Biology Paper 1

• Eukaryotic cells


  Animal and plant cells
• Prokaryotic cells


  Bacterial cells
• Chromosomes


  Genetic information found in the nucleus, containing coils of DNA
• Structures in eukaryotic cells


  • Cell membrane
  • Cytoplasm
  • Nucleus containing DNA
• Gene


  Short section of DNA that codes for a protein and controls a characteristic
• Structures in prokaryotic cells


  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Single circular strand of DNA and plasmids
• There are 23 pairs of chromosomes in each cell of the body, resulting in 46 chromosomes in total
• Sex cells (gametes) have half the number of chromosomes, resulting in 23 chromosomes in total
• Organelles


  Structures in a cell that have different functions
• Diploid


  The amount of chromosomes found in body cells (46 in humans)
• Organelles in animal and plant cells


  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Haploid


  Half the diploid amount of chromosomes (23 in humans), found in gametes
• Sexual reproduction


  Joining of male and female gametes, each containing genetic information from the mother or father
• Cell Cycle


  1. Interphase

  2. Mitosis

  3. Cytokinesis
• Organelles only in plant cells


  • Chloroplasts
  • Permanent vacuole
  • Cell wall
• Alfred Russel Wallace


  Developed the theory of speciation, and therefore evolution by natural selection
• Gametes


  • Sperm and egg cells in animals
  • Pollen and egg cells in flowering plants
• Gametes are formed by meiosis, as they are non identical
• Structures in bacterial cells


  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Chromosomal DNA (circular)
  • Plasmids
  • Flagella
• Alfred Russel Wallace


  • Had the idea that the individuals who did not have characteristics to help them survive a change in the environment would die out
  • Published joint studies with Darwin
  • Continued to work across the world to collect evidence – one of his most important works was on warning colouration in animals
• Mitosis


  • Chromosomes line up at the equator
  • Cell fibres pull each chromosome of the 'X' to either side of the cell
• A normal cell has 46 chromosomes, there are two sets of chromosomes (i.e. 23 pairs), one from the father and one from the mother
• Charles Darwin


  Scientist and naturalist who put forward the theory of evolution
• Daughter cells


  Two identical cells formed when the cytoplasm and cell membranes divide
• Differentiation


  A process that involves the cell gaining new sub-cellular structures in order for it to be suited to its role
• Each gamete has 23 chromosomes and they fuse in fertilisation
• Health


  A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity
• Mitosis produces 2 genetically identical diploid daughter cells
• Charles Darwin published 'On the Origin of Species' in 1859
• The genetic information from each parent is mixed, producing variation in the offspring
• Specialised animal cells


  • Sperm cells
  • Egg cells
  • Ciliated epithelial cells
• Growth and development in multicellular organisms


  • Cell division by mitosis
  • Replacing damaged cells
  • Asexual reproduction
• Theory of Evolution


  • Variation exists within species as a result of mutations in DNA
  • Organisms with characteristics most suited to the environment are more likely to survive to reproductive age and breed successfully – called survival of the fittest
  • The beneficial characteristics are then passed on to the next generation
  • Over many generations the frequency of alleles for this advantageous characteristic increase within the population
• Asexual reproduction


  Involves one parent with no gametes joining, happens using the process of mitosis, where two identical cells are formed from one cell
• Aspects of health


  • Physical
  • Mental
  • Social
• Specialised plant cells


  • Root hair cells
  • Xylem cells
  • Phloem cells
• Cell differentiation


  Cells specialising to perform specific functions
• Light microscope


  Has two lenses, usually illuminated from underneath, maximum magnification of 2000x and resolving power of 200nm
• Reasons for controversy surrounding Darwin's ideas

  • It contradicted the idea that God was the creator of all species on Earth
  • There was not enough evidence at the time as few studies had been done on how organisms change over time
  • The mechanism of inheritance and variation were not known at the time
• There is no mixing of genetic information in asexual reproduction