Category Archives: Functioning Organisms

Homeostasis – Regulation of Blood Glucose Levels

isle of langerhans

The pancreas is an important exocrine and endocrine gland located between the stomach and small intestine. It has two important roles (1) as an exocrine gland it releases digestive enzymes into the duodenum that aid in the break down of food (2) as an endocrine gland it releases insulin and glucagon into the bloodstream.

Insulin is produced in the beta cells of the islets of Langerhans in response to the stimulus of rising blood glucose levels. Insulin travels in the bloodstream and binds with receptor sites on the cell membranes, resulting in a cascade of events dependent on the cell type. In liver cells, for example, glucose in converted to glycogen, fat and carbon dioxide.

Glucagon is produced by alpha cells in the islets of Langerhans in response to the stimulus of falling blood glucose levels. Glucagon travels in the bloodstream and binds to receptor sites on liver cell membranes, resulting in the breakdown of stored glycogen into glucose. This results in an increase in blood glucose levels.

These two hormones act to regulate the body’s blood glucose levels, maintaining an average concentration of 5.0 mmol/Litre (between 3.5 mmol/Litre after several hours without food and 7.0 mmol/Litre soon after a meal). This is a negative feedback loop, as the response results in a change in the stimulus in the opposite direction. A person with diabetes is unable to regulate their own blood glucose levels without external intervention – it may be that their body does not produce enough insulin, as in Type 1 Diabetes mellitus.

Plant adaptations for dry environments.


Terrestrial plants need to maintain their water balance, while still allowing the exchange of gases between the plant cells and the external environment. Gas exchange occurs through stomata, which also allows the escape of water vapour. The image above shows a cross section of a leaf from Marram grass, common on sand dunes, where it is very salty and often dry. You can see how the leaf is rolled, creating an internal micro-climate that is much more humid than the external environment. This reduces water loss and allows stomata to remain open, even in the driest of climates. PIne needles (Pinus) and Casaurina also have cylindrical leaves, an adaptation for dry environments.


The sunken stomata in this image (cross section of a leaf) allows a moist layer of air above the stomata, protecting the leaf from excessive evaporation.


This image shows a cross section of a leaf from a plant adapted to a very arid environment. The stomata are sunken into pits with lots of epidermal hairs, which provide a humid micro-climate, allowing the stomata to remain open, despite very dry external conditions.


Mammalian Digestive System


Image Source – Attribution: By Leysi24 (Own work) [CC BY-SA 3.0  via Wikimedia Commons

Firstly, dismantle the human torso model in the science laboratory and describe what you know about each part of the alimentary canal and associated glands and organs. Draw and label  a detailed diagram, showing each of the organs above. Then complete the “Cut-and-Paste your Guts” activity, identifying each organ from it’s description and pasting each description into your book, in the order that food would pass through, on it’s 12 hour journey through the 7 metres of the digestive system.

Next, match the skulls (noting the teeth structure and position of eye sockets) with the corresponding herbivore, omnivore and carnivore digestive systems. Describe the diet of each organism, explaining your reasoning in terms of teeth structure, size of stomach and length of intestines, any enlarged organs and corresponding diet.

Week 6: The Immune Response

Image Source

If you suffer from allergies, you may be familiar with the image above. This person is having a ‘skin prick’ or ‘scratch’ test, in which a tiny drop of the possible allergen is pricked into the skin and the reaction measured. Allergens can be a wide variety of substances, from pollens and dust mite faeces to eggs, milk and nuts. Up to 40 different substances can be tested at once.

This is the link to our Google Presentation on the Immune System. I have allocated one slide with a topic for each pair of students. You can add another slide if you need to, but just a few brief dot points under the heading will be sufficient.

