Biodiversity

• Species

  A group of organisms with similar morphology ( form and structure ) ,

  physiology and behaviour

  A species can interbreed to produce fertile offspring (different species can breed to form infertile offspring.

  species are reproductively isolated from other species
• Reproductive isolation

  inability of some organisms of a species to breed with other related species successfully due to barriers:

  geographical barriers

  seasonal changes = reproductive timings do not match

  mechanical changes = reproductive body parts do not match

  behavioural changes
• Speciation

  process by which groups within species separate from each other by geographical barriers
• gene pool

  All alleles of all genes present in a population
• Larger populations

  Large gene pools

  more heterozygous individuals

  greater genetic diversity

  more advantageous alleles
• Ability of population to adapt

  strength of selection pressure

  size of gene pool

  reproductive rate of organism
• Habitat

  Place / area in which a species or group of organisms live
• Population

  A group of organisms of one species that interbreed and live in the same place at the same time
• Community

  Populations of different species living and interacting in the same place at the same time.
• Ecosystem

  Interaction between all biotic and abiotic factors in a given area
• Niche

  the role of an organism within its environment

  Every individual species has its own unique niche

  Two species that occupy the same niche cannot coexist. They will be in direct competition.
• Biodiversity

  The range of variation in organisms, species and populations
• Genetic diversity

  diversity of alleles and genes in the genome of species
• Small / isolated population

  Inbreeding in small, isolated populations leads to a high proportion of individuals being homozygous = lower genetic diversity

  genetic diseases caused by recessive alleles can become more common in these populations
• Species diversity

  the number of different species in an ecosystem and the abundance

  across the different species present

  The greater the number of species and the greater the abundance, the greater the species diversity

  Ecosystems with higher species diversity are more stable and more resilient to environmental changes
• Endemism

  Certain species only occur in a particular area of the world.

  These species endemic to that region and do not naturally occur anywhere else.

  endemic species are particularly at risk of extinction due to the limited range = geographical barriers
• Threat of human activity - Habitat destruction

  -Habitat loss

  -Habitat, fragmentation, separated species, more likely to suffer in breeding

  -deforestation

  -Fishing practices

  -Explosives in the sea
• threats of human activity:

  habitat destruction

  Overexploitation

  Hunting

  Agriculture

  Climate change
• Classification

  Domain

  kingdom

  phylum

  Class

  Order

  Family

  Genus

  Species
• Five kingdoms


  Animal

  plant

  fungi

  protist

  prokaryote
• Cell wall

  cell wall is made out of polysaccharide cellulose

  It provides structural support for the plant cell
• Parts of a cell wall

  Middle Lamella

  Pectin and hemicellulose

  Plasma membrane

  Cellulose microfibril
• Plasmodesmata

  Narrow threads of cytoplasm (surrounded by a cell membrane) called plasmodesmata connect the cytoplasm of neighbouring plant cells.

  This allows substances to be transported between plant cells and facilitates cell to cell communication
• pits

  • These are very thin regions of the cell wall
  • The pits in adjacent plant cells are lined up in pairs
  • This facilitates transport of substances between cells
• Amyloplast

  • Small, membrane bound organelle containing starch granules
  • They are responsible for storing starch in plants and converting it back to glucose when the plant needs it
• Vacuole and tonoplast

  • The vacuole is a sac in plant cells surrounded by the tonoplast (selectively permeable membrane)
  • Contains cell sap, which is a mixture of different substances such as water, minerals, waste and enzymes
• Vacuole function

  • They keep cells turgid, which stops the plant from wilting
  • They can break down and isolate unwanted chemicals in plant cells
  • The tonoplast controls what can enter and leave
• Cellulose function

  • Cellulose is the main structural component of cell walls due to its strength, which is a result of the many hydrogen bonds found between the parallel chains of microfibrils
  • The high tensile strength of cellulose allows it to be stretched without breaking which makes it possible for cell walls to withstand turgor pressure
  • The cellulose fibres and other molecules (e.g. lignin) found in the cell wall form a matrix which increases the strength of the cell walls
  • These strengthened cell walls provide support to plants
• Cellulose structure

  Beta glucose monomers

  Inverted glucose monomers

  1,4 Glycosidic bond

  Long straight chains of beta glucose arranged in parallel lines

  hydrogen bonds between glucose chains.

  60-70 cellulose molecules form cellulose microfibrils

  cellulose microfibrils are held together by hemicellulose and pectins
• Schlerenchyma

  Long, hollow tubes

  Have end walls

  lignification of cell walls

  Do not have pits

  Have a lot of cellulose in cell wall
• Phloem structure

  sieve plates = allow movement of assimilates in both directions

  no organelles in phloem cells= maximises space for translocation

  Companion cells have the organelles and nucleus, which provides metabolic support and have a lot of mitochondria to provide ATP for active transport

  Plasmodesmata allow assimilates to move easily from sieve plates to companion cells

  cellulose cell wall = provides support to withstand high hydrostatic pressure
• Xylem structure

  Lignified cell wall = provide support to withstand high hydrostatic pressure

  No organelles or vacuole = dead cells and maximise a space for transpiration

  No end plates= allows for movement of water in one direction by adhesion and cohesion forces

  small diameter of vessels = Allows for movement of water by capillary action
• Use of plant fibres

  Ropes

  fabrics in clothes = hemp and cotton
• Why are plant fibres used in ropes and fabrics?

  strength of cell wall:

  arrangement of microfibrils

  secondary thickening
• arrangement of microfibrils

  there are many hydrogen bonds between cellulose molecules. When arranged in a mesh-like structure, the hydrogen bonds form cross-links, so a lot of energy is required to break them which means that the cell wall is very strong.
• Secondary thickening

  Increase in thickness due to lateral meristem tissue, such as the Cambian. The increased thickness adds more strength to the cell walls.
• Identifying plant tissues

  I. Cut a very thin piece of a plant stem using a scalpel. if the piece of cutting is too thick light will be unable to pass through and will affect clarity of the image.

  2. Soak the piece in Toludine blue stain - Xylem and sclerenchyma will appear blue-green, phloem will appear pink, purple.

  3. Rinse and dry the cutting gently and place it on a slide.

  carefully lower a coverslip on the slide. Observe the plant structures under a microscope with objective lens x10.
• Investigating plant mineral deficiency

  Prepare 5 nutrient broths containing:

  • One contains all nutrients and One does not contain any nutrients
  • One has sufficient magnesium and nitrogen, but a lack of calcium
  • One has sufficient nitrogen and calcium, but a lack of magnesium
  • One has sufficient magnesium and calcium, but a lack of nitrogen
  • Take 5 seedlings, ensuring that they are from the same plant and are the same age, and record the mass of each at the start
  • Place the seedlings and suspend the roots 
• results of investigating plant mineral deficiency

  • Cover the test tubes with aluminium foil to keep light away from the broth. Place the test tubes near a source of light and leave them for a few days
  • Remove each plant from the broth and carefully blot it dry before measuring the mass again. Record the end mass and use that to calculate the mean change in mass of the plants for each of the different nutrient broths.
  • Make a note of any physical differences between the plants of the different groups 
• Zoo

  Increase number of individuals of species

  maintain genetic diversity

  reintroduce animals into the wild

  exchange animals between zoos