Biology Paper 2-Major Focus Of Exam Flashcards
What is homeostasis?
Regulation of internal body conditions
What is your body temperature monitored and controlled by?
The brain
What is the part of the brain that monitors and controls body temperature?
Thermoregulatory centre
How can the thermoregulatory system control blood temperature?
It contains receptors which are sensitive to the temperature of the blood
Besides the thermoregulatory centre containing receptors sensitive to blood, what is another way the thermoregulatory centre can control temperature?
The skin contains receptors, that send electrical impulses down sensory neurones to the thermoregulatory centre
Give 3 ways that body temperature can be returned to normal when it has gone too high
Sweating
Flushing
Hairs lie flat
How does sweating cool the body down?
Releases water on surface of the skin
Water evaporates, taking energy
What is flushing a result of ?
Vasodilation of blood capillaries
How does vasodilation of blood capillaries cool the body down?
More blood follows to surface of skin
Heat can transfer out of
Blood to surroundings
Give 3 ways body temperature can be returned to normal when too low
Vasoconstriction
Shivering
Hairs stand up
How does vasoconstriction warm the body up?
Less blood flow to surface of skin
Less heat lost to surroundings
How does shivering warm the body up?
Causes our skeletal muscles to contract
Increases rate of respiration to generate needy for the contraction
Releases heat
What is the control of body temperature an example of?
Homeostasis
What are 2 comparisons of the nervous system and the endocrine system?
The nervous system is faster
The effects of the nervous system are more short lived
What does the endocrine system consist of?
A number of glands
What do glands secrete?
Hormones directly into the blood
What is a hormone(3)
A chemical messenger that passes through the bloodstream to a target organ
Besides the endocrine system have a slower, but more long-lasting effect, what’s another key difference between the NS and the ES?
The nervous system uses electrical impulses, whereas the endocrine system uses hormones
What is the role of the pancreas?
Releases hormones- eg insulin - control blood glucose concentration
What do the ovaries and testes release?
Hormones involved in puberty and reproduction
What does the thyroid gland produce?
Hormones involved in growth and regulating the body’s basal metabolic rate
What does the adrenal gland release?
The hormone adrenaline
When is adrenaline produced?
In times of fear or stress
Where is the pituitary gland located?
In the brain
What is another word for the pituitary gland?
The master gland
What does the pituitary gland release?
A number of different hormones depending on the conditions
What do pituitary hormones cause?
Other hormones to be released
What do pituitary hormones act on?
Other glands
When does the pancreas produce insulin?
After a meal, when blood glucose concentration is high
Where does insulin travel and what does it trigger?
Travels in the bloodstream
And triggers body cells to take up
Glucose
Besides triggering cells to
Uptake glucose, what else can insulin trigger?
Liver and muscle cells to store excess glucose as glycogen
What is wrong with person with type 1 diabetes?
Their pancreas doesn’t produce enough insulin
What do people with type 1 diabetes do to counteract their problem?
Inject themselves with insulin
What’s wrong with people who have type 2 diabetes?
Cells stop responding to insulin
How can type 2 diabetes be treated?
A controlled carb diet
Take exercise
What is a major risk factor for type 2 diabetes?
Obesity
If the blood glucose concentration is too low, what hormone does the pancreas release?
Glucagon
What does glucagon trigger?
Liver cells to convert glycogen back to glucose
In a graph of blood glucose concentration against time, what does the line fluctuate?
The balance between the releasing of insulin and glucagon
What type of cycle do insulin and insulin form?
Negative feedback
What are 3 ways we can lose water?
Exhaling
Sweat
Urination
What substances can sweat contain?
Sodium ion and urea
How is urea removed from the kidney?
Blood enters kidney through an artery
Contains urea
Kidney removes this and excess substances
Leave kidney as urine and store in bladder
How does the kidneys adjust the level of molecules in the blood?
Blood passes through capillaries
Small molecules filtered out- eg urea and water and glucose
Pass into tube
All of glucose, some water and ions are reabsorbed back into the blood
Urea, excess water and ions are excreted as urine
How do we deal with excess amino acids?
Liver breaks down the amino acids to produce ammonia
Desmond room
Ammonia is converted to urea and excreted
What hormone does the pituitary gland release when the level
Of water in the blood falls?
