ANSWER KEY– LO 4.1

Which of the following statements concerning unsaturated fats is true?

A) They are more common in animals than in plants.B) They have only single bonds in the carbon chains of their fatty acid tails.C) They’re generally a solid at room temperature b/c their molecules are closely packed together.D) They’re generally a liquid at room temperature b/c their molecules have kinks caused by double bonds.

(sample drawing)

Suppose you have placed a protein in an aqueous environment. Where would you expect to find a region that is rich in polar amino acids? Why? A region rich in non-polar amino acids? Why? Draw and label this hypothetical protein.

A protein in an aqueous environment should be expected to have regions containing polar amino acids near the surface of the macromolecule because these polar amino acids will interact with the polar water molecules found within the aqueous solution. The regions containing non-polar amino acids should be found within the interior of the macromolecule because these non-polar amino acids will want to interact with each other, as far away from the presence of the polar aqueous environment as is possible.

Answer Key- L.O. 4.3M.C. Question: A protein undergoes a change in which an amino acid containing a sulfhydryl R-group is replaced with an amino acid containing a cationic R-group. Which of the following will likely be a result of this change?A) The secondary structure of the protein will change from a pleated sheet to a helix.B) The tertiary structure of the protein will be altered as a result of altered disulfide bridge interactions.C) The protein will denature at room temperature.D) The protein’s properties will not change.E) Both B and C are true.

FRQ: A) Describe the structural and functional differences between DNA and RNA.

DNA is double stranded and takes the 3-dimensional shape of a double helix. It contains the nitrogenous bases adenine, thymine, cytosine, and guanine and has a backbone composed of phosphate groups and deoxyribose sugars. Its primary function is to store the genetic code. RNA is single stranded, contains the nitrogenous bases adenine, uracil, cytosine, and guanine, and has a backbone composed of phosphate groups and ribose sugars. Its primary function is to carry the genetic code from the nucleus to the ribosome (mRNA) and to assist in transcription from gene to protein (tRNA.)

B) List and describe three specific biological examples of protein structure relating to function.

1) Aquaporin: protein channel containing a hydrophilic interior that allows for the passage of water in/out of cells via plasma membranes during osmosis.

2) Hemoglobin (sickle-cell): Sickle-cell anemia is caused by a point mutation in the β-globin chain of hemoglobin, causing the hydrophilic amino acid glutamic acid to be replaced with the hydrophobic amino acid valine at the sixth position, thus altering protein structure and leading to symptoms of sickle-cell such as reduced oxygen transport.

3) Enzymes: specific interactions among amino acids within an enzyme influence the tertiary/quaternary structure of an enzyme, which directly influences shape of the enzyme as a whole, and specifically the shape of an enzyme’s active site and/or allosteric site. Since enzymes work on specific substrates, which bind to specifically-shaped enzyme active sites, a change in amino acid make-up within an enzyme can deactivate the enzymes specificity to substrates.

ANSWER KEY– LO 4.4M.C. Question:

Which of the following sub cellular interactions are performed with the Golgi apparatus?

I. Vesicles form and leave Golgi, carrying specific proteins to other locations or to the plasma membrane for secretion

II.  Vesicles transport specific proteins backward to newer Golgi cisternae

III.  Vesicles transport certain proteins back to the ER

A.      I only

B.      I & II only

C.      I & III only

D.      II &III only

E.       I, II, & IILearning Log/FRQ-style Question Explain the functions of the cis Golgi of verses the trans Golgi. Describe their interaction with another sub cellular organelle and explain the relation between this and their location. In what direction do they move in?

