Paper 2 PPQs Flashcards
As milk decays, lipids in the milk are broken down and one of the products of the breakdown of lipids causes the pH of milk to decrease. what is the product that causes the pH to decrease
fatty acids
A student investigated the effect of temperature on the time taken for different types of milk to decay. what are some control variables the student should have used in this investigation.
- volume of milk
- exposure to air / oxygen
- sterilise test tubes
- freshness / age of milk (at start)
- time of day pH was measured
Earthworms: box
* live in soil
* feed on dead and decaying plant matter
* have soft, moist skin
* exchange gases through their skin.
Give two abiotic factors and two biotic factors that could affect the size of an
earthworm population.
abiotic: water levels, oxygen levels in soil, pH of soil, minerals / ion content of soil, temperature, size of soil particles or texture / type of soil
biotic: food (amount of dead / decaying
matter), predators, disease
Name one harmful substance that could cause air pollution.
carbon dioxide or acidic gas
Name three harmful substances that could cause water pollution. Do not refer to plastic or to litter in your answer.
fertiliser, sewage, toxic chemicals, herbicide, fungicide
Describe how substances that pollute air and water could be harmful to humans and
other living organisms.
air pollution:
- carbon dioxide causes global warming causing extreme weather resulting in loss of habitat and food
- acidic gases damage leaves causing less photosynthesis and damage roots and damage to lungs resulting in breathing difficulties
- particulates cover leaves so less photosynthesis so less glucose made and cause damage to lungs resulting in breathing difficulties
water pollution::
- sewage means bacteria multiply so use oxygen in respiration so water animals cannot respire and pathogens in water
- fertiliser means algae multiply and block light so plants cannot photosynthesise so lack of oxygen for respiration – fish die
- toxic substances harm cells and interferes with metabolism e.g. respiration & protein
synthesis
- plastics entrap animals or cause internal damage if swallowed
- oil damages birds’ feathers so cannot fly so cannot find food or escape predators
- acid rain lowers pH of water and damages fish gills and bleaches coral
The scientist measured the number of blue algal cells in a sample of pond water. Suggest why the scientist diluted the pond water before placing it on the special slide
to make it easier to count
A scientist measured the number of blue algal cells in a sample of pond water and a student repeated their method. The student used a thin coverslip over the diluted pond water instead of a
thick coverslip. The liquid pulled the thin coverslip downwards slightly. Explain how the use of the thin coverslip would affect the results for the cell count.
smaller volume so lower cell count
In the cold winter months, an echidna hibernates. Explain why a decrease in body temperature is an advantage to the echidna during hibernation.
loses less energy from its body so body energy store lasts longer / less energy transferred maintaining higher body
temperature so more energy available for
processes vital for life
During hibernation an echidna wakes up several times. Each time the echidna wakes up it becomes active and its body temperature increases to over 30 °C. Explain why the echidna has a higher body temperature when it is active
movement requires energy from respiration and respiration releases heat which increases body temperature
An echidna can dilate and constrict blood vessels in its skin. Explain how the dilation of blood vessels in the skin can help to decrease body temperature.
more blood flow near surface of
skin so more heat / energy is lost from the blood so cools blood which cools the
body
The data on a graph of the effect of time on pH of decaying milk were obtained at 20 °C. Where would you draw the line for the results you would expect at 25 °C?
similar shaped line drawn to left of 20°C line
with same start pH (pH changes faster)
What type of substance does a gene code for?
protein
Decay occurs in a compost heap. Describe:
* how microorganisms in the layers of soil help to recycle chemicals in the
dead plants
* how the chemicals are used again by living plants.
in microorganisms: there is digestion by enzymes, releasing mineral ions (eg nitrate, phosphate, magnesium). Respiration produces carbon dioxide.
in plants: carbon dioxide from air taken in by leaves by diffusion via stomata and is used in photosynthesis to make glucose. Ions taken in by roots by active transport ( nitrate ions for making amino acids and phosphate for making DNA)
A student estimates the number of daisy plants growing on a lawn and places a quadrat at 10 different positions on the lawn then counts the number of daisy plants in each quadrat. Using the mean from this investigation to calculate the number of daisy plants on the lawn may not be accurate. Give two reasons why.
- too few quadrats or quadrat too small
- sample may not be representative of the lawn
