Multicellular organisms

• Decrease in blood glucose levels

  1. Change detected in pancreas
  2. Pancreas releases glucagon into blood
  3. liver breaksdown glycogen into glucose
  4. increase in blood glucose
• increase in blood glucose levels

  1. change detected by pancreas
  2. pancreas releases insulin
  3. liver stores glucose as glycogen
  4. decrease in blood glucose
• stages of mitosis

  1. Each chromosome makes a identical copy of itself
  2. chromatid pairs line up at the equator of the cell
  3. spiral fibres pull apart the chromatids to each pole
  4. a nuclear membrane forms around each set of chromosomes
  5. the cytoplasm divides and 2 seperate (daughter) cells are formed
• purpose of mitosis

  • Growth
  • repair of damaged cells
  • maintains diploid chromosome complement
• 2 types of stem cell

  1. embronic - obtained at an early stage
  2. tissue - found throughout life
• what are stem cells involved in

  • growth
  • repair of damaged tissue
• features of stem cells

  • unspecialised
  • divide in order to self renew
• hierarchy 


  cells - tissues - organs - systems
• Stages of reflex arc

  1. Receptor detects sensory inputs/ stimuli
  2. sensory neuron passes information to the CNS
  3. inter neuron operates within the CNS, which processes info from the senses
  4. motor neuron enables a response to occur at an effector ( muscle/gland)
• electrical impulses carry messages along neurons
• synapse 


  gap between neurons
• reflexes protect the body from harm
• Endocrine gland releases hormones into the blood stream
• hormones are chemical messengers
• • A target tissue has cells with complementary receptor proteins for specific hormones, so only that tissue will be affected by these hormones.
• Cerebrum

  • controls conscious thought and memory
• cerebellum - controls balance and coordination
• medulla - controls heart and breathing rate
• Structure of brain

  
• cells are all diploid accept gametes, which are haploid
• in animals the male gamete, is the sperm cell, which is produced in the testes
• in animals, the female sex cell is called an egg, which is produced in the ovaries
• in plants, the male sex cell is called the anther, which is produced in the stamen
• in plants, the female sex cell (gamete) is called the ovule, which is produced in the ovary
• in animals, when the 2 sex cells fuse, the cell is now diploid and is called a zygote
• the zygote divides to form a embryo
• Single gene inheritance of characteristics showing discrete variation where measurements fall into distinct groups.
• • Polygenic inheritance of characteristics showing continuous variation where there is a range of values between a minimum and a maximum.
• gene


  section of dna which codes for protein
• allele


  different forms of the same gene
• phenotype


  physical description of the characteristic
• genotype 


  letters use to represent the characteristic
• homozygous 


  2 alleles are identical eg. BB
• heterozygous 


  2 alleles are different eg. Bb
• punnet square

  
• xylem features

  • dead cells
  • transports water (1 way)
  • contains lignin
• phloem features

  • living cells
  • transport glucose ( 2 way)
  • contain sieve plates
• stages of transpiration

  1. water enters through roots hairs (osmosis)
  2. water enters xylem in root
  3. water is drawn up xylem in the stem
  4. water moves along xylem into leaf
  5. water evaporates into air spaces in spongy mesophyll
  6. water vapour escapes through stomata.
• • In mammals the blood contains plasma, red blood cells and white blood cells.
• features of red blood cells

  • bioconcave shape (maximises surface area)
  • no nucleus (increases space for haemoglobin)
  • contains haemoglobin (helps to transport oxygen)