<h3>Answer:</h3><h3>Mitochondria and chloroplasts originated from the endosymbiotic association of aerobic (more...) A critical step in the evolution of eukaryotic cells was the acquisition of membrane-enclosed subcellular organelles, allowing the development of the complexity characteristic of these cells.</h3><h3>Hope this is fine for you
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Plants reduce the carbon dioxide (CO2) in the atmosphere and create more oxygen, which is needed by all organisms, through photosynthesis. :)
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The answers would be 1. (D) and 2. (B)
<h3>Explanation of Answer 1</h3>
Ice cores are in essence drilled cylinders that are acquired from glaciers or ice sheets. Ice sheets and glaciers are formed over many years as a result of deposits of snow layers. As these layers form, the lower layers become denser with each new layer, owing to pressure, and in the process it traps the air, which is preserved in the form of bubbles in the layer, therein preserving the composition of the air at a particular period of time. Scientists use ice cores to compare the atmospheric composition of previous years to those of recent years, and the gas mainly studied is carbon dioxide owing to its bringing about a climatic change.
<h3>Explanation of Answer 2</h3>
The Earth's orbit is caused by the gravitational attraction that is present between the Earth and the Sun, but changes due to the shape of the orbit (eccentricity), the wobble of the Earth about its axis (precession), and the axial tilt of the Earth (obliquity). These cause a change in the Earths orbit, which give rise to Milankovitch's cycles. Milankovitch's Cycles describes a revolutionary movement of the Earth around the Sun. These cycles are observed to be determinants of the climate of the Earth, in the regard of how much heat or energy the Earth is exposed to.
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<span>When sediments move and settle somewhere, they are being deposited. When, over a long time, layers and layers of sediments get deposited on top of each other, the weight of the top layers presses down on the bottom layers, forming them into rock called sedimentary rock. The oldest layers are on the bottom, and the youngest layers are on the top. Because sediments sometimes include once-living organisms, sedimentary rock often contains a lot of fossils. </span>
