The ecosystem requires a constant input of energy because energy cannot be stored. The enrgy always gets converted for supporting life in the ecosystem. Some amount of energy is also lost during this conversion. So if there is not a constant supply of energy, then the ecosystem will ultimately breakdown. In case of humans, the energy is received by consuming food. The energy of the food geets converted to the enrgy that helps a human being to complete his daily chores. So energy is being lost at every step. To regain this energy the humans have to eat food regularly. This way the humans need a constant supply of energy to survive. It is the same in the case of all living things in the ecosystem.
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Answer: C. a balance and a beaker</h3>
Explanation:
A balance would be used to measure the weight, which in turn effectively measures the mass (more or less). Imagine that we have a brick that we know is 1 pound. If we have an object that needs 5 bricks on one side to balance it out, then we know the object is 5 pounds.
The beaker is used to measure the volume. It's basically a measuring cup that you would find in the kitchen.
To get the density, you divide the mass over volume.
For example, if you have a material that has a mass of 100 grams and it's volume is 20 cm^3, then its density is 100/20 = 5 grams per cm^3.
natural selection, bc it is the process whereby organisms better adapted to their environment tend to survive and produce more offspring
The Precambrian era envelopes the major bulk of the history of the Earth, beginning from the creation of the planet approx 4.5 billion years ago and terminating with the origination of composite, multicelled forms of life approximately 4 billion years after.
The Precambrian refers to the earliest of the geologic ages that are signified by the distinct layers of sedimentary rock. The Earth was about more than six hundred million years old when life started. The planet had cooled down from its native molten state, creating a solid crust and oceans formed by water vapor in the atmosphere.
At about three billion years ago, the atmosphere of the Earth was virtually devoid of oxygen. At approximately 2.4 billion years ago, oxygen was discharged from the seas as a waste product of photosynthesis by cyanobacteria. The levels of the gas slowly raised, attaining about 1 percent around two billion years ago.
Approximately 800 million years ago, the levels of oxygen attained about 21 percent and started to breathe life into more composite species. The oxygen-rich ozone layer was also created, protecting the surface of the Earth from the harmful solar radiation.
