extra eq Flashcards
Describe the process of spermatogenesis leading to the production of four sperm
cells in a human male.
. in the seminiferous tubule ✔
b. diploid cells/spermatogonia grow/enlarge ✔
c. two divisions of meiosis ✔
d. primary spermatocyte carries out the first division and secondary spermatocytes carry
out the second division ✔
e. meiosis produces haploid cells/spermatids ✔
f. haploid cells/spermatids differentiate into spermatozoa/sperm cells
OR
develop tail/flagellum/helical mitochondrion/acrosome/sac of enzymes ✔
g. Sertoli cells help sperm to mature/differentiate
Outline the roles of estrogen and progesterone in females during human
reproduction.
a. estrogen/progesterone for repair/thickening/development/vascularisation of uterus
lining/endometrium ✔
b. estrogen (at high levels) stimulates LH secretion (which stimulates ovulation)
c. progesterone maintains the uterus lining/endometrium during pregnancy/prevents
miscarriage ✔
d. progesterone/estrogen inhibits FSH/LH secretion ✔
e. progesterone for development of breast tissue during pregnancy ✔
f. fall in progesterone/rise in estrogen leads to labour/contractions/childbirth ✔
g. estrogen/progesterone cause pre-natal development of female reproductive organs
OR
h. estrogen/progesterone cause secondary sexual characteristics
Explain the process of muscle contraction
a. muscle fibre contains many myofibrils ✔
b. made up of sarcomeres/labelled diagram showing one or more sarcomeres ✔
c. nerve impulse/signal from (motor) neuron causes release of calcium (ions)/Ca2+ ✔
d. calcium (ions)/Ca2+ released from sarcoplasmic reticulum ✔
e. calcium (ions)/Ca2+ link to troponin ✔
f. tropomyosin moves to expose actin binding sites ✔
g. ATP hydrolysis/ATP to ADP and phosphate/release of phosphate from ATP ✔
h. ATP binds to myosin heads and causes them to cock/change angle/release/gain
energy ✔
i. myosin heads bind/form cross-bridges to actin ✔
j. myosin heads push on actin and then detach from actin ✔
k. actin moved towards centre of sarcomere/sliding of filaments ✔
sarcomere becomes shorter resulting in muscle contraction
Explain how organic compounds are transported within plants.
a. transported in/translocated in/loaded into phloem✔
b. in sieve tubes ✔
c. by mass flow ✔
d. from sources to sinks ✔
e. from leaves/other example of source to roots/other example of sink ✔
f. loading (of sugars/organic compounds) by active transport ✔
g. cause high concentration of solutes (in phloem/sieve tubes) ✔
h. water uptake (in phloem/sieve tubes) by osmosis/water diffuses into phloem ✔
i. rise in (hydrostatic) pressure at source (in phloem) ✔
j. creates a (hydrostatic) pressure gradient/higher pressure in source than sink ✔
k. flow can be in either direction/bidirectional ✔
Outline how plants make use of the different wavelengths of light
a. light used in photosynthesis/light-dependent reactions/
photolysis/photosystems/photophosphorylation/excitation of electrons/switch to
flowering ✔
b. chlorophyll absorbs red AND blue light (more) ✔
c. chlorophyll/leaf/plant reflects/does not absorb/does not use green light ✔
d. absorption spectrum of chlorophyll has peaks in the red and blue/sketch graph to
show this ✔
e. action spectrum shows which wavelengths plants use in photosynthesis/sketch
graph of action spectrum showing peaks in the blue and red ✔
f. accessory/other (named) photosynthetic pigments absorb different
wavelengths/colours ✔
g. violet is the shortest wavelength and red the longest ✔
h. red light and far red/infra-red absorbed to measure length of light/dark periods
Outline how greenhouse gases interact with radiation and contribute to global
warming
carbon dioxide is a greenhouse gas ✔
b. methane/nitrogen oxide/water vapour is a greenhouse gas ✔
c. sunlight/light/(solar) radiation passes through the atmosphere (to reach the Earth’s
surface) ✔
d. CO2 in atmosphere/greenhouse gases absorb/trap/reflect back some radiation/heat
(emitted by the Earth’s surface) ✔
e. CO2 in atmosphere/greenhouse gases allow short wave radiation to pass (through
atmosphere) but absorb long wave/infra-red ✔
f. solar radiation/sunlight is (mostly) short wave ✔
g. radiation/heat emitted by the Earth is long wave/infra-red ✔
Explain the importance of hydrogen bonding for living organisms.