ADH
What does ADH cause?
The kidney tubules to become more permeable to water
Increased ADH=
Less____ produced
Urine
What does the ADH cause the kidneys to?
Reabsorb more water into the blood
If blood becomes too dilute, what does the pituitary gland stop releasing?
ADH
When the pituitary gland stops releasing ADH, is more or less
Water reabsorbed back in the blood by the kidneys?
Less
If a person has kidney failureX what will their blood contain?
A higher concentration of water, ions and urea
In kidney dialysis, where does the patients blood pass over?
A semi permeable membrane
What will the semi permeable membrane not allow through?
Large molecules like proteins
What’s on the other side of the semi permeable membrane?
Dialysis fluid
What does the dialysis fluid contain ?
Normal
Concentration of water and ions, and no urea
Why does the urea diffuse from the blood into the dialysis fluid ?
Because of the concentration gradient
Why is the dialysis fluid constantly refreshed?
To
Maintain a steep
Concentration gradient
What’s some disadvantage of kidney dialysis?
Inconvenient- visit hospital regularly
Controlled diet- low protein
What’s an alternative to kidney dialysis?
Kidney transplant
What is an advantage of dialysis?
No shortage of machines
What’s 2 advantages of a kidney transplant?
Allow for normal life
Only expensive initially
What are 2 disadvantages of kidney transplants?
Shortage of donors
Patients need to take anti rejection drugs for rest of their life
What is phototropism?
A response of a plant to light
How did scientists first suggest plant tips produced a hormone?
They removed the tips of shoots and found they didn’t grow towards the light
Then they put foil
Over the tip and found it didn’t grow towards the light either
What did scientists do to tell us that the lower parts of shoots aren’t sensitive to light?
They covered the lower parts of the shoot the shoot grew towards light
In shoots, what does auxin trigger?
Cell growth
Where does the light cause auxin to concentrate on?
The darker side of the shoot tip
Because of auxin, when plants are shone with light, does the darker side
Grow faster?
Yes
What do plant roots grow towards?
The force of gravity
What is gravitropism or geotropism?
Plant response to gravity
What does gravity cause the auxin to
Do?
Concentrate on the lower side
In roots, does auxin promote
Or inhibit
Cell growth?
Inhibit
In the roots due to auxin, does the lower side grow faster or slower than the upper side?
Slower
What are giberellins
Important for?
Seed germination
Flower
Production
What does Ethene control?
Cell division and ripening of fruits
What are producers important?
They are the source of biomass
What do scientists call molecules such as glucose?
Biomass
What type of consumer eats the producer?
Primary consumer
What type of consumers eat primary consumers?
Secondary consumers
What organisms eats a secondary consumer?
Tertiary consumer
What are predators?
Consumers that kill other animals
What’s the prey?
The animal being eaten
Describe the predator prey cycle using an example
Warm summer- lots of grass More of rabbits offspring survive Rabbit population increases Fox population increases- more prey Rabbit population falls- more predators Fox population falls- less prey Rabbit population increases- less predators Cycle
What is the predator and prey cycle only true in ?
A stable community
What is a stable community?
A community where all biotic and abiotic factors are balanced
What a couple of examples of abiotic factors?
Wind direction
Temperature
Levels of moisture
What is random sampling used to compare?
Numbers of organisms in different areas
What do we use to carry out random sampling?
A quadrat
How do we use a quadrat?
Place it on the ground
Count number of organisms inside it
In random sampling, where is the quadrat placed?
At random locations across the area - could use random numbers To select location
Describe how we can compare to areas, one with light conditions, one with dark conditions
Place quadrat randomly
Count number of organisms inside it
Move quadrat to different location
Count number of organisms
Repeat until we sample a large number of random locations
Dark conditions
Repeat the same steps and compare
Why do we place the quadrat down a large number of times ?
More likely to get valid results
Why don’t we use a quadrat in one area?
Won’t give sample that accurately represents the whole area
What’s the equation for total population size?
Total area/area sampled x number of organisms of specifies in sample
When do we use sampling along a transect?
How number of species change as we move across a habitat
What is a transect?
A line
How do we use a transect?
