1. B2 – Topic 3
Common systems

2. Fossils
Fossils are the preserved traces or remains of organisms that lived thousands or millions of years ago.

3. Fossil record
This is the collection of fossils identified from different periods of time that can be interpreted to form a hypothesis about the evolution of life on Earth.

4. Gaps in the Fossil record
There are gaps because: 1) fossils do not always form. 2) soft tissue decays 3) many fossils are yet to be found.

5. Growth
When organisms grow they get bigger. The easiest way to observe growth is to measure an increase in size, length or mass.

6. Percentile charts
These charts or graphs are used to compare a certain characteristic (e.g. mass) against the total population.

7. Plant growth Growth in an organism involves two processes.
Cell division where one cell divides to form two identical cells.
The cell gets longer by elongation.

8. Plant development
Plants grow all the time. As the plant stem or root continues to grow the older meristem cells start to become specialised – they differentiate.

9. Animal development
Animals stop growing when they become adults. In an animal, cells that can differentiate to form a number of different types of specialised cells are called stem cells.

10. Red blood cells White blood cells Plasma Platelets
Parts of the blood
Red blood cells White blood cells Plasma Platelets

11. Parts of the blood
A red blood cell has the shape of a biconcave disc. This increases the surface area for diffusion. Red blood cells contain the red pigment haemoglobin. Red blood cells have no nucleus.

12. Parts of the blood
White blood cells are part of the body’s defences against disease. Some white blood cells make antibodies. Other white blood cells surround and destroy any foreign cells like bacteria that get into the body. White blood cells have a nucleus.

13. Parts of the blood
Plasma is a yellow liquid. It transports dissolved substances, such as carbon dioxide, food substances and hormones.

14. Parts of the blood
Platelets are tiny fragments of cells (and so do not have a nucleus). They are important in making your blood clot if you cut or damage your blood vessels. The clot dries out and forms a scab which stops micro-organisms like bacteria getting into the body.

15. Cells, tissues, organs and systems
A group of the same specialised cells form a tissue. e.g. muscle tissue is made from muscle cells.

16. Cells, tissues, organs and systems
An organ contains several different tissues working together to carry out a particular job. The heart is an organ that pumps blood to the lungs and around the body.

17. Cells, tissues, organs and systems
Groups of organs that work together are called organ systems. e.g. the heart and blood vessels make an organ system called the circulatory system.

18. Cells, tissues, organs and systems
Groups of organs that work together are called organ systems. e.g. the heart and blood vessels make an organ system called the circulatory system.

19. The heart
The heart is an organ that pumps blood around the body. There are 4 major blood vessels associated with the heart.

20. The heart
The pulmonary artery takes deoxygenated blood to the lungs to get oxygen. The pulmonary vein takes oxygenated blood back from the lungs to the heart.

21. The heart
The aorta carries oxygenated blood around the body. The vena cava carries deoxygenated blood back to the heart where it is pumped back to the lungs.

22. The left atrium and ventricle pump oxygenated blood.
The heart
The left atrium and ventricle pump oxygenated blood.

23. The right atrium and ventricle pump deoxygenated blood.
The heart
The right atrium and ventricle pump deoxygenated blood.

24. The heart
Veins and the heart have valves to prevent backflow – to stop the blood going the wrong way.

25. The heart
The muscle wall of the left ventricle is thicker than the right ventricle because it has to pump blood all around the body rather than just to the lungs.

26. The heart

27. The heart Arteries transport blood away from the heart.
Arteries have strong, thick walls to withstand the blood at high pressure.

28. The heart Veins transport blood to the heart.
Veins are wide because the blood flows relatively slowly under low pressure.

29. The heart
Capillaries exchange materials with tissues by diffusion so they have very thin walls.

30. The digestive system
Food is broken down in the organ system called the digestive system.

31. The digestive system
In the mouth, teeth break up the food into small pieces. This increases the surface area for digestive enzymes to work on – like amylase.

32. The digestive system
The oesophagus is a muscular tube between the mouth and stomach.
Muscles contract in waves to push the food down it – this is called peristalsis.

33. The digestive system
The stomach is a bag that makes Hydrochloric acid and some enzymes like pepsin to break down proteins. It churns the food up.

34. The digestive system
The small intestine is a long tube where most of the large insoluble food molecules are broken down into smaller soluble molecules. There are lots of enzymes. Food is again moved by muscles in peristalsis.

35. The digestive system
The surface area of the small intestine is greatly increases by having lots of finger like projections called villi which contain capillaries.

36. The digestive system
Water diffuses back into the blood in the large intestine leaving the waste material called faeces behind.

37. The digestive system
The pancreas make digestive enzymes and releases them into the first part of the small intestine.

38. The digestive system
Digested food absorbed by the small intestine is taken in the blood plasma to the liver. Here some of the molecules are broken down even more. Some are built up into larger molecules. The liver also makes bile which helps in the digestion of fats.

39. The digestive system – Higher paper
The gall bladder is a small organ that stores the bile made by the liver. It releases the bile into the small intestine when it is needed.

40. The digestive system

41. Enzymes
Carbohydrases are digestive enzymes that break down carbohydrates into sugars.
Amylase breaks down starch into sugar.

42. Enzymes
Proteases are enzymes that break down proteins into amino acids.
Pepsin is an enzyme that breaks down proteins in the stomach.

43. Enzymes
Lipases are enzymes that break down fat molecules into fatty acids and glycerol.

44. Bile – Higher paper
Bile breaks down large globules of fat and oil into tiny droplets forming an emulsion. The smaller droplets have a larger surface area which lets the lipase enzymes break down the fat molecules quicker. Bile is also slightly alkaline and so will neutralise the Hydrochloric acid from the stomach.

45. Probiotics
Probiotics contain live bacteria which maybe helpful to the digestive system.
These bacteria are usually Lactobacillus and Bifidibacteria. They are found in yoghurts or yoghurt drinks.

46. Prebiotics
Prebiotics are substances that the body can’t digest. They act as food for the probiotic bacteria. Tomatoes, bananas, onions and asparagus all contain oligosaccharides, a common form of prebiotic.

47. Plant stanol esters
Plant stanol esters are oily substances found in plants. These can stop the small intestine absorbing cholesterol so lowering the level of cholesterol in the blood.
Plant stanols are now used in many yoghurt, drinks and spreads.