- total quantity of chemical energy stored in plant biomass (from photosynthesis) - plants use 20-50% of this - chemical energy left with losses from R is NPP

- expression of genes due to genetics and environment

A2 Exam Questions Flashcards by Aliyah Downes

how does succession take place? Vs secondary succession?

colonisation by pioneer species
which change conditions in environment forming humus/soil
environment becomes less hostile for other species
this increases biodiversity
leads to climax community
.
.
Secondary? (Use ALWAYS SAME POINTS AS ABOVE but add)
seeds and spores already present
soil/humus already present

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Sampling stationary organisms

make the habitat into a grid
computer generated random coordinates and place the quadrat
count frequency of organisms
repeat procedure with large sample of quadrats
find mean of organism per quadrat: sum of heights/plant total
calc running mean until constant
multiply by m2 whole area

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What does longer loop of henle suggest

Na+ conc in medulla/interstitial fluid is higher
maintaining water potential concentration gradient for longer
so more water is reabsorbed from loop of henle by osmosis

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How to write evaluations

write conclusions from graph table
comment on SD (doesnt overlap: RESULTS HAVE A SIGNIFICANT DIFFERENCE)
no stats test to see if diff is significant
large sample size suggest reliability and representative
## so small sample = ineffective-
environment? (Eg greenhouse is not, not in the body)
one type of species tested
other factors in natural environment (other bacteria/diet)
if a drug, may be possible side effects?
no control group w placebo

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How are carrier proteins limiting

they transport substances at maximum rate
they are saturated
so become a limiting factor

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How does blood pressure increase due to reabsorption of water (by osmosis)

ALWAYS mention method of transport if there is one
> co transport is better referred to as active transport
more water is reabsorbed so water volume increases
this increases blood pressure

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What is a control variable for colorimeters

same volume of solution upon testing for transmission of light
same wavelength of light
calibrate first

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Define GPP

total quantity of chemical energy stored in plant biomass (from photosynthesis)
plants use 20-50% of this
chemical energy left with losses from R is NPP

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If the question mentions amylase, mention..

Amylase breaks starch to maltose
> maltase breaks maltose into glucose

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Reasons for conserving rainforests

maintaining biodiversity
-tourism
provides and protects many habitats and niches
reduces climate change
reduces erosion and eutrophication

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Whys farming cattle less efficient fir humans than crops

less energy is lost in crops
wheras cattle loses lots of energy via excretion, respiration (heat)

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How to tell whether an organism showing a dominant phenotype is homozygous dominant or heterozygous

, a test cross is used.
> The individual is crossed homozygous recessive for the same gene(s).
> If all offspring show the dominant phenotype, the individual is likely homozygous dominant.
> If a mixture of dominant and recessive phenotypes appears, the individual must be heterozygous, because it produced gametes containing the recessive allele.

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Chi squared hypothesis example

The difference between the observed and expected numbers
-is due to chance; the offspring follow the expected 1:1:1:1 ratio

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Phenotype definition

expression of genes due to genetics and environment

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Whys rate of photosynthesis low between certain wavelengths of light

Less absorption and more reflection of light
> represents green light: colour of chlorophyll

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Whys it good to present comparison between results as ratio or percentage

as a valid comparison
as sample size may vary

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What is a control experiment for a the woodlice respiration

no woodlice
all other conditions the same

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Taxis, tropisms and kinesis definitions

• Taxis- Moving towards or away from a favourable stimulus (can be positive or negative)

• Kinesis - Increase in random movements in unfavourable environments

• Tropism - Growth movement of a plant towards or away from a stimulus

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Hormones and steroid hormones

## Hormones are Carried by blood: Slow and Affect different parts of the body. Widespread response. Long-lasting.
Steroid hormones are lipid soluble, so can quickly enter cells- they diffuse through the phospholipid bilayer.

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Chemical mediators

(e.g. histamine, prostaglastins) released from mammalian cells- effect cells in immediate vicinity. Spread directly by diffusion.

