paper one Flashcards
(457 cards)
1
Q
what do living organisms need to do to be considered living?
A
Movement
Respiration
Sensitivity (respond to surroundings)
Homeostasis
Grow
Reproduce
Excrete
Nutrition
2
Q
are plants multicellular or unicellular?
A
multicellular
3
Q
are animals multicellular or unicellular?
A
multicellular
4
Q
are fungi multicellular or unicellular?
A
usually multicellular but some are unicellular
5
Q
what are plant cell walls made of?
A
cellulose
6
Q
what are fungi cell walls made of?
A
chitin
7
Q
what do plants store carbohydrates as?
A
starch
8
Q
what organelles do plants have that animals don’t have?
A
- chloroplasts
- cell walls
- vacuoles
9
Q
what organelles do both animal cells and plant cells have?
A
- cytoplasm
- cell membrane
- mitochondria
- nucleus
- ribosomes
10
Q
what do animals (usually) store carbohydrates as?
A
glycogen
11
Q
what are fungi normally organised as?
A
mycelium made from hyphae (thread like structures) which contain many nuclei
12
Q
what kind of digestion do fungi use?
A
saprotrophic digestion
13
Q
what is saprotrophic digestion?
A
digestive enzymes are secreted outside of the cell onto the food, which is then broken down into small soluble molecules and absorbed by the decomposer
14
Q
can fungi photosynthesise?
A
no
15
Q
do animals have nervous coordination?
A
yes
16
Q
what are some examples of fungi?
A
- mucor (typical hyphal structure)
- yeast (single-celled)
17
Q
are protoctists multicellular or unicellular?
A
normally unicellular
18
Q
what are three examples of protoctists?
A
- amoeba (animal-like)
- chlorella (plant-like)
- plasmodium (pathogenic - responsible for malaria)
19
Q
are bacteria multicellular or unicellular?
A
unicellular
20
Q
what organelles do bacteria have?
A
- cell wall
- cell membrane
- cytoplasm
- plasmids (circular chromosome of DNA)
21
Q
can bacteria photosynthesise?
A
some can but most feed on other dead or living organisms
22
Q
what are two examples of bacteria?
A
- lactobacillus bulgaricus (yoghurt making)
- pneumococcus (pathogen for pneumonia)
23
Q
which kingdoms can be pathogenic?
A
bacteria, viruses, fungi, protoctists
24
Q
what are pathogens?
A
a pathogen are microorganisms which cause infectious disease. they harm the host by releasing toxins or damaging cells
all viruses are pathogens; fungi, bacteria and protoctists can be pathogenic (but not all of them are)
25
how big are viruses?
smaller than bacteria
26
what do viruses need to reproduce?
a host cell
27
can viruses infect every type of living organism?
yes
28
what makes up a virus cell?
- no cellular structure
- protein coat
- one type of nucleic acid (either DNA or RNA)
29
what are three examples of viruses?
- tobacco mosaic virus (causes discolouration of leaves of tobacco plants by preventing chloroplasts from forming)
- influenza (causes the flu)
- HIV (causes AIDS)
30
what are organelles?
small structures in the cell with a specific function
31
what are cells?
smallest functioning unit of life, contain organelles to carry out a specific function
32
what are tissues?
a group of similar cells working together to carry out the same function
33
what are organs?
made up of several different tissues working together to carry out a more complex function
34
what are organ systems?
made up of several different organs working together to carry out a complex function essential for life
35
what is the function of a nucleus?
controls the activity of the cell by making proteins, contains the chromosomes
36
what is the function of cytoplasm?
jelly-like liquid where chemical reactions occur
37
what is the function of mitochondria?
site of aerobic respiration
38
what is the function of the ribosomes?
protein synthesis from amino acids
39
what is the function of the chloroplasts?
site of photosynthesis
40
what is the function of cell walls?
keeps the shape of the cell, prevents the cell from bursting
41
what is the function of the cell membranes?
controls what goes in and out of the cell (selectively permeable)
42
what is the function of the vacuole?
contains cell sap, stores dissolved sugars, mineral ions, and other substances
43
what chemical elements are in carbohydrates?
CHO
44
what chemical elements are present in proteins?
CHON
45
what chemical elements are present in lipids?
CHO
46
what is starch and glycogen made up of?
glucose (simple sugars)
47
what are proteins made up of?
amino acids
48
what are lipids made of?
fatty acids and glycerol
49
how do you test for glucose?
1. place a small sample (approx. 2cm^3) of food in a test tube
2. then add 1cm^3 of Benedict’s solution, or enough for it to appear blue
3. then heat in an 85 degree celcius water bath for 5 minutes
4. if the mixture turns from blue to green/yellow/orange/brick red then sugar is present
50
how do you test for starch?
1. take a small sample of food and place it in a well on a spotting tile
2. add 10 drops of iodine solution/a roughly equal amount of iodine to food
3. if starch is present, the iodine changes from orange to black/blue
51
how do you test for proteins?
1. place a small food sample in a test tube
2. add a roughly equal amount of Biuret solution or enough for the pale blue colour to be seen
3. if the mixture turns from blue to mauve/purple, proteins are present
52
how do you test for lipids?
1. place a small food sample in a test tube
2. add roughly equal amount of ethanol and mix well
3. add roughly equal amount of water (1:1:1) and mix well again
4. if the mixture turns milky, fat is present
53
what is the role of enzymes?
biological enzymes in metabolic reactions
54
how do temperature changes affect enzymes?
as temperature increases, the enzymes and the substrate get more kinetic energy, so more enzyme-substrate complexes are formed as there are more collisions. as the temperature increases past the optimum temperature, enzymes denature, bc they have too much kinetic energy so the enzyme’s active site changes shape, so the substrate can no longer fit (is no longer complimentary), so there are less/no enzyme-substrates complexes formed
55
how would you test to see how temperature change affects enzymes?
1. place single drops of iodine solution in rows on the spotting tiles
2. label a test tube with the temperature to be tested (eg. 10 degrees celcius)
3. use cold water from the tap and hot water from the kettle to prepare a water bath at that temperature, and keep it at that temperature for the test using a thermometer
4. use a syringe to place 2cm^3 of amylase into the test tube, then place it in the water bath for 5 minutes
5. use another syringe to add 2cm^3of starch solution to the amylase solution (leaving the test tube in the water bath) start the stop watch and mix using the pipette
6. after 30 seconds, use the pipette to squirt one drop of iodine solution into the first drop of iodine, the squirt the rest of the pipette back in the test tube. the iodine solution should turn blue/black
7. after another 30 seconds, drop another drop of the solution into the next iodine drop
8. repeat step 7 until the iodine stays orange
9. count how many iodine drops you used, each equals 30 seconds of reaction time
10. repeat 1-9 for each temperature (eg 20, 30, 40, 50, 60)
11. repeat each temperature 3 times and work out a mean
56
how does change in pH affect enzyme activity?
as the pH increases up to the optimum, the enzyme’s active site becomes more complimentary to it’s substrate, so enzyme activity increases. after it reaches the optimum, the active site changes shape and so the enzyme denatures so enzyme activity decreases/stops
57
what is diffusion?
the random movement of particles from an area of high concentration to low concentration
58
what is osmosis?
the net diffusion of free water molecules from an area of high water potential to low water potential across a partially permeable membrane
59
what is active transport?
the movement of molecules from an area of low concentration to high concentration using ATP
60
how does sa:v affect diffusion?
the higher the sa:v is, the higher the rate of diffusion is
61
how does distance affect diffusion?
the greater the distance, the lower the rate of diffusion
62
how does temperature affect diffusion?
the greater the temperature, the higher the rate of diffusion
63
how does concentration gradient affect diffusion?
the higher the concentration gradient is, the higher the rate of diffusion is
64
how do you investigate osmosis in living systems?