The two poles of the Golgi are referred to as the “cis” face and the “trans” face. The “cis” face is considered to be the receiving department of the Golgi while the “trans” face is considered to be shipping department. This “cis” face is usually located near the ER, due to the fact that transport vesicles move material from the ER to the Golgi apparatus. A vesicle that buds from the ER is then able to add its membrane and the contents of its lumen to the cis face by fusing with the Golgi membrane. The “trans” face is located on the opposite side of the “cis” face, as it is on the “shipping” side of the Golgi apparatus. The “trans” face will give rise to vesicles which will then pinch off and travel to other sites. According to the cisteral maturation model, the cistaternae of the Golgi progress forward from the “cis” to the “trans” face of the Golgi.

Answer Key – LO 4.5

All of the following are true about the Golgi apparatus except…

A) The Golgi apparatus consists of stacks of flattened sacs, called cisternae, which are physically connected.B) The two poles of a Golgi stack are referred to as the cis face and the trans face, which act, respectively, as the receiving and shipping departments of the Golgi.C) In addition to sorting and shipping materials, the Golgi apparatus also manufactures certain macromolecules by itself.D) Products from the ER are usually modified during their transition from the cis region to the trans region of the Golgi apparatus.

Describe, using details, the process by which a cell synthesizes, modifies, transports, and then secretes the glycoproteins responsible for determining a person’s blood type. Be sure to include the roles of the endoplasmic reticulum, Golgi apparatus, vesicles, and the plasma membrane in your response. Pay particular attention to how these subcellular structures interact in order for a cell to successfully complete this process.

The synthesis of glycoproteins begins in the ribosomes studded on the rough ER. After the ribosomes create glycoproteins, they are deposited into the rough ER so that they can be placed into transport vesicles. The vesicles then travel to the Golgi apparatus where the glycoproteins are modified and then packed into another transport vesicle. The vesicles coming from the rough ER to the Golgi, containing the glycoproteins, fuse to the cis face of the Golgi so that the molecular composition and metabolic functions of the glycoproteins can be modified within the Golgi, and then the vesicles containing the modified glycoproteins bud off from the trans face of the Golgi. These transport vesicles take the glycoproteins to the plasma membrane for secretion. The plasma membrane expands by the fusion of vesicles, and the glycoproteins are then secreted from the interior of the cell onto the surface of the cell, where they serve as cellular markers that determine blood type.

Answer Key- LO 4.6

Which is mismatched?(A) Smooth endoplasmic reticulum: detoxification(B) Centrioles: cell division(C) Nucleolus: ribosome synthesis(D) Plasma membrane: transport(E) Lysosome: lipid synthesis

Describe the structure and function of both the chloroplast and mitochondria. Then describe the probable origin of both these organelles by applying the theory of endosymbiosis.

Chloroplasts are a type of plastid that specialize in photosynthesis, found only in plants and algae. The chloroplast contains grana, where the light reactions occur, and stroma, where the light-independent reactions occur. The grana consist of layers of membranes called thylakoids, the site of photosynthesis. The chloroplast is enclosed by a double membrane. The mitochondria, found in nearly all eukaryotic cells, is the site of cellular respiration, the metabolic process that generates ATP. The mitochondrion is enclosed by two phospholipid bilayer membranes. The outer membrane is smooth, whereas the inner membrane is convoluted, with infoldings called cristae. The inner membrane divides the mitochondrion into two internal compartments, the inner membrane space and the mitochondrial matrix. The matrix contains many different enzymes as well as the mitochondrial DNA and ribosomes. The theory of endosymbiosis proposes that both the mitochondria and the chloroplast likely evolved from prokaryotes that were engulfed by and lived symbiotically inside larger cells. Evidence that supports an endosymbiotic origin of these two organelles includes that the inner membranes of both organelles have enzymes and transport systems similar to those found in the plasma membrane of prokaryotes. Further, mitochondria and plastids replicate by a process similar to binary fission in prokaryotes.

