B2.3 Common Systems

Question 1

Evaluate the evidence the fossil record provides for evolution

Answer 1

The fossil record is the history of life on Earth as sown by fossils. It suggests that many organisms have changed gradually through time, they have evolved. However ten fossil record has many gals in it because of soft tissue decay, destroyed parts or fossils buried too deep to find. These gaps mean that scientists have to interpret the incomplete data, which can lead to different interpretations of fossils which do not align.

Question 2

How does the anatomy of the pentadactyl limb provide evidence for evolution?

Answer 2

Most vertebrates have limbs, which have very similarly constructed bones. Fossil ancestors, both with limbs and limbless have the same basic pentadactyl limb which vertebrates have today, suggesting that all vertebrates evolved from one common ancestor.

Question 3

Structure of the pentadactyl limb:

Answer 3

Humerus
Radius 
Ulna 
Carpals
Phalanges

Question 4

What is growth?

Answer 4

Growth is when an organism gets bigger in terms of size, mass or length.

Question 5

What is a percentile?

Answer 5

The value of a variable which falls below a certain percentage of all of the population.

Question 6

What is the difference between something getting bigger and something growing?

Answer 6

Growing involves the replication of cells and them getting bigger.

Question 7

How do plants grow?

Answer 7

Plants have special cells called meristems just behind the tips of their roots and shoots where the cells divide. Once the cells have divided they elongate, resulting in growth.
As the plant matures the older meristem cells differentiate into any type of plant cell. For example a meristem in a shoot cell can become a leaf cell containing chlorophyll.

Question 8

How do animals grow?

Answer 8

Animal cells also divide, but growth stops when the animals reaches adulthood. In an animal cells which can differentiate are called stem cells. These cells develop into specialised tissues and organs in an embryo, whereas adult stem cells can only really differentiate into blood cells are skeletal tissues, which is why humans cannot regrow limbs.

Question 9

What are the main components of blood?

Answer 9

Plasma
Red blood cells
White blood cells
Platelets.

Question 10

What is the role of the plasma?

Answer 10

Plasma is a yellow liquid which transports dissolved food substances, carbon dioxide, hormones etc.

Question 11

What is the role of the red blood cells?

Answer 11

Red blood cells contain haemoglobin which can combine reversibly with oxygen to form oxyhemoglobin. Red blood cells are bioconcave disks which gives them a large surface area to volume ratio. They also have no nuclei to allow for the maximum space for oxygen.

Question 12

What is the role of the white blood cells?

Answer 12

Some white blood cells make antibodies, which are proteins that bind with pathogens and destroy them other white blood cells surround and destroy any other foreign cells. All white blood cells have a nucleus.

Question 13

What is the role of platelets?

Answer 13

Platelets are tiny fragments of cells, which make blood clot if you cut yourself. The clot dries and forms a scan, stopping microorganisms from getting into the body.

Question 14

What is an organ?

Answer 14

An organ is group of tissues working together to perform an particular task.

Question 15

Describe the path blood takes thought the heart.

Answer 15

Deoxygenated blood enters the heart through the vena cava. First of all it enters the right atrium, which contracts when it is full, sending the blood through valves and into the right ventricle. When the ventricle is full, the blood goes through more valves and into the the pulmonary vein and then the lungs. Then the blood comes back through the pulmonary artery and into the left atrium. it then goes through valves into the leftventricle and into the aorta, which transports oxygenated blood around the body.

Question 16

What do the veins do?

Answer 16

The veins carry deoxygenated blood to the heart. They are wide and have thin must’ve layers so that the blood flows ate a low pressure.

Question 17

What do the arteries do?

Answer 17

The arteries carry oxygenated blood away from the heart. They have a tick layer of muscle and a tough connective tissue so that the blood flows under high pressure.

Question 18

What do the capillaries do?

Answer 18

Capillaries allow blood to diffuse into and out of them because they have very thin walls.

Question 19

Is Anna the best person ever?

Answer 19

Yes, of course, how could you think any differently 🤗😃🤓🙄

Question 20

What are fossils?

Answer 20

Fossils are preserved races or remains of organisms that lived thousands or millions of years ago.

Question 21

What is digestion?

Answer 21

The process by which food is broken down. It can be mechanical (chewing) or chemical.

Question 22

What is the alimentary canal?

Answer 22

A muscular tube running brought the body from mouth to anus.

Question 23

What does the mouth do during digestion?

Answer 23

The food is taken into the body through the mouth. During chewing teeth break down the food into small pieces, increasing the surface area on which digestion can take place. The tongue helps to form the food into a ball called a bolus. The bolus gets covered in saliva making it easier to swallow. It also contains an enzyme which starts to break down the starch in food.

Question 24

What does the oesophagus do during digestion?

Answer 24

The oesophagus is a muscular tube between the mouth and the stomach. The muscles contract in waves to push the food down into the stomach. This is called peristalsis.

Question 25

What does the stomach do in digestion?

Answer 25

The stomach is a muscular bag that makes acid and some enzymes, proteases in particular. It churns the food up with digestive juices to make a thick paste using peristalsis.

Question 26

What does the small intestine do during digestion?

Answer 26

The small intestine is a long coiled muscular tube where most of the large food molecules are broken down into smaller soluble molecules. It contains digestive enzymes made by the pancreas and made by itself. The molecules of food are absorbed into the blood using the villi. Food is moved by peristalsis.

Question 27

What does the pancreas do during digestion?

Answer 27

The pancreas makes digestive enzymes and releases them into the first part of the small intestine.

Question 28

What does the large intestine do during digestion?

Answer 28

Undirected food passes into the wide thin-walled tube. Water diffused back into the blood leaving faeces behind.

Question 29

What does the anus do during digestion?

Answer 29

This is where the undigested food passes out of the body.

Question 30

What does the liver do during digestion?

Answer 30

Once digested food has dissolved into the blood, it is taken to the liver to be processed. Some molecules are broken down even more and some are built into larger molecules. The liver also makes bile which helps to digest fat.

Question 31

What does the gall bladder to during respiration?

Answer 31

It is a small organ that stores the bile and releases it into the small intestine when it is needed.

Question 32

Who are carbohydrates broken down?

Answer 32

Simple carbohydrates are sugars and these can build into more complex molecules like starch. Digestive enzymes which break down carbohydrates are called carbohydrases. Amalyse is the carbohydrase which breaks down starch into sugars, which can then be absorbed by the small ingestion are broken down into glucose. An amylase is present in the saliva and another amylase is made in the pancreas and released into the small intestine.

Question 33

How are proteins digested?

Answer 33

Proteases are enzymes which break down proteins into amino acids. Pepsin is a protease made in the stomach which works best in acidic conditions. The optimum pH is about 2-3. The proteases used in the small intestine work best at about pH 8 because the small intestine is alkaline.

Question 34

How are fats digested?

Answer 34

Lipases are enzymes which break down fats into fatty acids and glycerol. Fat and water don’t mix well, so the fats you eat form globules in the digestive juices. This means they have a very small surface area to volume ratio, so the lipases can only break down the fat slowly. Bile emulsifies the fat into small droplets, giving them a large surface area. Bile makes faeces brown and is an alkaline, making the small intestine an alkaline environment.