1. use a cork borer to cut equal cylinders in a potato
2. cut the cylinders the same length (about 3cm) - have five
3. measure and record the mass of each
4. measure out 10cm^3 of 0M, 2.5M, 5M, 7.5M, 1M sucrose solution into 5 different test tubes
5. add one potato cylinder (of known mass) into each tube
6. leave for 30 minutes
7. take out each potato and gently dry them by tapping them with a paper towel then weigh them and record the new mass for each
65
how do you investigate osmosis in a non-living system?
connect a visking tube to a capillary tube, and fill the visking tube with sucrose solution and put into a beaker with 20 cm^3 of water. leave for 30 mins, then measure the volume of water. repeat with different concentrations of sucrose solution
66
how do you investigate diffusion in non-living systems?
put potassium permanganate crystals in a beaker of water. observe after 15 minutes, then observe after 1 hour
67
what does photosynthesis do?
convert light energy into chemical energy
68
what is the word equation for photosynthesis?
water + carbon dioxide --light--> oxygen + gluose
69
what is the balanced chemical equation for photosynthesis?
6CO2 + 6 H2O --> 6O2 + C6H12O6
70
how does varying carbon dioxide concentration affect the rate of photosynthesis?
a higher concentration of carbon dioxide increases the rate of photosynthesis because there are more molecules for the enzymes to collide with
at a certain point, increasing the concentration doesn't change anything, as it is no longer the limiting factor
71
how does varying light intensity affect the rate of photosynthesis?
increasing the light intensity increases the rate of photosynthesis because there is more energy for the reaction to occur
at a certain point increasing the light intensity doesn't change anything because something else has become the limiting factor
72
how does varying temperature affect the rate of photosynthesis?
enzyme shape
73
how are leaves specialised for photosynthesis?
- large surface area + thin
- upper epidermis is transparent
- palisade cells are long, thin, and tightly packed
- stomata allow gasses to diffuse into the air spaces of leaf
- xylem transports water into leaf
- phloem vessel transports sugars
74
how does the large surface area and thinness of a leaf help in photosynthesis?
- maximises absorption of sunlight by cells
- increases number of stomata so carbon dioxide can diffuse quicker
75
how does the upper epidermis being transparent help photosynthesis?
allows light to penetrate the palisade mesophyll
76
how does the palisade cells being long, thin, ad tightly packed together help photosynthesis?
contain lots of chloroplasts which maximises the absorption of sunlight energy - palisade is the main site of photosynthesis
77
how do the stomata help photosynthesis?
provides a short diffusion distance for carbon dioxide because it allows gasses to diffuse into the air spaces of the cell
78
how do the xylem help photosynthesis?
provide a short diffusion distance for water
79
what do plants require for growth?
mineral ions
80
what are magnesium ions needed for in plants?
chlorophyll
81
what are nitrate ions needed for in plants?
making amino acids
82
what is the symptom of deficiency of nitrate ions in plants?
stunted growth
83
what are phosphate ions needed for in plants?
needed to make nucleic acids and part of the cell membrane
84
what is the symptom of deficiency of magnesium ions in plants?
yellow leaves
85
what is the symptom of deficiency of phosphate ions in plants?
poor root growth or purple younger leaves
86
how can you investigate the effect of light intensity on photosynthesis?
1. place the beaker of pondweed 10cm away from the light source
2. count the number of bubbles produced in one minute (using a stopwatch
3. repeat twice more and record the mean
4. repeat 1-3 for 4 more distances, eg. 15cm, 20cm, 25cm, 30cm
5. record the results in a table
87
how can you investigate the effect of carbon dioxide concentration on photosynthesis?
1. de-starch the plant by putting it in a dark cupboard for 24 hours
2. put a conical flask containing potassium hydroxide around one leaf, this will absorb the carbon dioxide in the air
3. put an empty conical flask around another leaf as a control test
4. place the plant in a bright place
5. test both leaves for starch using iodine solution (drop it in boiling water, place it in hot ethanol for 5-10mins, spread on a white tile and drop iodine solution over it)
88
how would you investigate the effect of chlorophyll on photosynthesis?
1. use a variegated leaf
2. put the leaf in boiling water for 30 seconds to kill the tissue and break down cell wall
3. put the leaf in a boiling tube of hot ethanol for 5-10mins to remove the chlorophyll so the colour can be seen more easily
4. rinse the leaf under cold water to soften it
5. spread it out on a white tile and use iodine to test for starch, the white parts should stay orange and the green parts will turn blue/black
89
what are the components of a balanced diet?
- carbohydrates
- proteins
- lipids
- vitamins
- minerals
- water
- dietary fibre
90
what are the functions of carbohydrates?
- direct source of energy
- fuel for respiration
91
what is the function of dietary fibre?
- provides bulk for intestines to push food through it
- prevents bowel cancer and constipation
92
what is the function of lipids?
- storing and providing energy
- thermal and electrical insulation
- fuel for respiration
93
what is the function of protein?
- repairs and builds tissues
- fuel for respiration
94
what is the function of vitamin a?
- making a chemical in the retina and keeping the retina healthy
- protects the surface of the eye
- prevents night blindness
95
what is the function of vitamin c?
- needed for cells and tissues to stick together
- prevents scurvy
96
what is the function of vitamin d?
- needed to absorb calcium and phosphate ions from food
- prevents rickets
97
what is the function of iron?
- forms part of haemoglobin
- prevents anaemia
98
what is the function of calcium?
- needed to form bones and teeth
- prevents osteoporosis and rickets
99
what is the function of water?
it is an essential solvent, transports components of blood, is essential for temperature regulation
100
what are some sources of carbohydrates?
- bread
- rice
- fruits
- potatoes
- cereals
101
what are some sources of dietary fibre?
- fruits
- veggies
- grains
102
what are some source of lipids?
- butter
- cooking oil
- avocado
- cream
103
what are some sources of protein?
- meat
- fish
- eggs
- quinoa
- quorn
104
what are some sources of vitamin a?
- fish oils
- liver
- butter
- carrots
105
what are some sources of vitamin c?
fresh fruits and veggies
106
what are some sources of vitamin d?
- dairy products
- oily fish
107
what are some sources of iron?
- red meat
- liver
- spinach
108
what are some sources of calcium?
- milk and dairy products
- fresh fruits
- fish
109
what are some sources of water?
- water
- cucumber
- lettuce
110
what is the function of the mouth?
mechanical digestion, increasing the surface area of food (by making it into bolus), salivary amylase breaks down starch into maltose, saliva makes food easier to swallow
111
what is the function of the oesophagus?
mechanical digestion; peristalsis occurs to push bolus down towards the stomach
112
what is the function of the stomach?
chemical digestion: pepsin from stomach walls to break down proteins into peptides, mechanical digestion by muscle churning, stomach acid lowers pH for pepsin and sterilises food
113
what is the function of the duodenum?
chemical digestion - contains many enzymes (amylase, lipase, protease)
114
what is the function of the ilieum?
chemical digestion - enzymes break down food
villi and microvilli to absorb nutrients
115
what is the function of the colon?
reabsorbing water to form faeces
116
what is the function of the rectum?
egestion
117
what is the function of the pancreas?
secretes enzymes into stomach and small intestine for chemical digestion
118
how is food moved through the gut?
peristalsis
119
what enzymes are in the mouth?
salivary amylase
starch --> maltose
120
what kind of enzymes are there in the stomach?
pepsin (protease)
proteins --> peptides
121
what enzymes are produced in the pancreas?
pancreatic amylase, trypsin (protease), pancreatic lipase
122
what kind of enzymes are there in the duodenum?
pancreatic amylase, trypsin (protease), pancreatic lipase
starch –> maltose
peptides –> amino acids
lipids –> fatty acids + glycerol
in the walls (gets secreted out):
maltase
maltose –> glucose
123
what kind of enzymes are there in the ilieum?