Answer Key-LO 4.7

Which of the following displays the correct process of a cell differentiation?A) Surrounding cells send signals; cell receives signal; creation of proteins; genes activatedB) Regulatory gene activated; created proteins activate other genes; function/structural determining proteins created; cell sends signalC) Surrounding cells send signals; cell receives signal; point of no return; regulatory gene activated; function/structural determining proteins createdD) Surrounding cells send signals; cell receives signal; regulatory gene activated; proteins created; point of no return; function/structural determining proteins created

External stimuli and gene expression work together to create specialized cells, tissues, and organs. Describe how external stimuli and gene expression contribute to the creation of muscle cells and the vulva.

Nearby cells send out signals to other cells. These signals activate the myoD gene that acts as a master regulatory gene. Activation of the myoD gene leads to the production of MyoD proteins. This causes the cell to become a myoblast meaning that it is on a strict path to becoming a muscle cell. Stimulation of the myoD gene by MyoD proteins also leads to the activation of genes for muscle proteins. The myoD gene activates genes that code for muscle specific transcription factors that then transcribe those muscle proteins. MyoD also stops cell division and the many myoblasts fuse into muscle fibers.

An anchor cell secretes signal proteins that interact with and bind to the signal receptors of three of the six precursor cells. The other three precursor cells are too far away to receive the signal. The closest precursor cell ends up receiving the strongest inductive signals and becomes the inner part of the vulva. The two precursor cells on either side of the closest precursor cell end up receiving a weaker signal and become the outer vulva. The last three precursor cells receive so inductive signals and end up creating epidermal cells to be the epidermis. All of these inductive signals from the anchor cells binding to signal receptors cause intercellular signal transduction pathways that lead to the differential gene expression. The signals cause certain genes to be activated that in turn activate the transcription of certain proteins, creating cells with specific functions.

A sensory neuron of the peripheral nervous system take nerve impulses from sensory receptors to the ______ . A) motor neurons B) interneurons C) autonomic nervous system D) central nervous system

Communication occurs among the cells in a multicellular organism. Choose THREE of the following examples of cell-to-cell communication, and for each example, describe the communication that occurs and the types of responses that result from this communication.

• Communication between two plant cells• Communication between two immune-system cells• Communication either between a neuron and another neuron, or between a neuron and a muscle cell• Communication between a specific endocrine-gland cell and its target cell

Plant cells have a unique adaptation for exchanging and sharing information. They usually have a plasmodesmata, that acts as a channel between plants cells. In it materials are shared, and chemical messages are sent, such as, auxin traveling via the channel and promoting growth. Neurons also communicate with other neurons to perform task vital to an organisms success. Neurons intra- communication drive the nervous system. The foundation for their communication are axons and dendrites. An axon sends a nerve impulse, and a dendrite receives it. In the synaptic gap, neurotransmitters jump from the presynaptic area to the postsynaptic area. The jump is due to a stimulus that depolarizes the neuron membrane. The result of this communication is an impulse sent to the central nervous system which allows organisms to respond to their environment. Endocrine gland cells also communicate as they commonly secrete hormones to target cells. Endocrine cells first release their hormone into the blood to be distributed. The target cells are located due to chemical receptors on their plasma membrane. The next step in communication is then a signal transduction pathway. In this, the hormone goes though a series of steps in the target cell, which communicate the desired message. The messages may relate to the cell product which it decides to make or not.

ANSWER KEY- LO 4.8

L.O 4.9 Answer Key

MC:If a toxin was injected into a plant’s phloem which inhibited the activity of H+ pumps, what would result?

A) A decreased water potential in the phloemb) An increase in photosynthesisc) A large amount of turgid cells in the plantd) Sucrose excretion from the plant’s leaves

Suppose the guard cells around the stomata of a pea plant have been killed due to a new pesticide. If the guard cells are no longer functioning, how would transpiration be altered? What would happen to the plant in a time of drought? Explain.

Free Response: If the guard cells around the stomata of a plant are not functioning properly then the plant could not expel water and carbon dioxide in the correct amounts. This would completely alter the way the plant transpires. There would be less of a pull upward for the water so the plant would become waterlogged. In the case of a drought, the water would continue to transpire at the same rate as it would during a period of rain so this would cause the plant to lose too much water and it would then die due to thirst.