More sites for revision of Unit 3: Area of Study 2:


Plant hormones


“The growth and development of a plant are influenced by genetic factors, external environmental factors, and chemical hormones inside the plant. Plants respond to many environmental factors such as light, gravity, water, inorganic nutrients, and temperature.” ~ Biology Online ~ Growth and Plant Hormones

How does a seed ‘know’ when to germinate? How does a tree ‘know’ when to start changing leaf colour and drop it’s leaves for winter? How does a plant ‘know’ which direction to grow leaves and roots and where the light is? How does a plant ‘know’ when to produce flowers and what colour they should be? Instead of having a brain, central nervous system and endocrine system that co-ordinate communication, every plant cell can produce hormones (growth substances) that are transported throughout the plant via diffusion from cell to cell and through the xylem and phloem. (How mobile are plant hormones?).

Botanists recognize five major groups of hormones:

  • auxins
  • gibberellins
  • ethylene
  • cytokinins
  • abscisic acids

Although plants usually appear not to move, time-lapse photography shows that plants do, in fact, move and sometimes quite quickly. There are different types of movement, tropisms and nastic movements:

  • phototropism
  • thigmotropism
  • geotropism (or gravitropism)
  • chemotropism
  • thigmonastic movements
  • seasonal responses
  • photoperiodism

Draw up a table with three columns, with each of the key concepts above in the first column, a definition in the second column and an example in the third column. You can get your information from these resources:

Use digital tools to create a labelled image showing the different plant hormones, where they act (leaves, stems, roots, fruits, flowers etc) and what they do. Copy and paste a link to the image in the comment section below.



Image source

To survive, every multicelluar organism needs a way for cells in one part of the organism to ‘know’ what cells in another part of the organism are doing. If you think about the human body as a population, with each cell an individual person, the endocrine and nervous systems

Signalling molecules are chemical compounds that receive and transmit messages around an organism. These can include simple ‘neurotransmitters’ of the nervous system, or larger hormones (protein compounds) of the endocrine system.

  1. What is a neurotransmitters?
  2. What four criteria must be met to be classified as a neurotransmitter?
  3. What are the four steps in neurotransmission?
  4. There are two main types of neurotransmitters – Large peptides and smaller amino acids and amines. Draw up a table showing examples of each and briefly describe how they function. For example, dopamine influences the mood and behaviour.

10: Physiological Adaptations for Survival

koala and gum leaves

Learning Intention: Students will develop an understanding of the terms and definitions used and how physiological adaptations allow organisms to survive in their environment.

Success Criteria: Students will be able to describe a range of physiological adaptations and how those adaptations allow organsims to survive in their environment.

Adaptations to an organism’s environment can usually be identified as structual (physical – how an organism is built), functional (physiological – how an organism works inside) or behavioural (what an organism does). Chapter 10 deals with physiological adaptations. The following is an interesting article created by a student at Davidson College for an Animal Physiology course.

The Australian koala (Phascolarctos cinereus) is a remarkable animal, and is one of only a few animals, that is capable of surviving on a naturally foliar diet of eucalyptus leaves. Over time, the Koala has evolved several physiological adaptations that allow it to cope with this high fibre, low protein diet. Low metabolic rates allow koalas to retain food within their digestive system for a long period of time, maximizing the amount of energy able to be extracted. Cork and Warner conducted interesting studies on the digestion and metabolism of Eucalyptus foliage in koalas. Using radioisotopic markers, they examined the passage of particulate and solute digesta through the alimentary tract of the koala. They found that the solute marker was retained for longer periods of time than the particulate marker. The mean retention times for the solute and particulate markers were 213 hours and 99 hours respectively. These times are longer than those reported in most other mammals (1983). The selective retention of solutes and fine particles maximizes the energy withdrawn, particularly from non cell-wall constituents. More importantly however, the relatively quick passage of larger fibrous particles, or plant cell-wall constituents, is thought to reduce the “gut-filling” effect of the foliar diet. This extends the upper limits of food intake and ultimately increases the availability of nutrients, partially compensating for the constraints of small body size (1983). Passage of the larger fibrous particles is also beneficial because other researchers found that only 25% of the the cell-wall constituents that enter the alimentary tract are able to be digested (Cork et al., 1983). Breakdown of the cell contents is most important in the digestive process.”

