Summary OCR A Level Biology A* Biodiversity Detailed Notes
13 views 0 purchase
Course
Module 4 - Biodiversity, evolution and disease
Institution
OCR
These A-Level Biology notes are designed for students aiming for top grades and a future in medicine. They are both aesthetic and detailed, offering comprehensive coverage of the syllabus while being visually engaging.
Comprehensive Coverage: Every topic is fully covered, directly aligned with t...
Biodiversity
1. Biodiversity
Biodiversity
- Biodiversity = a measure of the varia3on found in the living world, the genes that each kingdom contains
and the ecosystems of which they form a part
- Habitat biodiversity = the range of habitats in which different species live e.g. sand dunes, woodland,
meadows, streams, ponds etc
- Species = individual organisms very similar in appearance, anatomy, physiological, biochemistry and
gene3cs, so can interbreed freely to produce fer3le offspring
- Species biodiversity = range of organisms found in a habitat, dependent on species richness – the number
of species of organisms, versus the species evenness = the representa3on of each species
- Gene3c varia3on = between individuals in the same species, can create breeds within a species
Using samples to measure biodiversity of a habitat
- Biodiversity of a habitat is measured through the species present and how many of each
- It is imprac3cal to count every fungi/bacteria/single-celled organism and es3mates vary
- A sample is used to count the organisms in a small por3on and mul3ply to create an es3mate
representa3ve of the habitat
Type of sampling How sampling is carried out Advantages Disadvantages
Random - Randomly select sample sites by Data not biased due May not cover all areas of the habitat
deciding where beforehand to random sampling equally -> species with low presence
- Use randomly generates numbers as may be missed -> underes3mate of
coordinates or use a portable global- biodiversity
posi3oning satellite system to find
the exact posi3on
Non- Opportunis3c - Researcher makes sampling decisions Easier and quicker Data may be biased as the presence of a
random based on prior knowledge or the data than random large/colourful species may en3ce the
they collected sampling researcher to include that one ->
- May deliberately sample an area they overes3mate of its importance ->
can see a par3cular species overes3mate of biodiversity
Stra3fied - Divide habitat into areas that appear All areas of a habitat May lead to over-representa3on of some
different and sample each separately are sampled and areas e.g. dispropor3onate samples
species are not taken in small areas that each look
under-represented different
Systema3c - Samples taken at fixed intervals Useful when there is Only species on the line/within the belt
across the habitat a clear gradient in can be recorded, others will be missed ->
- Line transects and belt transects some environmental underes3mate of diversity
used factor
2. Sampling plants
Sampling a habitat
Prepara<on
- Suitable clothing and footwear for expected weather condi3ons; sampling apparatus; clipboard, pen and
paper for records; appropriate keys to iden3fy plants; camera or smartphone to record specimens and grid
loca3ons; results table prepared for records
At the site
- Use a range of sampling techniques and modify random sampling if the habitat is not homogeneous
- Use opportunis3c/stra3fied sampling by moving some of the sample sites into areas that look different
- Consider the effect your presence has on the habitat and cause as liUle disturbance as possible
Sampling plants
- Iden3fy and count large plants individually
- For small plants calculate a value of percentage ground cover occupied by each species
Using random quadrats
, - Quadrat = square frame used to define the size of the sample area, oYen 50cm/1m per side
- Random sampling -> generate random numbers and use them as coordinates to place quadrats in a habitat
- Use a tape measure or count even paces to place at the correct loca3on
-
- Iden3fy plants inside quadrat + calculate % cover for abundance, using the smaller divisions of 100 squares
to es3mate more accurately
- Point frame = frame of long needles lowered into the quadrat, count plants touching the needles, do 100
readings so each plant touching = 1% cover
- Record bare ground too
- 300-400% is possible as one plant can touch mul3ple needles
- Place at regular intervals within quadrat to remove bias -> systema3c sampling
Using a transect
- Transect = line of string or tape measure taken across a habitat, samples taken along it
- Use a line transect in large habitats and record plants touching line at set intervals across
- Can use quadrat at set intervals along line – an interrupted belt transect – providing quan3ta3ve data
- Con3nuous belt transect = quadrat placed beside the line and moved along to study band/belt in detail
3. Sampling animals
Sampling animals by observa<on
- Hard to collect quan3ta3ve data: large ones can detect human presence and hide, small ones hide and
move too fast to count accurately
- Presence can be iden3fied from footprints/droppings/own pellets/rabbits’ burrows/deer damage on trees
- Popula3on size can be es3mated by using DNA sequencing of droppings to dis3nguish between individuals
Collec<ng samples of live animals
- Plan by bringing appropriate apparatus for chosen sampling technique
Catching invertebrates
- Low vegeta3on (not too woody) or water: Sweep nefng = walking through habitat with stout net,
sweeping through vegeta3on in wide arcs to catch small animals e.g. insects, and empty onto a white
sheet to iden3fy them -> a pooter can be used to collect animals before they fly away
- Trees: spread out a white sheet under a branch and knock the branch with a stout s3ck -> small animals
get dislodged and fall onto sheet (again may crawl/fly away)
- Pihall trap = trap set in soil to catch small animals, small container buried in the soil with rim below surface
-> animals moving through plants/leaf liUer fall into trap, some water/paper stop animals crawling out,
shelter from rain so doesn’t fill up
- Tullgren funnel = collects small animals from leaf liUer, leaf liUer placed in funnel -> light above liUer drives
animals downwards as liUer dries and warms -> fall through mesh screen -> collected in jar below
- Light trap = collects flying insects at night using UV light to aUract insects -> alcohol-containing vessel
under light catches insects
Trapping small animals
- Technique depends on habitat and type of animal, a licence is needed to trap some animals, and should
never harm the animal
- Longworth trap used for small mammals – humane so no harm, must be monitored regularly to release
trapped animals, popula3on size can be calculated with mark-and-recapture:
1. Capture sample of animals + mark each individual in some way to cause no harm = C1
2. Release marked animals + leave traps for another period of 3me
3. Number captured again = C2 + number of second capture with original markings = C3
4. Total popula3on = (C1 x C2) / C3
- Can calculate size of some insect popula3ons by this technique
- Bird popula3on can be es3mated by using a ringing technique to iden3fy individuals, larger mammals can
be tagged -> both require skill + experience so only done with permit from relevant authori3es
4. Calcula<ng biodiversity
Es<ma<ng biodiversity
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 alevelrevisionresources. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $9.06. You're not tied to anything after your purchase.
