Ch. 49 - An Introduction to Ecology

Freeman - Biological Science 8th Edition

Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook

Freeman 8th Edition

Ch. 49 - An Introduction to Ecology

Problem 9

Chapter 49, Problem 9

Like Earth, Mars has seasons—its Northern Hemisphere experiences winter when its Southern Hemisphere experiences summer. Which statement is the best explanation for seasonality on Mars?
a. Mars is tilted on its axis.
b. Mars has an elliptical orbit that brings it closer to the Sun in summer than in winter.
c. Mars has a circular orbit and maintains a constant distance from the Sun.
d. The Southern Hemisphere of Mars consistently receives direct solar radiation.

Verified step by step guidance

Begin by understanding the concept of seasonality on planets. Seasons are typically caused by the tilt of a planet's axis relative to its orbit around the Sun.

Consider option a: Mars is tilted on its axis. This is similar to Earth, where the axial tilt causes different parts of the planet to receive varying amounts of sunlight throughout the year, leading to seasons.

Evaluate option b: Mars has an elliptical orbit that brings it closer to the Sun in summer than in winter. While Mars does have an elliptical orbit, the primary cause of seasons is usually the axial tilt, not the distance from the Sun.

Examine option c: Mars has a circular orbit and maintains a constant distance from the Sun. A circular orbit would not cause significant seasonal changes, as the distance from the Sun would remain constant.

Consider option d: The Southern Hemisphere of Mars consistently receives direct solar radiation. This statement does not explain the alternating seasons between hemispheres, which is a characteristic of axial tilt.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Axial Tilt

Axial tilt, or obliquity, refers to the angle at which a planet's rotational axis is tilted relative to its orbital plane. This tilt is responsible for the changing seasons on planets like Earth and Mars, as it causes different hemispheres to receive varying amounts of sunlight throughout the year. Mars has an axial tilt of about 25 degrees, similar to Earth's 23.5 degrees, leading to its seasonal changes.

Elliptical Orbit

An elliptical orbit is an oval-shaped path that a planet follows around the Sun. While Mars does have an elliptical orbit, it is not the primary reason for its seasons. The variation in distance from the Sun due to this orbit is not significant enough to cause the seasonal changes observed on Mars. Instead, the axial tilt plays a more crucial role in the planet's seasonality.

Solar Radiation Distribution

Solar radiation distribution refers to how sunlight is spread across a planet's surface. The axial tilt of a planet affects this distribution, leading to varying intensities of sunlight in different regions and times of the year. On Mars, as on Earth, this results in one hemisphere receiving more direct sunlight during its summer, while the other experiences winter, contributing to the seasonal cycle.

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Related Practice

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Explain how the open ocean is similar to the desert, and how it is not.

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Temperate forest in China and temperate forest in North America are part of the same biome but are distinct ecosystems. Explain.

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Compare the distribution of the natural terrestrial biomes of eastern North America with the distribution of anthropogenic biomes.

Textbook Question

Scientists predict that global climate change will cause a greater increase in average temperature at higher latitudes than in the tropics. This seems like good news since most of the world's biodiversity occurs in the tropics. However, recent data suggest that a smaller temperature change in the tropics will cause a larger physiological response in organisms there than the larger temperature change will in organisms in temperate areas. Based on what you have learned about thermal niches in this chapter, propose a hypothesis to explain this result.

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Textbook Question

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The red lionfish, Pterois volitans, has beautiful red stripes, streaming fins, and a fearless disposition, and it is deadly. Native to the Pacific Ocean, the red lionfish was first discovered on coral reefs in the Bahamas in 1985. The species has spread to over 3 million square kilometers of the western Atlantic and Gulf of Mexico. Lionfish have a voracious appetite for native fish, are armed with venomous spines, and have no natural predators in their new range.

Why are species like the lionfish considered 'invasive'?

a. They are found in areas where they are not native.

b. They were accidentally introduced by humans.

c. They spread aggressively and displace native species.

d. They are predators of other fish.

Textbook Question

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Lionfish are usually found in full-salinity seawater (35 parts per thousand). However, lab studies show that lionfish can tolerate salinities as low as 4 parts per thousand for several days, suggesting that the low-salinity water of estuaries (such as at the mouth of the Amazon River) may not be a barrier to lionfish dispersal along the coasts. Sketch a niche model predicting lionfish abundance as a function of salinity.