(in the walls and gets secreted out)
maltase
maltose –> glucose
124
where is bile produced?
the liver
125
where is bile stored?
the gall bladder
126
what is the role of bile?
emulsifies lipids, neutralises stomach acid
127
how is the small intestine adapted for absorption?
thin cell wall - decreases diffusion distance for soluble molecules
large surface area to volume ratio - villi increases surface area for diffusion
large network of capillaries - maintain the concentration gradient
128
what does respiration produce?
ATP
129
what does ATP provide for cells?
energy
130
what is the difference between aerobic and anaerobic respiration?
aerobic: with oxygen, produced carbon dioxide + water, produces more ATP
anaerobic: without oxygen, produces lactic acid (in animals)
131
what is the word equation for aerobic respiration?
oxygen + glucose --> carbon dioxide + water (+ATP)
132
what is the balanced chemical equation for aerobic respiration?
6O2 + C6H12O6 --> 6CO2 + 6H2O
133
what is the word equation for anaerobic respiration in animals?
glucose --> lactic acid
134
what is the word equation for anaerobic respiration in plants (and fungi)?
glucose --> ethanol + carbon dioxide
135
what is the method to investigate the evolution of carbon dioxide from respiring seeds (or other organisms)?
1. pour some sodium hydroxide solution into the first conical flask. this is connected to the pipe that allows the inflow of air and removes the carbon dioxide from the air
2. pour some hydrogen carbonate indicator in the second flask. this is connected to the first flask with a delivery tube
3. place the respiring seeds in the third conical flask on some moist cotton. this is connected to the second conical flask
4. pour some hydrogen carbonate indicator in the fourth flask, which is connected to the pipe to allow the outflow of air
5. observe the colour of the hydrogen carbonate indicator
136
what colour does hydrogen carbonate indicator go in carbon dioxide?
yellow
137
what is the method to investigate the evolution of heat from respiring cells (and other organisms)?
1. set up two thermoflasks
2. place the respiring seeds with cotton wool in one of the thermoflasks
3. place the boiled seeds with moist cotton wool in the other thermoflask
4. use a thermometer to measure and record the initial temperature
5. after a certain number of days, measure and record the final temperature and work out the temperature difference
138
what are the ribs?
bone structures that protect internal organs (including lungs)
139
what are the intercoastal muscles?
muscles in between the ribs that move the ribs during inhalation and exhalation
140
what is the diaphragm?
a sheet of muscle at the bottom of the thorax that changes the volume of the thorax
141
what is the trachea?
wind pipe that connects the mouth + nose to the lungs
142
what are the bronchi?
thick tubes that divide into two bronchi in the lungs (one bronchus for each lung)
143
what are the bronchioles?
the bronchi will split to form them and are connect the bronchi to the alveoli
144
what are the alveoli?
air sacs where gas exchange occurs
145
what are the pleural membranes?
the thin moist membrane lining the outside of the lungs for lubrication to reduce friction, and to stick outside of lungs to chest cavity for lungs to follow chest movement
146
what happens during inhalation?
diaphragm contracts so it moves down and flattens, the intercostal muscles contract, which pulls the ribs up and out
volume of thorax increases, air pressure falls. the air pressure in the thorax is now lower than the atmospheric pressure, so air moves into the lungs
147
what happens during exhalation?
the diaphragm relaxes so it moves up and domes, the intercostal muscles relax, which makes the rib cage move down and in
the volume of the thorax decreases so air pressure rises. air pressure in the thorax is higher than atmospheric pressure so air moves out of the lungs
148
how are the alveoli adapted for gas exchange?
they have a large surface area to volume ratio which increases the rate of diffusion
they are surrounded by a network of capillaries which keeps the concentration gradient high
each alveolus is one cell thick which shortens the diffusion distance
149
what is the effect of smoking on the air passages?
- tar in cigarettes destroys cilia (which gets rid of dust and microbes trapped in mucus) so it causes a build up of mucus, and increased risk of bronchitis
- tar in cigs contains carcinogens which increases risk of lung cancer
150
what is the effect of smoking on the alveoli?
tar in cigs breaks down alveoli walls and makes them merge together, so it increases the surface area : volume
insufficient gas exchange will increase the risk of emphysema - shortness of breath due to insufficient oxygen transport in blood
151
what effect does smoking have on the circulatory system?
- nicotine in blood vessels cause the blood vessels to narrow, placing strain on circulatory system and results in increased blood pressure
- narrowing of blood vessels also cause the build up of fat globules, increasing the risk of coronary heart disease (CHD).
- the carbon monoxide from cigarette smoking will bind irreversibly to haemoglobin, reducing the amount of oxygen that can be carried in red blood cells, so it increases risk of emphysema (shortness of breath due to insufficient oxygen transport)
152
what is coronary heart disease?
it is when the lumen of the coronary arteries is blocked with fat, and irritation of the lining of the arteries causes it to harden until lumen is blocked. this means there's less oxygen taken to the heart, so there is more anaerobic respiration, so lactic acid is produced which causes chest pains (angina). this means less atp is formed, so the muscles stop contracting and die, causing a heart attack
153
what is the method to investigate breathing in humans and the release of carbon dioxide?
1. pour lime water into a boiling tube
2. using the straw, breathe into it
3. note the change in limewater
154
what is the method to investigate breathing in humans and the effect of exercise?
1. measure the breathing rate of the person at rest (breaths/minute)
2. carry out a specific exercise, like star jumps, for 1 minute
3. measure the breathing rate immediately after
4. repeat 2-3 for different intensities of exercise (still the same thing though)
155
why can simple unicellular organisms rely on diffusion for movement of substances in/out of the cell?
they have a large surface area to volume ratio (because of size and often shape) so very efficient for diffusion, unicellular organisms also often have moist membranes to allow substances to diffuse easily
156
why do multicellular organisms need a transport system?
they have a small surface area to volume ratio so diffusion is insufficient and they can't rely on diffusion to transport necessary substances, so they require a transport system to provide a constant supply of a necessary substance
157
what is the role of the phloem?
transporting sucrose and amino acids between the leaves and other parts of the plant, can flow both ways
158
what is the role of the xylem?
transporting water and mineral ions from the roots to other parts of the plant, can only move up
159
what is the composition of the blood?
- red blood cells
- white blood cells
- platelets
- plasma
160
what is the role of plasma?
- transport of waste carbon dioxide produced by aerobic respiration to the lungs for exhalation
- transports digested food to respiring for assimilation in the form of simple sugars (eg glucose) and amino acids
- transports urea from the liver to the kidney for excretion
- transports hormones made by the endocrine system to target organs to stimulate change
- maintains constant body temperature
161
how does plasma maintain body temperature?
mainly composed of water which has a high specific heat capacity which allows plasma to maintain a constant body temperature for optimum enzyme activity
162
how are red blood cells adapted to be suitable for transport of oxygen?
- haemoglobin
- no nucleus
- small and flexible
- thin cell membrane
- biconcave
163
why do red blood cells contain haemoglobin
haemoglobin binds with oxygen to form oxyhaemoglobin to transport oxygen to respiring cells
164
why do red blood cells have no nucleus?
allow more space for haemoglobin to bind with more oxygen
165
why are red blood cells small and flexible?
to allow them to squeeze through narrow capillaries and blood vessels for efficient transport
166
why do red blood cells have a thin cell membrane?
makes diffusion of oxygen more efficient because it shortens the diffusion distance
167
why do red blood cells have a biconcave shape?
increases surface area to volume ratio and decreases the distance to the centre of the cell so diffusion is more efficient/speeds up rate of diffusion
168
what are most diseases caused by?
pathogens entering the body and feeding and reproducing in it. they may damage the body or poison it by excreting toxic waste substances called toxins
169
what are the two types of white blood cell?
lymphocytes + phagocytes
170
what is the process of a phagocyte when it deals with microorganisms entering the body?
