GCSE Biology B4(OCR B722) It's A Green World

Year 11 revision topics

B4a Ecology in the local environment
  1. Be able to describe how to use collecting/counting methods, to include:
    • pooters
    • nets
    • pitfall traps
    • quadrats.
  • Be able to describe a method to show the variety of plants and animals living in a small area such as a 1m quadrat.
  • Be able to use keys to identify plants and animals.
  • Be able to explain how the distribution of organisms within a habitat is affected by the presence of other living organisms as well as physical factors.
  • Be able to define biodiversity as the variety of different species living in a habitat.
  • Be able to identify native woodlands and lakes as natural ecosystems and forestry plantations and fish farms as artificial ecosystems.
  1. Be able to use data from collecting/counting methods to calculate an estimate of the population size based on:
    • scaling up from a small sample area
    • the use of capture-recapture data, given the formula:
    • population size = number in 1st sample × number in 2nd sample ÷ number in 2nd sample previously marked
  • Be able to explain the effect of sample size on the accuracy of an estimate of population size.(HT)
  1. Be able to explain the need to make certain assumptions when using capture-recapture data, to include:(HT)
    • no death, immigration or emigration
    • identical sampling methods
    • marking not affecting survival rate
  1. Be able to explain the differences between:
    • ecosystem and habitat
    • community and population
  • Be able to describe how to map the distribution of organisms in a habitat using a transect line.
  • Be able to interpret data from kite diagrams showing the distribution of organisms.
  • Be able to explain what it means for an ecosystem to be described as self supporting in all factors other than an energy source(HT).
  • Be able to describe zonation as a gradual change in the distribution of species across a habitat.(HT)
  • Be able to explain how a gradual change of an abiotic factor can result in the zonation of organisms in a habitat.(HT)
  1. Be able to compare the biodiversity of natural ecosystems and artificial ecosystems to include:
    • native woodlands
    • lakes with forestry plantations
    • fish farms
  • Be able to explain reasons for the differences between the biodiversity of native woodlands and lakes compared with forestry plantations and fish farms.(HT)
B4B Photosynthesis
  1. Know and use the word equation for photosynthesis:
    • carbon dioxide + water (+light energy/chlorophyll) → glucose + oxygen
  • Understand that oxygen is a waste product in this reaction
  • .
  • Know that the glucose made in photosynthesis is transported as soluble sugars but is stored as insoluble starch.
  • Know that glucose and starch can be converted to other substances in plants to be used for energy, growth and storage products.
  1. Be able to explain why plants grow faster in the summer because of more:
    • light
    • warmth
  • Understand that plants carry out respiration as well as photosynthesis
  1. Know and use the balanced symbol equation for photosynthesis:
    • 6CO2 + 6H2O (+chlorophyll/light energy) → C6H12O6 + 6O2
  1. Be able to describe the development of the understanding of the process of photosynthesis, to include:
    • the view of Greek scientists that plants gained mass only by taking in minerals from the soil
    • Van Helmont's experimental conclusion that plant growth cannot be solely due to nutrients from the soil
    • Priestley's experiment which showed that oxygen is produced by plants.
  • Be able to explain how experiments using isotopes have increased our understanding of photosynthesis, to include: that oxygen produced by photosynthesis comes from the water and not the carbon dioxide.(HT)
  1. Be able to describe photosynthesis as a two stage process: (HT)
    • light energy is used to split water, releasing oxygen gas and hydrogen ions
    • carbon dioxide gas combines with the hydrogen to make glucose.
  1. Be able to describe the conversion of glucose and starch to other substances in plants and their use:
    • glucose for energy (respiration)
    • cellulose for cell walls
    • proteins for growth and repair
    • starch, fats and oils for storage.
  • Be able to explain why plants carry out respiration all the time.
  1. Be able to explain why insoluble substances such as starch are used for storage: (HT)
    • does not move away in solution from storage
    • does not affect water concentration inside cells
  1. Be able to describe how photosynthesis can be increased by:
    • more carbon dioxide
    • more light
    • higher temperature.
  1. Be able to explain the effects of limiting factors on the rate of photosynthesis:(HT)
    • CO2
    • light
    • temperature
  • Be able to explain why plants take in carbon dioxide and give out oxygen during the day and do the reverse at night, in terms of both photosynthesis and respiration. (HT)
B4C Leaves and photosynthesis
  • Understand why chloroplasts are not found in all plant cells.
  • Know that chlorophyll pigments in chloroplasts absorb light energy for photosynthesis.
  1. Know the entry points of materials required for photosynthesis:
    • water through root hairs
    • carbon dioxide through stomata.
  1. Know the exit point of materials produced in photosynthesis:
    • oxygen through stomata.
  • Understand that broader leaves enable more sunlight to be absorbed.
  1. Be able to name and locate the parts of a leaf:
    • cuticle
    • upper and lower epidermis
    • palisade and spongy mesophyll layers
    • stomata and guard cells
    • vascular bundle.