Anwswer Key LO 4.10MC: If Henry got infected with the chicken pox virus in whichorder would his body respond to fight off pathogens and create future immunity?A. Leukocytes kill some of the pathogens, macrophages release

cytokines to raise body temperature, helper T cells recognizeantigens on the surface of an APC, helper T cells release cyto-kines to make more helper T cells, numerous helper T cells release more cytokines to active cytotoxic T cells and B cells, memory T cells are produced for future immunity.

B. Helper T cells recognize antigens on the surface of an APC, helper T cells release cytokines to make more helper T cells,memory T cells are produced for future immunity.

C. Leukocytes kill some of the pathogens, macrophages release cytokines to raise body temperature, at this point you contain the cells to have future immunity

D. Mast cells release histamines, capillaries dilate, macrophages come to the area, temperature rises

E. A B cell recognizes an antigen, that specific B cell is clones, plasma cells are released to neutralize antigen, macrophages engulf tagged antigens

During blood transfusions the proper type of blood must be used for the recipient’s body to accept to blood. What causes unmatched blood to be rejected? Relate this to organ transplants and what causes the body to attack the transplanted organ if it isn’t a match.

Blood must be the correct type when transfused because the body contains antigens for your type of blood and if the transfused blood’s antigens don’t match the antigens that you have they will be attacked. However, our body does contain antigens for our blood type so our bodies wont attack the specific type of blood. The only case that you can get blood that isn’t your specific type is if you receive type O blood which contains no antigens. If you have type AB blood your body contains both types of antigens so you can receive any type of blood. A similar attack method happens if organ transplants aren’t a proper match. Cells display MHC molecules on the cell surface that identify the cell as self or foreign. When there is a organ transplant a lot of times the MHC molecules don’t match the organ recipient’s MHC molecule making the immune system mark the organ as foreign and attack the organ. In families there is a chance that MHC molecules can be the same between siblings and that is why families are always checked first for organ donation before asking others.

ANSWER KEY – LO 4.11

Which of these is true about exotic species?

a. They increase biodiversity in the community by creating new divergent species. b. They are usually killed by the native species before any damage is done. c. They decrease biodiversity by introducing disease to the native community. d. Only animals can be exotic species, not plants.

Relationships between populations affect the whole community in different ways. Give one example each of mutualism, competition, and commensalism, and explain how they affect the populations in question and the community.

Mycorrhizae are fungi that share a mutualistic relationship with plants, where both the fungus and the plant benefit. This relationship improves the ability of plants to survive, increasing the amount of photosynthesis in the community and the amount of air available for animals to live. Cheetahs and lions compete for food and as a result, they each have less food. The “losing” competitor is forced to find a new niche, disrupting the stability of the new niche within the community. The cattle egret hangs around grazing cattle and eats the insects that are stirred up by the cattle, and do not affect the cattle at all. Commensalism exerts evolutionary pressure on the commensal, but not the host. The commensal relationship allows the commensal population to survive and reproduce, increasing biodiversity in a community.

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Answer Key-L.O. 4.12• All of the following statements concerning characteristics of predator-prey relationships are

correct except:

• A. A rise in the population of prey is often followed by a rise in the population of predators.

• B. A rise in the population of predators is followed by a decrease in the population of prey.

• C. The production of large numbers of offspring within very short periods of time ensures the survival of some prey populations.

• D. The population of predators most often eliminates the population of prey.

• FRQ:• The predator plays the role of the regulator in the environment. Predators such as consumers

decrease the size and number of the prey population because the prey is most likely their main source of food. The populations of the prey and predator are directly related and the predator population keeps the prey population stable and at carrying capacity, so the environment remains normal. If this process is disturbed it can cause a population to go above carrying capacity because a decrease in predator population will cause an increase in prey population. The prey population goes above carrying capacity and causes the prey population to compete for resources and that in turn will cause a decrease in the prey population because only a certain amount of prey can be supported by the environment.

