Biology By2 Revision

Parasitic Nutrition 21 May 2011 10:43 = organisms that live on or in another organism obtaining nourishment at the expense of the host and causing harm.
Gut parasite (Taenia solium) = tapeworm Primary host = human (eat uncooked infected pork) Secondary host = pig (drainage channels contaminated by human faeces) Adaptations… – Suckers & hookers (attachment) – Body covering (immune responses) – Thick cuticle (inhibitory substances = enzymes) – Simple body systems (reproduction) – Very thin & large surface area (food absorbed over whole body surface = diffusion) – Male & female sex organs (gut can only accommodate 1 tapeworm) – Number of eggs produced (increase chance of survival) – Eggs have resistant shells (survive until eaten) Dormant embryos can form cysts in organs – damage surrounding tissue BY2 revision Page 1 Adaptions to different diets 21 May 2011 10:53 Reptiles & Amphibians = swallow food whole Mammals = cut up and chew (palate separates nasal cavity & mouth – kept in mouth longer) Carnivore = short gut (easily digest protein) Herbivore = long gut (plant digestion difficult)
Dentition Mechanical digestion = easier to swallow & increases surface area for enzyme action Herbivore Incisors Canines Lower jaw, cuts against horny pad (upper jaw) Indistinguishable from incisors Carnivore Sharp (tear flesh from bone) Large, curved, pointed = seizing prey, killing & tearing flesh Carnassial (slide past each other = garden shears) molars = cutting/crushing) Vertical (open wide to capture & kill prey) Not horizontal (dislocation) Jaw muscles = well developed/powerful (grip firmly on prey/crush bones) Cheek teeth Interlock. (W into M) Worn down = sharp enamel ridges (efficiency). Open roots (grinding) Jaw movement Other Circular grinding.

Horizontal plane Diastema = gap between front & side teeth. Tongue moves cut grass to grinding surfaces (cheek teeth) Ruminants Produce most protein eaten by humans eg. Cows/sheep Mutualism/Symbiosis = close association between members of 2 species, both derive some benefit from the relationship. – Can’t digest cellulose (no cellulose enzymes) – Cellulose-digesting bacteria live in gut of cow – Separated = food left long enough for digestion, bacteria isolated (optimum pH & conditions) Cellulose digestion… – Grass chopped (teeth), saliva, cud formed, swallowed – 1st stomach = cellulose digesting bacteria (glucose = fermented – organic acids into blood.
Waste = co2 & methane – Cud into next region, regurgitated & chewed again – 3rd stomach = water absorption – 4th stomach (‘normal’ stomach) = protein digestion – Small intestine = absorption Rumen = greater variety of mutualistic organisms than in caecum More efficient = more complete breakdown of cellulose Bacteria = source of protein when dead BY2 revision Page 2 Digestion 21 May 2011 11:35 = the break down of large insoluble molecules into smaller soluble molecules. Physical & chemical. Food passes through alimentary canal where it is digested & absorbed into the body. Digestive enzymes = hydrolases (catalyse hydrolysis of substrate – addition of water) – Carbohydrates (polysaccharides) > disaccharides > monosaccharides (Amylase = maltose >glucose) – Proteins >polypeptides >dipeptides >amino-acids (peptidase = endo/exo) – Fats > fatty acids & glycerol (lipase) Mouth (buccal cavity) – Mechanical digestion (teeth) – Saliva = salivary lands (mucus, salivary amylase & mineral ions = optimum pH – slightly alkaline) = lubrication & some protein digestion (amylase = starch > maltose) – Swallowed as bolus Oesophagus – Peristaltic contractions (longitudinal & circular muscles = not under conscious control) – Occurs all way through alimentary canal Stomach = muscular sac (2 sphincter muscles = cardiac & pyloric keep food in stomach) – Muscles in stomach wall contract rhythmically (mix food with gastric juice = secreted by stomach wall) – Gastric juice = optimum pH of enzymes (pH2. 0), kills most bacteria, peptidase enzymes = protein > polypeptides Pepsinogen (inactive) = activated by HCl to active peptidase enzyme – Mucus = form lining (protect wall from enzymes & acid/assist movement) – Food leaves as chyme – Purpose of HCl = optimum pH for enzymes, kill microbes, activate pepsinogen (pepsin) Gastric glands = peptic/chief cells (pepsinogen = inactive until HCl), oxyntic (secretes HCl) & goblet cells (mucus) Small Intestine = duodenum (first 20cm) & ileum Bile = produced in liver, stored in gall bladder, into duodenum via bile duct. = no enzymes.
