Biology Summary Qs

B1
4)How do narrow arteries increase the risk of a heart attack?
If coronary arteries become narrowed blood flow is restricted and heart muscle recieves less oxygen. A thromobosis also restricts blood flow. blood flow might be blocked off completely so heart muscle will be cut off from oxygen supply-heart attack
7)Explain how psychological disorders can cause under-nutrition
Anorexia nervosa-self-starvation, Bulimia nervosa-binge eating followed by self-induced vomiting. Both result in poor diet so causes other illnesses.
8)What is the meaning of the term 'parasite'?
An organism that lives off a host causing it harm
14)Describe how drinking too much alcohol can damage your liver
Alcohol is poisonous, Broken down by enzymes and some of products are toxic. Uf you drink too much over long peiod of time then death of liver cells forming scar tissue that stops blood reaching liver-cirrhosis. Can't clean blood.
16)Describe the path of light through the eye
Cornea refracts light into the eye, iris controls how much light enters the pupil, lens refracts light, focusing it onto the retina, retina is light sensitive (covered in rods and cones), optic nerve carries impulses from the receptors to the brain

17)Describe the path taken by the reflex arc
Sensory neurone, relay neurone (in spinal cord), links directly to right motor neurone
19)Explain how negative feedback helps to maintain a constant internal environment
Changes in environment triggers response that counteracts changes e.g rise in body temp causes respons to lower body temp
24)Shoots are negatively geotropic. how are auxins responsible for this?
When shoot is growing sideways, gravity produces an unequal distribution of tip, with more auxin on lower side. lower side grows faster, bending shoot upwards
25)Give three ways that plant growth hormones are used commercially
Selective weedkillers-Most weeds are broadleaved so selective weedkillers developed from plant growth hormones which only affect broad leaved
Rooting powder-Add it to cutting which contains plant growth hormone, they produce roots and start growing as new plants
Ripening of fruit-Plant hormones delay ripening. Fruit picked when unripe so less easily damaged. Ripening hormone added and fruit ripens before shelves
29)Why is your ability at sport determined by both your genes and your environment?
Genes determine your potential but training important

B2
2)Give two reasons why classification systems change over time
-Newly dicovered species might not fit any of the catergories
-DNA sequencing allows us to see genetic differences
5)Why might two unrelated species look very similar?
They share a recent common ancestor
17)Explain how conter-current heat exchange systems keep penguins from getting too cold
-Blood vessels flow in opposite directions
-Vessels pass close to each ojhter allowing heat to transfer
-Warm blood in arteries heat cold blood in veins
-Feet stay cold which stops cold blood from colling down the rest of the body
19)Describe two ways that desert plants are adapted to survive in dry conditions
-Rounded shape giving small surface area to volume ratio
-Thick waxy layer to reduce water loss
20)Describe Darwin's theory of evolution by natural selection
Organisms show variation. they compete for limited resources. Best adapted survive and pass on successful adaptations to offspring.

22)How did lamark's theory of evolution contrast with Darwin's?
Characteristic used a lot then developed. Acquired characteristics would be passed on to animal's offspring
23)Give two reasons why the theory of evolution by natural selection is now widely accepted
-Debated and tested so no one conclusively proved that theory is wrong
-Offers explanation for many observations
25)Describe two processes that release carbon dioxide into the atmosphere
Respiration and combustion
27)What role do nitrogen-fixing bacteria play in the nitrogen cycle?
Turn N2 into nitrogen compound that plants can use
28)What does the term carbon footprint mean?
Amount of greenhouse gases given off in a certain period of time
31)What are indicator species? Give examples
Used to show pollution e.g lichens for air quality, mayfl larvae for water pollution
32)Give one disadvantage of using indicator species to measure pollution
Factors other than pollution can influence the survival of indicator species so aren't always reliable

