Biology & Biological Sciences?

Density-dependent birth rate is a phenomenon in population ecology where the birth rate of a population decreases as the population density increases. This occurs because as the population density increases, there are fewer resources available for each individual, such as food, water, and space. This leads to a decrease in the overall health and fitness of the population, which in turn leads to a decrease in the birth rate.

What are key characteristics of density dependent birth rate?

• Negative relationship: The birth rate is negatively correlated with the population density.
• Limited resources: The decrease in birth rate is caused by the limited resources available to the population.
• Various factors: The resources that can be limited include food, water, space, nesting sites, mates, and other factors that are essential for reproduction.

What is the importance of density dependent birth rate?

• Density-dependent birth rate is an important concept in population ecology because

The carrying capacity of an ecosystem is the maximum population size of a species that the ecosystem can sustain indefinitely, given the food, water, and other resources available.

What are the key characteristics of carrying capacity?

• Dynamic: Carrying capacity is not a fixed number, it can change over time due to various factors such as environmental changes, resource availability, and technological advancements.
• Species-specific: The carrying capacity of an ecosystem varies for different species depending on their ecological requirements and resource use patterns.
• Influenced by multiple factors: The carrying capacity of an ecosystem is influenced by a complex interaction of factors including:
  • Abiotic factors: such as climate, soil quality, and water availability.
  • Biotic factors: such as competition, predation, and disease.
  • Human activities: such as pollution, habitat destruction, and resource exploitation.

What is the importance of carrying capacity?

• Understanding carrying capacity is crucial for sustainable ecosystem management and conservation efforts.
• It

Summary with the article: Epigenetics: Stress makes its molecular mark - Nestler (2012)

Some people who are exposed to stress are more vulnerable to negative outcomes than others. Differences in epigenetics may explain this vulnerability. Epigenetic mechanisms provide short and long-term responses to stress.

Aggressive mice

When a person is stressed, gene expressions in areas the brain will be activated or inhibited. Many stress-induced changes are adaptive, but some are also harmful and can be permanent. Research has been done using mice which were exposed to other, aggressive mice. After ten days of this experiment, the mice started to avoid these other mice. They also became less interested, less adventurous and more likely to be obese. These symptoms could last for months and could be treated with antidepressants. It turned out that mice that had been given cocaine a week before being exposed to aggressive mice had more stress-related