Biology help? Serious answers only, please.?
1. The role of gene expression in cells is best described by which one of the following statements? When cells divide in mitosis, they pass on only the genes that are required. Cells destroy the DNA of genes that they do not use. To become specialized, cells need to control the production of proteins coded for in their DNA. All genetic information in a cell?s DNA is fully expressed at all times. 6. Following which event has evolution happened? An animal?s white winter coat is replaced by a darker coat in the spring. An individual is born with six fingers on one hand instead of five. An allele frequency in a population changes over time. A new predator comes into an environment. 13. Plants, people, and flatworms share which of the following characteristics? They all undergo photosynthesis. They all use a muscular system for movement. They all have a digestive system that breaks down food. They all exchange gases with the environment. 15. What is the relationship between plants and oxygen? Plants do not need oxygen from the air because they produce it during photosynthesis. Plants do not need oxygen because they use carbon dioxide in cellular respiration. Plants produce oxygen during photosynthesis, and they also need oxygen gas from the air for cellular respiration. Plants do not need oxygen because they do not undergo cellular respiration. 16. Which statement best describes the difference between the life cycle of plants such as ferns and animals such as humans? Plants have a one-part life cycle and are entirely diploid. Humans spend their lives in a haploid phase. Plants have a two-part life cycle, spending part of their life in a diploid phase and part in a multicellular haploid phase. Humans spend their lives in a diploid phase and produce gametes that are haploid. Plants have a one-part life cycle and are entirely haploid. Humans have a two-part life cycle, spending part of their life in a diploid phase and part in a multicellular haploid phase. Different plants have a different number of phases in their life cycle. Humans always have two phases in their life cycle. 17. Which abiotic factor is found in a desert? a top predator a snake a primary consumer none of the above 18. What was the result of the overhunting of sea otters along the Pacific Coast? The sea otters on the Pacific Coast went extinct. The sea urchin population expanded and consumed the kelp and damaged the habitat. The kelp grew rapidly and created new habitat for fish. The sea urchin population was reduced to dangerous levels. 19. Identify the levels of the biosphere from smallest to largest, left to right. ecosystem?biome?community?population?individual individual?population?biome?community?ecosystem ecosystem?individual?population?biome?community individual?population?community?ecosystem?biome 20. The following flow of energy occurs in the trophic levels in an ecosystem: sedge --> arctic hare --> arctic fox --> wolf Which organism is located in the trophic level that contains the least amount of energy? sedge arctic hare arctic fox wolf 21. Global warming and climate change are important topics in environmental biology. In what way, if any, should scientists contribute to the discussion on global warming and climate change? The role of scientists is to present research that clearly represents their personal beliefs regarding the issue. Scientists provide sound scientific data to help society make informed decisions. Scientists should not get involved in decisions that affect modern society. Scientists cannot provide accurate information on environmental issues such as global warming. I know I'm asking for a lot, but Biology is my worst subject. I'm having a little trouble answering these questions. I know some of you see this as cheating, but others see it as helping. Your answers would be very helpful. Thanks in advance.

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Density of Yeast Cells in Solution Please HELP!!!?
Experiment 3 - The Density of Yeast Cells in Solution Test tube 1 10mL 2% yeast solution Test tube 2 1mL 2% yeast solution (poured from Test tube1) 1/10th original concentration yeast 9mL water Test tube 3 1mL 2% yeast solution (poured from Test tube2) 1/100th original concentration yeast 9mL water Cuvette 1mL 2% yeast solution (poured from Test tube3) 1/1000th original concentration yeast 9mL water Spectrophotometer Absorbance 0.63 450 wavelength 1. For the serial dilution that you performed, record the percent yeast concentrations (by mass) in each of the test tubes and in the cuvette. Initial Shelf Solution = 2% Test Tube 1 = Test Tube 2 = Cuvette = ----------------------------------- factor to multiply cuvette concentration to get Shelf Solution concentration = Yeast cells in cuvette from Absorbance reading (millons/mL) = Yeast cells (millions/mL) of Shelf Solution = 2. By what factor must the concentration of the yeast in the cuvette be multiplied in order to obtain the concentration of the original solution? 3. For dilute solutions, the absorbance reading of the spectrophotometer is proportional to the concentration of the yeast. The formula for this relationship is: Abs = e0 * l * C where: C = concentration in units of millions of cells per milliliter e0 = ?extinction coefficient? for yeast, equal to approximately 0.07 million cells per cm l = path length of the cuvette, i.e. the width of the cuvette, which is equal to 1cm for our cuvettes Abs = the absorbance reading, with no units of measure (a) Using this formula, how many yeast cells are there in 1 mL of solution in the cuvette? (b) Multiply the concentration of yeast cells in the cuvette by the dilution factor in Queston 2 to obtain the concentration of yeast cells in the original solution on the shelf. 4. While this number is useful, it must be understood that since we are talking about cells and cellular activity, not all of the yeast cells are alive or biologically active. In fact, up to 50% of the cells may be inactive. Another way to count the cell density is to take a small sample, say 1 microliter, of the yeast solution, place it on a microscope slide and actually count the individual cells in the sample. Viewing the cells allows you to distinguish between active and inactive cells. Question - If the field of view of a microscope allows for counting of up to 100 cells under a slide cover, how much must the original 2% yeast solution be diluted in order to prepare a sample for counting? * In estimating this, use the number of cells per mL that you calculated for the 2% yeast solution, and remember that 1 microliter is one one-thousandth of a mL.

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Use the lac operon to explain how genes can be turned on/off control the lac expression of a protein(enzyme).?
2) How do each of the representative organisms get rid of carbon dioxide, the waste product cellular respiration? 3)How is the nervous system of the flatworm different from that of a human? 4)Describe the nonspecific defenses that your body uses as the first line of defense to prevent pathogens from entering your body. 5)Why are bones important to muscles in the process of movement? 6)Why is diversity important in maintaining the stability of an ecosystem? THANKS

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