Biology Paper 2

maintains optimal conditions for enzyme action and all cell functions by regulating internal conditions of an organism

- blood glucose concentration
- body temperature
- water levels

brain, spinal cord, pancreas

relay neurone either in the spinal cord or the unconscious part of the brain

encased in protective membranes - meninges

consciousness, intelligence, memory, language

coordinating muscular activity, balance

unconscious activities - heartbeat, movement of the gut and breathing

- studying people with brain damage
- electrically stimulating parts of the brain (remove the top of the skull)
- MRI scans - can show which area of the brain is affected by a tumour / stroke - enables scientists to liken the loss of a function to damage to a particular region of the brain

- complex and very delicate - easily damaged
- not fully understood
- drugs don't always reach the brain through the membranes that surround it

white outer layer of eye - tough and strong

- transparent area of the sclera at the front of the eyeball
- lets light into the eye
- curved surface area important for changing direction of light rays so that they are focused on the retina

- circular muscles contract
- radial muscles relax
- pupil constricts

- circular muscles relax
- radial muscles contract
- pupil dilates

beyond the pupil - held in place by suspensory ligaments and ciliary muscles

filled with thick transparent jelly that maintains its spherical shape

- light-sensitive cell layer at the back of the eye
- cells are stimulated to send impulses along sensory neurones in the optic nerve

- point where the optic nerve leaves the eye has no retina
- brain 'fills the gap'

change direction of light rays onto the retina but always refract it by the same amount

diverges very strongly

travels in almost parallel rays

- ciliary muscles relax so that suspensory ligaments are pulled tight
- lens is pulled flat and thin
- only refracts light rays slightly so that they are focused on the retina

- ciliary muscles contract so that suspensory ligaments loosen
- lens is then thicker and more curved / rounded
- refracts light rays strongly so that they are focused on the retina

process of changing the shape of the lens to focus on near and distant objects

hardens as people get older - more difficult to focus on close objects

- short sightedness
- distant objects are blurred
- light focused in front of retina
- can be caused by an overly curved lens / particularly long eyeball

- concave lens glasses
- spreads out light from distant objects before it reaches the eye
- thicker lens can bring light into perfect focus on the retina

- long sightedness
- close objects are blurred
- light focused behind retina
- can be caused by an overly flat / thin lens or a particularly short eyeball

- convex lens glasses
- bring light rays together more before they reach the eye
- then thinner lens can bring light rays into perfect focus on the retina

- relatively rigid material and last long
- must be removed overnight and kept sterile to prevent eye infection

- more flexible and don't last as long
- must be kept in sterile solution overnight
- some last a month - others are disposable

- only available to adults whose eyes have stopped growing and vision become stable
- myopia - reduce thickness of cornea so it refracts light less strongly
- hyperopia - change curve of cornea so it refracts light from close objects more effectively

- add a permanent lens implanted into eye and leave natural lens in place
- or replace faulty lens with artificial lens

- damage to retina
- cataracts if natural lens left in place
- infections

composed of glands which secrete hormones into the bloodstream, to be carried to target organs

- pancreas produces insulin
- makes glucose move from blood into cells
- excess glucose in liver and muscle cells is converted to glycogen for storage

- pancreas produces glucagon
- causes glycogen to be converted into glucose and released into the bloodstream

pancreas doesn't produce enough insulin

body cells don't respond to insulin - can be treated with drugs

- FSH secreted by pituitary gland makes eggs mature and stimulates production of oestrogen
- oestrogen causes the lining to develop, inhibits FSH and stimulates release of LH
- LH triggers ovulation
- progesterone is secreted by empty egg follicle in the ovary, maintains the uterus lining and inhibits FSH and LH

contains oestrogen and some progesterone to inhibit FSH so no eggs mature

slow release progesterone to inhibit FSH and LH so maturation and release of eggs is stopped for months / years

prevent implantation of an embryo and some release progesterone

- mother given FSH and LH to stimulate maturation of several eggs
- eggs are collected from mother and fertilised with father's sperm in a lab
- fertilised eggs develop into embryos
- 1 or 2 embryos implanted into womb

- less likely to be successful in older parents
- can lead to multiple births which are a risk to both babies and mother

increases heart rate and boosts delivery of oxygen and glucose to brain / muscles

