BIOLOGY FINALS (expt sa nutrition sa plants

• Stimulus


  External and internal changes in the environment that causes response
• In plants, stimulus causes a sensitive cell to produce a particular hormone, which travels relatively slow through the phloem to reach responsive tissues
• Factors that plants may respond to

  • Light
  • Gravity
  • Mechanical stimuli
  • Water
  • Temperature
• Plants responses are simpler and slower compared to those of animals because they do not have specialized receptors like those found in animals
• There are many plant responses brought about by the different stimuli in the surroundings
• Photomorphogenesis


  Non-directional development responses of plants to light that can result in changes in form or flowering
• Phototropism


  Directional plant growth response to light
• Auxin


  A chemical signal that causes plants to elongate and grow cells faster on the side of the plant farthest from the light
• Phytochrome


  A pigment containing protein that exists in two interconvertible forms: Pr (Phytochrome red) and Pfr (Phytochrome far red)
• The two forms of phytochrome are essential in plant life cycle, playing a role in development and flowering of plants
• Seed germination


  Inhibited by far red (Pfr) light and stimulated by red (pr) light
• Shoot elongation


  Etiolation is explained by the absence of red light, plants only become normal once exposed to red light which increases the amount of pFr
• Plant spacing


  Both red light and far red light are involved, when plants are closer there is more far red light which causes plants to grow taller
• Phototropism


  A directional response of the light, including the bending of young stems and other plant parts toward the source of light, particularly the blue wavelength
• Gravitropism


  The response of plants to gravitational force, where the shoot shows negative gravitropic response and the root shows positive gravitropic response
• Amyloplasts


  Plastic that contains starch, may be involved in sensing gravity in plants
• Thigmotropism


  Directional growth response of a plant or a plant part in response to contact with an object
• Thigmonasty


  Response of Mimosa pudica (Makahiya) to touch, where changes in turgor pressure at the base of each pulvinus cell cause the leaflets to close or fold
• Seed dormancy is an adaptive measure in plants when environmental conditions are not favorable, allowing them to survive for a long period of time
• Abscission is the process by which leaves shed, helping plants conserve water and energy
• Vitamins


  Organic compounds that function as co-enzymes and co-factors of enzymes, divided into water-soluble and fat-soluble
• Minerals


  Inorganic molecules that provide ions essential for the functioning of many enzymes or proteins
• Intracellular digestion


  Digestion that takes place within the cells in simpler organisms like sponges
• In earthworms, the digestive tube is complete with a mouth, pharynx, crop, gizzard, intestine, and anus
• In simpler organisms, the products of cellular digestion pass through the epithelial lining of the gut into the blood, where they are distributed to all parts of the body
• The vertebrate digestive system includes highly specialized parts adapted to the type of food they eat
• Human digestive system


  1. Food is ingested through the mouth, chewed and ground into smaller sizes, mixed with saliva, and pushed backward by the tongue

  2. Food then swallowed and moved to the pharynx

  3. Epiglottis closes the opening to the lungs

  4. Food enters the esophagus and passes down by peristalsis

  5. Enters the stomach through the cardiac sphincter

  6. Food enters the duodenum from the stomach through the pyloric sphincter

  7. Enzymes from the pancreas assist in breakdown of carbohydrates, proteins, and fats

  8. Undigested food channeled into the large intestine where water and ions are reabsorbed

  9. Defecation reflex involves relaxation of internal and external sphincters
• Enzymes


  Organic catalysts that hasten chemical reactions, playing a big role in breaking down food substances into forms the body can absorb, process, and utilize
• Enzymes in the digestive system

  • Salivary amylase
  • Lingual lipase
  • Pepsinogen
  • Trypsinogen
  • Chymotrypsinogen
  • Pancreatic lipase
  • Nucleases
  • Pancreatic amylase
  • Sucrase
  • Lactase
  • Maltase
• Liver


  Largest gland in the body, contains hepatocytes, circulates blood through the portal vein and hepatic vein, neutralizes and eliminates toxic substances, stores vitamins/iron/glucose, synthesizes proteins, converts ammonia to urea
• Bile


  Fluid produced by the liver that contains cholesterol, bile acids, and bilirubin to aid in lipid digestion, stored and concentrated in the gallbladder
• Pathway of bile

  Canaliculi from liver merge to form bile ducts, drain into right and left hepatic ducts, merge to form common hepatic duct, joined by cystic duct from gallbladder to form common bile duct, merges with pancreatic duct to form ampulla of vater which drains into the duodenum
• Pancreas


  Both an endocrine gland (secretes insulin and glucagon) and an exocrine gland (secretes digestive enzymes)
• Asexual reproduction involves only a single parent and no sex cells, examples include budding, fragmentation, and binary fission
• Sexual reproduction involves two parents and the production of gametes (egg and sperm) through meiosis
• Hermaphrodite


  An organism that has both male and female reproductive organs
• Female reproductive system

  Produces eggs, secretes sex hormones, provides site for fertilization, gestates fetus, gives birth, and breastfeeds
• Male reproductive system


  Produces androgens like testosterone, promotes spermatogenesis, transports sperm into female reproductive system
• Thank you for listening, good luck and congratulations in advance!
• Unlike animals, plants can produce their own food