Wednesday 30 November 2011

Three major types of protists

Animal like protists are protists with animal characteristics. They are sometimes referred to as protozoa. They are heterotrophs, and they are mobile. An example is a paramecium.

Plant like protists are protists with plant like characteristics. Most carry out photosynthesis. Most of us are familiar with algae, which fall in this category.

Fungus like protists are protists with plant like characteristics. Their main characteristic is that they digest food externally. Most types of molds fall in this category.

Saturday 26 November 2011

Find out what makes good food go bad!

What makes your sandwiches go bad when you leave them in your school bag for a long time?
  • It's because of things called bacteria and fungi. Although it may surprise you, a mushroom is a type of fungi, a type that's actually good to eat. Other types of fungi can be poisonous and very bad for your health. They can be large or so small that you don’t even notice it.
  • Bacteria are very tiny and you need powerful microscope just to see them. Some bacteria can make you sick so it’s often a good idea to avoid dangerous bacteria when you can. Although a lot of bacteria can be harmful, other types are used to help us make foods like cheese and yoghurt.
  • Perhaps the most important thing fungi and bacteria do are to make things rot, returning all the nutrients back to the earth. Without the help of bacteria and fungi, most of our rubbish would be extremely difficult to get rid of, piling up constantly and leaving a bad smell too

Wednesday 23 November 2011

 

Microorganismes

Bacteria (Archae)

Bacteria ( Archae) were once thought to be a type of bacteria. After extensive research of their DNA and membrane structure, some scientists decided to put them into a separate group - Archaea. Another group of scientists is still not convinced and refers to them as Archaeabacteria.
Archaea are unicellular prokaryotes which make them bacteria-like organisms. Their DNA structure resembles the DNA of eukaryotic cells. Also, the cell walls of Archaebacteria are structurally different from the bacterial ones. Archaea live in environments that would not be suitable for most life forms. They can be found around hot geysers, volcanic vents, very salty lakes and on the ocean floor. Because Archaea thrive in such extreme conditions, they are sometimes called 'organism - extremists' or 'extremophiles. Archaeans can survive these extreme conditions due to their physiology. They synthesise different enzymes that keep their cells from being destroyed by high temperatures, salty or acidic water.
Because of their 'fondness' for extreme environmental conditions, Archaeans are believed to be the first living forms that appeared on Earth when it was still waterless, airless and a scorching hot planet.
Based on their habitat, all Archaeans can be divided into the following groups:
  • Methanogens - methane-producing organisms;
  • Halophiles - Archaeans that live in salty environments;
  • Thermophiles - Archaeans that live at extremely hot temperatures;
  • Psychrophiles - cold-temperature Archaeans.
Archaeans use different energy sources like hydrogen gas, carbon dioxide and sulphur. Some of them use sunlight to make energy, but not the same way as plants do. These creatures absorb sunlight using their membrane pigment, bacteriorhodopsin. This reacts with light, leading to the formation of the energy molecule, of adenosine triphosphate (ATP).

Bacteria

All bacteria are unicellular prokaryotes, meaning they do not have a defined cellular nucleus. Their genetic information is in their nucleoid, - single, circular tightly- packed DNA molecule. According to their shape, all bacteria are divided into three groups:
  • spirilla (with a spiral body shape);
  • cocci (with a spherical body shape);
  • bacillus ( with a rod (stick) shaped body).
Some types of bacteria live on their own and others form colonies. Some bacteria are quite mobile and others 'stay put' for their whole life. Bacteria move using their cytoplasmic tail - flagella, or by secreting slimy substances that allow them to slide along surfaces.
The cell walls of most bacteria contain a polysaccharide called peptidoglycan. Differences in their cell wall structure is a major feature used in classifying these organisms. The staining abilities of bacteria are also based on their cell wall structure. According to the way they stain, bacteria can be classified as either Gram - positive or Gram - negative..
According to the way they obtain energy, bacteria are classified as heterotrophs or autotrophs. Autotrophs make their own food by using the energy of sunlight or chemical reactions, in which case they are called chemoautotrophs. Heterotrophs obtain their energy by consuming other organisms. Bacteria that use decaying life forms as a source of energy are called saprophytes. See image 3.

