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• Growth


  Increase in the number of cells in an organism, an irreversible increase in size (mass)
• Development


  Increase in complexity, as cells differentiate into tissues and begin to carry out specific functions
• Growth and development are closely linked, as organisms usually 'develop' as they grow
• Phases of growth in an organism

  1. Cell division - increase in number of cells

  2. Cell enlargement - increase in size of cells

  3. Cell differentiation - specialisation of cells into tissues
• Apical meristems


  • Growing regions at the tips of roots and shoots where cells divide, enlarge, and differentiate into tissues
• Main groups of plant hormones

  • Auxins
  • Gibberellins
  • Cytokinins
  • Abscisic acid
  • Ethene (ethylene)
• Auxin


  Produced by cells in the tip of a shoot, promotes primary growth by increasing cell elongation
• Plant growth substances (hormones) interact differently in different plant species
• Measuring plant growth


  1. Measuring changes in length/height

  2. Measuring changes in mass (fresh and dry)

  3. Measuring leaf surface area

  4. Counting number of leaves
• Ideally, plants used to measure growth should be of the same genotype and grown in the same environmental conditions
• Exocrine gland


  Gland that transports secretions through ducts to other parts of the body
• Endocrine gland


  Gland that secretes hormones directly into the bloodstream
• The pancreas contains both exocrine and endocrine glands
• Main endocrine glands in the human body

  • Thyroid
  • Adrenal
  • Hypothalamus
  • Pituitary
  • Pancreas
  • Ovary
  • Testis
• Hormones help control and coordinate many body activities, including growth and development
• Pancreas


  Structure made up of both exocrine and endocrine glands
• Pancreas function


  1. Some cells make enzymes

  2. Some cells make insulin

  3. Insulin diffuses into blood vessels passing through pancreas
• Blood with no hormone (insulin) flows to pancreas


  Enzymes pass through a duct
• Insulin in the bloodstream

  Blood rich in insulin leaves the pancreas
• Hormones


  Produced by the endocrine system, help control and coordinate many body activities including growth and development
• Endocrine glands in the human body

  • Thyroid (thyroxin)
  • Adrenal (adrenalin)
  • Hypothalamus (manager)
  • Pituitary (master gland)
  • Pancreas (insulin)
  • Ovary (progesterone, oestrogen)
  • Testis (testosterone)
• Pituitary


  Master gland of the endocrine system
• Hypothalamus


  Regulates the secretion of some pituitary gland hormones, can be thought of as the manager
• Hormones


  Produced in very small amounts, travel through the body in the bloodstream to target organs, influence the activities of these target organs
• Hormones produced by the pituitary

  • Pituitary growth hormone
  • Antidiuretic hormone (ADH)
  • Follicle stimulating hormone (FSH)
  • Luteinising hormone (LH)
  • Thyroid stimulating hormone (TSH)
• Pituitary growth hormone


  Stimulates growth of the entire body, too much causes gigantism, too little causes dwarfism
• Antidiuretic hormone (ADH)


  Stimulates the kidneys to reabsorb more water from filtrate when the blood plasma becomes too concentrated
• Thyroid gland


  Produces hormone thyroxin, regulates basal metabolic rate and growth and development
• Thyroxin and growth hormone


  Stimulate growth by increasing the rate of protein synthesis
• Iodine deficiency


  Results in stunted growth and mental retardation
• Hyperthyroidism


  Overactivity of the thyroid gland, results in increased metabolic loss of body mass, can lead to goitre
• Hypothyroidism


  Underactivity of the thyroid gland, can cause cretinism in children (retarded physical, mental and sexual development)
• Testosterone


  Hormone produced by testes, influences sexual development and secondary sexual characteristics
• Insulin


  Hormone produced by the pancreas, helps regulate blood glucose level
• Insulin function


  1. Increases rate of conversion of glucose to glycogen in liver and muscle

  2. Increases rate of uptake of glucose by cells
• Insulin deficiency


  Leads to diabetes, no control of blood glucose level
• Diabetes


  Disease caused by insulin deficiency, results in high blood glucose, glucose in urine, breakdown of muscle tissue, weight loss, tiredness
• Adrenalin


  Hormone produced by the adrenal glands, prepares the body for 'fight or flight' in life-threatening situations
• Effects of adrenalin


  • Pupils dilate
  • Increased mental awareness
  • Hairs stand on end
  • Glycogen converted to glucose in liver
  • Bronchioles relax allowing more air flow
  • Heartbeat rate increases
  • Digestion inhibited
• Adrenalin surge cannot be sustained for long, can be dangerous for those with weak heart or high blood pressure