Archivo de la categoría: Biology

Reflect Arc

  1. Search in the internet a video showing an example of a reflex action.

2. Explain the term reflex action.

Reflex action is defined as the automatic or involuntary response to a sensory stimulus which is not under conscious control. Some reflex actions do not need to be learnt, as we inherit them when we are born. These are possible thanks to the reflex arcs, which act on an electrical impulse before the impulses reach the brain.

3. State the structures involved in a reflex arc.

The structures involved in the reflex arc are the sensory neurons, the motor neurones and the relay neurons. When the receptor detects a stimulus, the sensory neuron sends an electrical impulse to the relay neuron which is found in the spinal cord and connect the sensory neuron to the motor neuron. The motor neuron sends electrical impulses to an effector that then produces a response.

4. Explain how the reflex action in your video takes place.

In our video, it was explain how the reflex action takes place if a person accidentally touches a hot object, in this specific case a candle. If a person does this, a pain sensitive receptor cell in this fingertip detects the heat stimulus and triggers off the nerve impulse from here. The impulse travels along a sensory neuron to the spinal cord. The message is processed and the response is generated in the spinal cord itself and then this response travels down through a motor nerve to the muscles of the arm. This receives the response, and the arm muscles of the person contracts (the bicep) and lifting the person’s finger away from the hot object.  


Urinary System trash model

In our biology class, we were told to create a trash model of the urinary system.  As the task was in pairs, I worked with Valentina Re. Now, we are going to describe the process of how we did the model and explain the functions of each organ present in the system.

First, we look for a picture of the urinary system to know were each organ is supposed to be. This model should include the kidneys, the ureters, the bladder, the urethra, the renal veins, the renal arteries, the inferior vena cava and the abdominal aorta.

Second, we started the model. For the kidneys, we used old newspapers and magazines. For the ureters, we used shoelaces. Then, for the bladder, we used a tolem lid and for the urethra, a wine cork. Moreover, for the renal veins and renal arteries, we used thread. Finally, for the inferior vena cava and the abdominal aorta, we used straws.

Furthermore, we looked for the functions of each of this organs that form the urinary system. These are:

  • Kidneys are bean-shaped organs of a reddish brown color that are found in the sides of the vertebral column. Once the body has extracted what it needs from food and drink, it sends the wastes to the kidneys. The kidneys filter the wastes, including urea, salt and excess water, which are flushed out of the body as urine. Each kidney is supplied with blood from the renal artery
  • The ureter is a tube that carries urine from the kidney to the urinary bladder.There are two ureters, one attached to each kidney. The upper half of the ureter is located in the abdomen and the lower half is located in the pelvic area.The tube has thick walls composed of a fibrous, a muscular, and a mucus coat, which are able to contract.
  • The bladder, also known as the urinary bladder, is an expandable muscular sac that stores urine before it is excreted out of the body through the urethra. It is located in the lower abdominal area near the pelvic bones.
  • The Urethra is a tube which connects the urinary bladder to the outside of the body. It is responsible for allowing urine to leave the body as it empties from the bladder.
  • There are two renal veins, a left and a right. They branch off the inferior vena cava and drain oxygen-depleted blood from the kidneys.As they enter the kidneys, each vein separates into two parts. The posterior veins assist in draining the back section of each kidney, while the anterior veins assist the front part. These veins also are responsible for draining blood from the ureter, which transports urine away from the kidneys to the urinary bladder.
  • There are two blood vessels leading off from the abdominal aorta that go to the kidneys. The renal artery is one of these two blood vessels.The renal artery enters through the hilum, which is located where the kidney curves inward in a concave shape. Under normal circumstances, once the renal artery enters through the hilum, it splits into two main branches, which each then split into numerous smaller arteries, which deliver blood to different areas of the kidneys, known as nephrons.Once the blood has been processed here, it is sent back through the renal vein to the inferior vena cava and to the right side section of the heart.
  • The inferior vena cava is a large vein that carries de-oxygenated blood from the lower body to the heart.
  • The abdominal aorta is the largest artery in the abdomen that provides blood to the organs and tissues of the abdomen, pelvis, and legs. It descends from the thorax as a continuation of the thoracic aorta and branches several times to form the major arteries of the abdomen.

Finally, here we leave you a picture of our proyect finished:

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