Bile salts = emulsifying lipids (lowers surface tension = globules – droplets [surface area]) = neutralise acidity = exocrine glands in Pancreas via Pancreatic duct. = Contains enzymes. Trypsinogen – Trypsin (Enterokinase) = Endopeptidases (protein > peptides) Pancreatic Amylase (starch > maltose) Pancreatic Lipase (lipids >fatty acids & glycerol) Pancreatic juice Walls of duodenum = Brunner’s Glands (secrete alkaline juice & mucus) – correct pH & lubrication/protection Enzymes secreted by cells at tips of villi (Crypts of Lieberkuhn) Maltase = Maltose > 2 Glucose Sucrase = sucrose > glucose & galactose Endopeptidases/Exopeptidases = polypeptides > amino acids Endo = quaternary/tertiary – smaller polypeptides. Exo = peptides – amino acids Absorption Ileum adapted… – Long BY2 revision Page 3 –
Long Lining folded = large surface area Villi = finger like projections Epithelial cells = surface of villi (microscopic projections – microvilli) Large number of mitochondria = lots of energy required Glucose & Amino-acids = epithelium of villi (diffusion & active transport) into capillary network – hepatic portal vein to liver Fatty acids & Glycerol = lacteal (blindly ending lymph capillary) – lymphatic system into bloodstream (thoracic duct) Fatty acids, Glycerol & most vitamins = diffusion through epithelial cell membrane Glucose, Amino acids & dipeptides = need ATP (energy) – co-transport (Na+ ion) Dipeptides digested intracellularly-pump ions out and then draws more in – carries molecules in with it.
Large intestine – Caecum, Appendix, Colon & Rectum – Water & mineral salts absorbed in colon – vitamins secreted by micro-organisms (vitamin K & folic acid (Vitamin B9) – Faeces = semi-solid condition (undigested cellulose, bacteria, sloughed cells) – defaecation Uses… Soluble food products – bloodstream – tissues (assimilation/provide energy) – Glucose = energy release (respiration)/excess stored (fat cells) – Amino Acids = protein-synthesis. Cannot be stored (deaminated – urea {disposed} & carbs {stored}) – Lipids = membranes/hormones/excess stored as fat BY2 revision Page 4 Structure of the gut 24 May 2011 08:52 Peristalsis = aids movement of food through alimentary canal 1) 2) 3) 4) Ingestion Digestion (mechanical = increase surface area/chemical = enzymes, glands in wall/outside wall) Absorption Egestion
Structure of Mammalian Gut – Outer serosa = layer of connective tissue (protection/reduces friction from other organs as it moves) – Muscle layer = inner circular/outer longitudinal muscles = peristalsis – Sub-mucosa = connective tissue, contains blood/lymph vessels – absorption & nerves (co-ordinate muscular contractions – peristalsis) – Mucosa = innermost layer (lines wall of gut), secretes mucus (lubrication & protection), secretes digestive juices in some regions (stomach)/absorbs food (ileum) – Lumen = cavity of gut BY2 revision Page 5 Glands 1) Large glands outside gut – secretions pass through tubes/ducts into lumen Eg. Salivary gland, liver, pancreas 2) Glands in form of cells in sub-mucosa Eg.
