Sci Week 7

• Biodiversity describes how varied are life forms in different ecosystems
• The Philippines is known for its very rich biodiversity
• The country has more than 52,177 described species of which more than half is found nowhere else in the world
• The Philippines is considered a biodiversity hotspot due to the alarming rate of environmental destruction like damage of coral reefs, forests and other similar important resources
• Organisms


  Part of biodiversity and may be economically and ecologically valuable
• Products of organisms


  • Food
  • Medicine
  • Clothing
  • Shelter
  • Energy
• Organisms


  • Important in maintaining balance in the ecosystem as they perform their specific roles
  • Some maintain the quality of natural bodies of water
  • Some prevent soil erosion and floods
  • Some cycle minerals in the soil and absorb pollutants
  • Some feed on insects and pests which control the population of organisms in a certain environment, thus making the ecosystem balance and stable
• Value of species


  • Direct economic value
  • Indirect economic value
  • Aesthetic value
• Direct economic value


  Species whose products are sources of food, medicine, clothing, shelter and energy
• Indirect economic value


  Benefits produced by the organism without using them, e.g. maintaining chemical quality of natural bodies of water, preventing soil erosion and floods, cycling materials in the soil, and absorbing pollutants
• Aesthetic value


  Species that provide visual artistic enjoyment or are used for spiritual meditation
• Biodiversity is very important because it sustains the food web on earth through flow of energy and contributes to environmental stability
• Stability of an ecosystem

  The resilience to withstand changes that may occur in the environment
• Changes in the environment, whether natural or human-caused, may severely reduce biodiversity and result in the instability of the ecosystem
• Population


  A group of organisms of the same species that live in a certain area
• Factors that can cause a population size to change

  • Birth rate (Natality) - number of births
  • Death rate (Mortality) - number of organisms that are dying in a population
• If the birth rate is greater than the death rate, a population will grow. If the death rate is greater than birth rate, then the population will decrease
• Density-independent factors


  Limiting factors that can stop population from growing, such as natural disasters, temperature, sunlight and the activities of humans in the environment
• Density dependent factors


  Factors that come into play when population reaches a certain number of organisms, e.g. not enough resources (food, shelter, water) for all the organisms
• Carrying capacity


  The number of individuals that can be supported in a given area within natural resource limits, and without degrading the natural social, cultural and economic environment for present and future generations
• When resources are unlimited


  Populations exhibit exponential growth, resulting in a J-shaped curve
• When resources are limited


  Populations exhibit logistic growth, where population expansion decreases as resources become scarce and levels off when the carrying capacity of the environment is reached, resulting in an S-shaped curve
• Before the population reaches the carrying capacity, it experiences a period of rapid growth called exponential population growth, where there are plenty of resources available for all organisms, so more births are recorded than deaths