bio topic 4

• Biodiversity is the variety of living organisms
• Over time, the variety of life on Earth has become extensive
• Biodiversity is threatened by human activities such as deforestation
• Biodiversity can be measured in terms of:

  • Species richness: the number of different species in a habitat
  • Genetic diversity: a measure of the genetic variation found in a particular species
• Heterozygosity index:

  H= number of heterozygotes / number of individuals in the population
• Endemism is the state of a species being unique to a particular geographic location
• Natural selection is the process in which fitter individuals who are better adapted to the environment survive and pass on advantageous alleles to future generations
• Evolution is the process by which the frequency of alleles in a gene pool changes over time as a result of natural selection
• Hardy-Weinberg Equation:

  p = frequency of the dominant allele (represented by A)

  q = frequency of the recessive allele (represented by a)

  p^2 = frequency of AA (homozygous dominant)

  2pq = frequency of Aa (heterozygous)

  q^2 = frequency of aa (homozygous recessive)

  For a population in genetic equilibrium:

  p+ q = 1.0

  (p + q)^2 = 1 hence

  p^2+2pq +q^2=1
• Speciation occurs when two populations become reproductively isolated
• Classification is a means of organising the variety of life based on relationships between organisms
• Molecular phylogeny is the analysis of molecular differences in different organisms to determine the extent of their evolutionary relationship
• Plant cells have unique structures such as:

  • Cell wall made of cellulose
  • Plasmodesmata for transport between cells
  • Chloroplasts for photosynthesis
  • Amyloplasts for starch storage
  • Vacuole for cell sap
• Transport in plants involves:

  • Xylem vessels for water and mineral transport
  • Phloem vessels for translocation
  • Cambium cells for growth
  • Sclerenchyma fibres for structural support
  • Parenchyma cells for packing
• Carbohydrates are molecules consisting of carbon, hydrogen, and oxygen
• Drug testing involves 3 stages:

  • Phase 1: testing on a small group for safety
  • Phase 2: testing on patients with the condition
  • Phase 3: large group testing for effectiveness and side effects
• Conservation methods include:

  • Ex-situ: captive breeding programs and seed banks
  • In-situ: education programs and initiatives like National Parks
• The ecological niche of a species is its role within the community
• Species that share the same niche compete with each other
• The better-adapted species will outcompete the other, forcing it to alter the niche it occupies or it could die
• The idea that better adapted species survive is the basis of natural selection
• Organisms are adapted to their environment in various ways:
• Anatomical adaptations are physical adaptations, either external or internal
• Presence of long loops of Henlé allows desert mammals to produce concentrated urine and minimise water loss
• Behavioural adaptations are changes in behaviour which improve the organism's chance of survival
• Example: mating calls
• Physiological adaptations are processes that increase an organism's chance of survival
• Example: regulation of blood flow through the skin
• Natural selection is the process in which fitter individuals who are better adapted to the environment survive and pass on the advantageous alleles to future generations
• Xylem vessels transport water and minerals, as well as provide structural support
• Long cylinders made of dead tissue with open ends
• Thickened with lignin
• Phloem vessels are tubes made of living cells involved in translocation, which is the movement of food substances and nutrients from leaves to storage organs
• Cambium cells between xylem and phloem are undifferentiated and able to specialise as the plant grows
• Sclerenchyma fibres provide structural support
• Short structures made of dead cells with a hollow lumen and end walls
• Parenchyma cells (pith) act as packing between other cells and vessels