Protozoa

Protozoa is a subkingdom of unicellular, mostly aerobic, eukaryotic organisms. Sometimes they are also called protists. They are neither plants nor animals. They make up the largest group of organisms in the world in terms of numbers and biomass. Some protozoans, like Euglena, have chloroplasts like plants and make their own food, which makes them autotrophs. Others, like amoeba, are heterotrophs. Protozoans can be free-living or parasitic, unicellular or colonial. Some parasitic protozoans can cause diseases in humans. Protozoans move around using their flagella or pseudopodia - cytoplasmic temporary 'feet'.

Fungi

Fungi are saprophytic (feed on decaying organic matter) and parasitic organisms. Fungi include moulds, rusts, mildews, smuts, mushrooms and yeast. By breaking down dead organic material, they continue the cycle of nutrients through ecosystems. Some plants have a symbiotic relationship with fungi. Symbiosis is a mutually beneficial co-existence of dissimilar organisms. For example, there are mushrooms that live near tree roots and supply them with essential nutrients.
All fungi are made of eukaryotic cells. Fungican be single-celled or with cells arranged in filaments called hyphae. Yeasts are unicellular fungi. Masses of hyphae are called mycelia. Mycelia can be well structured, as in a mushroom, or tangled and unstructured, as in moulds. Some fungi can exist in the form of yeast and hyphae. These types of fungi are called dimorphic.

Viruses

Although viruses are not considered living organisms, they are sometimes classified as microorganisms. Viruses are much smaller than common microbes. They are made of a DNA molecule covered with a protein shell called a capsid. Retroviruses are made of an RNA molecule covered with a capsid. Capsids can take many shapes. Viruses cannot reproduce outside the host cell, but they cannot be called parasites either. Scientists still argue today about whether viruses are true living forms because they are not cells and they cannot metabolise on their own.

Saturday 12 November 2011

Test each substance with wet blue and red litmus paper






Enjoy doing experiment!!!

Human blood pH should be slightly alkaline ( 7.35 - 7.45 ).  Below or above this range means symptoms and disease.  A pH of 7.0 is neutral.  A pH below 7.0 is acidic.  A pH above 7.0 is alkaline.
An acidic pH can occur from, an acid forming diet, emotional stress, toxic overload, and/or immune reactions or any process that deprives the cells of oxygen and other nutrients.  The body will try to compensate for acidic pH by using alkaline minerals.  If the diet does not contain enough minerals to compensate, a build up of acids in the cells will occur.
An acidic balance will:  decrease the body's ability to absorb minerals and other nutrients, decrease the energy production in the cells, decrease it's ability to repair damaged cells, decrease it's ability to detoxify heavy metals, make tumor cells thrive, and make it more susceptible to fatigue and illness.  A blood pH of 6.9, which is only slightly acidic, can induce coma and death.
Generally, alkaline forming foods include: most fruits, green vegetables, peas, beans, lentils, spices, herbs and seasonings, and seeds and nuts.
Generally, acid forming foods include: meat, fish, poultry, eggs, grains, and legumes.
Acid - Alkaline
Understanding pH
pH is a measure of the acidity or alkalinity of a solution. It is measured on a scale of 0 to 14, the lower the pH the more acidic the solution, the higher the pH the more alkaline (or base) the solution. When a solution is neither acid nor alkaline it has a pH of 7 which is neutral.
The pH Scale - Acids and Alkali - ion theory: pH stands for the 'potential of hydrogen'. In pure water the concentration of hydrogen ions is equal to the concentration of hydroxide ions. The pH of pure water is 7. Therefore the pH of a solution depends on the concentration of hydrogen ions, H+(aq), present. pH (potential of hydrogen) is a measure of the acidity or alkalinity of a solution. It is measured on a scale of 0 to 14—the lower the pH the more acidic the solution, the higher the pH the more alkaline (or base) the solution. When a solution is neither acid nor alkaline it has a pH of 7 which is neutral. Water is the most abundant compound in the human body, comprising 70% of the body. The body has an acid-alkaline (or acid-base) ratio called the pH which is a balance between positively charges ions (acid-forming) and negatively charged ions (alkaline-forming.) The body continually strives to balance pH. When this balance is compromised many health problems can occur. Good For Your Health!...

Water is the most abundant compound in the human body, comprising 70% of the body. The body has an acid-alkaline (or acid-base) ratio called the pH which is a balance between positively charges ions (acid-forming) and negatively charged ions (alkaline-forming.) The body continually strives to balance pH. When this balance is compromised many health problems can occur.

Wednesday 9 November 2011