The obliquity (axial tilt), precession (wobble), and the eccentricity (how close to being circular) of the Earth’s orbit, comprise the Milankovitch cycle. These three factors affect the amount of heat energy from the sun (solar heat) directed to Earth, influencing climactic changes and patterns.
The tilt of the axis mainly affects the amount of solar heat each hemisphere receives. The greater the tilt, the more solar energy is directed at the northern hemisphere. Along with precession, they also affect the length of days and nights experienced by certain parts of the Earth.
The eccentricity of the orbit affects the distance of the Earth to the Sun during its revolution in orbit. The orbit is an elliptical path followed by the Earth, with the Sun not exactly at the center. Thus, there is a time when the Earth is closest to the Sun (perihelion) and this allows the Earth to experience radiation the most. On the other hand, there is also a time when Earth is farthest to the Sun (aphelion). This difference in distance creates a heat exposure retained by the Earth. From the time of perihelion it absorbs so much solar energy and is gradually expended revolving but at the same time still absorbing solar heat – hotter global temperature
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If the orbit was more circular, the distance of the Earth to the Sun will always be the same at any point in the orbit. Thus, allowing equal exposure to the Earth at all times. There will be no point in time in which the Earth will absorb so much heat. This will cause a cooler global temperature compared to the elliptical orbit.
Answer:
A. These homologous structures indicate that these four organisms all share a common ancestor.
Explanation:
Homologous structures mean the organs will have similar structure, but not necessarily function (human arm vs whale's flipper). While analogous structures are similar in function but not structure (wings of an airplane vs wings of a bird). Since the question states that they are similar in skeletal structure, we know they must be homologous structures, thereby eliminating B and C. D is not a choice because the question does not provide anything about the order of evolution. Therefore the answer is A. These homologous structures indicate that these four organisms all share a common ancestor.