- stimulates basal metabolic rate (how quickly substances are built up / broken down)
- plays important role in grwoth and development
- thyroxine levels are controlled by negative feedback involving TSH (secreted from the pituitary gland)

detected by brain - TSH released increases

- controls growth in children
- acts on thyroid gland, ovaries and testes

insulin, adrenaline

growth and sex hormones

- insulin protein injected
- careful about levels of carbohydrates consumed
- regular meals
- excercise - but with careful planning

- difficult and risky operation
- insufficient donors
- patient exchanges insulin for another medicine - immunosuppressants

- restore normal blood glucose balance naturally - balanced diet with controlled carbohydrate consumption, losing weight, regular excercise
- drugs that help insulin work better on cells, help pancreas make more insulin and reduce amount of glucose absorbed from gut
insulin injections if all else fails

phototropism

gravitropism / geotropism

- unequal distribution of auxin in plant / root
- unequal growth rate
- root /shoot bends in right direction - cells respond to hormone by growing more where hormone is most present

phototropism and gravitropism

important in initiating seed germination

controls cell division and ripening of fruits, gas hormone

- auxin solution sprayed onto leaves of plants - hormone absorbed
- extra auxin sends plants into rapid, uncontrollable growth, killing them
- crop plants mainly unaffected - cereals and grasses are narrow leaved
- most weeds are broad leaved - greater surface area for weed killer absorption

- auxin stimulates growth of new roots
- chances of success increased when cut end of a cutting is dipped in

part of cloning process - stimulates growth and cell division

- fruit harvested when it isn't ripe - firm green fruits can be transported chilled - less damage and smaller chance of over-ripening
- warm temperature and ethene added

- end seed dormancy in brewing industry - speeds up germination of barley seeds to make malt
- promote flowering throughout the year
- increase fruit size - seedless grapes would be very small because seeds produce gibberellins to make fruit grow

- in the brain
- monitors and controls body temperature
- contains receptors sensitive to the temperature of the blood
- skin also contains temperature receptors and sends nervous impulses to the thermoregulatory centre
- impulses sent from thermoregulatory centre to rest of body

- blood vessels that supply surface skin capillaries dilate
- lets more blood flow through capillaries
- skin flushes - more energy transferred by radiation from skin to surroundings

- water evaporates from skin, transferring energy to environment
- difficult in humid weather - sweat can't evaporate
- more water and mineral ion intake needed to balance loss

vasodilation, sweat glands produce more sweat, hairs lie flat

- vasoconstriction
- sweat production reduced / stopped
- skeletal muscles contract and relax rapidly - requires lots of respiration (exothermic process) so raises temperature
- hairs pulled erect - trap insulating layer of air

dissolved CO2 produces an acidic solution - would affect working of all enzymes

- diffuses out of cells into blood down a concentration gradient
- diffuses from blood into air in alveoli
- this air is removed in exhalation
- side effect - loss of water when moist air is forced out of body

- excess proteins from digestion / worn out tissues can't be stored - broken down into amino acids
- amino acids can't be used directly as fuel by cells
- liver removes amino group from the amino acids in the deamination process - forms ammonia (very toxic)
- ammonia immediately converted into urea (toxic but can be removed safely)
- rest of amino acid molecule then used in respiration / to make other molecules

brings urea to the kidneys in the blood

takes 'cleaned' blood away from kidneys

- H2O, urea, glucose and mineral ions pass into the nephron / kidney tubule
- blood cells are too big

- all glucose (unless excess due to diabetes)
- some of the mineral ions and water
- uses diffusion, osmosis and active transport at different stages

- negative feedback system involving hormone ADH
- ADH secreted by pituitary gland
- receptor cells in the brain detect the concentration of solutes in blood plasma

- lots of ADH released
- kidney tubules reabsorb much more water
- small volume of very concentrated urine

- blood leaves the body and flows between partially permeable membranes in the dialysis machine
- dialysis fluid is on the other side of the membranes
- dialysis fluid contains same concentration of useful substances as blood of a healthy person (glucose and mineral ions) - ensures no net movement of glucose out of the blood
- fluid has normal plasma levels of mineral ions - any excess ions are removed by diffusion
- dialysis fluid contains no urea - steep concentration gradient
- blood flows in opposite direction to dialysis fluid

