Environmental Resistance, Population Growth, and Sustainable Agriculture

Environmental Resistance and Carrying Capacity

Environmental resistance encompasses all factors influencing population growth and size. These factors include:

Biotic Factors

• Food availability
• Predators
• Competitors
• Disease

Abiotic Factors

• Temperature
• Oxygen availability
• Toxins and pollutants

Carrying capacity is the maximum number of individuals of a species that a habitat can support. When a population reaches its carrying capacity, environmental resistance becomes dominant, increasing the death rate and/or decreasing the birth rate.

Biotic Potential

Biotic potential refers to the inherent ability of a species to reproduce.

Human Population Growth

Medical Revolution

Improvements in sanitation and infectious disease control significantly reduced the death rate.

Industrial Revolution

Technological advancements increased agricultural efficiency and improved housing conditions.

Agricultural Revolution

Early human settlers developed more efficient farming practices.

Population Pyramids and Age Structure

A population pyramid visually represents the age structure of a population. Factors influencing age structure include:

• Food availability
• Hygiene
• Medical provision
• Working conditions
• Political stability

Population pyramids can be compared based on:

• Width of the base
• Height
• Angle of the sides

Monoculture: Advantages and Disadvantages

Advantages

• Specialized harvesting techniques: One machine can harvest the entire crop.
• Highly selected strains: Varieties with desirable characteristics can be matched.
• Mineral requirements: Scientists can determine precise crop needs for optimal fertilization.

Disadvantages

• Poor wildlife food sources: Limited weed variety for insects and birds.
• Spread of disease: Increased susceptibility to plant pathogens.
• Loss of genetic variety: Changes in environmental resistance can severely impact the entire crop.
• Soil damage: Repeated depletion of the same minerals.

Crop Rotation

Crop rotation typically involves a cycle of root crops, legumes, cereals, and a fallow period.

Advantages

• Reduced pest buildup
• Reduced mineral depletion
• Reduced need for pesticides and fertilizers

However, crop rotation can increase costs.

Land Use for Agriculture and Pollution

Many pollutants impact land, air, and water. For example, lead and mercury compounds can contaminate land, pesticides can enter terrestrial food chains, and acid rain can affect soil mineral availability. Pollution also includes the loss of wildlife habitat due to human competition for land.