N5 Biology U2

• Mitosis definition

  The division of the nucleus into two daughter nuclei
• chromosome compliment definition 


  the specific number of chromosomes in a cell
• Mitosis stage 1

  Individual chromosomes coil up and become visible.
• mitosis stage 2

  each chromosome replicates so an exact copy is made
• mitosis stage 3

  chromosomes line up at the equator of the cell
• mitosis stage 4

  spindle fibres contract and the chromatids are pulled to opposite poles of the cell
• mitosis stage 5

  nuclear membrane forms around each group of chromosomes
• mitosis stage 6!

  cytoplasm divides and two new daughter cells are formed
• stem cell definition 


  unspecialised cells which can divide in order to self renew
• name 2 types of stem cells

  embryonic and tissue
• what makes up the nervous system

  brain, spinal cord and nerves
• what makes up the central nervous system

  brain and spinal cord
• sensory neuron function


  carries electrical impulses from the sensory organ to the CNS
• inter neuron function


  process info from the senses that require a response
• motor neuron function 


  carries electrical impulse from the CNS to a muscle of gland and enables a response to occur at an effector
• what detects sensory stimuli

  sensory receptors
• what carries messages along neurons

  electrical impulses
• where do chemicals transfer messages between neurons

  synapses
• what is a reflex action

  a rapid automatic response to a stimulus
• cerebrum function


  controls thinking, reasoning and imagination
• cerebellum function

  controls balance and muscle co-ordination
• medulla function

  controls breathing and heart beat
• what is a hormone

  chemical messenger that travels in the bloodstream
• what produces/releases hormones


  endocrine gland
• what happens when blood glucose increases

  pancreas releases insulin

  insulin travels to the liver

  glucose is converted to glycogen

  Blood glucose decreases to normal levels
• what happens when blood glucose decreases

  pancreas releases more glucagon

  glucagon travels in bloodstream to liver

  glucagon is converted to glucose

  blood glucose increases to normal levels
• male gamete and where is it produced

  sperm, in the testes
• female gamete and where is it produced


  egg, in the ovaries
• fertilisation definition 


  the fusion of the nuclei of the two haploid gametes to produce a diploid zygote, which divides to form an embryo
• plant female gamete and where its produced


  ovules, in the ovary
• plant male gamete and where its produced

  pollen (collected in the stigma), in anthers
• what is variation 


  the differences that exist between individuals
• what is a species 


  a group of organisms that can interbreed to produce fertile offspring
• what is a phenotype 


  physical appearance of an organism resulting from inherited information
• what is discrete variation 


  controlled by single genes and can be divides into a small number of distinct groups
• what is continuous variation


  controlled by polygenic inheritance it shows a gradual between the two extremes within a species like height.
• what is polygenic inheritance 


  means many genes, a polygenic feature is controlled by more than one gene.
• what is an allele

  the different forms of a gene
• what is a genotype


  used to describe the genes of an organism using letters
• why are predicted ratios not always accurate

  fertilisation is a random process involving the element of chance