- carefully controlled diet
- regular, long sessions
- feel tired and unwell as next session approaches
- much more expensive than transplant in the long term
- eventually causes serious damage to the body

- don't last forever (but embryonic kidney tissue from stem cells could be used in future)
- risk that antibodies of recipient will attack antigens on donor organ

- antigen match as close as possible eg. similar 'tissue type'
- immunosuppressant drugs (-ve - prevent patients from dealing effectively with infectious diseases)

- copies of genetic info of the cell are made
- cell divides twice to form 4 gametes, each with a single set of chromosomes
- all gametes are genetically different from each other
- gametes join at fertilisation to restore normal number of chromosomes
- new cell divides by mitosis

asexually in human host, sexually in female mosquitoe

most reproduce asexually by spores but some alos reproduce sexually to give variation

- runners (eg. strawberry plants)
- bulb division (eg. daffodils)

- small section of DNA on a chromosome
- each gene codes for a particular sequence of amino acids, to make a specific protein

entire genetic material of an organism

- search for genes linked to different diseases - predict the risk for each individual so they can make lifestyle choices to reduce the risks
- understand and treat inherited disorders - more chance of overcoming them through medicines / repairing faulty genes
- use in tracing human migration patterns from the past

- sequence of 3 bases codes for a particular amino acid
- order of bases controls order in which amino acids are assembled to produce a particular protein

alternating sugar and phosphate sections - one of the 4 bases is attached to each sugar

- combination of sugar, phosphate and base
- DNA made up of repeating nucleotide units

AT, GC

- genes in the DNA in the nucleus of the cell produce a template for the protein
- template leaves the nucleus and binds to the surface of a ribosome
- carrier molecules in the cytoplasm, that are attached to a specific amino acid, attach themselves to the template in the order given by DNA
- amino acids are joined together to form a growing protein
- when complete, protein chain folds into a unique shape that enables it to carry out its function

- occur continuously
- most don't alter the protein, or only slightly so that appearance and function are unchanged
- a few mutations code for an altered protein with a different shape - an enzyme may no longer fit the substrate binding site or a structural protein might lose its strength
- any change in the order of bases in the DNA structure of a gene will alter the template made - different template may result in different sequence of amino acids, so change in protein synthesised

- single gene in some cases - each gene may have different forms (alleles)
- most characteristics are a result of multiple genes interacting

alleles present regarding a particular characteristic

physical appearance regarding a particular characteristic

caused by a dominant allele

caused by a recessive allele

due to differences in genes inherited and conditions of development

change in genetic material of an organism

- enzymes used to isolate and 'cut out' required gene from an organism
- gene is inserted into a vector using more enzymes (vector usually bacterial plasmid / virus)
- vector then used to insert gene into required cells at an early stage of development
- as the organism grows it develops with the new desired characteristics

desired genes often inserted into meristem cells which are then used to produce identical clones of the genetically modified (GM) plant

- effect on populations of wild flowers and insects
- effect on human health not fully explored

old but simple way of producing many identical new plants from a parent plant

modern and expensive - allows thousands of new plants to be made from one tiny piece of plant tissue

- use a mixture of plant hormones to make a small group of cells from the desired plant clone
- these cells go on to produce a big mass of identical cells called a callus
- use a different mixture of hormones and conditions to stimulate each cell to form a tiny new plant

- commercial - in plant nurseries to produce house and garden plants
- preserve rare plant species

- split apart cells from a developing animal embryo before they become specialised
- then transport identical embryos into host mothers
- eg. same cow can produce more high-quality calves

- nucleus removed from an unfertilised egg cell
- nucleus from an adult body cell (eg. skin cell) inserted into egg cell
- electric shock stimulates the egg cell to divide and form an embryo
- embryo cells contain same genetic info as adult cell
- when embryo has developed into a ball of cells, it is inserted into the uterus of an adult female to continue development

- clone animals that have been genetically modified to produce useful proteins in their milk
- save animals from extinction / bring back

reduces variety in a population - less able to survive environmental change

- genetically engineered microorganisms can make proteins humans need in large and pure quantities eg. insulin and growth hormone
- mice can mimic human diseases - find cures
- overcome inherited disorders

