Understanding Endangered Species and Their Main Causes

The question asks us to identify the two primary reasons why species become endangered, based on the information provided in the passage.

Let's carefully read the beginning of the passage to find the answer:

• The passage defines an endangered species as an organism threatened by extinction.
• It explicitly states, “Species become endangered for two main reasons: loss of habitat and loss of genetic variation.”

This sentence directly answers the question posed. The passage then goes on to explain these reasons in more detail, discussing how both natural events (like the asteroid impact affecting dinosaurs) and human activities (like development, logging, and clearing land) contribute to habitat loss. It also mentions how the loss of certain species (like fig trees) can indirectly impact species that rely on them for habitat (like those in the rainforest canopy).

Based on the clear statement in the passage, the two main reasons are loss of habitat and loss of genetic variation.

Analyzing the Options

Let's evaluate the given options against the information in the passage:

1. Loss of sunlight and Loss of water: The passage mentions reduced sunlight reaching Earth after the asteroid impact as a factor in habitat change for dinosaurs, but it does not list loss of sunlight and water as the *two main reasons* for species becoming endangered in general.
2. Loss of roads and loss of hunting grounds: The passage mentions development (which includes roads) as a human activity leading to habitat loss, but it does not list loss of roads or hunting grounds as the *two main reasons*.
3. Loss of habitat and Loss of genetic variation: This option directly matches the statement in the passage identifying the two main reasons species become endangered.
4. Acid rain and floods: These environmental factors are not mentioned in the passage as the *two main reasons* for species becoming endangered.

Therefore, the option that aligns perfectly with the passage is Loss of habitat and Loss of genetic variation.

Main Factors Causing Species Endangerment

According to the text, the critical factors are:

• Loss of habitat: This is when the natural home or environment of an organism is destroyed or severely altered. This can happen due to climate change (like the dinosaurs), or human actions such as clearing forests for farming, building cities, or logging.
• Loss of genetic variation: This refers to the reduction in the variety of genes within a species' population. A diverse gene pool helps a species adapt to changes in its environment. When the population size shrinks due to habitat loss or other factors, genetic variation decreases, making the species more vulnerable to diseases and environmental changes.

Revision Table: Endangered Species Factors

Additional Information on Species Endangerment

While the passage highlights habitat loss and genetic variation as the main reasons, it's important to understand that these factors are often interconnected and can be caused by a variety of pressures, primarily driven by human activities and environmental changes. Other factors not listed as the *main* reasons in this specific passage but often contribute to endangerment include:

• Invasive species that outcompete native species.
• Pollution of air, water, and soil.
• Overexploitation through hunting, fishing, or harvesting.
• Climate change effects beyond habitat loss, like altered weather patterns.

Understanding these interconnected factors is crucial for developing conservation strategies to protect endangered species and prevent further extinctions.