21. on first attachment is secondary succession
22. is the degree of variation of life....
genetic, species or ecosystem within a specific area, system or planet
23. the last one is wrong = )
<span>People depend on biodiversity in their daily lives, in ways that are not always apparent or appreciated. Human health ultimately depends upon ecosystem products and services (such as availability of fresh water, food and fuel sources) which are requisite for good human health and productive livelihoods. Biodiversity loss can have significant direct human health impacts if ecosystem services are no longer adequate to meet social needs. Indirectly, changes in ecosystem services affect livelihoods, income, local migration and, on occasion, may even cause political conflict.</span>
Answer:
'Aero' means air, which contains oxygen, leading to the name aerobic respiration. Aerobic respiration breaks down glucose and combines the broken down products with oxygen, making water and carbon dioxide. The carbon dioxide is a waste product of aerobic respiration because cells do not need it.
The changing quantities in an experiment are called variables. A variable refers to any trait, factor, or a condition, which can prevail in distinct amounts or kinds. An experiment generally exhibits three kinds of variables: independent, dependent, and controlled.
The independent variable refers to the one, which is modified. On the other hand, the dependent variable is implied to observe that how it reacts with the change made to the independent variable. The controlled variables refer to the quantities, which one wants to remain constant.
In the given case, that is, heating a cup of water to witness that whether the sugar will get more easily dissolve. In this, the independent variable refers to the temperature of the water determined in degrees Centigrade. The dependent variable refers to the amount of sugar, which dissolves completely measured in grams.
In this, the controlled variables are stirring and type of sugar. As more stirring might elevate the amount of sugar that dissolves, and different kind of sugars might dissolve in distinct concentrations. So, in order to make sure a fair test, there is a need to keep these variables similar for each cup of water.