a. cohesion in water/water molecules stick together (due to hydrogen bonds) ✔
b. cohesion helps transport under tension of water/sap in xylem / transpiration stream✔
c. adhesion between water and cell walls/cellulose/polar molecules ✔
d. adhesion/capillary action helps water to rise in plants/stems/xylem / helps keep leaf
walls moist ✔
e. solvent properties (due to hydrogen bonds) with polar/hydrophilic molecules ✔
f. solvent properties exemplified by glucose/other example of a polar solute ✔
g. high latent heat of evaporation / (much) energy required for evaporation so water
useful as coolant/for sweating ✔
h. high (specific) heat capacity so water temperature changes less ✔
i. base pairing between bases/nucleotides/strands in DNA by hydrogen bonding ✔
j. base pairing between bases in RNA and DNA for transcription/between codon and
anticodon for translation ✔
k. proteins have hydrogen bonding in secondary structure/α helix/β pleated sheet ✔
l. proteins have hydrogen bonding between R groups/in tertiary structure/to maintain
conformation ✔
m.habitats because water is liquid due to high boiling point/due to water freezing on the
surface ✔
n. habitats on water surface due to surface tension ✔
Outline how neurons generate a resting potential.
a. sodium-potassium pump ✔
b. sodium /Na+ out and potassium /K+ in ✔
OR
sodium/Na+ concentration higher outside and potassium/K+ higher inside ✔
c. three Na+ pumped for every two K+ (hence negative inside) ✔
OR
inside of axon holds negative ions/Cl- ions/negatively charged proteins/organic
anions (hence negative inside) ✔
d. by active transport / using ATP ✔
e. inside (of axon/neuron) is negative in comparison to outside ✔
OR
electrochemical concentration/charge difference (across the membrane) is the
resting potential ✔
f. resting potential is -70mV ✔
calcium is absorbed from food in the human gut by both active and passive processes. outline active transport inc the benefits
a. moved against a concentration gradient/lower to higher concentration ✔
3 max
b. energy/ATP required/used ✔
c. pump/carrier «protein» «carries out active transport» ✔
d. absorption «by active transport» into a cell is possible even if exterior concentrations
are «very» low
OR
allows all/nearly all of/more of the substance/calcium to be absorbed «whereas diffusion
can only even out concentrations»
OR
unidirectional/allows the direction of movement to be controlled
OR
allows a concentration gradient to be built up/potential energy to be stored/membrane
potential to be generated/maintained
OR
allows a specific concentration to be maintained «in a cell» ✔
describe the role of oxygen in aerobic cell resp
a. terminal/final electron acceptor ✔
5 max
b. at the end of electron transport chain ✔
c. oxygen also accepts protons/hydrogen ions ✔
d. water produced/ 12 O 2 electrons 2H H O 2 2 ✔
e. helps to maintain proton gradient «across inner mitochondrial membrane by removal of
protons from the stroma» ✔
f. oxygen is highly electronegative/electrons strongly attracted to oxygen ✔
g. avoids anaerobic respiration/buildup of lactic acid ✔
h. allows more electrons to be delivered to the electron transport chain
OR
allows NADFAD to be regenerated/reduced NAD/FAD converted back to NAD/FAD ✔
adult humans may absorb more than 500 litres of oxygen per day. explain how gas exchange is maintained in the human resp system
a. ventilation/inhaling brings fresh air/air with high oxygen concentration to the lungs OR
ventilation/exhaling gets rid of stale air/air with high concentration of carbon dioxide ✔ b. ventilation due to muscle contractions causing pressure/volume changes in the thorax ✓ contraction of external intercostal muscles AND diaphragm occurs during inspiration OR
C.