  1. Be able to explain how leaves are adapted for efficient photosynthesis:
    • broad so large surface area
    • thin so short distance for gases to diffuse
    • contain chlorophyll and other pigments to absorb light from different parts of the spectrum
    • have a network of vascular bundles for support and transport
    • guard cells which open and close the stomata.
  1. Be able to explain how the cellular structure of a leaf is adapted for efficient photosynthesis:(HT)
    • epidermis is transparent
    • palisade layer at the top containing most of the chloroplasts
    • air spaces in the spongy mesophyll allow diffusion between stomata and photosynthesising cells
    • internal surface area to volume ratio very large.
  • Be able to interpret data on the absorption of light by photosynthetic pigments (chlorophyll a and b, carotene and xanthophyll) to explain how plants maximise the use of energy from the Sun.(HT)
B4D Diffusion and osmosis
  • Know that substances move in and out of cells by diffusion through the cell membrane.
  • Be able to describe diffusion as the movement of a substance from a region of high to low concentration.
  • Know that water moves in and out of plant cells by osmosis through the cell membrane.
  • Know that the plant cell wall provides support.
  • Understand that lack of water can cause plants to droop (wilt).
  • Be able to describe how carbon dioxide and oxygen diffuse in and out of plants through the leaves.
  • Know that water moves in and out of animal cells through the cell membrane.
  • Be able to explain the net movement of particles by diffusion from an area of high concentration to an area of low concentration, as a consequence of the random movement of individual particles.
  • Be able to describe how molecules enter and leave cells by diffusion through the cell membrane.
  1. Be able to explain how the rate of diffusion is increased by:(HT)
    • a shorter distance
    • a greater concentration difference (gradient)
    • a greater surface area.
  • Be able to describe osmosis as the movement of water across a partially-permeable membrane from an area of high water concentration (ie dilute solution) to an area of low water concentration (ie concentrated solution).
  • Know that osmosis is a type of diffusion.
  • Be able to explain the term partially-permeable.
  • Be able to explain the net movement of water molecules by osmosis from an area of high water concentration to an area of low water concentration across a partially- permeable membrane, as a consequence of the random movement of individual particles.(HT)
  • Be able to predict the direction of water movement in osmosis. (HT)
  1. Be able to explain how plants are supported by the turgor pressure within cells:
    • water pressure acting against inelastic cell wall.
  • Be able to explain wilting in terms of a lack of turgor pressure.
  1. Be able to explain the terms:
    • flaccid
    • plasmolysed
    • turgid
  • Be able to explain how leaves are adapted to increase the rate of diffusion of carbon dioxide and oxygen.
  • Be able to describe the effects of the uptake and loss of water on animal cells.
  • Be able to understand and explain why there are differences in the effects of water uptake and loss on plant and animal cells(HT)
  1. Be able to understand and use the terms:(HT)
    • crenation
    • lysis
B4E Transport in plants
  1. Be able to describe how water travels through a plant:
    • absorption from soil through root hairs
    • transport through the plant, up the stem to the leaves
    • evaporation from the leaves (transpiration)
  1. Be able to describe experiments to show that transpiration rate is affected by:
    • light intensity
    • temperature
    • air movement
    • humidity
  • Understand that healthy plants must balance water loss with water uptake.
  • Be able to describe the arrangement of xylem and phloem in a dicotyledonous root, stem and leaf, to include vascular bundles.
  1. Be able to relate xylem and phloem to their function:
    • xylem - transpiration - movement of water and minerals from the roots to the shoot and leaves
    • phloem - translocation - movement of food substances (sugars) up and down stems to growing and storage tissues.
  • Understand that both xylem and phloem form continuous systems in leaves, stems and roots.
  1. Be able to describe the structure of xylem and phloem:(HT)
    • xylem vessels - thick strengthened cellulose cell wall with a hollow lumen (dead cells)
    • phloem - columns of living cells.
  • Know transpiration as the evaporation and diffusion of water from inside leaves.
  • Be able to describe how transpiration causes water to be moved up xylem vessels.
  • Be able to explain how transpiration and water loss from leaves are a consequence of the way in which leaves are adapted for efficient photosynthesis.(HT)
  1. Be able to describe the effect on transpiration rate of:
    • increase in light intensity
    • increase in temperature
    • increase in air movement
    • decrease in humidity
  1. Be able to explain why transpiration rate is increased by:(HT)
    • increase in light intensity
    • increase in temperature
    • increase in air movement
    • decrease in humidity.
  • Be able to interpret data from experiments on transpiration rate.
  • Be able to explain how root hairs increase the ability of roots to take up water by osmosis
  1. Know that transpiration provides plants with water for:
    • cooling
    • photosynthesis
    • support
    • movement of minerals.
  1. Be able to explain how the structure of a leaf is adapted to reduce excessive water loss:
    • waxy cuticle
    • small number of stomata on upper surface.
  1. Be able to explain how the cellular structure of a leaf is adapted to reduce water loss:(HT)
    • changes in guard cell turgidity (due to light for: intensity and availability of water) to regulate stomatal apertures
    • number, distribution, position and size of stomata.
