11 Animal physiology AHL

Topic 11: Animal physiology

This page lists the understandings and skills expected for topic eleven. Helpful for revision.
Detailed revision notes, activities and questions can be found on each of the sub-topic pages.

  • 11.1 Antibody production and vaccination
  • 11.2 Movement
  • 11.3 The kidney and osmoregulation
  • 11.4 Sexual reproduction

11.1 Antibody production and vaccination

Cells & pathogens

  • The surface of cells of an organism has unique molecules.
  • Pathogens can be species-specific or can cross species barriers.

Antibody production involves the following:

  • B lymphocytes are activated by T lymphocytes in mammals.
  • Activated B lymphocytes multiply to form clones of plasma cells and memory cells (giving immunity).
  • Plasma cells secrete antibodies which aid the destruction of pathogens.
  • Other white blood cells release histamine in response to allergens which causes allergic symptoms.

Vaccination and monoclonal antibodies

  • Vaccines contain antigens that trigger an immune response without causing the disease.
  • Fusion of a tumour cell with an antibody-producing plasma cell creates a hybridoma cell.
  • Monoclonal antibodies are produced by hybridoma cells
  • Monoclonal antibodies to HCG are used in pregnancy test kits.

Skills & applications

  • Smallpox was the first infectious disease of humans to have been eradicated by vaccination.
  • Human vaccines are often produced using the immune responses of other animals
  • Blood group antigens on the surface of red blood cells stimulate antibody production in a different blood group.
  • Skills to analyse epidemiological data related to vaccination programmes.

11.2 Movement

Skeletons and muscles

  • Bones and exoskeletons (e.g. insect legs) provide anchorage for muscles and act as levers.
  • Synovial joints allow certain movements but not others.
  • Muscles work in antagonistic pairs.

Muscle contraction

  • Skeletal muscle fibres are multinucleate and contain
    • specialised endoplasmic reticulum
    • many myofibrils
    • made up of contractile sarcomeres.
  • The sliding of actin and myosin filaments causes contraction.
  • Contraction requires ATP hydrolysis and cross bridge formation
  • Calcium ions and the proteins tropomyosin and troponin control muscle contractions.

Skills & applications

  • Know how to annotate a diagram of the human elbow. Include cartilage, synovial fluid, joint capsule, named bones and named antagonistic muscles.
  • The ability to draw labelled diagrams of the structure of a sarcomere, including Z lines, actin filaments, myosin filaments with heads, and the resultant light and dark bands.
  • The ability to find the state of contraction of muscle fibres in electron micrographs,
  • Experience of measurement of the length of sarcomeres using calibration of the eyepiece scale of the microscope

11.3 The Kidney and osmoregulation

Control of water balances in different animals

  • Some animals are osmoconformers - their cells have solute concentration equal to their environment (eg. marine invertebrates)
  • Vertebrates and insects are osmoregulators. (so are some single cells, eg.Amoeba)
  • Insects have malpighian tubules but vertebrates have kidneys to carry out osmoregulation and remove nitrogenous wastes.
  • The type of nitrogenous waste in animals is correlated with evolutionary history and habitat.

Kidney structure & function

  • The differences in composition of blood in the renal artery & the renal vein.
  • Ultrafiltration helped by the ultrastructure of the glomerulus and Bowman’s capsule.
  • Selective reabsorption of useful substances by active transport in the proximal convoluted tubule.
  • The loop of Henle maintains hypertonic conditions in the medulla.
  • ADH controls reabsorption of water in the collecting duct.
  • The length of the loop of Henle is positively correlated with the need for water conservation in animals.

Skills & applications

  • To be able to draw and label a diagram of the human kidney.
  • To be able to annotate diagrams of the nephron. Including glomerulus, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule; and the collecting duct
  • To have considered the consequences of dehydration and overhydration.
  • To know about treatment of kidney failure by hemodialysis or kidney transplant.
  • To know about urinary test for Blood cells, glucose, proteins and drugs.

11.4 Sexual Reproduction


  • Similarities in spermatogenesis and oogenesis include mitosis, cell growth, two divisions of meiosis and differentiation.
  • Students need to be able to annotate diagrams of seminiferous tubule and ovary to showing these details.
  • Differences between the processes in spermatogenesis and oogenesis are the different numbers of gametes produced and the different amounts of cytoplasm in these gametes.
  • Annotation of diagrams of mature sperm and egg to indicate functions.


  • Fertilization in animals can be internal or external.
  • Fertilization involves the acrosome reaction, fusion of the plasma membrane of the egg and sperm and the cortical reaction. (mechanisms that prevent polyspermy)

Early growth of the embryo

  • Implantation of the blastocyst in the endometrium is essential for the continuation of pregnancy.
  • HCG stimulates the ovary to secrete progesterone during early pregnancy.
  • The placenta facilitates the exchange of materials between the mother and fetus.
  • Estrogen and progesterone are secreted by the placenta once it has formed.
  • Birth is mediated by positive feedback involving estrogen and oxytocin.

Skills & applications

  • To make comparisons of gestation periods and animal size & to find the place of the average human (38-week) pregnancy on a graph showing the correlation between animal size and the development of the young at birth in mammals.
  • To annotate diagrams of stages of gametogenesis in seminiferous tubule and an ovary.
  • Ability to annotate diagrams with the function of the parts of mature sperm and egg.

  • Antibody production & vaccination 11.1 HL

    This topic covers the role of antigens in challenging the immune system leading to antibody production. There are many details required including knowledge of B lymphocytes, T lymphocytes, memory cells and plasma cells. Vaccination as a method of promoting