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What is IAA in plants : bending shoots to light and gravity

Plants have no nervous system - instead use plant growth factors.
These affect growth, made in cells throughout plant and can affect tissues that make them.
Spread by diffusion.

..
• IAA (indoleacetic acid) = plant growth factor; Causes shoots to grow towards light and roots towards gravity
- IAA causes bending shoots to light (for photosynthesis)
- IAA made in cells in tip of shoot diffuses down shoot on both sides
- Light causes IAA to move to shaded side of shoot
- Stimulates cells on dark side to elongate - shaded side grows more (& bends to light)
-
- bending roots to gravity
- IAA made in cells in root tip
Moves to lower side of root
- Inhibits growth on lower side (upper side grows more and makes roots grow down)

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How to carry out chi squared 🟡🟡

Write the formula (must be correct)
x^2 = Σ((O - E)^2/E)
Work out the expected values: Use the null hypothesis ratio/ genetic ratio
»Example (3:1 ratio): find expected for all categories like dominant, recessive and total offspring
..
Set up a table so each category on left and column labels..
O, E, O-E, (O-E)^2, (O-E)^2/E
Calculate the sum (chi squared )
Calculate degrees of freedom
df = number of categories - 1
..
Compare to the critical value (AQA uses p = 0.05)
•df = 1 → critical value = 3.84
Decision rule:
•χ² ≤ 3.84 → accept the null
•χ² > 3.84 → reject null
..
Eg. There is no significant difference between observed and expected results. Any difference is due to chance.

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Hardy weinberg: what it is and conditions

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The Hardy–Weinberg principle states that allele frequencies remain constant in a population if certain conditions are met.

Conditions
• Large population
• Random mating
• No mutation
• No migration
• No natural selection

Hardy weinberg key eqs 🟡🟡

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Key equations

p^2 + 2pq + q^2 = 1
p+q=1

Where:
•p= frequency of dominant allele
•q = frequency of recessive allele

And:
•p² = frequency of homozygous dominant
•2pq = frequency of heterozygous
•q² = frequency of homozygous recessive

Why hardy Weinberg may not apply

Mention: •Small population → genetic drift •Non-random mating •Selection pressures •Mutation or migration

Whys tissue culture preferred in growing plants in comparison to from seeds

- will be genetically identical clones produced by mitosis - all w desired characteristics

Whats primary productivity

Rate of production of biomass/chemical energy > by producers per unit area per time

How is atp useful

1. Releases energy in small, suitable amounts: 2. (Broken down) in one step: 3. Makes energy available rapidly: 4. Makes (phosphorylated substances) more reactive / lowers activation energy: 5. Can be reformed/made again;

How to measure NPP in grass

Dry mass measurement

How does natural selection work

1. Theres GENETIC VARIATION in resistance due to mutation 2. Insecticide forms SELECTION PRESSURE 3. Ones with resistance allele survive so reproduce 4. Pass allele to offspring increasing ALLELE FREQUENCY 5. Species becomes resistant to pesticide over time

Allopatric speciation

1. GEOGRAPHICAL ISOLATION 2. SEPARATE GENE POOL so no gene flow 3. GENETIC VARIATION due to mutations 4. Diff SELECTION PRESSURES due to diff environments 5. selected organisms survive longest so reproduce 6. Increase in ALLELE FREQUENCY

How to measure dry mass

- heat then weigh/measure mass - measure until mass is constant

Units of Q (and what it measures)

- in J (/1000 for kj) - heat energy released ( in chem, its converted to per mole) - if kj g-1 , divide q by the mass of sample burned

At high temps biomass decreases in plants. Explain why with NPP?

