Paper 2 - Is Assessed Flashcards
What happens in a pyramid of biomass?
As you go up a trophic level, the mass of an organism decreases
Why aren’t food chains very long?
So much energy is lost at each level that there isn’t enough to support a long chain
Why does the mass of an organism decrease as the tropic levels go up?
As most biomass is lost, it can’t provide enough energy to support the same mass of organisms in a higher level
Where is biomass (energy) lost in plants?
During respiration / photosynthesis
Where is biomass (energy) lost in animals?
During respiration, heat given off to surroundings, undigested material (part of animal that doesn’t get eaten)
How do you calculate efficiency of each trophic level?
Energy transferred to next level
——————————————— X100
Energy available at previous level
How do you calculate the energy lost at each trophic level?
Energy available at previous level - energy transferred to next level
SA:V ratio
The larger an organism is, the…
…smaller it’s surface area is compared to its volume
How are substances transported in a single-celled organism?
Directly into and out of the cell across the cell membrane due to their large SA:V, so enough substances can be exchanged
What is multicellular organism’s SA:V?
Smaller SA compared to V
How do multicellular organisms transport substances?
Through a mass transport system over an exchange surface
How do exchange surfaces allow the maximum substances to cross?
By having a larger surface area so more so space for diffusion
What is Fick’s law?
rate of diffusion = SA x conc difference
—————————
Thickness of membrane
If the rate of diffusion doubles, so will…
…the SA or the difference in concentration
If the rate of diffusion doubles, what will half?
The thickness of membrane
How are alveoli specialised to maximise diffusion of O2 and CO2?
- moist lining for dissolving gases
- very thin walls minimising distance
- huge SA
- good blood supply to maintain conc gradient
How does distance affect the rate of diffusion?
Substances diffuse quicker when they don’t have as far to move
How does conc difference (gradient) affect the rate of diffusion?
substances diffuse faster if there’s a big difference in conc from and to the area of diffusion
How does SA affect the rate of diffusion?
the more SA there is for molecules to cross at, the faster they can move from one side to another
How does gas exchange happen in the alveoli?
- blood arrives at alveoli from the rest of the body, containing lots of CO2 and no O2
- this maximises conc gradient
- O2 diffuses out of air in the alveoli and into blood
- CO2 diffuses in the opposite direction to be breathed out
What is the job of the lungs?
to transfer O2 to the blood and to remove waste CO2 from it
What is the cardiac output formula?
Cardiac output = heart rate x stroke volume
What are the units for cardiac output, heart rate and stroke volume?
Cardiac output = cm3 / min
Heart rate = bpm
Stroke volume = cm3
What is the process of cellular respiration?
Transferring energy from the breakdown of organic compounds (usually glucose)
Is respiration exothermic?
Yes because energy is transferred to the surroundings
What is the energy used for that is produced in respiration?
- metabolic processes
- contracting muscles
- maintaining a body temperature
What is aerobic respiration?
Respiration when oxygen is plentiful - most efficient way
What is the formula for aerobic respiration?
glucose + oxygen —> carbon dioxide + water
What is anaerobic respiration?
Without oxygen - much less efficient as the glucose is only partially broken down
What is the formula for anaerobic respiration?
glucose —> lactic acid
How do pants respire when no oxygen is present?
Glucose —> ethanol + carbon dioxide
What are the control variables when investigating respiration?
Mass of maggots, atmosphere, mass of soda lime
What is the independent variable when investigating respiration?
Temperature of water bath
What is the dependent variable when investigating respiration?
Distance the fluid moves
What do phloem tubes do?
Transport food substance (mainly sucrose)
What is the process of translocation in phloem cells?
Transport food substances made in the leaves to the rest of the plant for immediate use or for storage in both directions
What makes up phloem tubes?
Made of columns of elongated living cells with small pores in the end walls to allow stuff to flow through
What do xylem tubes do?
Take water and mineral ions UP from the roots to the stem and leaves
What makes up xylem tubes?
made of dead cells joined end to end with no end walls between them and a hole down the middle
What strengthens xylem tubes?
A material called lignin
What is a transpiration stream in xylem tubes?
Movement of water from the roots, through the xylem and out of the leaves
What is transpiration?
caused by the evaporation and diffusion of water from a plant’s surface (mostly at the leaves)
What happens when a water shortage is created from transpiration in leaves?
More water is drawn up from the rest of the plant through the xylem vessels to replace it, meaning more water is drawn up from the roots
What are stomata?
Tiny pores on a plant’s surface mostly on the lower surface of a leaf
What do stomata allow?
Allow CO2 and O2 to diffuse directly in and out, and allow water vapour to escape in transpiration
How do stomata open and close?