- recognise the pathogen
- phagocyte engulfs the pathogen in a process known as phagocytosis
- they lysozymes containing enzymes move towards the pathogen
- enzymes break down the pathogen
- waste products are removed from the phagocyte
171
what kind of proteins do lymphocytes produce>
antibodies
172
what shape are antibodies?
y-shaped
173
what is an antigen?
proteins on the surface of cells
174
what do the antibodies attach to?
the antigens
175
which blood cell allows organism to build up an immunity towards certain diseases?
lymphocytes
176
what is the process of lymphocytes dealing with foreign bodies?
- lymphocytes detect pathogen's antigens
- splits into two cells (one becomes memory cell)
- lymphocyte identifies the correct type of antibody to make, which is complimentary to the pathogen's antigen
- lymphocyte releases large numbers of correct antibody
- pathogens either clump together resulting in death or the antibodies trigger phagocytes. some pathogens can even burst
- lymphocytes produce cells that produce lots of the antibody very quickly if they detect the same pathogen again - called memory cells
177
what are anti-toxins?
antibodies specialised to combat toxins - chemicals released by the pathogen which cause cell damage
178
what are the adaptations of a phagocyte?
- sensitive cell surface membrane
- enzymes (lysozymes)
- lobed nucleus
179
why do phagocytes have a sensitive cell surface membrane?
allows them to detect and locate pathogens via chemicals produced
180
why do the phagocytes have digestive enzymes in the lysozymes?
to digest and remove the pathogen from the body
181
why do phagocytes have a lobed-nucleus?
to squeeze through narrow gaps in the capillaries, allowing them to digest and remove the pathogens quickly
182
what are the adaptations of a lymphocyte why?
a large nucleus containing multiple copies of DNA to produce antibodies in large amounts, preventing spread of diseases and infections
183
what is the function of the circulatory system?
transport substances around the body
184
which vessel goes from the heart to the lungs?
the pulmonary artery
185
which vessel goes from the lungs to the heart?
the pulmonary vein
186
which vessel brings deoxygenated blood to the heart?
the vena cava
187
which vessel takes oxygenated blood away from the heart?
aorta
188
which vessel brings blood to the liver?
hepatic artery
189
which vessel brings blood to the gut?
mesenteric artery
190
which vessel brings blood to the kidneys?
the renal artery
191
which vessel transports blood between the gut and the liver?
the hepatic portal vein
192
which vessel takes blood away from the kidney?
the renal vein
193
which vessel takes blood away from the liver?
hepatic vein
194
what kind of circulation do humans have?
a double circulation
195
how is the circulation system usually divided?
- pulmonary circulation
- systemic circulation
196
what is pulmonary circulation?
deoxygenated blood is pumped to the lungs and oxygenated blood returns back to the heart
197
what is systemic circulation?
oxygenated blood is pumped to all the other organs of the body and deoxygenated blood returns back to the heart
198
what four chambers is the heart divided into?
two atria and two ventricles
199
where are the atria?
the two chambers at the top of the heart
200
where are the ventricles?
below the atria
201
do the ventricles or the atria have thicker muscular walls?
atria have thinner muscular walls, the ventricles have thicker muscular walls
202
what separates the left and right sides of the heart?
the septum
203
which side of the heart pumps oxygenated blood around the body?
the left side
204
which side of the heart pumps deoxygenated blood to the lungs?
the right side
205
which ventricle has thicker walls?
the left ventricle has thicker walls, allowing it to pump blood at higher pressures so that the blood can travel around the whole body
206
how does the heart pump blood?
the atria contract, emptying blood into the ventricles, then the ventricles contract, pushing blood into the arteries. then the valves close to ensure the blood flows in the correct direction
207
on a diagram, is the right ventricle on the left or right side?
on the left side
208
what is the process of the right hand side of the heart?
- Deoxygenated blood from respiring cells are carried by the Vena Cava to the Right Atrium
- Right Atrium will contract to increase pressure, pushing blood into Right Ventricle through Atrioventricular Valve
- Atrioventricular Valve closes to prevent backflow of blood from Ventricle to Atrium
- Right Ventricle will contract to increase pressure, causing blood to be carried out via Pulmonary Artery to be Oxygenated at the Lungs through the Semilunar Valve
- Semilunar Valve closes to prevent backflow of blood from Artery to Ventricle
209
what is the process of the left side of the heart?
- Pulmonary Vein carries Oxygenated blood from Lungs to the Left Atrium
- Left Atrium will contract to increase pressure, pushing blood into Left Ventricle through Atrioventricular Valve
- Atrioventricular Valve closes to prevent backflow of blood from Ventricle to Atrium
- Left Ventricle will contract to increase pressure, causing Oxygenated blood to be carried out via Aorta to respiring cells around the body
210
what is special about the heart?
it is myogenic, so doesn't need external stimulation to pump blood
211
what is the atrioventricular valve?
prevents the backflow of blood from the ventricle to the atrium - also known as the tricuspid between right atrium and right ventricle, and bicuspid between left atrium and left ventricle
212
what are semilunar valves?
valve that prevents the backflow of blood from the artery to the ventricle
213
what controls changes in the heart rate?
nerve impulses from a part of the brain called the medulla
214
how does the heart rate change when exercise begins?
- when exercise begins, muscles produce more carbon dioxide in aerobic respiration
- sensors in the aorta and carotid artery detect the increase
- they send nerve impulses to the medulla
- the medulla responds by sending nerve impulses along the accelerator nerve
- the accelerator nerve increases the heart rate
- more blood is supplied to the muscles to meet the demands of increased aerobic respiration
215
what triggers an increase in heart rate when we are stressed or angry or afraid?
triggered by the secretion of the hormone adrenaline
216
what does plasma transport?
-dissolved nutrients (eg. glucose/amino acids)
- dissolved waste products (incl. urea and carbon dioxide)
- hormones
- proteins
- heat energy
217
why does heart rate continue to increase after exercise?
extra oxygen is needed to breakdown lactic acid produced by anaerobic respiration - oxygen debt
218
what risk factors make coronary heart disease more likely?
- diet; eating lots of saturated fats (and salts and alcohol) increases blood cholesterol and increases the risk of fatty deposits
- smoking; increases blood pressure and increases risk of fatty deposits, causes vasoconstriction
- high blood pressure; damages the artery lining and increases the risk of fatty deposits forming. high salt levels in your diet increases the risk of high blood pressure
- obesity; being obese will increase blood pressure and may be linked to a poor diet
- lack of exercise; causes high blood pressure
- stress; stimulates the secretion of hormones that increase blood pressure so increases the risk of fatty deposits
219
what is the structure of an artery?
- thick outer wall
- thick layer of elastic tissue
- thick layer of muscular tissue
- small lumen
220
what is the structure of a vein?
- fairly thin outer wall
- thin layer of muscle and elastic tissues
- has semilunar valves
- large lumen
221
what is the structure of a capillary?
