
Phototropism is the bending, curvature and growth of plants according to its light source. This is because plants produce their own food and light is necessary for that production. Phototropism is the plant's response when sunlight becomes blocked by another plant or some other physical object. When the hormone auxin is redistributed in the plant according to the amount of light it is receiving, the plant bends toward more light in order to equalize the auxin throughout the plant. When light hits one side of the shoot, it causes auxin to move to the other side where it acts to lengthen the cells on the far side. This effects makes the shoot curve towards the light.
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As the picture shows, the hormone auxin shifts to the dark side of the plant signaling to the cells to elongate themselves on a certain side of the plant. This process causes the bending of the plant toward the light source.
Another process of the plant responding to the environment is called photoperiodism.

Another response to the environment occurs through
gravitropism which is the plants response to gravity; the fact that the roots desire to grow down toward the water and minerals that the plant needs, and the shoots want to grow upwards to access the sunlight. Roots have a positive gravitropic response because of they grow downwards. Shoots have a negative gravitropic response because they grow against gravity, upwards. This process is required in order for the plant to survive. For example, if a root's tip were to be snipped off then there would be no bending with regards to gravitropism, but instead a continuation of straight horizontal grows. It shows that cells or substances in the root cap are essential for root gravitorpism. Similarly to phototropism, the movement of the hormone auxin during gravitropism signifies the the plant a need to slow down the elongation some cells causing the plant to bend in a certain direction (http://www.microgravity.ac.uk/subjects/Plantgrav.htm).



Cellular Respiration – C6H12O6 +6O2+ ADP à 6CO2 + 6H2O + ATP
C6H12O6 is glucose which stores chemical energy. 6O2 is needed as the final electron accepter.
Products are carbon dioxide and water and energy in the form of ATP.
Glycolysis is one of the sole sources of energy transfer. Electron Transport Chain requires the ability to use oxygen. Thus, the products of glycolysis feed into the Krebs cycle and the oxygen-using electron transport chain. All three stages are oxygen dependent. In the absence of oxygen, glycolysis can substitute. The separation between glycolysis and the other two steps takes place in the Krebs cycle and the electron transport chain within cell structures (mitochondria that are immersed in cytosol).

The main function of these phases is the transfer of electrons to the electron carriers. These carries then move to the electron transport chain, where they are oxidized (losing electrons). The movement of these electrons through the chain yields about 32 molecules of ATP.
-The first stage, Glycolysis, means “sugar splitting”. First, the molecule of glucose has to be prepared for energy release. ATP has to be used in two of the first steps of glycolysis so that the relatively stable glucose can be put into the form of a less stable sugar. Then the sugar is split in half. The two molecules formed have three carbons each, once this split has occurred it continues to duplicate.
- The second stage is the Krebs cycle. The Krebs cycle supplies energy bearing electron carriers. It takes place in the inside of the inner membrane (inner compartment). Acetyle CoA combines with oxaloacetic acid (4 carbon). The CoA fragment separates and it results in the energetic citric acid to be oxidized

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Works Cited:
Alters, Sandra. Biology: Understanding Life. 3rd ed. Sudbury, MA: Jones and Bartlett Publishers, 2000. Print.
Campbell, Neil A., and Jane B. Reece. Biology AP Edition. Upper Saddle River: Prentice Hall College Div, 2004. Print.
Krogh, David. Biology: A Guide To The Natural World. 2nd edition. New Jersey: Prentice Hall, 2002. 496-520. Print.

http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookflowersII.html