33)Give four factors you'd look at to evaluate a conservation programme
Genetic variation, viability of populations, available habitats, interaction between species
35)What are the commercial value of whale?
Tourist attractions, meat and oil used for cosmetics
36)Name two aspects of whale biology that we don't fully understand
Whale communication, migration patterns

4)What evidence did watson and crick use to build a model of DNA?
X-ray data showing  that DNA is a double helix formed from two chains and other data showing that bases ocured in pairs
6)Briefly describe how DNA codes for a protein
It can't get out of the nucleus to the ribosomes as it's too big so uses mRNA to copy the code from DNA.
10)An enzyme with an optimum temp of 37 degrees is heated up to 60 degrees. Suggest what will happen to the enzyme
Bonds holding enzyme will break so it will lose it's shape so can't catalyse the reaction and it stops. It is now denatured and an irreversible change in shape
11)What does the Q10 value of an enzyme-controlled reaction show?
How much the rate changes when temp is raised by 10 degrees
14)Give three advantages of being multicellular
-Can be bigger so travel further, get nutrients in different ways and fewer predators
-Allows for cell differentiation-different tupes of cells for different jobs-specially adapted
-More complex so have specialised organs, different shapes and behaviour

18)Describe two diefferences in the way plant cells and animal cells grow and develop
-Animals-finite size and then stop growing, cell division
-Plants-Continuously, cell division in meristems
20)Give one advantage and disadvantage for each of the following ways of measuring growth:
a)Length
Easy to measure, Doesn't tell about changes in width, diameter
b)Wet mass
Easy to measure, Changeable
c)dry mass
Not affected by water or food eaten, kill the organism
24)Name seven things that blood plasma transports around the body
RBC,WBC,Platelets, water, carbon dioxide, urea, hormones, antibodies
27)Explain how capillaries are adapted to their function
Carry blood really close to every cell to exchange substances, permeable walls so substances can diffusem supply food and oxygen and take away wastes like co2, walls are one cell thick so increases rate of diffusion

30)What is selective breeding?
When humans artificially select plants or animals that are going to breed and have their genes remian in the population according to what we want from them
32)Give one advantage and one risk of genetic engineering
-New and useful features produced ver quickly
-Inserted gene might have unexpected harmful effects
33)Describe three examples of genetic engineering
-Some parts of world rely heavily on rice. Vitamin A defiency as sources scarce so gene that controls beta-carotene production from carrot plants and put into rice plants
-Human insulin production put into bactera. Cultured in fermenter and extracted
-Some plants have resistance to things like herbicides, frost damage and disease. Not plants we want to grow so cut it out and sick into useful plants
35)Why is gene therapy involving gametes controversial
-Unexpected consequences which causes problems for future generations
-Designer babies

36)Describe the method of cloning that was used to produce Dolly the sheep
Nucleus of egg cell removed so no genetic info, Another nucleus inserted (diploid nucleus fro udder cell of different sheep) and all genetic info, given electric shock so divide by mitosis, implanted into uterus of surrogate mother
37)Give two potential benefits and two potential risks of cloning animals
-Cloning allowes you to mass produce animals with desired characteristics
-Human embryos produced by clong adult body cells to suppluy stem cells
-Cloned animals no healthy s normal ones
-Cloning is a new science and it might have consequences that we're not aware of yet
38)Suggest three reasons why some people are concerned about cloning humans
-Many surrogate pregnancies with high rates of miscarriage and stillbirth
-Unhealthy clones which might die prematurely
-Psychologically damaged

39)Describe how plants can be cloned using tissue culture
-Remove small peices of tissue from parent plants (fast growing root and shoot tips)
-Grow in growth medium containing nutrients and growth hormones. Under aseptic conditions to prevent growth of microbes
-Moved to potting compost
40)Suggest two advantages and two disadvantages of the commercial use of cloned plants
-Genetically identical so only get good nes
-Mass produce plants that are hard to grow from seeds
-Lack of genetic variation
-if suffers disease becuase of change in environment they'll all have same problems