Problem 9 - Campbell Biology

Question

Evolution conNECTION In 1847 , the German biologist Christian Bergmann noted that mammals and birds living at higher latitudes (farther from the equator) are on average larger and bulkier than related species found at lower latitudes. Suggest an evolutionary hypothesis to explain this observation.

Step-by-Step Solution

Answer

Larger body sizes help animals retain heat and survive better in colder environments, leading to this evolutionary trend.

Step 1 - Understanding Bergmann's Observation

First, understand that Christian Bergmann observed that mammals and birds living farther from the equator are generally larger and bulkier than those living closer to the equator.

Step 2 - Considering Environmental Factors

Recognize that higher latitudes are usually colder than lower latitudes. Larger body size could help animals maintain body heat in these colder environments.

Step 3 - Linking Body Size to Heat Retention

Larger animals have a smaller surface area relative to their volume, which helps them retain more heat. This could reduce the energy expenditure required for maintaining body warmth.

Step 4 - Formulating the Hypothesis

Suggest that natural selection might favor larger body sizes in colder environments because those individuals with larger sizes are better at retaining heat and reducing energy loss, giving them a survival advantage.

Key Concepts

evolutionary biology

Evolutionary biology is the branch of biology that studies how organisms evolve over time. It examines the changes in species' genetic and physical traits across generations. A key focus is on how these changes help species adapt to their environments.

• Evolutionary biology looks at genetic mutations and how they affect an organism's survival.
• It also considers how certain traits can become more common in a population through a process called natural selection.

Bergmann's Rule is a perfect example of evolutionary biology in action. It shows how animals at higher latitudes evolve to become larger to retain heat better in colder climates. This is not just a random change; it's a clear adaptation to the environment, guided by the principles of evolutionary biology.

natural selection

Natural selection is a core concept in evolutionary biology. It explains how certain traits become more or less common in a population based on their impact on survival and reproduction.

• Traits that improve an organism's chances of survival and reproduction tend to become more common over generations.
• Conversely, traits that hinder survival are less likely to be passed down.

In the context of Bergmann's Rule, natural selection favors larger body sizes in animals living in cold climates. This is because larger animals can retain heat more effectively, giving them a better chance of surviving harsh winters. As a result, these traits become more common in populations living farther from the equator. It's a clear example of how natural selection drives the evolution of species to better suit their environments.

body size and heat retention

Body size plays a crucial role in an animal's ability to retain heat, especially in colder climates. This idea is central to understanding Bergmann's Rule.

• Larger animals have a smaller surface area relative to their volume.
• This means they lose less heat compared to smaller animals.

For example, think about how a small cube and a large cube cool down. The small cube cools faster because it has more surface area relative to its volume. The same principle applies to animals. In cold climates, larger body sizes help animals stay warm by reducing heat loss.

This adaptation is beneficial because maintaining body heat is crucial for survival. Less energy spent on keeping warm means more energy available for other vital functions, such as finding food and reproducing. So, natural selection favors larger body sizes in these environments, as it gives individuals a survival advantage.