Bio- unit 2

• Diploid

  2 sets of chromosomes
• Haploid

  One set of chromosomes
• Why do cells divide

  Growth repair replacement of damaged tissues
• Mitosis

  Process when a cell divides
• Chromosome

  Structure of DNA
• Stem cells are needed for

  Growth repair
• stem cells can

  Self renew become specialised
• Multicellular

  More than one cell
• Uncontrolled mitosis

  Cancerous tumours
• Body order 


  Cell tissue organ system organism
• Central nervous system 


  Brain spinal cord
• Cerebrum 


  Memory and muscle movement
• Cerebellum 


  Balance and coordination
• Medulla 


  Breathing and heart rate
• Nerves are made of

  Neurons
• Neurons carry signals by

  Electrical impulses
• Sensory neuron

  Pass information from a receptor to the CNS
• Inter neuron 


  Allow information from the senses to be processed
• Electrical impulses are unable to pass

  Synapses
• Signals are transferred across synapses by

  Chemicals
• Receptors 


  Cells that detect a stimulus. Ears eyes
• Effectors 


  Enable a response to occur . Muscles glands
• Pathway of an impulse

  Receptor sensory inter motor effector
• Reflex arcs 


  Special type of pathway that avoids going to the brain so the response is quicker
• Reflex arcs are needed to

  Protect the body from injury
• Endocrine system 


  Produces hormones
• Target tissue have 


  Complementary receptor proteins
• Insulin 


  Lowers blood sugar . TT - liver . Converts glucose to glycogen
• Glucagon 


  Increases blood sugar . TT - liver . Glycogen converts to glucose
• Insulin and glucagon 


  Made in the pancreas
• variation 


  Differences within a population
• Discrete variation 


  Single gene inheritance. Distinct groups
• Continuous variation 


  Polygenic inheritance. Range of values
• Homozygous 


  Both alleles are the same
• Hetrozygous 


  Alleles are diffrent
• Gene 


  Short Strand of dna
• Allele 


  Diffrent versions of the same gene
• Phenotype 


  Physical description
• Genotype 


  Allele description
• Dominant 


  Determine a phenotype