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Wednesday, 11 April 2012

GM Food

5.15 evaluate the potential for using genetically modified plants to improve food production (illustrated by plants with improved resistance to pests)
Genetically modifying plants can have some advantages and disadvantages. Despite the fact that the world produces enough food to feed the whole world many times over, some people are still starving. Others are suffering from malnutrition and many are hungry. Genetic modification has great potential; it can allow certain crops to survive in harsher conditions so that for example, people in Africa can grow crops despite the harsh conditions there. Scientists can even genetically modify foods so that they are more nutritious, for instance they genetically modified rice plants to produce 'Golden Rice' which has a higher vitamin A content. So here you see that GM foods can help address certain nutrient deficiencies too. Not all of a crop planted will be harvested; a percentage will be lost to disease, some to pests, others to weeds. So GM plants can be designed to have resistance to not only harsher conditions, but to pests too. This way crop yield is increased. But of course, there are disadvantages too. I'll just list a few of each, and then include a table for some benefits of genetic engineering applications to society.
Advantages, GM crops:
  • Need fewer chemical sprays
  • Could give bigger yields
  • Could grow in harsher conditions
  • Could result in cheaper food (if there were higher crop yields, supplies increase and with the same demand, prices are lowered)
  • Could be more nutritious
Adv. -Research into the genetic modification of plants hopes to provide (or provides already) plants with:
  • Increased resistance to a range of pests
  • Resistance to pathogens so they don't contract diseases
  • Increased heat and drought tolerance
  • Increased salt tolerance
  • A better balance of proteins, carbohydrates, lipids, vitamins and minerals-more nutritious crop plants
  • Accidental transfer of new genes to other wild plants-unpredictable
  • GM crops could reduce biodiversity
  • The new proteins in GM crops could cause allergies
  • GM seeds are expensive, but the costs of production are lower as sometimes less water is needed, or expensive chemicals such as herbicides and pesticides are not needed if the crops are resistant towards diseases and pests and weeds
Applications of genetic engineering
Benefits to society
Low-cost production of medicines
Genetic engineering of important drugs such as human insulin has dramatically reduced the cost of these medicines. This makes it more affordable and therefore more accessible to people who need them, so they can be treated.
Production of crops that grow in extreme conditions (e.g. high-salt environments)
Examples of such crops include:
  • Drough-resistant crops;
  • Salt-tolerant crops; and
  • Crops that make more efficient use of nitrogen and other nutrients.

This allows farmers to grow crops even when the soil conditions are not suitable for cultivating most crops.
Development of:
  • Crops that produce toxins that kill insect pests; and
  •  Pesticide-resistant crops
The use of costly pesticides that may damage the environment is reduced. For example, the Bt gene from t
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Cell Structure

a) Levels of Organisation
2.1 describe the levels of organisation within organisms: organelles, cells, tissues, organs and systems

 b) Cell Structure
2.2 recognise cell structures, including the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole

 2.3 describe the functions of the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole

 2.4 describe the differences between plant and animal cells
Animal cell

  1. A cell membrane is like a sieve, it controls what goes in and out of the cell. 
  2. The cytoplasm is where the chemical reactions take place, the mitochondria in the cytoplasm is where respiration takes place to release energy. The cytoplasm also contains enzymes that control the chemical reactions. 
  3. The nucleus is like the 'brain' of the cell, it controls the cell, telling it what to do. It also contains DNA which is important when the cell reproduces. 


10.1_plant_cell_V2
Plant cell

Plant cells have extra features:

  1. They have a cell wall, this is made of cellulose. It gives the cell shape and structure and provides support. It also means the cell can't burst, it becomes turgid when it is full of water. (The cell walls are actually impermeable to water, which is why they have small gaps in them called plasmodesmata which allow water to enter via osmosis..)
  2. They have chloroplasts which contain chlorophyll-the green pigment that allows it to absorb light energy and convert it to chemical energy during photosynthesis. Plants are autotrophs-they can make their own food. 
  3. Plant cells have a permanent vacuole that contains cell sap, it provides support. It is also basically a storage and removes waste, and provides/maintains the cell structure. 

Feature
Animal Cell
Plant Cell
Nucleus
Yes
Yes
Cytoplasm
Yes
Yes
Cell Membrane
Yes
Yes
Mitochondria
Yes
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Wednesday, 4 April 2012

Nature and Variety

The specification for section 1 pretty much says it all, I didn't really add anything: 


a) Characteristics of living organisms

1.1 recall that living organisms share the following basic characteristics: 

  • they require nutrition
  • they respire
  • they excrete their waste
  • they respond to their surroundings
  • they move
  • they control their internal conditions
  • they reproduce
  • they grow and develop
b) Variety of living organisms

1.2 describe the common features shared by organisms within the following main groups, plants, animals, fungi, bacteria, protoctists and viruses, and for each group describe examples and their features as follows (details of life cycle and economic importance are not required).

Plants: These are multicellular organisms; they contain chloroplasts and are able to carry out photosynthesis; they have cellulose cell walls; and they store carbohydrates as starch or sucrose.

Examples include flowering plants, such as a cereal (for example maize) and a herbaceous legume (for example peas or beans). 

Animals: These are multicellular organisms; they do not have chloroplasts and are not able to carry out photosynthesis; they have no cell walls; they usually have nervous coordination and are able to move from one place to another; they often store carbohydrates as glycogen.

Examples include mammals (for example humans) and insects (for example housefly and mosquito).

Fungi: These are organisms that are not able to carry out photosynthesis; their body is usually organised into a mycelium made from thread-like structures called hyphae, which contain many nuclei; some examples are single-celled; they have cell walls made of chitin; they feed by extracellular secretion of digestive enzymes onto food material and absorption of the organic products; this is known as saprotrophic nutrition; they may store carbohydrates as glycogen.

Examples include Mucor, which has the typical fungal hyphal structure, and yeast which is single-celled. 

Bacteria: These are microscopic single-celled organisms; they have a cell wall, cell membrane, cytoplasm and plasmids; they lack a nucleus but contain a circular chromosome of DNA; some bacteria can carry out photosynthesis but most feed off other living or dead organisms.

Examples include Lactobacillus bulgaricus, a rod-shaped bacterium used in the production of yoghurt from milk, and Pneumococcus, a spherical bacterium that acts as the pathogen causing pneumonia. 

Protoctists: These are microscopic single-celled organisms. Some, like Amoeba, that live in pond water, have features like an animal cell, while others, like Chlorella, have chloroplasts and are more like plants. A pathogenic example is Plasmodium, responsible for causing malaria. 

Viruses: These are small particles, smaller than bacteria; they are parasitic and can reproduce only inside living cells; they infect every type of living organism. They have a wide variety of shapes and sizes; they have no cellular structure but have a protein coat and contain one type of nucleic acid, either DNA or RNA. 

Examples include tobacco mosaic virus that causes discolouring of the leaves of tobacco plants by preventing the formation of chloroplasts, the influenza virus that causes 'flu' and the HIV virus that causes AIDS. 

1.3 Recall the term 'pathogen' and know that pathogens may be fungi, bacteria, protoctists or viruses. 
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