ANSWER KEY: LO 4.13

M.C. Question: Scientists are studying a population of sparrows and discover that an influx of immigrant sparrows due to a hurricane has led to an increase in conflict between the birds. These sparrows are a ______ population and are exhibiting ________.

A) Density-Independent, mating ritualsB) Density-Dependent, territorialityC) Density-Independent, predationD) Density-Dependent, reciprocal altruism

An elephant population exhibits exponential population growth in its native habitat. Predict how the elephant population would change if food became a limiting factor. Also discuss the exponential model and what model would be appropriate in the hypothetical situation.

Answer: The exponential model is used when a population increases under ideal conditions and will theoretically grow indefinitely. Limiting food resources, however, would place a carrying capacity on the population, or the maximum population size the environment can support. The introduction of this carrying capacity would effectively end the exponential growth because elephant population will no longer be able to expand indefinitely. Instead the logistic growth model is appropriate, because it includes a carrying capacity and a limited population size. The logistic growth model slows as it approaches the carrying capacity (K) of the environment. This model will become applicable once food becomes a limiting factor in the elephant population.

Answer slide LO 4.14• Multiple choice answer B• Free response During the hours of 1-4 the bacteria are experiencing exponential growth. At the hour of 5-

6 they have reached caring capacity and population numbers are starting to even out. Hours 6-8 show the decline of population size due to the limiting factors of the environment such as limited space, oxygen, and nutrients. If a virus were introduced the bacteria population would decline untill a mutation in bacterial DNA occurred that made the bacteria resistant to the virus, then the population would increase again.

Answer Key- L.O. 4.17

M.C. Question: How does a noncompetitive inhibitor decrease the rate of an enzyme-mediated reaction?A) By changing the shape of a reactantB) By changing the free energy dynamics of the reactionsC) By acting as a coenzyme of the reactionsD) By decreasing the activation energy of the reactionsE) By binding at the active site of the enzyme

FRQ:a) Graph the data and calculate the rate from 0 to 30 minutes.

Rate – 0.35 mM/min

b) Explain why a change in rxn rate was observed after 30 minutes.The reaction rate slows/levels off because the substrate is used up, therefore decreasing the substrate concentration.

c) Draw and label another line on the graph to predict the results if the concentration of amylase was doubled. Explain.The line will mimic the original data line, but will be higher, leveling off at a higher point. More enzyme = moreproduct (maltose) formed over time, but product will level off as substrate concentration decreases.

d) Identify TWO environmental factors that can change the rate of an enzyme-mediated reaction. Discuss how each of those two factors would affect the reaction rate of an enzyme.

Temperature increase will cause an increase in reaction rate due to faster molecule movement (kinetics.) However, if temperature increases past a certain point, reaction rate will slow/stop due to the enzyme becoming denatured. Denaturation results from bonds holding together the tertiary structure of the enzyme breaking, which leads to altered enzyme/active site shape. Also, a change in pH away from the optimal pH for the enzyme will slow reaction rates.

L.O. 4.19 Multiple Choice:As Meerkats (Suricata suricatta), an k-selected species, have reached their carrying capacity within their native biome of the African savannah their population size often fluctuates. What kind of data model trend would we expect to see?

A) A curve of exponential growth (J-Curve) showing a seemingly limitless growth of the meerkats without any apparent affect from external environmental factors.B) A boom-and-bust cycle showing expansions and contractions within the size of the meerkat population.C) A dispersed age-structure diagram of the meerkats where majority of the population is either more than 10-years-old or younger than 8-months-old.D) A major, rapid decline in meerkat population size that comes with the change of seasons. FRQ:Alaskan Grizzly Bear and Salmon populations have been measured closely over the past 75 years. These bears are known to prey on the salmon in the nearby freshwater rivers. Describe the relationship these two species share and draw a graph predicting trends you would expect to find in the data found on the populations over the past 75 years.