Check out the Hawkesdale Biology wiki page for more links and information about the physiological adaptations of organisms that enable them to extend their tolerance limits and therefor their distribution and abundance. One of last year’s students created this set of Chapter 10 Flashcards to assist her to remember the terms and definitions from this chapter of work.

Chapter 7: Sexual and Asexual Reproduction


This week we are starting the topic “Reproduction” by looking at Asexual methods of reproduction. In plants, asexual reproduction is also called vegetative reproduction.  Complete the table titled “Types of Vegetative Reproduction” using your text and activity manual. Plants that are produced by vegetative reproduction are genetically identical to their parent plants, which is a very useful trait for horticulturalists. They may use the following methods:

  • Runners (strawberries, water hyacinth)
  • Cuttings (geraniums, roses)
  • Rhizomes (underground stems, as in ferns, irises, ginger and galangal)
  • Tubers (potatoes)
  • Bulbs (daffodils, tulips, onions)
  • Suckers (underground stems that arise a distance from the parent plant eg. elm trees and blackberries)

Some other organisms also reproduce asexually: (Asexual reproduction in Animals)

  • Binary fission (Paramecium, bacteria)
  • Budding (Hydra)
  • Fragmentation (Planarians)
  • Regeneration (Echinoderms such as seastars)
  • Parthenogenisis (some lizards, aphids)

This is a useful Powerpoint presentation to learn about the methods of asexual reproduction:

Chapter 6: Distribution of Materials

tube worm respiratory system

Image Source and information about the White Christmas Tree Worm

This chapter looks at three systems: circulatory, respiratory and excretory systems.

The Circulatory System: Once food has been digested, these nutrients needs to be distributed to every cell within the body to enable cellular respiration to occur. These nutrients, as well as hormones, waste products (CO2 and urea), salts and heat are transported in the circulatory system. The circulatory system of mammals includes  a four-chambered heart, arteries, veins and capillaries that allow the movement of blood to every cell within the body.

The Respiratory System: The mammalian respiratory system includes the lungs, trachea, bronchi and alveoli that allow the transfer of oxygen and carbon dioxide between the internal blood supply and the external environment. Insects have an open respiratory system in which the air and the internal cells are in close contact, oxygen entering through spiracles and passing in to branching tubes within the organism. Don’t get confused between cellular respiration and breathing! Cellular respiration is the process that converts glucose and oxygen to energy within the cells. Oxygen is supplied to those cells by the red blood cells, which carry oxyhaemoglobin to cells and remove carbon dioxide from cells.

The Excretory System: Our kidneys are part of our excretory system, to remove nitrogenous wastes from our body. The nephron is the functioning unit that removes urea from the blood and allows water, nutrientsand salts to be re-absorbed to the body. Ureters are the tubes that carry urea from the kidneys to the bladder and urine leaves the body via the urethra.


Hindgut versus Foregut Fermenters

hidgut vs foregut

Horses are hindgut fermenters, while sheep are foregut fermenters.

Obtaining and transporting nutrients is a vital function for all multicellular organisms and different species have evolved some interesting ways of gaining, storing and digesting their nutrients. Amongst herbivores, for example, almost all have cellulose digesting bacteria within their gut that live symbiotically, assisting with the break down of vegetation. Some are classified as “hindgut fermenters”, which have microbes and fermentation in their hindgut, the caecum and proximal colon. These animals are less effecient at digesting their food and can sometimes be observed practising coprophagy (eating faeces).

  • Horses
  • Koalas
  • Wombats
  • Possums
  • Pigs
  • Rabbits
  • Rats

Other herbivores are “foregut fermenters”, or ruminants, which have pouches with microbes in the stomach. These microbes consume glucose from cellulose but produce fatty acids that the animal can use for energy. Microbes can also be digested further along the digestive tract as they are also a source of protein. Forgut fermentation, or rumination, is a slower digestive process, but has the advantage of providing more nutrients and wasting less energy. Foregut fermenters include:

  • Sheep
  • Cattle
  • Hippopotumus
  • Kangaroos and Wallabies

Good information about different types of digestive systems from a UK Veterinary site, Comparative Digestion.