- the wall is one cell thick
- very small lumen
222
do the arteries carry high or low pressure blood?
high
223
do veins carry high or low pressure blood?
low pressure
224
what are capillaries the site of?
exchange of materials by diffusion
225
where do capillaries carry blood?
through all the tissues
226
what is the function of the thick outer wall of the artery?
allows them transport blood at high pressure without bursting
227
what is the function of the thick layer of elastic tissue of the arteries?
allows artery to stretch and recoil to keep the blood flowing at high pressure
228
what is the function of the thick layer of muscular tissue of arteries?
helps control the flow of blood by widening (dilating) and narrowing (constricting)
229
why do veins have a thin outer wall?
blood is flowing at lower pressure so thick wall is not needed
230
why do veins have a thin layer of muscle and elastic tissue?
wall can contract to keep blood flowing
231
why do veins have semilunar valves?
prevents blood flowing backwards
232
why do capillaries have walls that are one cell thick?
short distance for diffusion of substances from blood into tissues
233
why do capillaries have very small lumen?
to fit between cells for branching, which increases surface area to volume ratio for efficient material exchange
234
why do veins have wide lumen?
to support transport of large volumes of blood
235
why do arteries have small lumen?
to maintain high blood pressure to pump blood around the body
236
which vessels normally transfer deoxygenated blood?
veins (excluding pulmonary vein)
237
which vessels normally transfer oxygenated blood?
arteries (excluding pulmonary artery)
238
which vessels carry blood away from the heart?
arteries
239
which vessel carries blood towards the heart?
veins
240
what is carbon dioxide a waste product of in plants?
aerobic respiration
241
what is oxygen a waste product of in plants?
photosynthesis
242
how does oxygen and carbon dioxide diffuse out of a plant as waste products?
through the stomata
243
what are the excretory products of the lungs?
carbon dioxide (waste product of aerobic respiration)
244
how is carbon dioxide excreted out of the lungs?
through exhalation
245
what are xylem made up of?
- thick walled dead cells which contain no cytoplasm - they're completely hollow
- cell contains lignin (waterproof)
- end walls have been broken down
246
what are phloem made up of?
- contains living cells
- tubes are formed by cells arranged end to end but have cell walls made of cellulose
247
where is urea made?
the liver cells
248
what is the excretory product of the kidney?
urea, excess water, and salts
249
what are the excretory products of the skin?
urea and water (sweat)
250
what is excretion?
the removal of metabolic waste from the body
251
what does a coordinated response require?
a stimulus, a receptor, and an effector
252
what does coordinated mean?
the body is able to make things happen in different parts of the body
253
what are the two organ systems in humans that make coordinated responses?
the nervous system and the endocrine system (hormone)
254
what is the link between the stimulus and the response made by in a coordinated response?
the nervous or endocrine system
255
what do receptors do?
they detect the stimulus and change its energy into nerve impulses
256
what does the central nervous system consist of?
the brain and the spinal chord
257
what is homeostasis?
the maintenance of a constant internal environment
258
what are examples of homeostasis?
body water content and body temperature
259
can plants respond to stimuli?
yes
260
what are the three types of neurones?
- sensory neurones
- relay neurones
- motor neurone
261
what kind of neurone do impulses travel through to the CNS from the receptors?
sensory neurones
262
what kind of neurone is the impulse passed to in the CNS from the sensory neurones?
relay neurones
263
what neurone does the impulse travel through to the effectors from the CNS?
motor neurones
264
what makes up a motor neurone?
- nucleus
- dendrite (tree like branch things)
- cell body (main section of the cell)
- axon (long section - impulses travel long distances through the axon)
- myelin sheath (insulates axon and speeds up transmission of impulse)
265
which neurone's cell body is in the middle of the axon?
the sensory neurone
266
do relay neurones have a myelin sheath?
not normally i don't think
267
what links the CNS to sense organs?
nerves
268
what are the similarities between the responses of the endocrine system and nervous system?
need a stimulus, receptor, and an effector
269
what are the differences between the responses of the endocrine system and nervous system?
- nervous is electrical, endocrine is chemical
- nervous is faster
- nervous is short-lived, endocrine is long lived
- nervous acts on a precise area, endocrine acts on a more general area
270
what are reflexes?
automated actions which do not involve the brain
271
what is the gap between neurones called?
a synapse
272
how do impulses travel between neurones?
- the impulse travels along an axon
- which triggers the nerve-ending- of a neurone to release chemical messengers called neurotransmitters
- chemicals diffuse across the synapse and bind with receptor molecules on the membrane of the next neurone
- receptor molecules on the second neurone bind only to the specific chemicals released from the first neurone. this stimulates the second nerone to transmit the electrical impulse
273
what does the conjunctiva do?
it lubricates and protects the surface of the eye
274
what is the scelera?
the tough outer layer that protects the eye
275
what does the cornea do?
it refracts the light into the eye, it's transparent and has no blood vessels to supply it with oxygen so oxygen diffuses in from the outer surface. it's the curved transparent disc at the front of the eye
276
what does the iris do?
controls the diameter of the pupil and therefore how much light enters the eye - it's a ring of muscle
277
what does the lens do?
focuses the light onto the retina
278
what does the optic nerve do?
carries impulses from the receptors to the brain
279
what are the ciliary muscles?
a ring of muscles at the edge of the eye which circle the lens
280
what are suspensory ligaments?
strong fibres which attach the lens to the ciliary muscle
281
what is the retina?
the light sensitive part of the eye - contains lots of rods and cones
282
what is the fovea?
the region of the retina with the greatest number of cones
283
what are rods?
they are light receptors that are more sensitive in dim light but can't sense colour
284
what are cones?
light receptors which are sensitive to colours but aren't so good in dim light
285
what happens to the eye in dim light?
the radial muscles contract and the circular muscles relax so the pupil dilates
286
what happens to the eye in bright light?
the radial muscles relax and the circular muscles contract so the pupil constricts
287
what is light intensity detected by in the iris reflex?
the retina
288
what are the changes that take place in the eye which allow us to see objects at different distances called?
accommodation
289
what happens to the eye when looking at distant objects?
- the ciliary muscles relax
- which allows the suspensory ligament to be pulled tight
- so the lens is pulled thin and has a less convex shape
- so there is less refraction of light
290
what happens to the eye when looking at a near object?
- ciliary muscles contract
- which slackens the suspensory ligaments
- so the lens becomes fat/thicker with a more convex shape
- so more refraction of light
291
what are short-sighted people's eyes like?
- short-sighted = can't focus on distant objects
- happens when the cornea or lens bends the light too much or if the eyeball is too long
- images of distant objects are brought into focus in front of the retina
292
what are long-sighted people's eyes like?
- can't focus on near objects
- happens when cornea or lens doesn't bend the light enough or if the eyeball is too short
- images of near objects are brought into focus behind the retina
293
what does the skin do when it is too cold?
- thermoreceptors detect decrease in temperature
- blood vessels (arterioles) near the surface of the skin constrict (vasoconstriction) so less blood flows through the capillaries near the surface of the skin so less heat is lost through radiation, more blood flows through shunt vessels
- less sweat produced
- hair erector muscles contract to make them stand on end, which traps an insulating layer of air (like blubber), less heat lost through conduction
- shivering increases rate of respiration
294
what does the skin do when it's too hot?
- increase in temperature detected by thermoreceptors
- blood vessels (arterioles) near the surface of skin widen (vasodilation) so more blood flows through capillaries near the skin so more heat lost
- more sweat is released, when sweat evaporates, heat energy is taken away from skin as evaporation of water requires energy
- hairs lie flat so no insulating layer is formed (hair erector muscles relax)
295
what is vasodilation?
