Biology 24

• Active transport

  Energy required, energy used to move molecules from low concentration to high concentration against concentration gradient
• Excretion

  Removal from the body (elimination) of waste products of metabolism. Metabolic waste removed during excretion.
• Why excretion is important

  Buildup of poisons would lead to death
• Organ

  A group of tissues working together. Excretory organ in plants = leaf
• Ectotherm


  An organism that can regulate their body temperature with environmental temperature. Gain/lose heat from external environment
• Endotherm


  Humans are capable of regulating their internal body temperature from metabolic reactions
• Homeostasis


  Process by which organism maintain a constant internal environment. Important as it allows normal metabolic activities
• Egestion


  Removal of undigested material
• Piloerection


  Hair stands up, how it keeps human body warm = air is trapped, air insulates
• Vasoconstriction


  Blood vessels narrow, how it keeps human body warm = reducing heat loss, less blood to skin
• Excretion of gaseous waste in plants takes place through stomatal pores on leaves. Excretory organ in plants = stem, leaf
• Method of excretion in flowering plants

  1. Diffusion

  2. Transpiration
• Excretory products

  • Urea derived from protein
  • CO2 derived from carbohydrate
• Role of excretory system in homeostasis

  The excretory system maintains homeostasis through the elimination of excess water and wastes from the body and regulating body temperature
• Types of temperature regulation in animals

  • Ectotherm (e.g. fish, snakes)
  • Endotherm (e.g. dogs, cats)
• Main excretory organs


  • Lungs (water and carbon dioxide)
  • Skin (water and salts)
  • Kidneys (main excretory organ - water, salts, and urea)
• Skin's role in temperature regulation

  Production of sweat by sweat glands
• Skin is produced from the germ layer ectoderm
• Functions of the skin

  • Protection of body from damage
  • Vitamin D production, fat storage
  • Sense organ - touch and temperature
  • Excretion - sweat glands
• Skin has a role in the nervous and defence systems
• How skin helps retain heat in cold conditions

  1. Piloerection (hair stands up, traps air as insulator)

  2. Vasoconstriction (blood vessels narrow, less blood flow to skin, less heat lost)
• How skin helps reduce temperature in warm conditions

  1. Sweat produced and released onto skin

  2. Blood vessels in skin expand/dilate, increasing heat loss through skin
• Structures in skin involved in temperature regulation

  • Hair
  • Sweat glands
• Kidneys

  Location in body = lower abdomen (abdominal cavity)

  
• Parts of human urinary excretory system

  • 2 kidneys
  • 2 ureters
  • Bladder
  • Urethra
• How kidneys prevent dehydration on warm day

  1. High solute concentration in blood detected by hypothalamus

  2. ADH released by pituitary gland

  3. ADH acts on collecting duct, makes it more permeable to water

  4. More water reabsorbed
• Blood vessel that supplies blood to a kidney

  Renal artery arising from aorta

  
• Kidney is an exocrine gland as it has ducts and does not produce hormones

  
• Urine


  Urea produced in the liver, substances excreted = urea and salt, formed when proteins are deaminated (derived from protein/amino acids)
• Ureter

  Structure through which urine travels to bladder
• Filtration occurs in the cortex (location - Bowman's capsule)
• Location of reabsorption

  Proximal convoluted tubule
• Bladder

  Stores urine, urine excreted through urethra
• Functions of the kidneys


  • Excretion of water, salts and urea
  • Osmoregulation - control water, salt, pH of blood and body fluids
• Nephron

  Carries out function of kidneys, located in cortex and medulla of kidney

  
• Features of nephron that aid filtration

  • Large surface area
  • Porous capillary walls
  • Arterioles in, arterioles out
• Main/vital processes in urine production (nephron)

  • Filtration
  • Reabsorption
  • Secretion

  
• Urine production in a nephron

  1. Filtration (in glomerulus/Bowman's capsule)

  2. Reabsorption (in proximal tubule - substances from tubule into blood by active transport, diffusion, osmosis)

  
• Reasons why blood in glomerular capillaries is under pressure

  Afferent arteriole leads directly from renal artery

  Efferent arteriole is narrower than afferent arteriole
• Reason blood entering glomerulus is under high pressure is that renal artery leads directly from aorta