The following set of three separate experiments was conducted. Two strains of Escherichia coli are used. Strain 1 needs histidine added to the medium to grow. Strain 2 needs methionine added to the medium to grow. (8 points) Experiment 1: After strain 1 and strain 2 are mixed in a culture flask containing a minimal medium (containing no added amino acids) and allowed to grow overnight. Results: It is possible isolate new strains that grow on the minimal medium. Experiment 2: Strains 1 and 2 are mixed in a culture flask containing a minimal medium but also containing the enzyme DNAse and grown overnight. Results: It is NOT possible isolate new strains that grow on the minimal medium. Experiment 3: Media is placed in a U-shaped tube that contains, at the bottom, a membrane filter that prevents cells from crossing between the two chambers of the U-tube, but allows anything small (for example DNA and bacteriophages) to pass between the chambers. The strains are put in different sides of the U-tube. Results: It is possible to isolate new strains that grow on the minimal medium. Conclusions: Genetic exchange is observed in experiments 1 and 3, but not experiment 2. 1. Why was Experiment 1 performed? What information does it give us? 2. Why was DNase added in Experiment 2? 3. What is the purpose of the U-shaped tube in Experiment 3? 4. Taking the evidence from all three experiments together, what type of genetic exchange was observed from these strains?

d concave shape of wave rock

explanation:

the concave shape of wave rock is a very good evidence that supports the evolution of earth due to chemical weathering. if we talk about structure of   wave rock, studies have estimated that it is around 2.7 billion years old. it also serves as the foundation of evidence that it was the place where australian continent began to form.

how the structure of wave rock was created?

studies suggest that structure of wave rock was created when the surrounded area was started to weather due to which deposition of material started on the part of land which now contains wave rock.

the structure of wave rock is considered to be one of the best-known landforms in australia. at the height of around 15 cm, there can be found flared slopes which formulate the margins of hyden rock. it is now assumed by geologists that wave rock was created by subsurface water-induced weathering and not by glaciers, waves or wind.

due to deposition of material over the period of long time, the wave rock became tougher and tougher due to weathering from surrounding terrain. this makes it a physical evidence that supports   the evolution of earth due to chemical weathering.

hope it !

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.