- heat exchange occurs at the body's surface as this is where the blood comes into closest proximity to the environment
- one way to increase heat loss is to supply the capillaries in the skin with a greater vol of blood, which loses heat to environment via radiation
- arterioles have muscles in their walls that can relax or contract to allow more or less blood to flow through them
- during vasodilation, these muscles relax, causing the arterioles near the skin to dilate, allowing more blood to flow through, so less blood flows through shunt vessel
296
what is the source of adrenaline?
adrenal glands (on top of the kidneys)
297
what is the role of adrenaline?
readies the body for a 'fight or flight' response
298
what is the effect of adrenaline?
increases the heart rate, blood flow to muscles, breathing rate, and blood sugar level
299
what is the source of insulin?
pancreas
300
what is the role of insulin?
helps control the blood sugar level
301
what is the effect of insulin?
stimulates the liver to turn glucose into glycogen for storage
302
what is the source of testosterone?
the testes
303
what is the role of testosterone?
main male sex hormone
304
what is the effect of testosterone?
promotes male secondary sex characteristics (eg. facial hair)
305
what is the source of progesterone?
ovaries
306
what is the role of progesterone?
supports pregnancy
307
what is the effect of progesterone?
maintains the lining of the uterus
308
what is the source of oestrogen?
ovaries
309
what is the role of oestrogen?
main female sex hormone
310
what is the effect of oestrogen?
controls the menstrual cycle and promotes female secondary sexual characteristics (eg wide hips)
311
what is an example of a plant responding to predators to avoid being eaten?
white clover can produce substances that are toxic to cattle. cattle start to eat lots of white clover when the fields are overgrazed - the white clover responds by producing toxins to avoid being eated
312
what do carrots do at low temperatures?
they produce antifreeze proteins - the proteins bind to ice crystals and lower the temperature that water freezes at, stopping more ice crystals from growing
313
what are auxins?
- plant hormones which control growth at the tips of shoots and roots, they moved through the plant in solution (dissolved in water)
- produced in the tips and diffuse backwards to stimulate the cell elongation process, which happens just behind the tips
- promotes growth in shoots but inhibits growth in the root
314
what are phototropisms?
growth responses to light from one direction
315
what is positive phototropism?
growth towards the light
316
are shoots positively or negatively phototropic?
positively (grow towards light)
317
what happens when a shoot is exposed to light?
- accumulates more auxin on the side that's in the shade than the light
- makes the cell grow faster on the shaded side
- so shoot bends towards the light
318
are shoots positively or negatively geotropic?
negatively
319
what happens when a shoot is growing sideways?
- gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side
- so lower side grows faster
- so shoot bends upwards
320
are roots positively or negatively phototropic?
negatively
321
what happens if a root is exposed to light?
- more auxin accumulates on the shaded side
- auxin inhibits cell elongation on the shaded side
- root bends downwards (back to ground)
322
what happens if a root grows sideways?
it will have more auxin on its lower side
- in a root extra auxin inhibits growth
- ells on top elongate faster
- root bends downwards
323
how does auxin alter the growth of cells?
- changes the elasticity
- increased elasticity means more water can be absorbed
- so cell size increases
- plant bends
324
what is asexual reproduction?
- involves only one parent
- genetically identical offspring (clones)
- no variation between parent and offspring
- uses mitosis
- no gametes
325
what is sexual reproduction?
- fusion of male and female gametes
- two parents
- offspring contain a mixture of parents' genes
- genetically varied offspring
- uses gametes
326
what does fertilisation involve?
fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo
327
what are the advantages of asexual reproduction?
- rapid increase in population
- thrive in suitable environment
328
what are the disadvantages of asexual reproduction?
- decreased variation
- more susceptible to disease because less genetic variation
- vulnerable to change in environment due to inadaptability
329
what are the advantages of sexual reproduction?
- more genetic variation
- less susceptible to disease
- offspring are able to adapt to a new environment better
330
what are the disadvantages of sexual reproduction?
- time consuming to find a mate
- not possible for isolated members
331
what is the stamen?
the male reproductive part of the flower
332
what is the carpel?
the female reproductive part of the flower
333
what does the stamen consist of?
the anther and the filament
334
what is the anther?
the bit at the top of the male one which contains pollen grains - they produce the male gametes (sperm)
335
what is the filament?
the male tube bit (the one that there's more of) - the stalk that supports the anther
336
what does the carpel consist of?
the ovary, the style, and the stigma
337
what is the stigma?
the end bit of the female bit that the pollen grains attach to
338
what is the style?
the tube bit of the female bit, rod-like section that supports the stigma
339
what is the ovary (of a plant)?
contains the female gametes (eggs) inside the ovules
340
what is pollination?
the transfer of pollen from an anther to a stigma so that the male gametes can fertilise the female gametes in sexual reproduction
341
what is cross pollination?
a type of sexual reproduction where pollen is transferred from the anther of one plant to the stigma of another
342
how are plants adapted for insect pollination?
- brightly coloured petals
- scented flowers and nectaries (glands that secrete nectar) to attract insects
- make big, sticky pollen grains to stick to the insects as they go from plant to plant
- the stigma is also sticky so that any pollen picked up by insects on other plants will stick to the stigma
343
what are the adaptations of wind pollinated plants?
- small, dull petals
- no nectaries or strong scents
- a lot of pollen grains which are small and light so they can be carried by the wind
- long filaments that hang the anthers outside of the flower so pollen gets blown away
- large and feathery stigma to catch pollen, often hangs out of the flower as well
344
what is the process of fertilisation in plants?
- pollen grain deposited onto the stigma
- pollen grain will grow a pollen tube which grows down through the style
- enzymes are secreted at the tip of the tube which digest the tissues of the style
- when the tube reaches an ovule, the nucleus of the pollen grain travels through the tube, entering the ovule through the micropyle
- nucleus fuses with ovum (fertilisation)
- forms a zygote
- zygote divides by mitosis to form an embryo
345
what becomes the seed of the fruit?
the ovule (each fertilised female gamete)
346
what forms the fruit of the plant?
the ovary
347
what three conditions are needed for germination?
- oxygen (for respiration for energy)
- water (to activate the enzymes that break down the food reserves in the seed)
- warmth (optimum temperature for enzymes)
348
what is the cotyledon?
the food reserve of the seed
349
what does a seed get glucose from when it starts to germinate?
from the cotyledon (food reserve)
350
what are the three methods of natural asexual reproduction in plants?
- runners (a new plant is produced where the runner touches the ground)
- tubers (swollen underground stems containing lots of stored food - one plant can produce many tubers which can each grow many shoots which form new plants)
- bulbs (underground buds with thick fleshy leaves containing stored food. a main shoot will grow out of the parent bulb and another will grow out of the side 'daughter' bulb, forming two plants)
351
what is the artificial method of asexual reproduction in plants?
cuttings
352
how are cuttings used for artificial asexual reproduction?
- take the cuttings from a healthy plant's stem with a few leaves
- planted in damp compost, where it will grow roots and develop into a new plant
353
what are the secondary sexual characteristics caused by oestrogen?
- extra hair on under arms and pubic area
- hips widen
- develop breasts
- ovum release and periods start
- voice deepens but doesn't break
- possible mood swings and ane
354
what are the secondary sexual characteristics caused by testosterone?
- extra hair on face and body
- muscles start to develop
- sperm production
- deepening of voice
- shoulders broaden
- possible mood swings and acne
355
what is the role of oestrogen in the menstrual cycle?
- causes the lining of the uterus to grow
- stimulates the release of LH
- (inhibits production of FSH)
356
what is the role of progesterone in the menstrual cycle?
- maintains uterus lining (during the second half of cycle)
- inhibits FSH and LH
357
what hormone does the placenta secrete?
progesterone, to maintain the uterus lining
358
what does the amniotic fluid do
protects the embryo against knocks and bumps (mechanical shocks), drying out, and temperature fluctuations (due to water's high specific heat capacity)
359
what does the placenta do?
- anchors the embryo in the uterus
- allows nutrients (eg. amino acids, glucose, and salts) and oxygen to move from the mother to the embryo
- allows metabolic wastes (carbon dioxide and urea) to move from the embryo to the mother
360
how do the nutrients pass from the mother to the embryo?
through diffusion
361
do the embryo's and the mother's blood mix at all?
no, they only get very close
362
why do the embryo and the mother's blood not mix?