- insects may become pesticide-resistant if they eat a constant diet of pesticide-forming plants
- GM crops originally often made infertile - could spread into wildlife

- cross bred different types of peas and found that characteristics were inherited in clear and predictable patterns
- suggested that there were separate units of inherited material - realised that some characteristics were dominant over others and they never mixed together
- work only accepted when chromosomes had been seen through a microscope - their behaviour during cell division was observed

- every type of animal evolved from primitive worms
- evolution due to inheritance of acquired characteristics 'use it or lose it'

- independently proposed the theory of evolution by natural selection
- published joint writings with Darwin
- prompted Darwin to publish 'On the Origin of Species'
- worked on warning colouration in animals as evidence
- did much pioneering work on speciation

- hard parts that don't easily decay (eg. teeth and bones)
- parts of organism have not decayed due to one or more of the conditions for decay not being present (no O2, poisonous gases kill decay bacteria, very low temp)
- mineralisation - most common, hard parts of organism replaced by other minerals
- traces of organisms left behind eg. footprints, burrows, faeces

- many early life forms were soft bodied
- majority of any fossils formed in early days destroyed by geological activity
- conditions for fossilisation are rare
- fossils yet to be discovered

- doctors shouldn't prescribe inappropriately (non serious / viral infections)
- complete course so all bacteria are killed and none survive to mutate and form resistant strains
- agricultural use restricted

organisation of living things into groups according to their similarities

classified living things into kingdom, phylum, class, order, family, genus and species

developed the 'three domain system' due to evidence available from chemical analysis
- archaea (primitive bacteria - usually extremophiles)
- bacteria (true bacteria)
- eukaryota

show how organisms are related - use current classification data for living organisms and fossil data for extinct organisms

interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment

- all species and environmental factors in balance - population sizes remain fairly constant
- predator and prey numbers fall and rise in cycles

- often grow and flower very early in the year when lots of light gets through the bare branches of trees
- dormant trees take up little water
- leaves shed from previous autumn have rotted down to provide mineral ions in the soil

allow plants to climb up artificial structures and large trees to reach light

some 'cry' very salty tears from a special salt gland to get rid of excess salt

produce a chemical in cells that acts as an antifreeze - stops water in the cell freezing

lots of big air spaces in their leaves to float on the surface and photosynthesise

survive and reproduce at very high / low temperature pressure or salt concentration (eg. bacteria living in deep sea vents)

- structural (eg. shape and colour)
- behavioural (eg. migration, basking and tool-using)
- functional (eg. reproduction and metabolism)

functional kidney adaptations - can produce very concentrated urine

- a few are broad leaved to collect evening dew and funnel to roots
- curled leaves - minimises SA for water loss and traps layer of moist air around leaf to reduce water evaporation
- most have a small SA
- some have a cuticle

- plants and algae more difficult due to cellulose
- other animals easier - high in protein and fat

mostly carbon, oxygen, hydrogen and nitrogen

- detritus feeders (maggots, some worms and beetles) often start process - eat dead animals and produce waste material
- bacteria and fungi digest everything (dead animals, plants and detritus feeders plus their waste)
- bacteria use some of the nutrients to grow and reproduce
- bacteria also release CO2, water and mineral ions as waste products
- CO2 is returned to atmosphere to be used by producers in photosynthesis
- mineral ions are returned to the soil to be taken up by plant roots and used to make proteins and other chemicals in cells

- evaporation from surface of land and from water bodies
- released when organisms decay
- released in respiration, transpiration, urine and faeces

- fossil fuels
- combined with other elements in carbonate rocks (eg. limestone and chalk)
- CO2 in the air
- CO2 dissolved in water bodies

- cycling of carbon through the living and non-living world
- green plants and algae remove CO2 from atmosphere for photosynthesis
- use the carbon to make carbs, proteins and fats - make up their biomass
- carbon passed on through food chains
- carbon returned to atmosphere as CO2 when living organisms, including decomposers, respire

fossil fuel / wood + oxygen ---> carbon dioxide + water

- chemical reactions in microorganisms work faster in warm temp - but enzymes in decomposers can denature
- moisture - makes it easier for microorganisms to digest food and prevents them drying out
- oxygen - some microorganisms can respire anaerobically but most decomposers need oxygen

