Wednesday, 26 December 2012

Nature spotting!

If you have started nature spotting, you can send your photos to: sciencemagazinesheilabastian@gmail.com
Wishing you all a Merry Christmas!!

Monday, 3 December 2012

CLASSIFICATION OF LIVING THINGS

We are studying the classification of all living things in ESO 1. In this post I have summarised the groups we have seen so far.  At the moment, I only intend to mention the groups, without going into detail. Make sure you know these groups well!
 Living things are classified into  5 kingdoms:
ALL LIVING THINGS:
  • Monera Kingdom               bacteria and cyanbacteria
  • Protoctist Kingdom               protozoa and algae
  • Fungi Kingdom                     yeast, mould, mushrooms
  • Plant Kingdom                      mosses, ferns, flowering plants
  • Animal Kingdom                        invertebrates, vertebrates

ANIMAL KINGDOM - INVERTEBRATES:
  • Porifera                                     sponges
  • Cnidaria                jellyfish,polyps,sea anemones
  • Worms           nematodes,platyhelminthes,annelids
  • Molluscs           gastropods,bivalves,cephalopods
  • Echinoderms           echinodea,stelleroidea,crinoidea,holothuroidea,ophiuroidea
  • Arthropods        insects,arachnids,myriapods,crustacean
Look at these posters of invertebrates, these are last years. We will do something similar soon.







Now check out this really interesting link! It's an extremely exhaustive web page about insects. It has photographs and commentaries of a great number of insect species. Remember, insects are athropods, so they have a segmented body, an exoskeleton and jointed appendages. Insects have 3 body parts (head, thorax and abdomen), 6  legs, 2 antennae and 2,4 or no wings.
Click here:







ANIMAL KINGDOM - VERTEBRATES
  • Fish                                  cartilaginous, bony
  • Amphibians                           frogs, toads, newts, salamaders
  • Reptiles                             snakes, lizards, turtles, crocodilians
  • Birds
  • Mammals                            monotremes, marsupials, placentals

Saturday, 1 December 2012

FERMENTATION - BREAD AND BEER MAKING!

Saccharomyces cerevisae is the species of yeast used for bread making. It is often known as baker's yeast. But if you look carefully at its name you will notice that this species is not only used in bread making but also in the making of beer (cerveza in spanish). The making of both of these products is based on a chemical reaction carried out by these unicellular living things, called fermentation. Fermentation is the process by which yeast cells metabolize the sugar in wheat, in the case of bread or malted barley in the case of beer to obtain energy. Fermentation is usually occurs in the absence of oxygen and is known as an anerobic reaction. In the presence of oxygen cells obtain energy through respiration which is known as a aerobic reaction. Although some species of yeast tend to prefer fermentation. In this process carbon dioxide and alcohol (ethanol) are formed. The carbon dioxide is a gas and forms bubbles of air in the bread making it rise. The alcohol is evaporated by the heat of the oven in the case of bread.

                      C6H12O6 → 2C2H5OH + 2 CO2
                           a molecule of glucose is converted into 2 molecules of ethanol and 2 of carbon dioxide

This simple experiment shows how gas is released during fermentation. After some time the balloon fills with carbon dioxide. The water must be warm and sugar must be added. This is exactly what happens during bread and beer making.
Materials
Erlenmeyer flask with a balloon attached
After some time the balloon fills with carbon dioxide released during fermentation carried out by this one celled fungus.
You can smell a scent of alcohol too when you pull the balloon off.

Check out these two Discovery Channel videos on bread and beer making! 

Click here:      Bread Making!
Click here:   Beer making!

THE INTERACTION FUNCTION IN UNICELLULAR LIVING THINGS

All living things react in some way to changes in their environment. This is what we call the interaction function and it is one of the three vital functions performed by living things. The others are nutrition and reproduction. We call these changes in the internal or external environment of an individual, stimuli. Stimuli can be physical, changes in temperature, pressure etc. chemical, the presence or absence of chemical substances or biotic, that is, produced by another living thing. The way in which a living thing reacts to the stimulus is called the response.
We have done an experiment to study how temperature affects cell division in unicellular living things.
Natural yeast is very easy to find in any supermarket and is a great way to obtain cells for experiments.Only one gram of this yeast contains billions of cells!
We dissolved some yeast in water and added some sugar. We placed a small amount of this mixture in the fridge and some in the bain Marie at 37ºC.
Yeast cells in the fridge

Yeast cells in the bain Marie at 37ºC
After a couple of days we took samples of both preparations and observed them through the microscope.
This is what we saw:

Cells kept in the fridge
Cells kept at 37ºC
We noticed a difference in the number of cells. Does temperature affect cell division? How do the cells react to the different temperature conditions? Can we consider this interaction? What do you think?. If we put the cells at a very high temperature, would they divide even more?