Surrounded by guard cells
Guard cells = turgid = stomata open
Guard cells = flaccid = closed
What does turgid and flaccid mean?
Turgid = swollen with water Flaccid = low on water and limp
What 3 factors affect the transpiration rate?
Light intensity, temperature, air flow
How does light intensity affect the transpiration rate?
The brighter the light, the greater the rate
Stomata begin to close as it gets dark and photosynthesis can’t happen in the dark, so not much water can escpae
How does temperature affect the transpiration rate?
The warmer it is, the faster transpiration happens
Water particles have more energy to evaporate and diffuse out the stomata
How does air flow affect the transpiration rate?
Better the air flow, the greater the transpiration rate
If air flow is poor then the water vapour doesn’t move away it just sits around the lead so diffusion doesn’t happen as quickly
Why are leaves broad?
Gives a large SA for photosynthesis
What does the palisade later have which gets the most light?
Chloroplasts near the top of the leaf
What quality does the upper epidermis have and why?
Transparent so that light can pass through it to the palisade layer
How do xylem and phloem cells help a cell in gas exchange?
Provide leaf with water and take away glucose produced as well as supporting the structure of the leaf
Why are epidermal tissues covered with a waxy cuticle?
Helps to reduce water loss from evaporation
Why does the spongey mesophyll layer have air spaces?
To increase the rate of diffusion of gases into and out of the leaf
Why does the lower epidermis have lots of stomata?
To release CO2 directly out of the leaf
Go to picture 5 and describe the leaf
Picture 5
Investigating Respiration
What are the control variables?
Mass of maggots / atmosphere / mass of soda line
Investigating Respiration
What is the independent variable?
Temperature
Investigating Respiration
What is the dependent variable?
Distance fluid moves in manometer
Investigating Respiration
Why do you add soda line to two test tubes?
It absorbs CO2 produced by respiring woodlice
Investigating Respiration
Where do the wood lice go in the test tube?
Placed on cotton wool above soda lime
Investigating Respiration
Why do you use a control with glass beads?
To ensure that nothing else is respiring
Investigating Respiration
Why is there a decrease in the volume of air in the test tube with woodlice?
Wood lice use up oxygen in the tube as they respire (CO2 is absorbed so doesn’t affect the experiment)
Investigating Respiration
What causes the fluid in the manometer to move towards the test tube contains wood lice?
A decrease in volume reduces the pressure in the tube, causing the coloured liquid to mvoe
Investigating Respiration
How can the rate of respiration be calculated?
The distance moved by the liquid in a given time is measured, which can be used to find the volume oxygen taken in by the woodlice per minute
Investigating Respiration
What can you change in the experiment to decide what affects the rate of respiration
Temperature of the water bath
How do selective weed killers know how to kill weeds?
Developed from auxins which only affect broad-leaved plants (often weeds)
How do auxins in selective weed killer kill the weeds?
Disrupt their normal growth patterns, which kills them while leaving grass untouched
How do cuttings grow using root powder?
Root powder contains auxins, which helps produce roots rapidly to help grow a new plant from cuttings
Why do people want to use rooting powder to grow cuttings?
To create clones of a really good plant, and very quickly
How can plants be made to flower earlier than usual or under certain conditions?
Using gibberellins (plant hormones that stimulate seed germination)
How can gibberellins help produce a better fruit crop?
By limiting flower formation, so the tree doesn’t produce too many fruit which it can’t sustain, worsening the fruit
How can fruit be grown seedlessly?
Gibberellins are applied to unpollinated flowers, so the fruit will grow but the seeds won’t
How can the ripening of seeds be controlled?
fruit is picked while unripe, and then ethene is added so the fruit will ripen on the way to the supermarket
How can seeds be made to germinate at any time of year and all germinate at the same time?
Seeds can be treated with gibberellins
How do auxins control growth at the shoots?
Auxins is produced in tips and diffuses backwards to stimulate the cell elongation process
How do auxins travel in a plant?
Auxins move through the plant in solution (dissolved in water)
What do auxins do in the root?
Inhibit growth
What does it mean if shoots are positively phototropic?
Grow towards light
What does it mean if shoots are negatively gravitropic?
Grow away from gravity
Positively phototropic
What happens when a shoot tip is exposed to light?
It accumulates more auxin on the side that’s in the shade than the side that’s in the light
This makes it elongate faster on the shaded side, so it bends towards the light = more photosynthesis
Negatively gravitropic
What happens when a shoot is growing sideways?
Gravity produces an unequal distribution of auxin in the top, with more auxin on the lower side
This caused the lower side to grow faster, bending the shoot upwards
What does it mean if a root is positively gravitropic?
Grows towards gravity
What does it mean if a root is negatively phototropic?
