13th+March+lesson

OK Biol clan, here is the work for while I am away lapping up the company of year 9 students. I wonder if you still have fond memories of your 3 week experience.


 * IF YOU HAVE VIEWED THIS PAGE RECENTLY YOU WILL NOTICE THAT IT IS DIFFERENT! THERE HAS BEEN A CHANGE OF PLANS.**

It occurred to me that it would be better if you did the area of study 1 test while I was away on camp.

So, now that we have finished area of study 1, its time for a test! You will have a ~40min test on Thursday 13th March. This is not a SAC but it will be used as part of you getting an "S" for Unit 3. Here is a list of revision tasks.
 * Read the study design under the heading Key knowledge for Molecules of Life area of study.Check that you are familair with each dot point.
 * Read the glossary and add at least 5 more terms.
 * Do "Compare and contrast" for 1) catabolic and anabolic reactions 2) photosynthesis and respiration and any others you wish.
 * Create flow charts to show each of the key steps in the synthesis of the major biomacromolecules (proteins, carbohydrates and nucleic acids)

After the test you are to refer to the chapter (5) on homeostasis and answer the chapter review questions. All of them! Complete unfinished questions for homework. In our next lesson on Monday I will want you to hand in the answers to the questions in the **second lot of course notes** (not those in the current one) that I didn't collect last lesson due to you doing a test today.

BUT** you need to write something that flows on from what is already written here (except if you happen to be the first entry). So, as the saying goes, first in best dressed. The longer you wait the more difficult it will be to write something extra and different to what has already been said. It's up to you.
 * Finally**, in the space below I want you to each to write a short paragraph on what you currently know about homeostasis. **To be done before our next lesson on Monday.

I will start the notes with an opening paragraph. Write your intials after your entry.

1. Cells, whether an entire organism or part of a multi-cellular organism, need to be able to cope to fluctuations in their immediate external enviroment. In single-celled organisms this represents the environment they live in. In multi-cellualr organisms this is represented by the interstitual fluid that the cells are "bathed" in. Subsequently, all living organisms rely on some degree of homeostasis, although some more than others. VM

2. Complex organisms, such as humans maintain internal conditions within a very narrow range. Some of the factors controlled are: - body temp - levels of chemicals in the blood and tissues, such a oxygen, carbon dioxide, glucose, water and ions - blood volume and blood pressure In order to maintain these stable conditions, organisms need to be ablle to detect changed in the internal or external environments, transmit information about those changes to a control centre, coordinate a plan to deal with the challenges and carry out an appropriate response. 'Chicken Wing' - "(chicken fillet is a scout and scouts love camp)"

3. Regulation (as mentioned above) is carried out via a stimulus-response mechanism which involves: STIMULUS ---> DETECTED BY RECEPTOR ---> MESSAGE SENT TO THE CONTROL CENTRE -USUALLY THE BRAIN (VIA NERVES/HORMONES) ---> CONTROL CENTRE SENDS A MESSAGE TO A GLAND/MUSCLE (EFFECTOR) VIA NERVES/HORMONES ---> RESULTS IN A RESPONSE. This system can function in two ways: positive feedback or negative feedback. Negative feedback: Response of organism reduces the original stimulus Positive feedback: Response of organism increases the original stimulus. 'lozz :) And yes VM i remember year 9 camp. those were the days of my life.

4. **Two Regulation Systems:** The nervous system receives and carries information from receptors, processes responses and directs those responses through nerves. In order to achieve these functions the nervous system contains many types of specialised cells known as neurons. The nervous system is divided into two parts, the central nervous system (CNS), which consists of the brain and spinal cord and the peripheral nervous system (PNS) which contains all other nerve tissue.
 * The Nervous System:**

The endocrine system consists of a number of endocrine glands which produce hormones. When stimulated these glands release hormones into the interstitial fluid and general circulation. The hormones then travel in the bloodstream until they reach cells with special receptors on their surface. These target cells bind with the hormone molecules and are stimulated into action.
 * The Endocrine System:**

tamm. (year 9 camp was fun..BUT dont worry voj biology camp will be way better!) Oh really, and why will biol camp be so much better? and what makes you think there will be a biol camp this year? VM Yeh tamara, i agree with VM. 'Chicken shnitzle'

Receptors are specialised molecules able to receive and respond to specific stimuli. Sensory receptors convert environmental stimuli into signals manifest in nerves. The stimuli in the form of either: light, chemical, sound electrical or pressure, are converted into nerve impulses which act (generally) on receptors on the cell membrane (either on the entire cell or a specialised site) of the sensory cell. Sensory receptors can be categorized according to what they detect.
 * 5)** **Receptors**

//Chemoreceptors:// as the name suggests are stimulated by specific chemical in the external and internal environment. In the external environment chemicals are detected via taste and smell meaning external chemoreceptors are most often use for fidning: food, mates or detecting predators. 'Tastes' receptors detect chemicals in food and 'smell' receptors detect chemicals carried in the air.

