Answer:
Humans are modifying the world in many ways, and not all of them for the better. The changes we cause are often severe challenges to animals, plants and microbes in nature, from the introduction of pathogens or exotic invasive species to adding toxic substance or excessive nutrients, or causing climatic change. Often several changes occur at once. Nelson Hairston's lab focuses on freshwater environments, especially lakes and ponds, where some of the species present respond to environmental change with decreases in their numbers, even to the point of extinction, while others may benefit to excess, becoming so dominant that they present problems, as in the case of harmful algal blooms stimulated by nutrient enrichment or climate warming. Hairston's lab studies how individual species, food webs, and whole ecosystems are altered when the environment changes.
One way that some freshwater organisms respond to environmental change is to evolve rapidly. A marked change in the environment favors some characteristics of plants, animals and microbes over others. These character differences are often genetically based so that favored characteristics may increase in the next generation. The shorter the generation time, the faster this evolutionary change can occur. For example, tiny but abundant plankton, eaten by fish and other larger animals, can become adapted to the changed environment within a few years because their generation time is only a few days. Hairston's lab has shown that planktonic "water fleas" (Daphnia), major consumers of suspended algae in lakes, evolved to be tolerant of harmful algae within a decade of the appearance of blooms. This rapid evolution (termed "evolutionary rescue" in conservation biology) raises many intriguing questions, for all environments, not just freshwater: To what extent can we rely on species adapting rather than going extinct when their environment changes? How does the evolution of a species that plays a critical ecological role alter the interactions it has with other species, and the functioning of the entire ecosystem?
Answer:
7,881 g/L
Explanation:
Iron volume = 30.58 mL - 29.40 mL = 1.18 mL
1.18 mL / 1000 mL = 0.00118 L
Iron density = mass/volume
= 9.3g / 0.00118 L
= 7,881 g/L
Answer:
10 L
Explanation:
The only variables are pressure and volume, so we can use Boyle's Law:
p1V1 = p2V2
Data:
p1 = 125 atm; V1 = 4.0 L
p2 = 50 atm; V2 = ?
Calculation:
125 × 4.0 = 50V2
500 = 50 V2
V2 = 500/50 = 10 L
The new volume will be 10 L.
In this question, we have the following reaction:
5 F2 + 2 NH3 -> N2F2 + 6 HF
The enthalpy change is -96.3 kJ
As we can see, in order to form 1 mol of N2F2 it is released -96.3 kJ, but we need to know how much energy is released with 12.7 grams, and using the molar mass of N2F2, 66.01g/mol, we can find how many moles we have:
66.01g = 1 mol
12.7g = x moles
x = 0.192 moles of N2F2 in 12.7 grams
Now, if 1 mol released -96.3 kJ, what abour 0.192 moles:
1 mol = -96.3 kJ
0.192 moles = x kJ
x = -18.5 kJ of energy is released, letter C
