Archivos de la categoría Biology

Respiration + Gas exchange

October 4th

Respiration + gas exchange

-Activity 11.3 (book page 143)

(Lime water & hydrogen carbonate indicator→ to detect carbon dioxide)

A1; Why it is important to boil the water?

It is important to boil the water because doing so will take away any dissolved air.

A2; Why must the sugar solution be cooled before adding yeast?

The sugar solution must be cooled before adding the yeast because if the yeast is added before it is cooled (when water is hot) it will die without releasing carbon dioxide for the experiment.

A3; What is the liquid paraffin for?

The liquid paraffin is used to separate the yeast from the air (oxygen).

A4; What happened to the limewater or hydrogen carbonate indicator solution in each of your pieces of apparatus? What does this show?

The limewater turned cloudy in apparatus A . We can observe that the yeast respired CO2 and that the limewater absorbed it. However, in the other apparatus the yeast did not respired CO2, and therefore the lime water was clear and couldn´t absorb the carbon dioxide.

A5; I would expect to find ethanol (alcohol), as the process of anaerobic respiration in yeast results in the production of alcohol.


-Activity 11.8 (book page 149)


What happens when we swallow?

After reading chapter 7 of the IGCSE biology book, we made a test which consisted in eating a biscuit thinking in what happens to the food after we put it into our mouth, and more especifically, when we swallow.

Once we put the food in the mouth, our teeth are responsible for biting into smaller pieces the food (in the case of the incisors and canines) and chewing (in the case of premolars and molars). Then, the amylase (which is secreted by saliva) breaks down starch into maltose, helping the food to dissolve and expand its surface, and making it start to be called a bolus. The tongue is responsible for moving the bolus into the mouth, and then helps to swallow and reaches the esophagus (a long tube that carries food to the stomach). In this way, we can see that chemical and mechanical digestion is present in the mouth, saliva is part of the chemical digestion and the movement of the tongue is mechanical.

Biology Project (The Brain)

In Biology, our teacher assigned us a presentation, using the platform ScreenCast O’matic, about Human Physiology. The work consisted in searching for information about the following topics;

  • The organ system that contains your organ
  • Your organ’s main functions
  • If your organ works with other systems to keep the body healthy
  • Which diseases or disorders affect your organ
  • If we can live without the organ

I worked with Trinidad Porretti and Anouk Laferrere. This is our presentation;

Biology notes – 9/8

August 9thC

Chemicalsof life (Ch. 4)

Note taking


-We call them chemicals of life as it is what we are made of.

-These are carbohydrates, lipids and proteins.


  • There are small carbohydrates with only one sugar, called monosaccharide. This is soluble in water.

E.g; Glucose

  • An example of monosaccharide  is glucose or fructose.
  • When monosaccharide get together, a disaccharide is formed. This is soluble in water, and therefore, storages energy. An example of disaccharide is starch (plants) or glycogen (animals).
  • When a long chain of many carbohydrates is formed, it is called polysaccharide. This isn’t soluble in water and it is heavy. An example is sucrose.
  • Carbohydrates are the body’s main source of energy and storages it too. They contain the elements carbon, hydrogen and oxygen.
  • C-H-O


  • C-H-O
  • Function; To store energy as fats.


  • C-H-O-Nς

Differences and similarities between solids, liquids and gases

In biology class we worked in pairs with a simulation of the states of matter bases. Then, we wrote a summary explaining the differences and similarities between the three states; solids, liquids and gases. I worked with Marcos Okecki

When water molecules are solids we can see they are all packed together at the bottom of the beaker, as we heat the water molecules and temperature start increasing they begin to separate until they reach the liquid state. Solid molecules do not present much movement.

When water molecules are liquid they present more movement than solids, but they do not expand through all the beaker. When you heat liquid molecules and temperature increases they separate until they reach the gas state. If you cool the molecules, and temperature decreases,  they start packing together until they reach the solid state.