Secrete mucus in duodenum (Brunner’s glands – alkaline juices also) 3) Glands in form of cells in mucosa Eg. Gastric glands(stomach) = gastric juice Crypts of lieberkuhn(in base of villus of small intestine) = enzymes (complete digestion) – maltase = maltose – Sucrase = sucrose – Endopeptidase/exopeptidase = peptides/dipeptides BY2 revision Page 6 Adaptions for nutrition 24 May 2011 09:37 Nutrition = obtain energy to maintain life functions and matter to create/maintain structure (from nutrients) Autotrophic plants Use simple organic materials CO2 & H2O to manufacture energy & make complex compounds (make own food) – provide food for others = producers Green plants build up complex organic molecules eg sugars from CO2 & H2O.
Source of energy = sunlight (absorbed in chlorophyll & related pigments) [6CO2 +6H2O > C6H12O6 + 6O2] Use energy from special methods of respiration to synthesize organic food Consume complex organic food material (cannot make own food) = consumers. Take food into bodies and break down by digestion. Usually internal in digestive system. Digested material – absorbed (body tissues – used by cells) Herbivores/Carnivores/Detritivores Dead/decaying matter – no specialized digestive system. Secrete enzymes outside body & absorb. (extracellular digestion). Microscopic = decomposers (important recycling valuable nutrients – nitrogen) – Photosynthesis
Plants/algae/ certain bacteria Autotrophic bacteria Animals, fungi, some protoctists & bacteria Most animals – Chemosynthesis Heterotrophic – Holozoic feeders – Saprophytes (saprobionts) – Parasites – Mutualism (symbiosis) Fungi & some bacteria Tapeworm Organism that live in/on another organism and receive nutrition from it. Host suffers harm. Highly specialized. Cellulose Involves close association between members of2 different species. digesting bacteria Both derive some benefit from the relationship BY2 revision Page 7 Reproductive Strategies 24 May 2011 10:08 Life cycle = sequence of changes through which it passes during its life from origin in reproduction until death. Reproduction = ability to produce other individuals of the same species
Asexual – Rapidly produces large numbers (identical genetic composition = clone) – Binary fission (eg. Unicellular organisms – bacteria/amoeba) – Budding (eg. Hydra/yeast) – Bulbs (eg. Onion/daffodil) – Runners (eg. Strawberry) – Tubers (eg. Potato) Sexual – Involves 2 parents – Less rapid than asexual – Offspring are genetically different – Fusion of haploid gametes Advantages/Disadvantages… Asexual = lack of variety (adapting to environmental change) = if well suited to environment conditions, large numbers of successful type built up quickly Sexual = genetic variety (adapt to environmental change) = development of resistant stage in life cycle (can withstand adverse conditions) = formation of spores, seeds, larvae = dispersal of offspring.
Reduces intraspecific competition – enables genetic variety to develop as required. = more chance of mutation (complexity of process) Production of Gametes Diploid = body cells (mitosis) Haploid = sex cells/gametes (meiosis) Haploid Sperm + Haploid Egg = Diploid Fertilized Egg Zygote formed – mitosis to grow Male gamete = small& extremely motile Female gamete = large/sedentary (presence of stored food) Mammalian eggs have only enough to survive until formation of placenta External Fertilization – Discharge gametes directly into sea/freshwater – Considerable wastage = eggs may not encounter sperm – Vast numbers of gametes produced – Frogs – joining of sperm/egg assisted by coupling.
