Lecture on Biotic and Abiotic Factors Affecting Communities
Introduction
- Biotic Factors: Living parts of the environment.
- Abiotic Factors: Nonliving parts of the environment.
Biotic Factors
There are four key biotic factors:
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Availability of Food
- Essential for animal survival.
- Examples: Lions eat animals; zebras eat plants.
- A fall in food availability leads to a decrease in organism populations.
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Arrival of a New Predator
- Can reduce prey species populations.
- Affects existing predators due to competition for prey.
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Competition Between Species
- If a species is outcompeted, its population may decline or become extinct.
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Introduction of New Pathogens
- Infectious diseases can decimate species populations.
Abiotic Factors
There are seven key abiotic factors:
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Light Intensity
- Affects plant growth through photosynthesis.
- Low light intensity results in slower plant growth, impacting the food chain.
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Temperature
- Changes can alter species distribution.
- Examples of responses: Migration of animals, disappearance of plant species.
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Water Availability
- Essential for survival of plants and animals.
- Adaptations to low water levels will be discussed in the next video.
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Soil pH and Mineral Content
- Affects plant growth.
- Soil must have appropriate pH and minerals (e.g., nitrates for amino acids).
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Wind Intensity and Direction
- Influences water loss in plants.
- Example: Plants in sand dunes are adapted to reduce water loss.
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Carbon Dioxide Levels
- Required for photosynthesis in plants.
- Low CO2 levels can decrease photosynthesis rates.
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Oxygen Levels
- Needed for aerobic respiration.
- Oxygen levels in air remain constant, but dissolved oxygen in water can decrease.
- Low dissolved oxygen is harmful to aquatic organisms.
Conclusion
- Biotic and abiotic factors are crucial in determining the structure and dynamics of communities.
- Further resources and questions on this topic are available in the revision workbook.