Grows away from light
Positively gravitropic
What does it mean if a root is growing sideways?
It will have more auxin on the lower side, inhibiting growth
The cell will elongate faster and the root will bend downwards
Negatively phototropic
What happens if a root becomes exposed to light?
More auxin accumulates on the more shaded side
The auxin inhibits cell elongation on the shaded side, so the root grows downwards back into the ground
Endocrine system
What does the pituitary gland do?
Regulates body conditions, and directs other hormones to bring about change
Endocrine system
What do the ovaries do?
Produce oestrogen, involved in the menstrual cucle
Endocrine system
What do testes do?
Produce testosterone which controls puberty and sperm production
Endocrine system
What does the thyroid gland do?
Produces thyroxine which regulates rate of metabolism, heart rate and temperature
Endocrine system
What does the adrenal gland do?
Produces adrenaline which is used to prepare body for a ‘fight or flight’ response
Endocrine system
What does the pancreas do?
Produces insulin which is used to regulate the blood glucose level
Characteristics of neurones
Very fast action
Act for a short time
Act on precise area
Characteristics of a hormonal response
Slower action
Act for a long time
Act in a more general way
How does adrenaline increase heart rate and blood pressure?
Adrenaline binds to specific receptions in the heart, causing the heart muscle to contract more frequently so cells receive more oxygen as blood flow increases
How does adrenaline impact the liver?
Binds to receptors in the liver causing it to break down its glycogen stores to release glucose, increasing blood glucose level in blood
How does thyroxine regulate metabolism?
- when blood thyroxine is lower, the hypothalamus is stimulated to release TRH
- TRH stimulated the pituitary gland to release TSH
- TSH stimulates the thyroid gland to release thyroxine so blood thyroxine level rises back towards normal
- process is inhibited when levels are too high
Thyroxine
What does TRH stand for?
Thyrotropin releasing hormone
Thyroxine
What does TSH stand for?
Thyroid stimulating hormone
Stage 1 of Menstrual Cycle
Day 1 = lining of uterus breaks down and is released
Stage 2 of Menstrual Cycle
Day 4-14 = uterus lining is repaired until it becomes a thick sponge layer full of blood vessels ready for a fertilised egg to implant
Stage 3 of Menstrual Cycle
Day 14 = an egg develops and is released from the ovary
Stage 4 of Menstrual Cycle
Day 14-28 = lining is maintained and if no fertilised egg has landed in the uterus, the spongy lining breaks down again
Menstrual Cycle
What does Follicle-Stimulating Hormone do?
- released by pituitary gland
- causes a follicle (an egg) to mature in one of the ovaries
- stimulated oestrogen production
Menstrual Cycle
What does oestrogen do?
- released by ovaries
- causes the lining of the uterus to thicken and grow
- a high level stimulates an LH surge
Menstrual Cycle
What does Luteinising hormone do?
- released by pituitary gland
- LH surge stimulates ovulation where the follicle ruptures and egg is released
- stimulates the remains of the follicle to develop into a structure called a corpus luteum
Menstrual Cycle
What does Progesterone do?
- released by corpus luteum after ovulation
- maintains lining of uterus
- inhibits release of FSH and LH
- when level of prog. falls, and low oest. level, the uterus lining breaks down
- a low prog. level allows FSH to increase
How does Clomifene therapy work to increase fertility in women who doesn’t ovulate regularly?
Causes more FSH and LH to be released, which stimulates egg maturation and ovulation - by knowing when a woman is ovulating a couple can have intercourse at this time
How does IVF fertilise a woman’s egg?
By collecting eggs from the ovaries and fertilising them with sperm in a lab, which can then be grown into embryos - once the embryos are tiny balls of cells, a few can be transferred to the woman’s uterus
What is ART?
Assisted Reproductive Technology - a fertility treatment involving eggs being handled outside the body
What hormone is given to a woman before IVF?
FSH and LH to stimulate egg production so more than one egg is collected
What are unpleasant side effects of hormonal contraceptives?
Headaches, acne, mood changes, and they don’t protect again STI’s as a condom would
What hormone is contained in the mini-pill or contraceptive injection
Progesterone only
What are barrier contraceptive methods?
Condoms or diaphragms
What hormone does the contraceptive patch and the combined pill contain?
Oestrogen and progesterone
How does progesterone reduce fertility?
By stimulating the production of thick, cervical mucus which prevents any sperm getting the the entrance to the uterus (cervix) and reaching an egg
What happens if oestrogen is taken every day?
Inhibits production of FSH and egg development / production stops
What causes Type 1 diabetes?
Where the pancreas produces little to no insulin, causing a rise in blood glucose levels that can be fatal
How can Type 1 diabetes be controlled?