Male rubs hind legs on female for her to lay eggs, he immediately releases seminal fluid over them. – Amphibians usually terrestrial, must return to water to breed = external fertilization Internal Fertilization – Occurs inside body of female – Requires intermittent organ to introduce sperm to female’s body – Less chance of gametes being wasted BY2 revision Page 8 – Less chance of gametes being wasted Allows male gamete to be independent of water for movement Fertilized egg can be enclosed with protective covering before leaving female. (Animals lay eggs) Embryos develop within parent and derive nourishment from her (placenta) = greatest adaption (mammals)
Development of Zygote – Usually outside body – easy prey for predators – Many eggs produced to ensure some survive – Insects, internal fertilization (ensure sperm deposited in female’s reproductive tract), external development (laid on food source) – Evolution of amniote egg (reptiles/birds) = fluid filled cavity, surrounded by membrane & protective shell, encloses embryo within yolk sac – Birds incubate eggs = embryo development (external) – Mammals = young retained in mother’s womb/uterus (no shell). Embryo nourished from mother’s blood supply (placenta). Born in relatively advanced state of development. Parental Care – Very little usually – Stickleback looks after eggs, defends territory, fans eggs to provide o2 until they hatch – Birds & mammals = provision of shelter, feeding, protection from predators, training for adult life. More parental care provided = fewer offspring produced Unisexual/Hermaphrodite – Plants = male and female gametes produced in one individual – Every individual capable of forming fertilized eggs – Possibility of self-fertilization = inbreeding (reduced genetic variability) – No intromittent organs – special techniques evolved for transferring gametes Success of Insects – Mainly terrestrial – Depend on these to pollinate crops – Competition for food also – Carry disease eg. Malaria Incomplete Metamorphosis (eg. Grasshopper) – Egg – Intermediate form = nymph (resembles adult – smaller) – Hard exoskeleton – doesn’t grow, must shed skin/molt – Does this a series of times until it reaches full size Complete metamorphosis (eg.
Butterfly/housefly) – Egg – Lava (specialized for feeding/growing) – Pupa/chrysalis – complete change – Emerges as adult specialized for dispersal and reproduction Plants Simple plants = algae (seaweeds = confined to sea) & mosses & ferns (confined to damp areas -male gamete can swim to egg) Successful plants = conifers & flowering plants (independent of water for reproduction – able to colonize land) Flowering plants = morphology (Efficient water carrying xylem vessels & reproduction) – Male pollen grains with hard coat = withstand desiccation (transfer to stigma of female – affect by environmental conditions) – Plants & grasses = small inconspicuous flowers – pollen carried by wind – Brightly coloured flowers & scent = attraction by insects (carry pollen to stigma) BY2 revision Page 9 –
Brightly coloured flowers & scent = attraction by insects (carry pollen to stigma) Male gametes travel through pollen tube to female part and egg (no longer needs film of water to reach egg) Fertilised egg develops into seed containing food store (with resistant coat) Key to success = relationship with animals (attract insects which pollinate/seed dispersal) & enclosure of eggs in ovary and evolution of seed – Can survive adverse conditions Flowering plants are so successful because of… – Short interval between flower production and setting of seed (few weeks) – Seed with food store = embryo develops until leaves are produced above ground (photosynthesis) – Seed protects embryo from desiccation & other hazards = resistant coat – Leaves deciduous & succulent = decay when fall to ground – humus produced. (rapid recycling of ions for reuse) BY2 revision Page 10 Translocation 24 May 2011 14:41 = transport of soluble organic materials, sucrose and amino acids (bi-directional movement) Products of photosynthesis = phloem.
From source (area that makes the photosynthate – sucrose = leaves) to sink (where needed for growth/storage) Phloem structure – Sieve tubes (adapted for longitudinal flow of material = no nucleus ,have pores =sieve plates allows rapid flow of manufactured food substances) – Companion cells (linked to sieve tubes by plasmodesmata with fibres & parenchyma, dense cytoplasm = lots of mitochondria – lots of metabolic activity, large nucleus – controls activity) – Phloem fibres – Phloem parenchyma “Mass flow” hypothesis – There is a passive flow of sucrose from source to sink – Does not account for observations such as movement in opposite directions at same time & rate – Other hypotheses = diffusion, cytoplasmic streaming Evidence for translocation… 1) Aphid (greenfly) – Feed (proboscis), leave embedded proboscis, liquid = sucrose & amino acids. Sectioning stem shows proboscis is in phloem sieve tube 2) Ringing Experiments – Cut off ring of bark (including phloem, leave xylem), immerse in water. Swelling above cut = accumulation of organic solutes, cannot continue. Will eventually die 3) Radioactive isotopes – Carbon-14 supplied to plant – fixed in glucose upon photosynthesis (14C6H12O6) – Stem cut, x-ray = phloem contains radioactivity BY2 revision Page 11

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