- NPP=GPP-R - at high temps photosynthesis rate decreases due to denatured enzymes so GPP decreases - reducing biomass

How does an inversion mutation cause production of a different protein

- dna base sequence is inverted/reversed - change in sequence of amino acids - change in H, ionic and disulfide bonds - therefore tertiary structure is altered

What's phenotype

Expression of genetic constitution/genotype - AND due to interaction with environment

What is autosomal linkage? Explain relative proportions of diff genotypes of gametes

- Two genes occur on same chromosome (opposite chromatid same loci). - same chromosome means both allleles = either dominant or recessive, >>only 3 genotypes (AABB, aabb or AaBb) - - unless crossing over/recombination has taken place - crossing over has occurred: gN gametes appear=fewer of these. -So fewer offspring with genotypes & phenotypes from these alleles (give examples

Route of red blood cell from kidney yo lungs

- renal vein to vena cava - to RIGHT ATRIUM - to RIGHT VENTRICLE to pulmonary artery

Advantages of taxis

- less visible to predators - move away from heat - move towards food

Conclusions using table from stats test (chi squared)

- degrees of freedom is number of categories -1 - calculated value is MORE than table value - at 0.05 level of measurement so we - reject null hypothesis - less than 5% probability results due to chance - so is a significant difference

How to describe a correlation value above 0.8

Strong OR significant negative/positive correlation

Chloroplast structure

- have double membrane - are thylakoid membranes: stacks of them are grana - grana are linked by lamellae - thick fluid surrounding membranes is stroma - large spheres in organelle is starch

Photosynthesis affected in plants w fewer thylakoids

- less chlorophyll and less light absorbed - less photosynthesis

Why do tropical forests for eg have high biodiversity of animal species

- large variety of plants species - which lead to high variety in food sources - more habitats and niches available

Abiotic factors in rainforests enable rapid rate of recycling?

- high optimum temp/pH for enzymes in cycles like respiration , nitrification, ammonification - water produced for metabolic processes - high O2 conc for cyclic processes like ammonification for saprobionts, respiration

Farming practices that prevent natural regeneration of rainforests by secondary succession

- growing crops - animal farming - ploughing - weedkiller/herbicides and pesticides - burning fields and plants

How regular contraction of the heart is coordinated (not mentioning pns)

1. SAN releases wave of electrical activity/wave of excitation 2. So atria contract (systole) at the same time 3. AVN relays/passes electrical activity/wave of depolarisation or excitation after a short delay; 4. (Via) Purkyne tissue and bundle of His; 5. So ventricles contract/systole at same time from bottom upwards

What is cell wall plasticity

- results in cell elongation

How to dilute 10-1 solution to 10-3

- 1cm3 10-1 and 9cm3 distilled water - then 1cm3 of 10-2 then 9 of distilled water

How pacinian corpuscle generates potential

1 . Stretch mediated Na+ channels in membrane 2. Inc pressure deforms/changes sensory neuron membrane 3. Changes Na+ channels so open 4. Na+ diffuse in 5. Depolarisation leading to generating pot

How structure of myelin sheath inc speed of transmission of action potential

- myelin sheath (ms) is electrical insulation - prevents ion movement across membrane so no action potential - depolarisation only at nodes of ranvier - APs jump node to node - Saltatory conduction - fewer AP needed = faster transmission so energy efficient bc less Na K pump activity

Roles of ATP in contraction

- form actinomyosin cross bridges - bend myosin head - move actin filaments (slide) - ACTIVE TRANSPORT for Ca2+

Difference in glycogen conc comparing diff muscle fibre properties

- fast twitch contract quicker and slow contract slower - fast = anaerobic and slow twitch is aerobic - fast makes ATP quick, slow makes ATP slowly - glycogen stores glucose. HYDROLYSED to glucose in glycogenolysis

How cDNA prevents transcription

Binds to dna To promoter region

Factors affecting separating in ge

Charge Size = NUMBER OF AMINO ACIDS / POLYPEPTIDES

Why enzymes added prior to pcr

Remove dna present As wd be amplified

Why primers to detect rna from diff viruses in patients

Base sequences differ Diff complimentary primers needed

A2 Exam Questions Flashcards

(57 cards)