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[OCR A2 Biology] Central Concepts questions

"Describe the classification of species into taxonomic groups, and appreciate the significance of the various concepts of the species."

This is taken from the OCR spec, but I don't get the second part, in bold.

I don't get what to do for this either:

"Outline, with examples, structural and physiological adaptations of organisms to their environment."
Reply 1
Basically speciation is based on similarities and differences. I'm guessing that's what you have to appreciate.

As for the later, the first one that springs to mind is the evolution of certain organisms to adapt to life in thermal springs, having heat resistant enzymes.
Reply 2
god i hate this chapter

biology is hardest subject ever.
Reply 3
Help!

In an experiment to investigate the effect of light intensity on the rate of photosynthesis, the following procedure was carried out by some students.

1. Discs were cut from the photosynthetic weed of the brown alga Fucus serratus, a common rocky seashore weed, using a cork borer.
2. Ten discs were placed in each of four beakers filled with 50cm3 of sea water. The discs are denser than sea water and therefore sink to the bottom of the beaker.
3. Each beaker was illuminated with a bench lamp placed at different distances (d) from the beaker.
4. The time, in minutes, at which the third disc from each batch reached the surface (t) was recorded.
5. The rate of photosynthesis was determined by calculating 1000/t.

QUESTIONS:

(c) Explain why the discs float after being illuminated for a length of time [3]
(e) State the environmental factor limiting the rate of photosynthesis in this experiment. [1]
(g) Suggest why the student is not likely to find an increase in the rate of photosynthesis when two lamps are placed 5cm from the beaker. [2]

Also...

Q: List FOUR ways in which the structure of a dicot. leaf is adapted for GAS EXCHANGE. [4]

Q: Explain why it is important for mammals to be able to detect changes in their INTERNAL environment. [3]

Q: Explain how NAMED receptors in mammals convert energy into action potentials.

Q: In Feb 01...'new species' of camel discovered...in Asia...differ from domesticated camels.

- Describe how changes in DNA could occur. [3]
- Describe what further evidence is required to show that this 'new species' is a different species from the dom. camels. [3]
- Suggest two physiological adaptatiojns that would allow some camels to survive when their only source of water is salty. [2]
- Explain how genetic variation in the ancestral wild camelpopulation enabled the development of this 'new species'. [2]
Reply 4
has it got something to do withthe discs photosynthesising and producing oxygen, the o2 bbbles form around the discs, causing it to float up in the water (i think)
Reply 5
SiAnY
Help!

In an experiment to investigate the effect of light intensity on the rate of photosynthesis, the following procedure was carried out by some students.

1. Discs were cut from the photosynthetic weed of the brown alga Fucus serratus, a common rocky seashore weed, using a cork borer.
2. Ten discs were placed in each of four beakers filled with 50cm3 of sea water. The discs are denser than sea water and therefore sink to the bottom of the beaker.
3. Each beaker was illuminated with a bench lamp placed at different distances (d) from the beaker.
4. The time, in minutes, at which the third disc from each batch reached the surface (t) was recorded.
5. The rate of photosynthesis was determined by calculating 1000/t.

QUESTIONS:

(c) Explain why the discs float after being illuminated for a length of time [3]


Oxygen is produced in photosynthesis. When enough oxygen has been produced to make the discs less dense that water, they float. The discs must be photosynthesising at a rate greater than the compensation point so that there is a net production of O2.

(e) State the environmental factor limiting the rate of photosynthesis in this experiment. [1]


Did they give you results? graph? If the rate of photosynthesis increases as light intensity increases, then light intensity is the limiting factor.

(g) Suggest why the student is not likely to find an increase in the rate of photosynthesis when two lamps are placed 5cm from the beaker. [2]


Other factors are limiting the rate ... eg CO2 concentration.
Also...

