unit 2, plants as natural resources, species and evolution, the importance of biodiversity

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detailled revision notes on the 'plant' side of biology Unit 2 edexcel 

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Chapter 4.2 Plants as natural resources
I can describe how the uses of plant fibres and starch may contribute to sustainability, e.g. Plant-based products to
replace oil-based plastics:
Sustainability ­ using resources in a way that meets the needs of the current generation without having particularly
damaging consequences on future generations.
Making products sustainable means you would need to use renewable resources.
Renewable resources ­ a resource that can be used indefinitely without running out, e.g. plants are renewable
because harvested plants can be regrown (plenty for the future)
Fossil fuels are not renewable ­ once they've been used there will be no more
Sustainable practice example ­ replantation after logging, environment is not significantly damaged afterward
Using plant fibres and starch can contribute to sustainability:
1. Ropes and fabrics can be made from plastic, which is made from oil. They can also be made from plant fibres.
2. Making products from plant fibres is more sustainable - less fossil fuels is uses, crops can be regrown to
maintain a good supply
3. Products made from plant fibres are also biodegradable ­ they can be broken down by microbes, plastics
mainly cannot and therefore pollute the environment horrendously taking up much needed space also
4. Plants are easier to grow and process (extract the fibres) than to process oil. Making them also cheaper and
easier to do in developing countries
1. Starch is found in all plants ­crops like potatoes and corn are particularly rich of this resource
2. Plastics are usually made from oil, but some can be made from plant-based materials, like starch ­
3. Making plastics from starch is more sustainable as less oil/fossil fuels are used and crops can be regrown
4. Vehicle fuel is also normally made from oil, but an alternative is starch i.e. bioethanol can be made from starch
5. Making fuel from starch is also more sustainable because of reasons discussed above.
I can explain how the arrangement of cellulose microfibrils in plant cell walls and secondary thickening contribute to
the physical properties of plant fibres, which can be exploited by humans:
Plant fibres are made up of long tubes of plant cells e.g. sclerenchyma made up of tubes of dead cells.
They're strong which makes them useful for loads of things e.g. ropes or fabrics like hemp.
They're strong for a number of reasons:
The arrangement of cellulose microfibrils in the cell wall:
1. The cell wall contains cellulose microfibrils in a net like arrangement
2. The strength of the microfibrils and their arrangement in the cell wall gives plant fibres strength
The secondary thickening of cell walls:
1. When some structural plant cells (like sclerenchyma) have finished growing, they produce a secondary cell
wall between the normal cell and the cell membrane
2. The secondary cell wall is thicker than the normal cell wall and usually has more lignin
3. The growth of a secondary cell wall is called secondary thickening
4. Secondary thickening makes plant fibres even stronger.
I can describe how to determine the tensile strength of plant fibres practically:
Tensile strength = maximum load it can take before it breaks. Knowing the tensile strength can be really important,
especially when exploiting their resource for rope (something that could potentially hold someone's weight).
How you find out tensile strength:
1. Attach the fibre to a clamp stand and hang a weight from the other end.
2. Keep adding weights, one at a time, until the fibre breaks
3. Record the mass needed to break the fibre - the higher the mass, the higher the tensile strength.
4. Repeat the experiment with different samples of the same fibre ­ increases the reliability
5. The fibres being tested should always be the same length

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Throughout the experiment all other variables, like temperature and humidity, must be kept constant
7. Take safety measures ­ wear goggles to protect eyes, leave the area where weights are being attached
clear so they will fall safely and don't hurt your toes.
I can compare historic drug testing with contemporary drug testing protocols, e.g. William Withering's digitalis soup;
double blind trials; placebo; three phased testing:
William Withering's digitalis soup
1.…read more

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Sterile forceps
Marker pen
Incubator set at 25 C
1. Agar plates seeded with the suitable bacteria will have been prepared for you, now you need to collect these
disks and return it to an appropriate, sterile area.
2. Obtain a mint leaf by crushing 3g of plant material with 10cm3 of industrial denatured alcohol
3. Shake well, and in timely intervals, for 10 minutes (30 seconds on/off vigorously); be sure to maintain the same
strength of shake
4. Pipette 0.…read more

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Taxonomy is the science of classification. It involves naming organisms and organising them into groups based
on their similarities and differences. This makes it easier for scientists to identify them and to study them.
1. There are 7 levels of groups (called taxonomic groups) used in classification
2. Similar organisms are first sorted into large groups called kingdoms, e.g. all animals are in the animal
3. Similar organisms from that kingdom are then grouped into a phylum.…read more

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New data has to be evaluated by other scientists to check if it's actually there. If all scientists agree it can lead
to a new organism being reclassified or leads to changes in the classification system structure
Tentative nature has been portrayed in this way
Three domains vs Five Kingdoms
1. A new, three domain classification system has been proposed based on new data
2.…read more

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Anatomical adaptions ­ structural features of an organism's body that increase its chance of
survival. For example: Pipistrelle bats have light, flexible wings that allow them to hunt fast-flying insects.
I can describe how natural selection can lead to adaption and evolution:
Alleles in a population will be affected by natural selection (survival of the fittest). A mutation in a gene may result in a
change in the physical appearance of an organism, in its physiology or even in its pattern of behaviour.…read more

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Species diversity ­ the number of different species and the abundance of each species in an area. For
example, a wood could contain many different species of plant, insects, birds and mammals
Genetic diversity ­ the variation of alleles within a species (or a population of a species). For example,
human blood type is determined by a gene with four different alleles.
I can describe how biodiversity can be measured within a habitat using species richness and within a species using
genetic diversity, e.g.…read more

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The larger the number of different phenotypes, the You can measure the number of different alleles a
greater the genetic diversity species has for one characteristic to see how genetically
diverse the species is.
For example, humans have different eye colours due to The larger the number of different alleles, the greater
different alleles. Humans in northern Europe show a the genetic diversity
variety of blue, grey, green or brown eyes. Outside this
area, eye colour shows little variety ­ they're usually
brown.…read more

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Reintroduced animals may not behave as they would if they'd been raised in the wild. E.g. they may have
problems finding food or communicating with wild members of their species
Seedbanks and zoos contribute to scientific research
Seedbanks Zoos
Scientists can study how plant species can be Research in zoos increases knowledge about the
successfully grown from seeds. This is useful for behaviour, physiology and nutritional needs of
reintroducing them to the wild animals. This can contribute to conservation efforts in
the wild.…read more



Amazing stuff,thanks loads. **

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