Exam (elaborations)
Topic 6_A Level Biology Edexcel Salters Nuffield Questions and Solutions
- Course
- Institution
Topic 6_A Level Biology Edexcel Salters Nuffield Questions and Solutions
[Show more]
Seller
Follow
modocko752
Content preview
Topic 6:A Level Biology Edexcel SaltersNuffield Questions and Solutions
4 trophic levels - ANS--Producers (photosynthesising organisms e.g. plants)
-Primary Consumers (herbivores)
-Secondary Consumers (carnivores)
-Decomposers - (bacteria, fungi)
Why is the transfer of energy between trophic levels only about 10% efficient? -
ANS-Producers do not obtain all available solar energy - reflection, transmission
through leaf, incorrect wavelength
Photosynthesis converts light to chemical energy, but the reaction process uses some
energy e.g. respiration and photosynthesis reactions
Consumers - feeding is inefficient e.g. urine and faeces of undigestible materials,
respiration and heat loss
Describe the 4 key contributors of the carbon cycle - ANS-1. Combustion - CO2
released when fossil fuels are burnt
2. Decomposition - saprotrophic microorganisms secrete hydrolytic enzymes to break
down complex carbon-containing organic molecules - absorbed and used for respiration
-> CO2 released
3. Oceans - CO2 diffuses in and out, forming carbonic acid - too much CO2 in the sea
can cause acidification and be dangerous for organisms
4. Plankton - phytoplankton photosynthesise and use carbon to produce cacium
carbonate shells - sink to ocean floor and form limestone and chalk, locking away
carbon
Describe the carbon cycle - ANS-Carbon is fixed from atmosphere CO2 by
photosynthesising plants and plankton to form organic compounds Returned
to atmosphere by respiration (of plants, animals and decomposers),
combustion
Describe the 4 stages of the nitrogen cycle - ANS-1. Nitrogen Fixation - from
atmospheric N2, nitrogen fixing bacteria (on root nodules of legumes) and lightning
cause N2 to be converted into ammonia and then into nitrogen compounds in plants 2.
Ammonification - decomposers convert nitrogen compound from dead organisms into
, ammonium compounds
3. Nitrification - ammonium is converted by nitrifying bacteria into nitrites and then into
nitrates
4. Denitrification - denitrifying bacteria convert nitrates from soil into nitrogen gas, which
is released into atmosphere
Describe how decomposers break down plant and animal compounds - ANS--
hydrolysis
- enzymes
- produced by saprotrophic microorganisms and excreted
- cellulose broken into B glucose monomers
- starch broken into A glucose monomers
Describe the structure/components of a bacterial cell - ANS-Peptidoglycan cell wall -
prevents swelling/bursting, maintains shape and provides support and protection
Cell Membrane - smaller than eukaryotic, site of respiration enzymes as no
mitochondria, infoldings called mesosomes increase SA
Flagellum - helical rotations for movement
Chromosomal DNA - single circular DNA, in cytoplasm
Plasmids - smaller circles of extra DNA, coding for advantageous genes that can be
passed between bacteria during conjugation
Pili - attach to host cells/ used in sexual reproduction, vulnerable to viral infection
Capsule - protects pathogenic cells from being recognised as foreign as their markers
are hidden from antibodies
Explain the classification of bacteria - ANS-- shape - cocci (spherical), bacilli (rod),
spirilla (squiggly)
- gram stain - positive (thick peptidoglycan cell wall so remains purple), negative (thin
cell wall so red dye can be taken up as alcohol disrupts the purple dye) - respiration -
obligate aerobe, obligate anaerobe, facultative aerobe (can respire both aerobically and
anaerobically but aerobic more efficient so where possible, it will respire aerobically)
Describe the process of binary fission - ANS-- DNA and plasmids replicate - the
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller modocko752. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
83750 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now