contraction of internal intercostal muscles/abdomen wall muscles during «forced» expiration ✔ d. alveoli surrounded by «many» capillaries✔
e. blood flow/pumping of heart «brings blood to/takes blood away from alveoli/lungs» ✔
f. concentration gradients «of oxygen/ CO2» maintained «by ventilation/blood flow» ✔
g. O2 AND CO2 diffuse✔
h. CO2 from capillaries/blood/vessel to alveolus/air AND O2 from alveoli into capillaries/blood/vessel ✔ i. large numbers of alveoli increase surface area ✔
j. short distance so rapid diffusion/gas exchange ✔
k. type I pneumocytes/alveolus wall/capillary walls are one cell thick/very thin✔
I.
alveoli «lining» moist for dissolving of gases/rapid diffusion
OR
type II pneumocytes keep the «<lining of» the alveolus moist✔
m. type II pneumocytes secrete surfactant to reduce surface tension/prevents alveoli from collapsing ✔
describe the inheritance of red green colour blindness
a. sex linked/gene is on the X chromosome ✔
b. allele «for red-green colour blindness» is recessive/colour blindness is recessive trait/disorder ✔
c. heterozygous females are unaffected/carriers ✓
d. XB denotes normal allele and Xb denotes colour blindness allele ✔
e. more frequent in males because they only have one X chromosome ✔
f. 50% chance of colour blindness in sons whose mother is heterozygous/XBXb✔
outline hte causes of vaiation
a. height/skin colour/other valid example ✔
b. with continuous variation any level of the variable/phenotype is possible/OWTTE✔ c. polygenic inheritance/combined effect of more than one gene on the trait ✔
d. additive effects on the trait of alleles of multiple genes/OWTTE ✔
e. histogram showing effects of alleles of multiple genes ✓
f. environment «may» also affect the trait/sunlight affects skin colour/other example ✔
g. normal distribution curve drawn or described to show typical pattern with continuous variation ✔
how does evolution occur and which factors cause the process to be rapid
a. evolution is a change in the heritable characteristics «of a species» ✔
b. natural selection «causes evolution» ✔
c. overpopulation/over-reproduction/more offspring «than the environment can support» ✔ d. competition «for resources/mates» ✔
e. variation in population/species✓
f.
mutation/meiosis/sexual reproduction contributes to variation ✔
g. adaptation increases chance of survival ✔
h. reproduction/offspring produced «by the better adapted/by those that survive⟫✔ characteristics passed to offspring by reproduction/variation is heritable ✔
i.
j. allele frequencies/number of organisms carrying a gene changes/gene pool changes ✔
k. environmental change stimulates/triggers/speeds up natural selection/evolution ✔ increase in rainfall/introduction of antibiotic/pollution on tree trunks/other valid example of environmental change/new selection pressure ✔
I.
m. artificial selection/selective breeding can speed up evolution ✔
distinguish between the sustainility of natural ecosystems such as rainforests and the sustainability of areas used for agriculture
a. sustainable communities/ecosystems allow continued survival of organisms/OWTTE✔ b. natural ecosystems can be sustainable over long periods of time/OWTTE ✔
c. natural ecosystems/rainforest more sustainable than agricultural areas/plantations ✔ d. diverse community/high biodiversity/higher biodiversity in natural ecosystems/rainforest OR
less/low biodiversity in agricultural areas/agricultural soils ✔
e. agricultural areas/monocultures more affected by pests/diseases✔
f. nutrient recycling «efficient» in natural ecosystems/rainforest ✔
g. nutrients removed with crops/nutrients removed when crops are harvested OR
less formation of humus/less organic matter in agricultural soils ✔
h. more water recycling/more rainfall/more transpiration in natural ecosystems/rainforest ✔
i. larger biomass/more carbon stored «in biomass» in natural ecosystems/rainforest ✔
j. shallower soils/less soil erosion/degraded soils/infertile soils in agricultural areas✔