B4F Plants need minerals
  • Know that fertilisers contain minerals such as nitrates, phosphates, potassium and magnesium compounds and that these are needed for plant growth.
  • Be able to interpret data on NPK values to show the relative proportions of nitrates, phosphates and potassium in fertilisers.
  1. Be able to describe experiments to show the effects on plants of mineral deficiencies in plants:
    • soil-less culture
    • each trial missing one mineral
  1. Be able to describe how minerals are absorbed, to include:
    • dissolved in solution
    • by the root hairs
    • from the soil.
  1. Be able to explain why plants require:
    • nitrates: for proteins which are needed for cell growth
    • phosphates: for respiration and growth
    • potassium compounds for respiration and photosynthesis
    • magnesium compounds for photosynthesis
  1. Be able to describe how elements obtained from soil minerals are used in the production of compounds in plants limited to:(HT)
    • nitrogen to make amino acids
    • phosphorus to make DNA and cell membranes
    • potassium to help enzymes (in photosynthesis and respiration)
    • magnesium to make chlorophyll.
  1. Be able to relate mineral deficiencies to the resulting poor plant growth:
    • nitrate - poor growth and yellow leaves
    • phosphate - poor root growth and discoloured leaves
    • potassium - poor flower and fruit growth and discoloured leaves
    • magnesium - yellow leaves.
  • Know that minerals are usually present in soil in quite low concentrations.
  • Be able to explain how minerals are taken up into root hair cells by active transport.(HT)
  • Understand that active transport can move substances from low concentrations to high concentrations (against the concentration gradient), across a cell membrane, using energy from respiration.(HT)
B4G Decay
  1. Know the key factors in the process of decay:
    • presence of microorganisms
    • temperature
    • oxygen
    • moisture.
  • Be able to explain why decay is important for plant growth.
  • Be able to describe how to carry out an experiment to show that decay is caused by the decomposers bacteria and fungi.
  1. Know that microorganisms are used to:
    • break down human waste (sewage)
    • break down plant waste (compost).
  1. Recognise that food preservation techniques reduce the rate of decay and methods include:
    • canning
    • cooling
    • freezing
    • drying
    • adding salt/sugar
    • adding vinegar.
  1. Be able to describe the effects on the rate of decay of changing:
    • temperature
    • amount of oxygen
    • amount of water.
  1. Be able to explain why changing temperature, and the amounts of oxygen and water,
    affect the rate of decay in terms of the:(HT)
    • effect on microbial respiration
    • effect on growth and reproduction of micro-organisms.
  • Know that detritivores, including earthworms, maggots and woodlice, feed on dead and decaying material (detritus).
  • Be able to explain how detritivores increase the rate of decay by producing a larger surface area.
  • Be able to explain the term saprophyte.(HT)
  • Be able to explain how saprophytic fungi digest dead material, in terms of extracellular digestion.(HT)
  • Be able to explain how food preservation methods reduce the rate of decay.
B4H Farming
  1. Know that examples of pesticides include:
    • insecticides to kill insects
    • fungicides to kill fungi
    • herbicides to kill plants (weeds).
  • Know that intensive farming means trying to produce as much food as possible from the land, plants and animals available.
  1. Be able to describe how intensive farming methods can increase productivity methods limited to:
    • fish farming
    • glasshouses
    • hydroponics
    • battery farming
  1. Be able to describe organic farming methods:
    • no artificial fertilisers
    • no pesticides.
  • Be able to describe how pests can be controlled biologically by introducing predators.
  1. Be able to explain the disadvantages of using pesticides:
    • pesticides may enter and accumulate in food chains
    • pesticides may harm organisms which are not pests
    • some pesticides are persistent
  • Be able to describe how plants can be grown without soil (hydroponics)
  1. Be able to describe possible uses of hydroponics, to include:
    • glasshouse tomatoes
    • plant growth in areas of barren soil.
  • Understand that intensive farming methods may be efficient but they raise ethical dilemmas.
  1. Be able to explain the advantages and disadvantages of hydroponics:(HT)
    • better control of mineral levels and disease
    • lack of support for plant
    • required addition of fertilisers.
  1. Be able to explain how intensive food production improves the efficiency of energy transfer by reducing energy transfer:(HT)
    • to pests, including competing plants (weeds)
    • as heat from farm animals by keeping them penned indoors (battery farming) so that they are warm and move around less.
  1. Be able to describe organic farming techniques:
    • use of animal manure and compost
    • crop rotation including use of nitrogen-fixing crops
    • weeding
    • varying seed planting times.
  1. Be able to explain the advantages and disadvantages of biological control:
    • advantages:no need for chemical pesticides
    • does not need repeated treatment
    • disadvantages:predator may not eat pest
    • may eat useful species
    • may increase out of control
    • may not stay in the area where it is needed.
  • Be able to explain the advantages and disadvantages of organic farming techniques.
  • In the context of biological control, be able to explain how removing one or more organisms from a food chain or web may affect other organisms.

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