Fossil records are incomplete because:
1) Very few dead plants and animals actually turn into fossils. Most just decay away
2) Some body parts like soft tissue tend to decay away completely
3) There are fossils yet to be discovered
How does the pentadactyl limb provide evidence for evolution
1) You can see the pentadactyl limb in many species
2) In each of these species the pentadactyl limb has a similar bone structure, but usually a different function
3) The similarities in bone structure provides evidence that species with a pentadactyl limb have all evolved from a common ancestor. If they had evolved from different ancestors, it’d be highly unlike that they’d share a similar bone structure
Growth can be measured by:
1) Size
2) Wet mass
3) Dry mass
Growth involves…
1) CELL DIFFERENTIATION - the process by which a cell changes to become specialised for its job
2) CELL DIVISION - by mitosis
3) CELL ELONGATION - only in plants! It’s where a plant cell expands, making the cell bigger so making the plant grow
A tissue is…
A group of similar cells that work together to carry out a particular function
An organ is…
A group of different tissues that work together to carry out a particular function
An organ system is…
A group of organs working together to perform a particular function
The heart
1) The right atrium receives deoxygenated blood from the body through the vena cava
2) The deoxygenated blood moves through the right ventricle which pumps it to the lungs via the pulmonary artery
3) The left atrium receives oxygenated blood from the lungs through the pulmonary vein
4) The oxygenated blood then moves through the left ventricle, which pumps it out round the whole body via the aorta
How is the heart adapted well to perform its function
1) The left ventricle has a much thicker wall than the right ventricle. It needs more muscle because it has to pump blood around the whole body, whereas the right ventricle only has to pump it to the lungs
2) Valves prevent the backflow of blood
Job of red blood cells
1) RBC carry oxygen
2) They have a biconcave disc shape to have a large surface area for absorbing oxygen
3) They contain haemoglobin
4) They have NO nucleus - so they have more room for haemoglobin
Job of White blood cells
1) WBCs defend against disease
2) They can ingulf bad microorganism say changing shape
3) They can produce antibodies to fight microorganisms, as well as antitoxins to neutralise any toxins produced by microorganisms
Job of platelets
1) Platelets help blood clot
2) They are small fragments of cells
3) They help stop microorganisms getting in wounds
Job of Plasma
1) Transports RBCs, WBCs and platelets
2) Carries nutrients like glucose and amino acids
3) Transports carbon dioxide to the lungs, where it is removed
4) Transports urea to kidneys where it is removed
5) Transports hormones from glands to target organs
6) Carries antibodies and antitoxins produced by WBCs
Fossils found in rock layers tell us 3 things:
1) What the creatures and plants look like
2) How long ago they existed. Generally, the deeper the rock, the older the fossil
3) How they have evolved
Role of arteries
To carry blood away from the heart
Role of capillaries
These are involved in the exchange of materials with a tissue
Role of veins
These carry blood to the heart
How do arteries work
1) They carry blood under pressure
2) The heart pumps the blood out at high pressure so the artery walls are strong and elastic
3) The walls are thick compared to the lumen. They contain thick layers of muscle to make them strong
How do capillaries work
1) They are really small
2) Arteries branch into capillaries
3) They carry blood really close to every cell in the body to exchange substances with them
4) They have permeable walls so substances can diffuse in and out
5) They supply food and oxygen, and take away wastes like carbon dioxide
6) Their walls are only one cell thick. This increases the rate of diffusion by decreasing the distance over which it occurs
How do veins work
1) They take blood back to the heart
2) The capillaries eventually join up to form veins
3) The blood is at low pressure in the veins so the walls don’t need to be very thick (unlike artery walls)
4) They have a big lumen
5) They have valves to keep the blood flowing in the right direction
Carbohydrases e.g. Amylase digest
Starch to sugars
Proteases e.g. Pepsin digest
Protein to amino acids
Lipase digests
Fat to fatty acids and glycerol
In the mouth
1) Food is moistened with saliva
2) The salivary glands produce amylase enzyme in the saliva, which breaks down starch
3) Food is chewed to form a bonus before being swallowed
In the oesophagus
1) Food is taken from the mouth to the stomach
2) It is lined with muscles that contract to help the bolus move along by peristalsis
In the stomach
1) Food is pummelled by its muscular wall
2) The protease enzyme pepsin is produced
3) Hydrochloric acid is produced to kill bacteria and to give the right PH for pepsin to work
In the liver
1) Bile is produced. Bile neutralises stomach acid and emulsifies fats
In the gall bladder
1) Bile is stored before being released into the small intestine
In the small intestine
1) Protease, amylase and lipase enzymes are produced to complete digestion
2) Where ‘food’ is absorbed out of the digestive system and into the body
In the pancreas
1) Protease, amylase and lipase enzymes are produced and released into the small intestine
In the large intestine
1) Excess water is absorbed from the food
Benedict’s Reagent tests for
Sugar. It starts off blue and changes colour of sugar is present. The more sugar there is, the further the colour change goes towards brick red.
Peristalsis involves
Longitudinal and circular muscles
Waves of circular muscle contractions
Push the food along the gut
Waves of longitudinal muscle contractions
Help keep the food in a ball
Three features of Villi that make absorbing digested food into the bloodstream really efficient:
1) Big surface area - digested food is absorbed much more quickly into the blood
2) Single layer of surface cells - digested food can diffuse quickly over a short distance
3) Very good blood supply via capillary network - to assist quick absorption of digested food
A functional food is one that has
Some kind of health benefit beyond basic nutrition
What are probiotics
1) Live bacteria (similar to those found naturally in the gut) e.g. Bifidobacteria and Lactobacillus
2) Added to yoghurt, soya milk and supplements
3) Thought they keep your digestive system healthy and your immune system strong
What are prebiotics
1) They promote growth of ‘good’ bacteria
2) Carbohydrates we cannot digest
3) Occur in leeks, onions, oats and supplements
4) May improve the health of your digestive system and may also help to strengthen your immune system
What are plant stanol esters
1) Chemicals that lower blood cholesterol and reduce the risk of heart disease
2) Occur naturally in plants
3) Produced commercially by using bacteria to convert sterols into stanols
4) Sometimes added to spreads or dairy products
5) PROVEN TO WORK
Things to watch out for about health claims
1) Is the report a scientific study, published in a reputable journal?
2) Was it written by a qualified person (not connected with the people selling it)?
3) Was the sample of people asked/tested large enough to give reliable results?
4) Have there been other studies which found similar results?
3 adaptations of the heart
1) LHs - thick muscular wall so it can pump blood around the body
2) Valves - stop backflow of blood and maintains blood pressure
3) Septum - separates oxygenated and deoxygenated blood