Limiting the intake of foods rich in simple carbohydrates, regular exercise, insulin injections
What causes Type 2 diabetes?
When a person becomes to resistant to insulin, so it causes blood glucose levels to rise
How can Type 2 diabetes be controlled?
Healthy diet, regular exercise, losing weight
Thermoregulation
What is vasoconstriction?
- erector muscles contract
- hair stands on end to trap insulating layer of air
- very little sweat is produced
- blood vessels near surface constrict
- less blood flows near the surface
- less energy is transferred to surrounding
- shivering increases rate of respiration
Thermoregulation
When does vasoconstriction happen?
When you’re too cold
Thermoregulation
What is vasodilation?
- erector muscles relax so hair lies flat
- lots of sweat is released which transfers energy to surroundings
- blood vessels dilate
- allows more blood to flow near the surface
- so more energy is transferred out
Thermoregulation
When does vasodilation happen?
When you’re too hot
What is excess glucose stored as, and where in the body?
Glycogen in the liver and muscles
What happens to glucose when glycogen stores are full?
Excess glucose is stored as lipid (fat) in the tossues
What happens when blood glucose concentration is too high?
- blood = too much glucose
- insulin secreted by pancreas
- mix of glucose and insulin
- glucose moves from blood to live and muscle cell
- insulin makes liver turn glucose into glycogen
- blood glucose is reduced
What happens when blood glucose concentration is too low?
- blood has too little by glucose
- glucagon secreted by pancreas
- mix of few glucose and glucagon
- glucose released into blood by liver
- glucagon makes liver turn glycogen into glucose
- blood glucose increased
Thermoregulation
What does the hypothalamus do?
Act as your own personal thermostat as :
- contains receptors that are sensitive to blood temp. In the brain
- receives impulses from receptors in the skin that provide info about external temperatures
Thermoregulation
Where are the receptors providing info about external temperature in the body?
Epidermis (outer layer of skin)
Dermis (deeper layer of skin below)
Cons to fish farming
- waste leaks into open water
- predators are attracted to nets and become trapped in them
- breeding ground for parasites, that may kill wild animals too
- farmed fish may escape causing problems for indigenous soecies
How can the introduction of non-indigenous species reduce biodiversity?
- compete with indigenous ones for food and shelter
- bring new diseases with them
What is the process of eutrophication?
- fertiliser enter the water, adding excess nitrates
- excess nitrates cause algae to grow fast and block light
- plants can’t photosynthesis, dying and decomposing aerobically
- plants are good for microorganisms, using up oxygen in water
- organisms that need oxygen (fish) die
What are some conservation methods?
- protecting a species natural habitat
- safe areas eg. Protected zoos
- use of seed banks to conserve seeds
What are the benefits to maintain biodiversity?
- protecting human food supply
- minimal damage to food chains
- providing future medicines
- cultural aspects
- ecotourism
- providing new jobs
Food security
How does the increasing population threaten food security?
More people = more food is needed
Food security
How does the increasing consumption of meat and fish threaten security?
- meat and fish are higher up the food chain
- less biomass and energy transferred
- needs more to feel full
- more crops can be grown in a field than cows grazing on it
Food security
How do new pests and pathogens impact food security?
Cause damage to crops and livestock, and may damage the yield and quality of food
Food security
What are the issues with sustainability?
- high input costs is too expensive for farmers for what they get in return
- balance between renewable alternatives to fossil fuels on land that could be used for crops
Food security
How does burning fossil fuels impact food security?
Release CO2, causes climate to rise, impacts the growth of crops and reduces yields
Soil pollution/ eutrophication too
Indicator species for polluted water
Bloodworms and sludge worms
Indicator species for clean water
Stonefly larvae and freshwater shrimp
Indicator species for air pollution
Number / type / location of crusty lichen, which are sensitive to sulfur dioxide in atmosphere
Indicator species for clean air
Bushy lichen, black spot fungus on rose leaves
How does temperature affect the rate of decomposition?
Warm temp = speeds up rate of enzyme-controlled reactions in microbes, so decay happens faster
How does temperature affect the rate of decomposition?
Warm temp = speeds up rate of enzyme-controlled reactions in microbes, so decay happens faster
How does temperature affect the rate of decomposition?
Warm temp = speeds up rate of enzyme-controlled reactions in microbes, so decay happens faster
How does water content affect the rare of diffusion
Decay happens faster in moist environments as organisms need water to shrvice
How does water content affect the rare of diffusion
Decay happens faster in moist environments as organisms need water to survive
How does oxygen availability affect the rate of decomposition?
microorganisms need oxygen for aerobic respiration, so decay is faster when oxygen is plentiful
How can food be preserved?
Freezing it, airtight cans, drying food to reduce moisture
