Lecture Notes: Biotic and Abiotic Factors Affecting a Community

Introduction

• Objective: Understanding biotic and abiotic factors affecting communities.
• Definitions:
  • Biotic Factors: Living parts of an environment.
  • Abiotic Factors: Non-living parts of an environment.

Biotic Factors

• Availability of Food

  • All animals depend on other living organisms.
  • Example: Lions eat other animals; zebras eat plants.
  • Impact: Reduction in food availability reduces organism numbers in a community.

• Arrival of New Predator

  • Can decrease prey population.
  • Affects existing predators through competition for prey.

• Competition Between Species

  • Outcompeted species may see a drastic fall in population.
  • Extreme cases may lead to extinction if they can't breed sufficiently.

• Introduction of New Pathogens

  • Infectious diseases can devastate populations.

Abiotic Factors

• Light Intensity

  • Essential for photosynthesis in plants.
  • Low light reduces photosynthesis rate, leading to slower plant growth.
  • Affects food availability for plant-eating animals.

• Temperature

  • Changes can alter species distribution.
  • Examples: Animal migration, plant disappearance.

• Water Access

  • Critical for survival of both plants and animals.
  • Adaptations to low water levels will be discussed in a future lecture.

• Soil pH and Mineral Content

  • Influences plant growth.
  • Plants require specific pH levels and minerals (e.g., nitrates for proteins).

• Wind Intensity and Direction

  • Affects water loss in plants, particularly near seashores.
  • Plants in sand dunes often adapted to minimize water loss.

• Gases: Carbon Dioxide and Oxygen

  • Carbon Dioxide: Needed for photosynthesis; low levels reduce photosynthesis.
  • Oxygen: Required for respiration; constant in air, varies in water, affecting aquatic life.

Closing Remarks

• Study Resources: Biotic and abiotic factors are extensively covered in the vision workbook available online.