Module 3

• Biotic Factors

  • Seasonal availability & abundance of food
  • Number of competitors
  • Number of mates available
  • Number of predators
  • Number & variety of disease-causing organism
• Abiotic Factors

  • Temp -> enzymes in cell
  • Light availability
  • Water
  • Availability of gases (oxygen & carbon dioxide)
  • Soil type
  • Exposure to natural forces (wind, tide, waves)
• Cane Toad: Change in Abundance and Distribution

  • Abundance as they have no predators to kill them
  • Destruction: they were introduced from Hawaii in 1935
• Cane Toad: Selection Pressure-Change

  • Due to having no predators & natural diseases
  • Cane toad has become a pest in Australia
  • No successful selection pressure
  • Companion with themselves so they eat each other
• Prickly Pears: Change in Abundance and Distribution

  • Introduced in 1800's
  • Adapted quickly to Aus diverse & dry environment
• Prickly Pears: Selection Pressure-Change

  • No predators
  • Cactoblastis moth (biotic pressure reduced numbers)
• Structural Adaptation

  Shape & size of organism and its various body parts. E.g. kangaroo's powerful leg muscles assist it in hopping at high speeds
• Physiological Adaptations

  Relating to the way organisms function, how it's body works. E.g. humans sweating which assist in heat loss
• Behavioural Adaptations


  How organism responds to its environment. E.g. penguins huddling together to stay warm
• Hakea Plant Structural Adaptation

  • Waxy coating on upper surface (Prevents water loss)
  • Hair on lower surface (Vapour prevents water loss bein trapped in hairs)
• Elephant Ear Structural Adaptation

  • Large flat leaf (Large SA)
  • Dark green (Means more chlorophyll in chloroplast)
  • Lives in low light for photosynthesis
• Eucalyptus Structural Adaptation

  • Waxy coating (Prevents water loss)
  • Pale colour (Reflects heat therefore less evaporation of water)
• Darwin's Theory of Evolution by Natural Selection

  1. In any population there is variation between individual. More offspring are produced than needed and there is constant struggle for survival
  2. Individuals with favourable characteristics are selected by environment to survive and reproduce
  3. Individuals with favourable characteristics reproduce and pass on favourable characteristics to their offspring
  4. Over time the favourable characteristics become more common in population
• Finches in Galapagos Islands

  • Finches on island show distinctive characteristics in beak structure
  • Only a few finches migrated to island and that each of different finches had evolved from common ancestor
  • Evolved different beak structures to make use of different four sources on island
• Genetic Diversity

  Total number of genetic characteristics in genetic makeup of species
• Species Diversity


  Measure of diversity of different species in an ecological community
• Ecosystem Diversity

  Variation of different ecosystems found in a region
• Microevolution

  Evolution changes on scale within single population, a change in gene freq. over a short period of time

  E.g. Horse

  • Fossil record of lower leg bones
  • Hooves
  • Teeth
• Macroevolution

  Evolution on a large scale that takes place over millions of years and results in new species
• Speciation

  Process which produces two or more species, often because of geographical isolation

  • Diversification of species and branching into two or more species. Occurs as groups adapt to different environments
  • Isolation occurs when new species may from into distinct breeding populations. Selection pressures often not the same when population is in different environments
• Divergent Evolution

  Evolution occurs when different species arise from common ancestor due to isolation from one another and adaptation to different environments
• Convergent Evolution

  A process that leads to superficial similarities in different species that are not closely related. E.g. convergent evolution led to dolphin, shark and penguin all having streamline shape due to the environment selection pressures of aquatic environment
• Punctuated Equilibrium 


  Model of evolution that is backed by sufficient evidence which shows that some species remained essentially the same way for millions of years and then underwent short periods of very rapid major change
• Gradualism

  Darwin's long-held view that evolutionary change occurs gradually over a long period of time
• Advantages for Biochemical Evidence

  • Allows comparisons of organisms
  • Result are quantitative and the degree of difference can be measured
  • Allowing judgement based on scientific critter rather than observation
  • DNA reveals most detailed information
• Limitations of Biochemical Evidence

  Techniques are:

  • Complex
  • Expensive
  • Rely on highly specialised technology
  • Can only be performed in labs