chapter 4C

• Biodiversity


  The number and variety of different organisms found in an area
• Aspects of biodiversity


  • Diversity within species
  • Diversity between species
  • Diversity of ecosystems
• The earth's biodiversity is decreasing rapidly
• Genetic diversity


  The variety of alleles in a gene pool
• Gene pool


  All the genes found within a population or a group of organisms
• Genetic diversity


  • A high variety of genes in a population means that the species has a greater chance of survival in a changing environment
  • If population size is small, inbreeding increases and the gene pool is reduced resulting in higher homozygosity and lower genetic diversity
• Species richness

  The variety of species within a region or the number of species in a region
• Organisms in an ecosystem are interdependent
• Healthy biodiversity allows large-scale ecosystems to function and self-regulate
• The air and water of the planet are purified by the action of a wide range of organisms
• Photosynthesis plays an important role in stabilizing the atmosphere and world climate
• Plant pollination, soil fertility and nutrient recycling depend on thriving biodiversity
• Biodiversity provides the genetic diversity that has allowed us to develop the production of crops, livestock, fisheries and forests, and enables further improvements
• Biodiversity provides the potential of plants to produce chemicals that are important in many areas of human life
• Plants lower down the food chain have an important role in preserving biodiversity
• Wet tropics are generally areas of highest biodiversity
• Biodiversity hotspot


  A region with a very high biodiversity, containing more than 1250 different plant species and greater than 0.5% of total global plant diversity present as endemic species
• In areas where organisms grow and reproduce more rapidly, more mutations can occur which introduce more variety, enabling organisms to adapt to particular niches and evolve to form new species
• The risks to biodiversity are not evenly spread around the world, with small areas such as islands, rainforests, coral reefs, bogs and wetlands being more vulnerable
• Diversity index


  A measure of species diversity within a habitat, calculated as D= N(N-1)/Σn(n-1) where N is the total number of organisms and n is the total number of organisms of each species
• An environment with a large number of species will be more stable, as there will be more interactions among various species (more complex food webs)
• High species diversity increases the chances of survival of species by providing more alternate food sources
• Genetic diversity


  The variety of genes and alleles within a population
• Cheetahs have low genetic diversity, making them vulnerable to being wiped out by a disease or change in their environment
• Heterozygosity index

  A measure of genetic diversity in a population, calculated as the proportion of genes which are present in heterozygous form
• Advantages of high genetic diversity within a species

  • Organisms can fit into various environments and utilize resources in different ways, reducing competition and increasing survival
  • If the environment changes, there will likely be some organisms with adaptations that help them survive
• Endemism


  A species which only occurs in a very specific small area and is unique to that area
• Examples of endemism


  • Endemic species of Madagascar
  • Endemic species of the isolated Hawaiian islands
• Species abundance


  The number of individuals per species, and relative abundance refers to the evenness of distribution of individuals among species
• Ecology


  The study of relationships between living organisms and their environment
• Ecological niche


  The role of an organism within an ecological community, including its food niche and habitat niche
• Ecosystem


  An environment that includes all the living organisms interacting together, the nutrients cycling through the system, and the physical and chemical environment
• Habitat


  The place where an organism lives, including microhabitats which are small parts of a habitat
• Community


  All the populations of living organisms living in a habitat at any one time
• Population


  A group of organisms of the same species, living and breeding together in a particular niche in a habitat
• Adaptations


  • Anatomical adaptations (adaptations of structure)
  • Physiological adaptations (adaptations of biochemistry and body function)
  • Behavioural adaptations (adaptations of action)
• Examples of adaptations


  • Thick blubber in seals and whales
  • Sticky hairs on sundew plants
  • Mammalian diving response in diving animals
  • Orientation to sunlight in insects and reptiles
  • Social behaviours like hunting in teams or huddling for warmth
• Gene and allele frequency

  Mutations can cause changes in genes, increasing the size of the gene pool, and the relative frequency of a particular allele is known as the allele frequency
• Insect and reptile adaptations

  • Orient themselves to get maximum sunlight when temperature is low to warm them up and allows them to move fast enough to escape predators
  • Social behaviour includes hunting as a team or huddling together for warmth
  • Migrating to avoid harsh conditions, courtship rituals and using tools
• Mutation

  Causes small changes in genes