There is a biological relationship of predation between the Grizzly Bear and the Freshwater Salmon, the two should be very closely correlated in population size changes. Their relationship is tied together, but the change in population of the Grizzlies should fall right behind the change in population of the salmon. As more salmon are hunted, more grizzlies starve, therefore their population dynamics follow closely behind the fish. A graph of this would show that the salmon and their population would peak, then the bear’s would peak, but then the salmon would fall drastically, and the bear population would follow.

L.O. 4.20 M.C. Question: Which is not an example of primary succession?A) Vegetation colonizing on a volcanic island years after an eruptionB) Salt marsh vegetation on a mud flatC) Moss growing on a mountain topD) Grassland growing on a site of a previous rainforest

• (a) Over the period of time, biodiversity such as plants, animals, and decomposers would increase. As more plant life start to develop, more habitats and niches will start to form. Some populations inhibit biodiversity by developing more conditions that are more suitable for certain species.

• (b) There initial absence of soil in primary succession while in secondary succession, there is a presence of soil initially. Secondary succession is the regeneration of the living community after a major disturbance. For example, after a forest is clear-cut the trees are removed but some small plants, the soil, and soil organisms remain. The forest will slowly regenerate.

Learning Log/FRQ-style Question:

The diagram shows the succession of a community over the course of 150 years.(a) Describe the changes in biodiversity as succession progresses over

the period of time. (b) How do primary and secondary succession differ?

Answer Key-L.O. 4.21• The correct answer to the multiple choice question is B. A major consequence to human

interaction with the environment is cultural eutrophication, which leads to a decrease in aquatic dissolved oxygen content.

• Because coral are a very valuable indicator species for scientists due to their extreme environmental sensitivity, this question is a good example of how human interaction with the environment would affect an ecosystem such as a coral reef. When fertilizer runs off of crops and into lakes, rivers, and eventually oceans, those excess nitrates and phosphates cause blooms of algae to occur. These algae then die off, and are decomposed. This leads to lower dissolved oxygen content in the water. This process is known as cultural eutrophication. Humans can also affect the salinity of oceans through water purification and chemical dumping. When water from the oceans and rivers is taken for purification and cannot be returned to the environment in a non-polluted condition, the salinity of the ocean increases. Often times, the salt and minerals left over from desalinization are simply returned to the ocean without the freshwater to compensate. Conversely, as the polar ice caps continue to melt, fresh water land ice is being added to the oceans. This causes a rise in sea levels, as well as the salinity of the oceans decreasing. As for increases in temperature, by burning fossil fuels, the protective ozone layer in the atmosphere is thinning, allowing more sunlight to reach the Earth’s surface, especially over the coral-dense locations of the Great Barrier Reef in Australia and New Zealand. Coral are dramatically sensitive to even slight temperature changes, so a rise in even a few degrees could cause the coral polyps major damage.

Answer Key – LO 4.23• Which pair of organism and physical change is due to genetic/phenotypic reasons?

A) Moose; losing antlersB) Elderly man; graying of hair

C) Arctic Hare; White Fur turning into gray fur D) Snake; Shedding skin

• Explain how diet can have an impact on the phenotypic traits of a person. How is this significant to the overall health of a person?

The diet of a person can have a huge impact on their phenotypic traits. If a person increases their diet and begins to eat too many unhealthy foods to a point where they become obese, the physical and phenotypic traits of their body will change drastically. This will in turn affect the overall health of a person because the cells in their body and other vital functions will have to adapt to the rate at which fat can be burned and how internally the body can attempt to stay the way it had previously been running. While phenotypic changes cannot always have a significant impact on the genes of a person, this does not mean that it does not affect the person internally. If the body is not prepared to take on certain differences of diet or temperature than it will have to change certain internal functions in order to adapt and continue living.