- mother's blood is much higher pressure than foetal blood
- mother's blood has white cells and other chemicals that would see the foetal blood as foreign and attack it
363
what is the genome of an organism?
the entire DNA of an organism
364
what is a gene?
a section of DNA that codes for a specific protein
365
what does the nucleus of a cell contain?
chromosomes, on which genes are located
366
what are alleles?
alternate forms of genes that code for specific characteristics
367
what is homozygous?
both alleles are the same
368
what does dominant mean?
Variant of a gene for particular characteristic that will always express itself whether it is partnered by Recessive Allele or by another like itself
369
what does recessive mean?
needs two alleles to be present to be expressed
370
what does polygenic mean?
the characteristic is controlled by more than one gene
371
are most phenotypic features the result of polygenic inheritance or not?
they are polygenic
372
what is the sex of a person controlled by
one pair of chromosomes, XX in females, XY in males
373
what does the division of a diploid cell by mitosis produce?
two cells that contain identical sets of chromosomes
374
when does mitosis occur?
during growth, repair, cloning, and asexual reproduction
375
what is the process of mitosis?
- the DNA duplicates
- the copies (chromatids) are joined together at a single point to form the X shaped chromosomes
- the chromosomes line up at the centre of the cell
- cell fibres pull the chromatids apart and move them to opposite ends of the cell
- the cytoplasm and cell membrane divide to form two identical cells
376
what does division of a cell by meiosis produce?
four cells, each with half the number of chromosomes, results in the formation of genetically different haploid gametes
377
what is the diploid number of chromosomes in humans?
46
378
what is the haploid number of chromosomes in humans?
23
379
what is a mutation?
a rare, random change in genetic material that an be inherited
380
what is the process of meiosis?
- cell duplicates its DNA
- chromatids join together at a single point (X shaped)
- chromosomes line up in pairs in the centre of the cell
- one chromosome from each pair come from the mother, and the other came from the father
- the pairs are pulled apart and moved to opposite ends of the cell
- some of the mother's chromosomes and some of the father's chromosome goes into each cell
- each cell will have a mixture of the mother's and the father's chromosomes
- in second division, chromosomes line up again
- chromatids pulled apart by cell fibres
- four haploid gametes produced
381
why is it important that each cell from the first division in meiosis has chromosomes from the father and the mother?
mixing up the genes creates genetic variation in the offspring
382
how many divisions are there in meiosis?
two
383
what does random fertilisation produce?
genetic variation of offspring
384
what kinds of variation can their be within a species?
genetic, environmental, or a combination of both
385
what things aren't affected by environmental variation (eg what is only affected by genes)?
- eye colour
- hair colour
- inherited disorders (like haemophilia, cystic fibrosis, etc)
- blood group
386
what are the four main aspects of the environment that affects plants?
- sunlight
- moisture levels
- temperature
- mineral content of the soil
387
what is the theory of natural selection?
- organisms with the most suitable characteristics will be the more successful competitor for resources and so will have a better chance of survival
- the successful organism will have an increased chance of breeding and pass on their genes
- a greater proportion of individuals in the next generation will have the better alleles for the desired characteristic that help survival
- over many generations, the characteristic that increases survival in population becomes more common, making the species become better able to survive
388
what happens to individuals who are less suited to an environment?
they are less likely to survive so have less chance to pass their alleles on so (gradually) results in a population which is extremely well suited to the environment they live in
389
are variations caused by the environment involved in natural selection?
no, because only variations caused by genes will be passed down to the next generation
390
how do bacteria evolve and become antibiotic resistant?
- bacteria can develop random mutations which sometimes mean a bacterium is less affected by a particular antibiotic
- for the bacterium, this is a huge advantage. it's better able to survive even in a host who's being treated to get rid of the infection so it lives longer and reproduces many more times
- this leads to the allele for resistance being passed on to lots of offspring (natural selection)
- allele becomes more common in bacteria over time
- this is a problem for those infected as you can't easily get rid of them with antibiotics
- sometimes drug companies come up with a new antibiotic that's effective, but 'superbugs' that are resistant to most known antibiotics are becoming more common
391
what is the definition of population?
all the individuals of one species in a given area at a given time (all the organisms of one species in a habitat)
392
what does the term community mean?
all the species in a given area at at a given time (all the different species in a habitat)
393
what does the term habitat mean?
the place where an organism lives
394
what does the term ecosystem mean?
all living and non-living organisms (abiotic and biotic) in a given area at a given time (all the organisms living in a particular area and all the non-living (abiotic) conditions)
395
how do you investigate the population size of an organism in two different areas?
1. put down two 10m tape measures at right angles (like a grid)
2. use a random number generator to get a coordinate and place the quadrat at that coordinate
3. count the number of individuals of the species in the quadrat
4. repeat 2-3 9 more times and work out the mean number
5. estimate population size by using the formula: total area/quadrat area x mean number
6. repeat 1-5 in the other place you are investigating
396
what two abiotic factors can affect communities?
- environmental conditions (temp, light intensity, moisture, soil pH, etc)
- toxic chemicals (eg. from chemical pesticides causing bioaccumulation)
397
what are the biotic factors which can affect communities?
- availability of food
- number of predators
- competition
398
what do decomposers do?
break down (decompose) dead material and waste
399
what is a pyramid of numbers?
each bar shows the number of organisms at that stage of the food chain, not always in a pyramid shape (because 1 fox can feed like 500 fleas), bottom bar are the producers, pyramid goes up in order of trophic level
400
what is a pyramid of biomass?
each bar shows the mass of living material at that stage of the food chain - basically how much all the organisms at each level would 'weigh' if you put them all together
401
around what % of energy is transferred between trophic levels?
around 10%
402
how is energy lost between trophic levels?
- respiration
- incomplete digestion (as in selective eating)
- egestion / excretion
403
what are the transfers of carbon dioxide in the carbon cycle?
- respiration
- photosynthesis
- decomposition
- combustion
404
what do green plants use the carbon from carbon dioxide for?
to make carbohydrates, lipids, proteins
405
how does eating transfer carbon?
transfers carbon compounds in the plant along to animals in a food chain/food web
406
how does respiration transfer carbon?
carbon dioxide is released back into the air by respiring animals and plants
407
how do decomposers transfer carbon?
when plants and animals decompose they're broken down by bacteria and fungi (decomposers) which release enzymes and catalyse the breakdown of dead material into smaller molecules. they release carbon dioxide back into the air by respiration as they break down the material
408
how does combustion transfer carbon?
some useful plant and animal products are burned (combustion) which releases carbon dioxide back into the air
409
what is acid rain caused by?
sulphur dioxide
410
what is carbon monoxide mostly released from?
car emissions, though most modern cars are fitted with catalytic converters that turn the carbon monoxide into carbon dioxide, decreasing the amount of CO that's released into the atmosphere
411
where does sulphur dioxide/acid rain come from?
- sulphur dioxide comes from sulphur impurities in the fossil fuels
- when when the gas mixes with rain clouds, it forms dilute sulphuric acid
- this then falls as acid rain
- internal combustion engines and power stations are the main causes of acid rain
412
what are the biological consequences of acid rain?
- Acid rain leaches Minerals and Nutrients out of the soil, causing death of Plants and Trees
- Acid rain damages the waxy layer of leaves, reducing ability of Plants and Trees to absorb Mineral ions needed for growth
- Acid rain acidifies rivers and lakes, resulting in death of aquatic organisms
- Acid rain corrodes Metals (steel) and Limestone in buildings
413
what are the greenhouse gases?
- water vapour
- carbon dioxide
- methane
- nitrous oxide
- CFCs
414
what is the greenhouse effect?
- gases in the atmosphere absorb most of the heat that would normally be radiated back out into space, and re-radiate it in all directions (including back to Earth). these gases that help keep the energy in are called greenhouse gases
415
what is the result of the enhanced greenhouse gas effect?
the earth is heating up (global warming) which leads to:
- changing of rainfall patterbs
- extreme weather
- rising sea levels
- flooding due to polar ice caps melting
- habitat loss
- affects food webs and crop growth
416
how does human activity produce carbon dioxide?