Place so it runs across the habitat
After placing the transect across the habitat, what do we do next?
Use a quadratic to count number of organisms at intervals on the transect
When using a transect and quadrats on sand dunes inland from the sea, how can we get valid results?
Repeat the whole process with the line shifting along
Describe how to measure the population size of a common species in a habitat
Use 2 tape measures to lay out an area(eg 10 by 10m)
Use a random number generator to create a set of co ordinates(4,5)
Count number of species within it
Record number and repeat none more times to get a 10 time sample
Estimate whole population using an equation
If we thinks there’s a big difference in the percentage of daisies within an area, what should we do?
Throw more quadrats- cover a higher percentage of the area
Describe how we use transects and quadrats to see how number of daisies changes from the tree outwards
Place tape measure at tree
Use quadrat to count daisies at start
Record light intensity - light meter
Move transect 1m down transect and repeat
How does carbon enter the carbon cycle?
By photosynthesis
How does carbon dioxide return back to the atmosphere?
By aerobic respiration
Describe the steps in the carbon cycle
CO2 in atmosphere Plants gain it by photosynthesis Return it by respiration Organisms eat plants and gain carbon They respire Carbon in waste Broken down by decomposerss They respire- co2 returned Combustion of fossil fuels- release
If decomposes can’t function effectively, what happens?
Carbon is dead remains is converted to fossil fuels
Why are decomposers important?
They cycle materials
Return co2 and release mineral
Ions
Describe the steps in the water cycle
Energy from sun causes water to evaporate from surface of the sea
Water vapour condenses in air, forming clouds
Transpiration and exhalation
Water in clouds fall as precipitation
Some water reevaporates, some
Passes in rocks to make aquifers
What role do organisms play in the water cycle?
Animals- exhalation
Plants- transpiration
What are examples of decomposers?
Bacteria and fungi
What do gardeners use compost as natural fertilisers?
Compost is rich in minerals
What are some conditions for decomposers?
Temperature
Water
Oxygen
Why does decomposition take place at warmer temperatures?
Enzymes work faster
Why is compost usually quite warm?
Decomposers release energy when they respire
Why is it important that the compost isn’t too hot?
Enzymes in decomposers denature and die
Why do decomposers work faster if compost is moist?
Many chemical reactions in decay require water
Why is a plentiful supply of oxygen important for decomposers?
They carry out aerobic respiration
What’s an adaptation of compost bins?
Holes
Why do some compost bins have holes?
Allow oxygen in for decomposition
Why do gardeners mix up the compost?
Allow oxygen to distribute evenly
Break up large clumps/ increase surface sea for decomposition
In the absence of oxygen, what do decomposers carry out?
Anaerobic decay
What does anaerobic decay mainly produce?
Methane- biogas
What are biogas generators used to provide?
Fuels for homes
Explain what goes wrong on the regulation of blood sugar levels in a person with type 1 diabetes
Pancreas produces little insulin
Liver is unable to remove glucose from blood
This causes levels to rise to a dangerous level
Hypopituitsrism is a condition in which the pituitary gland stops secreting hormones, why could people have certain symptoms of all are linked to low Thyroid hormone levels?
Pituitary gland releases hormones that act on other glands, directing them to release hormones
Oof a pituitary gland hormone that acts in the thyroid gland isn’t released, the thyroid gland may stop releasing hormones, causing the symptoms
Why after exercise does your urine go a dark colour?(6)
Sweat while running=water loss
Receptors in brain detect decreased water content in bloor
Coordination centre in brain receives this and coordinates a response- pituitary gland
Pituitary gland released ADH
ADH caused kidneys to reabsorbed more water, resulting in less water being released in urine
Explain how toxic waste substances are removed from the bloodstream during dialysis
There’s a partially permeable membrane between fluid and machine
Fluid contains normal conc of glucose and ions so glucose didn’t lost
Urea sissies into fluid and released into good then excreted
Protein molecules are too large so can’t diffuse
Describe the role of kidneys in selective reabsorption to produce urine
Kidneys act as filters and filter blood
All of glucose is selectively reabsorbed
Some water and ions are reabsorbed
Waste produces like excess water and urea are released through urine
What’s meant by a positive gravitropic response?