- can be made with / without oxygen
- with oxygen, microorganisms respire aerobically and transfer energy to their surroundings - kills off weeds and speeds up process
- compost used as natural fertiliser

- plant / animal waste put in
- decomposers produce methane gas due to anaerobic conditions
- exothermic process - if mixture is heated at the start and well insulated, generators will work anywhere

reduces dependence of one species on another for food, shelter and maintenance of the physical environment - other species take its place

- landfill
- sewage pollution in soil
- toxic chemicals from industrial waste and landfill sites spread to soil
- herbicides and pesticides

- fertilisers washed off fields into streams, ponds and rivers
- levels of nitrates in water rise
- algae and other water plants grow rapidly
- some plants die as they can no longer photosynthesise (competition)
- decomposing microorganism numbers rise
- microorganisms respire, removing oxygen

- measure oxygen / pH levels with instruments
- bioindicators (eg. salmon and bloodworms only found in very clean or very polluted water)

- fossil fuels contain sulphur and nitrogen impurities
- impurities react with oxygen when burnt to form sulphur dioxide and nitrogen oxides - released into air
- with sunlight, sulphur dioxide and nitrogen oxides dissolve in water droplets in air to form sulphuric acid and nitric acid
- prevailing winds can carry pollutants for long distances

- kills leaves, buds, flowers and fruit
- soaks into soil - can damage roots
- makes water bodies acidic

- low sulfur petrol and diesel
- catalytic converters - remove polluting gases from exhaust fumes
- strict emission levels set
- low sulfur fuels (eg. gas rather than coal)
- more renewable energy sources and nuclear
- systems in power station chimneys to clean flue gases before they are released - also produce sulfuric acid as a useful byproduct

- increases number of particulates in air - reflect sunlight, causing global dimming - could lead to cooling temperature
- particles breathed in can damage the lungs and cardiovascular system

- haze of small particles and acidic gases that can be seen in air
- formed from smoke and chemicals such as sulphur dioxide and nitrogen oxides

- made of plant material that can't decay properly due to very acidic and oxygen-lacking conditions
- formed over thousands of years, originally in peat bogs
- bogs may dry out over time to form peatlands
- acts as a massive carbon store and is home to unique ecosystems that have evolved to thrive there

- burnt as a fuel
- used by gardeners to improve properties of soil and provide ideal environment for seed germination
- when peat is burnt / used in gardens, CO2 is released and carbon store is lost
- peat is being destroyed faster than it's made
- UK gov trying to persuade gardeners to use peat-free compost

- energy from sun warms up the earth
- much of the energy is radiated back into space
- greenhouse absorb some of the energy transferred
- earth and surrounding atmosphere kept at ideal temperature for life

- loss of habitat due to rising sea levels
- changes in distribution - conditions more favourable for some animals
- changes in migration patterns - changing climates and seasons
- reduced biodiversity

- restore an endangered species to a sustainable population
- can be slow
- must avoid inbreeding
- habitat needed often has been lost

- were removed to produce huge fields in which to grow a single crop
- reduced biodiversity
- led to soil erosion and loss of fertility in some places
- gradually being replanted

positions of organisms within a food chain

apex predators

- secrete enzymes into the environment
- small soluble food molecules then diffuse back into the microorganism down a concentration gradient

- not all organisms or parts are eaten (meat easy to digest but parts no eaten)
- lost in faeces (herbivores don't have the enzymes to digest cellulose)
- lost in urine
- some used in respiration - CO2 and water are waste products, transfers energy to surroundings
- energy released in respiration used for movement and maintaining constant body temperature

some areas of land can produce grass but not crops

- reduces need for respiration (movement and temperature)
- less labour intensive - animals contained in small area
- predators
- cheaper

- diseases spread faster
- constant monitoring

- restricted movement
- high protein food
- grow and mature rapidly

- control size of holes in nets so younger (smaller) fish can escape and live to grow large enough to breed
- bans on fishing in breeding season
- strict quotas - but fishermen often throw dead fish back into sea to avoid quotas

- produced using fungus Fusarium
- Fusarium grows and reproduces rapidly on relatively cheap glucose syrup
- made in large specialised containers (fermenters)
- fermenters provide oxygen (for aerobic conditions) and maintain optimum temperature
- fungal biomass is harvested, purified, dried and processed