When water molecules are in gas state they are spread through all the beaker and present a lot of movement. If you continue heating them, they will continue separating and if you cool them they will reach the liquid state and then the solid. 


The three states will always present more movement and separate when you heat them, the more temperature increases them they are more spread. Moreover, when you cool molecules they pack together and present less movement.

                SOLID                        LIQUID                          GAS

Questions / Biology

In biology class, Ceci told us to elaborate between 7 and 10 questions of the chapter 19 of the book which could be possible questions for a test.

These are the questions I prepared with Marcos Okecki.

1)Elaborate a comparative chart comparing continuous variation and discontinuous variation.

2) Which are the organisms more likely to survive? Will these organisms be able to reproduce?

3)How can we describe evolution?

a) The result of natural events in living organisms

b) The passing of time.

c) The change in adaptive features over time. The result of natural selection.

4) Name the ways in which genetic variation is produced.

5) Explain how certain organisms can be selected for breeding.

6) What is the name given to the chemical which can cause mutations?

a) Mutants

b) Mutagens

c) Mutaters

7) Explain one of the factors which make mutation more likely.

8) Complete the phrases


  • It is called _________ when a gene may suddenly change.
  • Blood groups are controlled by _________
  • Other reason for the difference between individuals is that their __________ are different


Note Taking-Biology


  • Descent: Descent is called to a living organism that we produce by sexual reproduction.  
  • As we do not reproduce by mitosis we suffer modifications (we are not a copy of our parents)
  • We are different from our parents because of mutation ( sudden change in the genetic material in the cell’s nucleus).
  • Ex: sunshine produces mutation
  • Common Descent: Theory developed by Charles Darwin in which he explained the idea we all came from the same thing, from a common ancestor.
  • Mimicry: Some living organisms have the ability to protect themselves by changing their appearance in something poisonous.
  • Common Descent is a conclusion based on facts found independently in the study of fossils, genetics, comparative anatomy,mathematics, biochemistry and species distribution.
  • Charles Darwin: He was a naturalist, he traveled the world by ship and got interested in the idea of natural selection, and mainly, common descent. He noticed, for example, that islands contained unique species that were not found in any other place. However, he realized that had similarities from the ones of other islands or continents. Nevertheless, there was one fact that he did not understand, how species could be adapted to their environment and have such different characteristics if they came from the same ancestor. Finally he could give an explanation although it was a very slow process. For example, a tortoise reproduced, and, even though, almost all the descents were equal, at least one of them had something different. This exception then would reproduce and one or more of the new organisms would be a little different. This would happen subsequently and new species coming from the same ancestor would be produced.
  • Natural Selection is called to the process by which new species can be reproduced. Nature, by its own, decide which organism continue reproducing. It is consider the process by which random evolutionary changes are selected by nature in a consistent, orderly, non-random way.  Ex: A Camaleon choose the insects it will eat, the others will survive and continue reproducing.



Variation: Differences between individuals from the same species.


Continuous variation: A type of variation which cannot be classified in one, two or three groups.

IGCSE book´s definition: It is called to the differences in the features of a group of organisms in which there are not definite categories; each individual’s features can lie anywhere between two extremes.

Ex: Weight

Discontinuous variation: Type of variation where the living organisms can be grouped into very definite categories.

IGCSE book´s definition: Differences in the features of a group of organisms where each fits into one of a few clearly defined categories.

Ex: Blood groups

Environmental variation: All the variation that happens due to the changes of the environment. Individuals may develop variation due to different environmental conditions such as climatic conditions, etc.

Ex: Sunshine

Genetic variation: Type of variation given by the genetic information. Genetic variation is defined as a change in genes due to DNA mutation. Genetic variations can be seen in DNA, Chromosomes, genes, etc.

  • Genotype: Information given by the genes we have inside. The total number of genes transmitted from parent to offspring.


  1. Artificial Selection: Human intervention in living organism’s reproduction. They make them adapt to the conditions and characteristics they prefer.