Plants grow upwards, against gravity
Explain how some of shoots from seedlings bend towards light
Unequal distribution of auxin
More aux in on darker side
Causes elongation of darker sode
Why does asexual reproduction lead to genetically identical offspring?
No mixing of genetic information as there’s no fusion of gamete’s
Similarities and differences between meiosis and mitosis
Mitosis- 1 parent, produces genetically identical offspring
Meiosis- 2 parents , produce variant offspring
Both involve the replication of dna
Describe the structure of dna
Polymer made up of repeating sun units
It’s 2 strands form a double helix structure
Consists of sequences of nucleotides
Nucleotides contains a sugar phosphate and base
T pairs with A and c with g as complementary base pairs
How can cystic fibrosis lead to damage if the lungs
Produces mucus
Trapped in respiratory pathways
Affects cell membranes and can lead to death
Why do many compost heaps have air holes?
Rate of decay is faster because it slows oxygen in so microorganisms can respire aerobically
Explain how carbon form desd organisms is recycled
Decomposers break down dead organic matter through the use of enzymes
As they respire aerobically, they releases carbon dioxide
This carbon dioxide is returned to atmosphere and absorbed by plants for photosynthetic
Similarities and differences between quadrats and transects
Both used with each other
Quadrats- used in random sampling to avoid bias+ count number of organisms in specific area
Transects- used in systematic sampling and show distribution in an area
Independent variable for required practical 8- effect of light on seedling
Conditions - light/dark
Direction of light
Dependent variable for required practical 8
Mean height of seedlings
Control variables of seedling practical
Number of seeds
Temperature
Volume of water seedlings are given
What can you do to decide where you place your first quadrat?
Use a random number generator to generate a set of coordinates
Describe the negative feedback lol that takes place when blood glucose levels are too low
Stimulates pancreas to release glucagon
Causes glycogen in liver to be converted to glucose
Blood sugar Returns to normal
Glucagon no longer released
Explain how the brain is altered to changes in external temperature
Temperature reflected in skin and thermoregulatory centre has receptors that detects blood temp
Send impulse to brain
Suggest what effect replacing a cotton wool pad with a ball of cotton wall has
Hall is uneven so can change volume and distribution of water
Describe the plant hormones practical
Put cotton wool into 3 Petri dishes and add same vol of water
Add 10Seeds to each dish and place them in warm place
Allow seeds to germinate and add water if cotton wool dries out
Once seeds have germinated, ensure dishes contain same number of seeds
1 dish sits in full light , 1 sits in dark cupboard , 1 sits in partial light
Every day for a week, measure height of each seedling and record results
Calculate mean of seedlings each day and compare mean heights in different locations
State some control variables and how they can be controlled
Number of seeds- use same number of seeds in each dish and remove any if need be
Type of seeds- use seeds that come from same packet
Vol of water- use measuring cylinder to add same vol of water
Temperature- keep dishes in place where temp is stable
Explain why more water is lost by breathing during a race
More energy needed
More respiration
Increased breathing rate to supply oxygen
What’s the end 2 marks for the question explain how carbon is recyclables into the growth of new leaves ?
Glucose is produced in photosynthesis and used to make amino acids and proteins , required for growth of new leaves
Explain how can a mutation could cause the enzyme not to work
Changes from c to t- changes in bases Changes amino acid Change protein Shape if active site changes Enzyme no longer fits substrate
Disadvantage of factory farming
Disease spreads rapidly
Antibiotics can build up on food chain
Explain how effiecincu of factor farming can be increased
Kept in temp controlled and restrict environment
Less energy lost in movement and less energy lost in regulating temp
More muscle
Mass
On each pig
Suggest what would happen in the body of a person that has a disorder due to an overactive thyroid gland
Too much thyroxine released into blood
Raises BMR
Increase in respiration
2 biological reasons why kidney transplant is better than dialysis
Blood ain’t in contact with machine, so lower risk of infection
Changes in concentrations of minerals are minimised , so less chance of causing damage to crlls
3 differences between mitosis and meiosis
Mitosis produces 2 daughter cells, whereas meiosis produces 4
One cell division in mitosis, but 2 in meiosis
Mitosis produces genetically identical offspring, meiosis produces variant
