MODULE 4

• The purpose of this module is to help you understand the concepts about adaptation and causes of species extinction among organism in an ecosystem
• Lessons in this module

  • Lesson 1 - Patterns of Population Distribution
  • Lesson 2 - Factors causing Species Extinction
• After going through this module, you should be able to

  • Relate species extinction to the failure of certain populations to adapt to abrupt changes in the environment
• Specifically, you are expected to

  • Describe the distribution of species in a community
  • Compute for the population density in an area
  • Determine the patterns of population distribution
  • Explain the probable causes of species extinction
  • Relate some local and global environmental issues to species extinction
• Binomial Nomenclature


  The two-name classification system
• Carolus Linnaeus classified living things based on Binomial Nomenclature
• Levels of Linnaean classification from highest to lowest

  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Natural Selection


  Mechanism of evolution proposed by Charles Darwin
• Population density


  The number of individual species per unit area at a given time
• The maximum population size that an environment can support is called carrying capacity
• Biotic potential


  The maximum reproductive capacity of an organism under optimal environmental conditions
• When the environment nears its carrying capacity, the population size remains stable
• Factors that naturally limit the growth of insects in a community

  • Presence of insect eating animals
• Conservation status of species

  • Extinct
  • Critically endangered
  • Threatened
  • Vulnerable
• Draining a swamp for agricultural purposes does not support the government's program in the prevention of extinction among organisms
• Charles Darwin proposed the theory of natural selection
• Jean Baptiste de Lamarck proposed the theory of use and disuse
• Evidences of evolution

  • The fossil record
  • The chemical and anatomical similarities
  • The geographic distribution of related species
  • The recorded genetic changes
• Alfred Wegener's theory of continental drift explains the uneven distribution of living organisms of the same species in different environments
• Factors that influence the distribution of organisms

  • Temperature
  • Water
  • Light
  • Soil pH
  • Salinity
• Biotic potential


  Ability of a population of living species to increase under ideal environment
• Carrying capacity


  Maximum population size that can be sustained by a specific environment
• Population density


  Number of individuals per unit of area
• Distribution patterns


  How the individuals in a population are distributed in space at a given time
• Population Density


  Number of people per unit of area, usually measured in per square kilometer or square mile, and which may include or exclude areas of water or glaciers
• Distribution patterns describe how the individuals in a population are distributed in space at a given time
• Measuring Population Density

  1. Determine the pattern of population density using mathematical formula

  2. Describe pattern of distribution of different population
• Limiting Factor


  A supply or environmental condition which limits the growth, distribution or abundance of an organism or population within an ecosystem
• Density-independent factors have effect on the size or growth of the population and the population density
• Density-independent factors include food or nutrient limitations, pollutants in the environment, and extreme climate, including seasonal cycles such as monsoons
• If an organism meets the requirements identified as abiotic factors in their respective habitat, they can freely reproduce, and remain stable in their place
• Probable Causes of Species Extinction

  • Loss of habitat
  • Global warming
  • Natural disaster
  • Overexploitation of species for human use
  • Evolutionary changes in their members (genetic inbreeding, poor reproduction, decline in population numbers)
• The Philippines contains a large and diverse group of mammalian species in the past but they became extinct due to several factors
• Dugong is threatened by coastal development and poor catchment management resulting in siltation and therefore the loss of sea grass beds
• Dugong is also vulnerable by incidental mortality in commercial gillnets, entanglement in shark nets and collisions with boats
• The Monkey-eating eagle has only an estimated 400 left in the wild
• The tamaraw has suffered from heavy hunting and continuous habitat destruction during the last century
• The Philippine tarsier is endemic to the Philippine archipelago and several laws have been passed to protect and conserve it
• The Asian elephant was introduced to the Philippines but later became extinct in the sultanates of Sulu and Maguindanao
• Dugong, a marine mammal inhabiting the warm coastal waters of the Indian and Pacific Oceans that feeds on sea grasses, was classified as vulnerable species