Net Primary Production (NPP) in ecosystems can be controlled either by limiting resources for photosynthetic (autotroph) organisms, such as nutrients, light, and temperature, or by the abundance of herbivores (primary consumers), which in turn may be controlled by predators (secondary consumers). The first scenario is called bottom-up control of NPP and the second top-down control.

1. Consider the saltwater ecosystem. Define the three important trophic levels. What are the most important photosynthetic organisms, herbivores, and carnivores in the saltwater ecosystem?
2. Outline an experiment to determine if NPP in the saltwater ecosystem is controlled bottom-up or top-down. What is the main variable to be measured in your experiment? What are your experimental treatments? Include controls and replication.

3)   Draw a diagram which shows a cross-section of a stem after one year of secondary growth and label all the tissues that are found in the stem at this stage, including the 2 meristems associated with secondary growth.

Scenario
Five-year-old Thomas is looking forward to starting kindergarten in the next few weeks. As a last summertime activity, his parents take him and his four older siblings to the county fair to enjoy the rides and see the animals. While at the fair, the family snacks on the fair food, drinks lemonade and soda, and wanders through the barns to visit with the horses, cows, sheep, goats, and chickens being kept there for the week.

Signs and Symptoms
Three days after the fair, Thomas and two of his sisters start to complain about feeling sick. Within a day, the entire family has severe stomach cramps, vomiting, and diarrhea. Over the next few days, the rest of family gradually starts to feel better, but not Thomas. His diarrhea continues and becomes tinged with blood.

His mother takes him to the family physician, who notes that Thomas is pale and anemic. He asks Thomas to try to "pee in the cup" for a urine sample, but Thomas says he cannot pee. The physician tells the family to go immediately to the hospital.

At the hospital, Thomas was diagnosed with acute renal failure and catheterized for a urine specimen. Samples of blood and stool were also collected and sent to the clinical lab.

Testing
The fecal specimen was plated on several types of differential and selective media, including MacConkey Agar and ChromAgar 0157, a selective and differential medium specifically for Escherichia coli 0157:H7, a pathogenic strain of E. coli.

Question 2: MacConkey Agar contains lactose as the differential agent. Lactose-fermenting bacteria (like E. coli) produce pink-colored colonies and non–lactose fermenting bacteria (S. dysenteriae) do not. What does the MacConkey Agar culture result shown here indicate about the bacteria isolated from Thomas’s stool?

"Mauve"-colored colonies were observed on the surface of the ChromAgar 0157 agar plate, which is a positive test result for E. coli 0157:H7. This strain and others like it are also known as enterohemorrhagic E. coli (EHEC) or Shiga toxin-producing E. coli (STEC).

Question 4: E. coli is a human commensal that normally does not cause disease. Why is the lab reporting E. coli as the cause of Thomas’s disease?

E. coli 0157:H7 is different from commensal strains because it produces a toxin, called a verotoxin or Shiga toxin, that destroys small blood vessels, such as those found in the glomeruli of kidneys.

This toxin is the product of the stx gene. There are two variants, stx-1 and stx-2. The Stx-2 toxin is 400 times more toxic than Stx-1. Serological or DNA tests for the toxin are confirmatory for STEC.

PCR was done using primers specific for stx DNA. The primers amplify a DNA fragment approximately 900 base pairs long. PCR products were separated by gel electrophoresis, along with a 100 bp DNA ladder for size comparison. On the gel shown here, the largest fragment in the ladder is 1,000 bp, and the smallest is 500 bp.



Question 5: What do the results of the PCR analysis show?

To determine which variant of the toxin the bacteria were producing, restriction fragment length polymorphism (RFLP) analysis was also done, using two restriction endonucleases, AccI and HincII. Using these enzymes, the expected restriction fragment lengths for the two gene variants are:
Sxt-1: 705 bp, 158 bp, and 32 bp
Sxt-2: 555 bp, 262 bp, and 62 bp



Question 6: What do the results of the RFLP analysis show?

Diagnosis
Based on the lab report, Thomas’s diagnosis was changed to hemolytic uremic syndrome (HUS) caused by an infection with E. coli 0157:H7, which is the most common strain of STEC.

Question 7: The "A" subunit of the Stx toxin inhibits protein synthesis and induces apoptosis. How could this lead to the massive tissue damage seen in HUS?

1. Which part of the tRNA molecule pairs with mRNA?

A. gene

B. anticodon

C. duplex

D. rRNA

1. All of the following items are found in the bases of RNA except

A. sulfur

B. adenine

C. uracil

D. phosphate

E. cytosine

1. Three different eukaryotic RNA polymerases are required to synthesize messenger RNA molecules, and translate them into proteins. Which two types of eukaryotic RNA polymerase are required to make the ribosomal RNA components of the ribosome?
2. Three different eukaryotic RNA polymerases are required to synthesize messenger RNA molecules, and translate them into proteins. Which type of eukaryotic RNA polymerase is required to make the small nuclear RNA molecules required for splicing?
3. Three different eukaryotic RNA polymerases are required to synthesize messenger RNA molecules, and translate them into proteins. Which type of eukaryotic RNA polymerase is required to synthesize the transcripts that will become messenger RNA molecules?
4. Which of the following options is correct?

5. When mRNA molecules are formed, they are complementary to DNA with the exception that

6. an A in DNA matches a T in mRN
7. a T in DNA matches a C in mRNA.
8. an A in DNA matches a G in mRNA.
9. an A in DNA matches a U in mRNA.
10. What does mRNA do in protein synthesis? What does tRNA do?

Hydrogen ions and carbon dioxide promote the release of oxygen from hemoglobin. This regulation of oxygen binding by hydrogen ions and carbon dioxide is called the ________ effect.

Fetal hemoglobin binds oxygen more tightly than does adult hemoglobin owing to weaker ____________ binding, stabilizing the T state and lowering the oxygen affinity of hemoglobin. This allows oxygen transfer from maternal to fetal blood.

Sickle-cell anemia is caused by the substitution of a single specific amino acid in one hemoglobin chain. ____________, the other prevalent inherited disorder of hemoglobin, is caused by the loss or substantial reduction of a single hemoglobin chain.

Biological Psychology

How might the events of COVID-19 impact our neurological and/or biological processes? Find one relevant article and discuss how the findings may impact your life or the lives of others.

how do the resorbable polymers PLGA and PCL differ in their mechanisms of resorption? how are the resorption rates affected by molecular weight, degree of crystallinity and crosslinking. in considering the biocompatibility of a resorbable polymer, how do the rates of resorption and resorption by-products affect the cellular response? describe the inflammatory response associated with resorbable polymers.

First: What is the difference between a resistant variety and a resistant original? When are they used in IPM programs with examples?
Second: What are IGRs? And why are they used in IPM programs? And how it works if used in IPM programs
Third: Through your study of the components of IPM programs in protected tomatoes (combating the use of agricultural means or resistant varieties or sterilization
Soil before planting or using biological or chemical control (), answer the following questions:
- How does the IPM program for Butritz disease work on protected tomatoes?
- How does IPM program whitefly fly on protected tomatoes?

a- What is the function of centrioles in sperm? b- Please write and explain in detail the polyp and medusa stages of Obelia.