ANSWER KEY-LO 4.24

Which of the following does not affect gene expression?A) Epigenetics is the study of gene expression, and includes DNA methylation and histone modification, both serving to regulate gene

expression.B) Lac operons accomodates to digest the nutrients (lactose) the particular organism obtains. Lac promoter, lac p, and the lac operator,

and lac o affects gene expression, although they are short sequences, not genes.C) Bacterial conjugation is used to pass forward genetic material; it does not change gene expression.D) Minimal/Normal radioactive exposure may be fixed by DNA repair mechanisms, but intensive exposure to radiation can affect gene

change altogether, also affecting gene expression.E) Transcription is the first step in gene expression. A particular segment of DNA is copied into RNA by RNA polymerase.

Based on the life cycle ofnon-evergreen trees, what environmental effect causes the treesto change their leaf colors from green to orange and yellow?What causes the trees’ leaves to fall down? How do these treesaccomplish this task of color changing and leaf falling in autumnand winter?

During winter, there is not enough sunlight or water hitting the treesfor photosynthesis. Therefore, the trees must live off the food they storedduring the summer, shutting down their food-making factories. This causeschlorophyll to disappear from the leaves, making them yellow/orange. Treeleaves fall when transduction pathways close due to the trees’ photoperiodism.Abscisic acid is produced in the roots in response to decreased water potential.Abscisic acid then alters the osmotic potential of stomatal guard cells, causing themto shrink and stomata to close. Also, the veins of vascular cells (cells that transport water and sap via root to leaf tip) slowly close off, creating a development called theabscission layer. When this layer is completely formed at the base of a leaf’s stem, the leaf falls off.

Answer Key- LO 4.26

M.C. Question: Of all mutations that occur, why do only a small fraction become widespread in a gene pool?A)Mutation rates tend to be low in animals and plants.B)Most mutations occur in somatic cells that do not produce gametes and die out with the organism.C)Gene duplication is a more important source of variation.D)Most mutations occur in gametes and without sexual recombination the mutation only spreads through a small population.Learning Log/FRQ-style Question: Genetic variation is the raw material for evolution.A)Explain three cellular and/or molecular mechanisms the introduce genetic variation into the gene pool of a plant or animal population.A mutation is a change in the DNA of an organism. A point mutation is a change of as little as one base in a gene, these mutations tend to be harmless. Deletion of a gene can also cause an alteration in the genetic makeup which provides genetic variation within a population. Crossing over during sexual recombination allows for genes to be shifted within the gene pool creating no two strands of DNA alike.

L.O. 4.27 Which of the following would be most immediately disrupted by the extinction of a keystone predator species in a local ecosystem?A) Natural resource availabilityB) Food web relationshipsC) Population of producer speciesD) Population of primary and secondary level species

What are some potential consequences caused by a loss in biodiversity?25% of all pharmaceutical drugs in the United States contain substances originally derived from plants. For example, the rosy periwinkle, native to Madagascar, is used in treating Hodgkins disease and childhood leukemia. However, one type of rosy periwinkle is approaching extinction, and if the plant goes extinct, so do any medicinal properties that can be derived from the plant.

The loss of species also means a loss of genes, because each species has certain unique genes that can be used for human benefit. For example, scientists intend to use the ploymerase chain reaction to mass produce DNA from thermophilic prokaryotes in order to make enzymes useful for the development of new medicines, foods, petroleum substitutes, industrial chemicals, and other products. Many millions of species may go extinct before humans are even able to discover them, rendering the possibility of using them forhuman-benefit impossible. In addition, a loss in genetic diversity within a species makes the species more susceptible to disease or predation. The extinction of species can also disrupt food webs, leading to extinction of other species because of population imbalances.

The introduction of a new species that outcompetes indigenous species can disrupt food webs and population cycles in an ecosystem. Ex. kudzu or North American Beavers in Tierra del Fuego.