//Mechanoreceptors:// is a receptor which is stimulated by any change in the shape of the receptor. When tissues (in which mechanoreceptors are located) are sufficiently: stretched, compressed (such as in the skin) distorted or vibrated (inner ear) then a message is generated and passes along sensory nerves to the brain or spinal chords where a response is initiated.

//Photoreceptors:// detect light and color and enable the formation of images. Photoreceptors contain pigment that absorb light of a particular wave length. For a sensory nerve to be stimulated its threshold must be reached; that is a sufficient amount of light of the appropriate wave length must be absorbed.

//Thermoreceptors:// detect heat and cold via receptors located in the body of an animal.

6.**//Regulation in Plants//** Plants also need to withstand fluctuations in external conditions. TROPISMS are growth responses of plants to a particular stimulus, and are a way that plants cope with the variations in external environment conditions. - Positive tropisms = responses towards a stimulus - Negative tropisms = responses away from a stimulus Three main plant tropisms are PHOTOTROPISM (response to light), GEOTROPISM (response to gravity) and THIGMOTROPISM (response to touch). Currently, it is thought that responses are carried out in plants as a result of hormonal activity, like the endocrine system for humans. There is no biological evidence suggesting that plants use neural messages for responses. There are five known plant hormones, each with their own specific functions, and they are referred to as //plant growth regulators.// Basic Functions: -- Alexandra. :-) I still think Year 9 camp was the BESTEST camp! ...except that a certain someone in this class almost killed me and Leya with unripened pears in the orchard :-P I I deny all accusations
 * Auxins (eg. Indole Acetic Acid) -** the key hormone in phototropism (a plant's bending response to light). It is responsible for stem elongation, root growth, branching, fruit development and apical dominance.
 * Cytokinins -** promote plant cell reproduction in growing tups, roots and fruits
 * Gibberellins -** promote cell elongation during growth in all plant tissues, including seed germination, flowering and fruits, root growth.
 * Abscisic Acid -** inhibits growth, involved in closing of stomata and encourages leaf and ripe fruit dropping
 * Ethylene -** ripening of fruit

7. **Immune system** an immune system the collection of mechanisms within a organism that protects against disease, by identifying and killing **pathogens** (disease causing organisms). detection however is complicated because pathogens are able to adapt and evolve new ways of infecting host organisms. to survive this challenge, several mechanisms evolved that are able to recognise and neutralise these pathogens. Even single celled bacteria utilize a enzyme based systems that protect against viral infection. in more complicated organisms such as fish, reptiles, plants and insects have more complicated mechanisms for protection. These include **antimicrobial peptides** called defensin, the use of **phagocytosis** and the use of the **compliment system**. These mechanisms make up a very necessary defence system to insure cells function normally. the mechanisms used by vertebrates are much more extensive and complex in humans for instance consist of many types of proteins, cells, organs, and tissues, which interact in an elaborate and dynamic network. As part of this more complex immune response, the vertebrate system adapts over time to recognize particular pathogens more efficiently. The adaptation process creates **immunological memory** and allows even more effective protection during future encounters with these pathogens. the immune system is extremely vital in ensuring cells function normally disorders in the immune system can cause disease. **immunodeficiency** diseases occur when the immune system is less active than normal, resulting in recurring and life-threatening infections.

8. **Regulating blood glucose levels** In mammals the amount of glucose in the blood needs to be just right and therefore needs to be regulated, hence glucose regulation is referred to as a homeostatic mechanism. Glucose is an essential reactant in respiration for the production of ATP. Without it organisms cannot survive.

Hormones maintain the delicate glucose balances in the body. The main hormones involved are //Insulin// and //Glucagon//. These hormones are manufactured and released from different types if cells in the pancreas, present in clusters known as //Iselts of Langerhans//. The //Iselts of Langerhans// contain two types of endocrine cells; alpha cells and beta cells. Beta cells produce insulin and alpha cells produce glucagon. They also act as the //receptor// for blood glucose level.

Insulin is a protein molecule that can lower blood glucose levels, and is produced in response to increasing blood glucose levels, e.g. after a meal, and travels in the plasma of the blood. Insulin increases the rate at which cells take up glucose from the blood. Glycogen is the storage unit in animals. If glucose levels are too high, the release of insulin will lead to the eventual conversion of glucose into glycogen in the liver or muscle cells, thereby decreasing the amount of glucose in the blood. Glucagon increases blood glucose levels, in response to decreasing blood glucose levels. It acts on liver and muscle cells, causing them to break down glycogen and return glucose to the blood.

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