Monthly Archives: April 2015

Rat Dissection

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rat_dissection

Today we planned to do a rat dissection, but due to the frosty state of our subjects, we have postponed this investigation until Tuesday. In the meantime, we will answer the questions we can, using digital resources:

Plant adaptations for dry environments.

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stomata_marram

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.

stomata_sunken

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.

stomata_hairs&sunken

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.

 

“Body at War” at Federation University, Ballarat

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Stephanie_2015

On Friday 17th April, four VCE Biology students attended the “Your Body at War” program, facilitated by the Gene Technology Access Centre at Federation University. Kiri, Leah, Che and Stephanie travelled to Ballarat to participate in the program, which celebrates the “Day of Immunology”.

Together with about 100 students from three other schools, they had the opportunity to hear from Associate Professor Robyn Slattery (Monash University) about the history of vaccination, current research in immunology and exciting new discoveries about immunotherapy in cancer treatment.

They then donned lab-coats and entered the science laboratories at Federation University, where they learned how to use specialist equipment and techniques, such as the Enzyme-linked Immunosorbent Assay (ELISA). They also had the opportunity to discuss career perspectives in science with staff and Dr Misty Jenkins from the Peter MacCallum Cancer Centre.

One of the sponsors of this event is the Walter and Eliza Hall Institute of Medical Research. Later this year we have three Year 11 students who have been very fortunate to obtain a work experience placement at WEHI in Melbourne. This is an exciting opportunity for them to find about authentic medical research, working with expert scientists in a world-leading facility.

Also in science news, students in Year 10 have the opportunity to attend the Science Experience Ballarat, at Federation University from 29th June to 1st July. This three day, hands-on program is a great introduction to the diverse world of science and it’s connection to a range of interesting careers. Please apply online prior to 8th June. Speak to Mrs Gow for further information.

Distribution of Materials

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circulatory

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In this unit of work we are looking at the ways plants and animals distribute nutrients, hormones, gases, water and waste products to and from different cells throughout the organism. In animals, this involves the circulatory, respiratory and excretory systems. In vascular plants, we consider gaseous exchange, transpiration and substances moving through the xylem and phloem.

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.

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.

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, nutrients and 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.

Gaseous Exchange in Plants: Plant cells need to exchange oxygen and carbon dioxide with the environment and they do so through stomata (pores) in their leaves.

Transpiration: How do the tallest trees draw water from the soil to hydrate leaves many metres in the air?

Xylem and Phloem in Vascular Plants: What are vascular plants and how do they transport water with dissolved minerals and nutrients to cells in the roots, stems and leaves?

Please let me know in the comments below if any of these links are no longer working!

Co-ordination and Regulation – Endocrine Systems

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Signal_Transduction_Pathways_Model

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In this chapter you need to become familiar with the following concepts:

  • homeostasis (maintaining a stable internal environment in terms of temperature, hydration, pH, blood pressure and volume, oxygen and carbon dioxide concentration in the blood and the concentration of various ions, including sodium and glucose).
  • stimulus-response and sensors-effectors
  • positive and negative feedback mechanisms
  • glands and hormones, including phermones
  • signal transduction and signaling molecules

it is important to understand that lipid soluble hormones (lipophilic or hydrophobic) can pass through the cell membrane directly, but water-soluble hormones (hydrophilic or lipophobic) bind to a receptor molecule embedded in the cell membrane, which results in the activation of a secondary protein or messenger. This secondary messenger causes the cell to initiate a response. Signal transduction is a series of events (sometimes called a ‘cascade’) that changes the signal received by the cell.