B2.3 Common systems page 90 Flashcards
Why are there gaps in fossil records?
- fossils don’t always form
- soft tissue decays
- some fossils haven’t been found yet
What is the fossil record?
A collection of fossils from different periods of time that can be used to form a hypothesis about the history of life on Earth
What is a pentadactyl limb?
A five fingered limb structure
How does the pentadactyl limb provide evidence for evolution?
It suggests that all vertebrates evolved from one common ancestor because most vertebrates have a pentadactyl limb
What is growth?
An increase in size, length or mass
What are meristems?
Places just behind the tips of roots and shoots where plant cells keep dividing
How do plants get bigger?
- cells in the meristem divide
- these then elongate
What is elongation in plant cells?
The lengthning of cells after division
What is differentiation in plants?
The specialisation of plant cells after elongation
What are stem cells?
Cells that can differentiate into a specialised cell
What is the difference between adult and embryonic stem cells?
Embryonic stem cells can differentiate into almost any kind of cell whereas adult stem cells have a more limited range
How much blood does the average adult contain?
5 litres
What is blood made up of?
- plasma
- red blood cells
- white blood cells
- platelets
What percentage of blood is plasma?
55%
What percentage of the blood are white blood cells and platelets?
<1%
What percentage of the blood are red blood cells?
45%
What colour is plasma?
Yellow
What does plasma do?
Transport dissolved substances like carbon dioxide, food substances and hormones
What pigment causes red blood cells to be red?
Haemoglobin
What do red blood cells do?
Transport oxygen to cells in the form of oxyhaemoglobin
What is formed when oxygen combines with haemoglobin?
Oxyhaemoglobin
What type of reaction is the combining of oxygen and haemoglobin?
A reversible reaction
When does oxygen combine with haemoglobin?
When the blood passes through the lungs
What is the shape of a red blood cell?
A biconcave disc
Why does a red blood cell’s biconcave shape make oxygen absorbption more efficient?
It gives a larger surface area to volume ratio
Why does a red blood cell’s lack of nucleus increase the amount of oxygen it can carry?
It makes more room to carry as much haemoglobin as possible
Do white blood cells or red blood cells have a nucleus?
White blood cells
What do white blood cells do?
Defend the body against disease
How do white blood cells destroy pathogens and foreign cells?
- they produce antibodies that match the antigens of the pathogen and bind to them
- they surround the foreign cells
Why don’t platelets have a nucleus?
Because they are fragments of cells
What do platelets do?
Make the blood clot
What is a tissue?
A group of the same types of specialised cells
What is an organ?
A group of several different tissues working together to carry out a particular function within the body
What is an organ system?
A group of organs working together to carry out a particular function
What is deoxygenated blood?
Blood low in oxygen
What is oxygenated blood?
Blood high in oxygen
What do arteries do?
Transport blood away from the heart
What do veins do?
Transport blood to the heart
What does the pulmonary vein do?
Bring oxygenated blood from the lungs to the heart
What does the pulmonary artery do?
Bring deoxygentated blood from the heart to the lungs
What do valves do?
Make sure the blood in the heart goes in the right direction
What do tendons in the heart do?
Stop valves from turning inside out
What does the superior vena cava do?
Bring blood from the upper body to the right atrium
Which side of the heart is bigger?
The left
What does the inferior vena cava do?
Bring blood from the lower body to the right atrium
What seperates the two different sides of the heart?
The septum
What happens when the right atrium is full?
Muscles in the wall contract to force blood through the valves into the right ventricle
What happens when the right ventricle is full?
The muscles of the ventricle wall contract to force blood through the valves into the pulmonary artery
What happens to deoxygenated blood when it reaches the lungs?
It becomes oxygenated because it picks up oxygen
What atrium does the pulmonary vein go to?
The left atrium
What happens when the left atrium is full?
It contracts to force blood through the valves into the left ventricle
What happens when the left ventricle is full?
It forces the blood through a valve into the aorta
What does the aorta do?
Carry blood from the left ventricle to the rest of the body
What type of blood is found in the left side of the heart?
Oxygenated blood
What type of blood is found in the right side of the heart?
Deoxygenated blood
Why is the muscle wall on the left side of the heart thicker than the right side?
It has to pump blood all around the body instead of just around the lungs so it takes more energy
What are the three types of blood vessels?
- arteries
- veins
- capillaries
Why do arteries have strong, thick walls?
The blood has to be under high pressure to reach all parts of the body
What do capillaries do?
Allow substances to diffuse into and out of the blood from tissues and cells
What type of blood vessels have the thinnest walls?
Capillaries
Why do veins have a large space for blood to flow?
Because the blood flows slowly and at low pressure
What makes up the circulatory system?
The heart and blood vessels
What is digestion?
The process of breaking down the large insoluble molecules in food into smaller soluble ones
What is a bolus?
A ball of chewed food
Why does the mouth chew food to break it up into small pieces?
To increase the surface area for digestive enzymes to work on
What does saliva do in the digestive system?
- lubricate the bolus to make it easier to swallow
- start to break down the starch in food because of the amylase found in it
What is the digestive system made up of?
- mouth
- oesophagus
- stomach
- small intestine
- large intestine
- pancreas
- anus
- liver
- gallbladder
What process pushes food down the alimentary canal?
Peristalsis
What happens to the bolus once it reaches the stomach?
It turns into a thick paste when it’s churned up with stomach acid and enzymes by peristalsis
What absorbs digested food into the blood in the small intestine?
Villi
What organ does most digestion happen in?
The small intestine
What does the pancreas do in the digestive system?
Produce enzymes which are released in the first part of the small intestine
What happens in the large intestine?
Water diffuses back into the blood
Where does digested food go once it is absorbed into the blood?
The liver
What does the liver do when it gets digested food molecules?
It breaks them down even more or builds them up into larger molecules
What does the liver produce?
Bile
What does the gall bladder do?
Store bile to be released when the small intestine needs it
What are the three main types of food molecules?
- carbohydrates
- proteins
- fats
What are the simplest forms of carbohydrate called?
Sugars
What enzymes break down carbohydrates?
Carbohydrases
What does amylase do?
Break down starch into sugars
Where is amylase found?
- in the saliva
- in the small intestine
What produces amylase?
The pancreas
What enzymes digest proteins?
Proteases
What are proteins broken down into?
Amino acids
Where is pepsin produced?
The stomach
What type of enzyme is pepsin?
A protease
What pH is stomach acid?
pH 2-3
What pH do proteases released in the small intestine work best at?
pH 8
What pH do proteases released in the stomach work best at?
pH 2-3
What type of enzymes digest fats?
Lipases
What do lipases break down fat into?
Fatty acids and glycerol
What does bile do to fat?
Emulsify it
Why does bile emulsify large globules of fat?
To increase the surface area to volume ratio so that it’s digested more quickly
Is bile acidic or alkaline?
Alkaline
Why is bile alkaline?
It helps neutralise the acid from the stomach so that the protease enzymes work better
What happens to large globules of fat when bile emulsifies them?
They are broken down into tiny droplets
Why do villi increase the amount of digested food that can diffuse into the blood?
They increase the surface area of the small intestine
