biology paper 2

• What is extinction?


  when no remaining individuals of a species still alive
• Why can bacteria evolve rapidly?

  They reproduce at a fast rate
• how does bacteria become resistant?

  A random mutation for resistance allows bacteria to survive when antibiotics are trying to kill them. Resistant bacteria survive and reproduce more resistant bacteria.
• which bacteria is resistant to antibiotics?

  MRSA
• why is it hard to keep up with resistant strains?

  development of new antibiotics is costly and slow
• What is the three domain system?

  Bacteria, Archaea, Eukarya
• What is archaea?


  Primitive bacteria usually living in extreme environments
• what is bacteria?


  true bacteria
• what is eukaryota?


  protists, fungi, plants, animals
• What is the binomial system?

  Kingdom, Phylum, Class, Order, Family, Genus, Species
• how do you reduce the rate of development of antibiotic resistant strains?

  doctors should not prescribe antibiotics inappropriately

  patients should complete their course of antibiotics

  agricultural use of antibiotics should be restricted
• Why is Darwin's theory now accepted?

  it has been shown that characteristics are passed on to offspring genes
• what are fossils?


  the preserved remains or traces of organisms that lived in the past
• How are fossils formed?

  • from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent

  • when parts of the organism are replaced by minerals as they decay

  • as preserved traces of organisms
• why aren't scientists sure how life began on earth?

  many early forms of life were soft bodied so they left few traces behind
• What was Lamarck's theory?


  Changes that occur in an organism during its lifetime can be inherited
• what are the steps which give rise to new species?

  genetic variation

  natural selection

  speciation
• what did Mendel observe?

  pea plants
• what was observed in the early 20th century?


  That chromosomes and Mendel's 'units' behaved in similar ways. This led to the idea that the 'units, now called genes, were located on chromosomes.
• what is the first part of Darwins theory of evolution by natural selection?

  individual organisms within a particular species show a wide range of variation for a characteristic
• what is the second part of Darwins theory of evolution by natural selection?

  individuals with characteristics most suited to the environment are more likely to survive to breed successfully
• what is the third part of Darwins theory of evolution by natural selection?

  characteristics that have enabled these individuals to survive are then passed onto the next generation
• why was Darwins theory gradually accepted?

  - The theory challenged the idea that God made all the animals and plants that live on Earth

  -There was insufficient evidence at the time the theory was published to convince many scientists

  -The mechanism of inheritance and variation was not known until 50 years after the theory was published
• What is a dominant allele?


  an allele that is fully expressed in the phenotype of a heterozygote
• What is a recessive allele?


  A form of a gene that is not expressed when paired with a dominant allele
• What does homozygous mean?


  two of the same alleles
• What does heterozygous mean?

  two different alleles
• what is a genotype?

  collection of alleles that determine characteristics
• What is a phenotype?


  physical appearance
• what is the difference between meiosis and mitosis?

  meiosis- non-identical cells

  mitosis- identical cells
• what is sexual reproduction?

  fusion of gametes
• sexual reproduction in animals


  sperm and egg cells
• sexual reproduction in flowering plants

  pollen and egg cells
• what does the formation of gametes involve?

  meiosis
• What happens in sexual reproduction?


  mixing together of genetic information which leads to the variety in offspring
• What does asexual reproduction involve?

  only one parent and no fusion of gametes
• Is asexual reproduction mitosis or meiosis?

  mitosis
• what does meiosis do for chromosomes?

  halves the number of chromosomes in gametes
• what does fertilisation do for chromosomes?

  restore full number of chromosomes
• how do cells in reproductive organs divide?

  By meiosis to form gametes