- in car exhausts, industrial process, as we burn fossil fuels, etc
- deforestation for timber and to clear land for farming
417
how does human activity produce methane?
- produced naturally from various sources (eg rotting plants in marshland)
- also from manmade sources;
- rice growing
- cattle farming
418
how does human activity produce nitrous oxide?
- released naturally by bacteria in soils and the ocean
- a lot more is released from soils after fertiliser is used
- also released from vehicle engines and industry
419
how does human activity produce CFCs?
- they're man-made chemicals that were once used in aerosols and fridges
- they're powerful greenhouse gases
- most countries have agreed not to produced them anymore because they also damage the ozone layer that prevents UV radiation from reaching the earth
- some CFCs are still released eg by leaks from old fridges
420
what are the biological consequences of pollution of water by sewage?
- sewage contains lots of minerals and nutrients (eg phosphates and nitrates from urine and faeces) which decomposers feed on
- so more food for bacteria/other microorganisms that decompose so they respire more so less oxygen for everything else
- also provides more nutrients for algae growth which blocks out sunlight for plants
421
what are the biological consequences of eutrophication caused by leached minerals from fertiliser?
- nitrates and phosphates are in fertilisers
- too much fertiliser with rain allows nitrates to be easily 'leached' (washed through the soil) into lakes and rivers
- causes eutrophication
- fertilisers enter water and add extra nutrients which allow algae to grow
- algae block out sunlight and cause plants to die
- decomposers feed on dead plants and respire more so less oxygen for fish so they all die
422
how do glasshouses increase crop yield?
- small scale allows internal conditions to be controlled
- easier to keep pests and diseases away
- able to control water supply
- artificial light for more photosynthesis
- trap the sun's heat for warmth
- can also use heaters
- can increase carbon dioxide levels using a paraffin heater - as paraffin burns it produces carbon dioxide as a by-product
- all increase rate of p/s so plants can grow bigger and faster so crop yield increases
423
how can polythene tunnels be used to increase crop yield?
- large scale to allow farmers and machines to work inside
- enclosed environment to create a warmer climate
424
how does increased carbon dioxide affect crop yield?
increases because more photosynthesis
425
how does increased temperature in glasshouses affect crop yield?
increases because more photosynthesis because of enzymes
426
how do fertilisers increase crop yield?
provide/replace mineral ions that plant is missing (eg nitrogen, potassium, and phosphorus)
427
why do plants need potassium?
regulates the opening and closing of stomata
428
why does pest control increase crop yield?
pests that feed on crops are killed
429
what are the two methods of pest control?
- pesticides
- biological control
430
what is biological control?
the alternative to pesticides; uses other organisms (predators, parasites, or disease-causing) to reduce number of pests
431
what are the advantages of pesticides?
- efficient and quick method
- immediate effects
- targets and kills the entire population
432
what are the disadvantages of pesticides?
- pests can develop resistance
- could harm other organisms
- could lead to bioaccumulation
- needs continuous application
433
what are the advantages of biological control?
- natural
- no resistance
- ability to target specific species
- long-lasting
- efficient because it needs minimal effort
434
what are the disadvantages of biological control?
- might kill other organisms
- time lag in effect
- cannot kill the whole population
- organism may be unadaptable to new habitat and die
435
why is water needed to make bread?
to activate the yeast
436
why is flour needed to make bread?
it's starchy, amylase enzymes break it down into glucose for respiration
437
how is yeast used to make bread?
- dough is left to rise in a warm place
- enzymes break down carbohydrates in flour into sugars
- yeast uses sugars in aerobic respiration, producing carbon dioxide
- then yeast has to switch to anaerobic (fermentation) and produces carbon dioxide and ethanol
- carbon dioxide is trapped
- gas expands so dough rises
- dough is baked where yeast continues to ferment until temp rises enough to kill it
- any alcohol/ethanol produced is boiled away
438
why is bread kneaded?
distributes the cells evenly and increases surface area
439
what is the method to investigate anaerobic respiration in yeast in different conditions?
1. measure 10ml of yeast suspension and add to the boiling tube
2. put the boiling tube in a water bath
3. add a bit of oil to cover the top of the solution to prevent oxygen/air getting in
4. connect a delivery tube and a bung to the boiling tube and a test tube half filled with lime water
5. count the number of bubbles produced in one minute
6. repeat 1-5 2 more times and work out a mean
7. repeat 1-6 at different water bath temperatures
440
what bacteria is involved in yogurt production?
lactobacillus
441
what does lactobacillus do in yogurt production?
ferments lactose into lactic acid which denatures proteins to make the texture gloopy, and gives it the acidic taste
it ferments to produce lactic acid (anaerobic respiration glucose --> lactic acid)
442
how is yogurt produced?
- equipment is sterilised to kill off unwanted microorganisms
- milk is pasteurised (heated to ~72 for 15s) to kill harmful microorganisms
- milk is cooled
- lactobacillus added
- mixture incubated at ~40 degrees in a fermenter
- bacteria ferments lactose sugar in milk into lactic acid
- lactic acid causes milk to solidify into yogurt
- flavours/colours added and yogurt is packaged
443
what is the liquid inside the fermenter called?
the culture medium
444
what are the nutrients provided by in fermenters?
the nutrients needed are provided by the culture medium
445
how does the fermenter maintain the pH?
it is monitored and kept at optimum level for microorganism's enzymes to keep rate of reaction high
446
how is temperature maintained in a fermenter?
it is monitored and kept at optimum temperature. cooling jacket makes sure it doesn't get so hot that the enzymes denature
447
why are the fermenters sterilised between uses?
to maintain aseptic conditions to increase yield because it decreases competition for nutrients and prevents product being contaminated
448
what do the paddles in the fermenter do?
ensure that microorganisms, nutrients, oxygen, temperature and pH is evenly distributed
449
how can selective breeding develop plants with desired characteristics?
select plants with the desired characteristic and cross pollinate them. take the offspring and continue to cross pollinate them with plants that have the desired characteristic over many generations
450
how can selective breeding develop animals with desired characteristics?
select animals that show that characteristic and breed them together
the gene for it will be passed down to offspring
then select the offspring that best shows the characteristic and breed it with another animal that shows that characteristic and repeat this over many generations
451
what do restriction enzymes do?
- recognise specific sequences of DNA and cut out desired gene of DNA
- create sticky ends
452
what do ligase enzymes do?
join the two pieces of DNA together (between vector and gene to form recombinant plasmid)
453
what are the two kinds of vectors?
plasmids and viruses
454
how are things genetically engineered?
- DNA that you want to insert is cut out with a restriction enzyme
- vector DNA is cut open using same restriction enzyme
- vector DNA and inserted DNA are joined together with ligase enzymes
- produces recombinant DNA
- recombinant DNA is inserted into other cells (eg. bacteria)
- these cells can now use the gene inserted to make the protein you want
- cells with the inserted recombinant DNA are now trangenic
455
what does transgenic mean?
they contain genes transferred from another species
456
how can genetically modified plants improve food production?
- can be genetically modified to increase food production in lots of different ways
- can be made resistant to insects or resistant to herbicides
- insect resistant plants mean farmers don't have to spray as many pesticides so wildlife eating crops aren't harmed and increases crop yield
- herbicide resistant plants means farmers can spray their crops to kill weeds without affecting the crop which can increase crop yield
457
what could be the problems with genetically modified food?
- transplanted genes may get out into environment, so weeds may become herbicide resistant for example
- could affect food chains or even human health
- some are against genetic engineering all together bc they are worried that changing an organism's genes might create unforeseen problems which could be passed on to future generations