Q: List FOUR ways in which the structure of a dicot. leaf is adapted for GAS EXCHANGE. [4]


Stomata for gas to diffuse in and out easily
Spongy mesophyll has many air spaces for easy diffusion
Moist layer on surface of cells to enable gasses to dissolve and then diffuse across membrane
Only one layer of pallisade cells so gas only has to cross one membrane

Q: Explain why it is important for mammals to be able to detect changes in their INTERNAL environment. [3]


Enzymes only work efficiently under a narrow set of conditions so must keep temperature/blood pH constant to ensure enzymes are not denatured.
Tissue fluid must be kept at a constant composition so metabolites etc can diffuse in and out of cells easily

Q: Explain how NAMED receptors in mammals convert energy into action potentials.

Q: In Feb 01...'new species' of camel discovered...in Asia...differ from domesticated camels.

- Describe how changes in DNA could occur. [3]


random mutations ---> natural selection ---> many generations ---> evolution

- Describe what further evidence is required to show that this 'new species' is a different species from the dom. camels. [3]


can not interbreed to produce fertile young .... contain different morphological, biochemical etc characteristics.

- Suggest two physiological adaptatiojns that would allow some camels to survive when their only source of water is salty. [2]


High concentration of solutes in their cells so they do not lose water by osmosis
Use water produced from respiration?

- Explain how genetic variation in the ancestral wild camelpopulation enabled the development of this 'new species'. [2]
Reply 6
Thank you so much!

Can anyone help with these?

# Explain how genetic variation in the ancestral wild camelpopulation enabled the development of this 'new species'. [2]
# Explain how NAMED receptors in mammals convert energy into action potentials. [8]
Reply 7
SiAnY
Thank you so much!

Can anyone help with these?

# Explain how genetic variation in the ancestral wild camelpopulation enabled the development of this 'new species'. [2]
# Explain how NAMED receptors in mammals convert energy into action potentials. [8]


I have to go out now, but in case no one else replies, look up speciation (allopatric and sympatric) for the camels one, and for the other one - have you studied the eye or the ear yet? Rods and cones in the eye are probably easiest to talk about.
I did this paper as a mock exam.

SiAnY
Thank you so much!

Can anyone help with these?

# Explain how genetic variation in the ancestral wild camelpopulation enabled the development of this 'new species'. [2]

-Some camels are more tolerent to salt - advantageous alleles
-Salt tolerent camels breed and pass on their allele to offspring.

SiAnY

# Explain how NAMED receptors in mammals convert energy into action potentials. [8]

I'll type out the mark scheme - probably the best way!

-rods/cones/retina/photoreceptors, detect light
-taste buds/olfactory cells/chemorepcetors detect chemicals
-Pacinian corpuscle detects pressure/touch
-..Ruffini's endings in skin/thermoreceptors detect temp changes;
-Proprioreceptors/stretch receptors in muscle, detect mechanical displacement
-hair cells in semicircular canals detect movement
-baroreceptors detect blood pressure changes
-osmoreceptors detect changes in blood water potential

-stimulus causes sodium channels to open
-Na ions enter cell
-depolarisation
-receptor potential/generator potential
-greater than threshold/all or nothing response
-increased stimulus leads to increased frequency of action potentials
-AVP eg hyperpolarisation in rod cell
-AVP- deformity of capsule in Pacinian corpuscle.
-QWC :wink:



PS - most of oxymoron's answers in his long post were all spot on (matched mark scheme)!
I'm just gonna add in a few points on top of oxymorons' which were mark worthy exam wise.

SiAnY

QUESTIONS:


Q: Explain why it is important for mammals to be able to detect changes in their INTERNAL environment. [3]

-mention homeostasis
-and its definition of maintaining a stable internal environment
-give example - eg blood sugar too high->insulin released



SiAnY

Q: In Feb 01...'new species' of camel discovered...in Asia...differ from domesticated camels.

- Describe how changes in DNA could occur. [3] -random mutations
-eg ionising radiation
-mutations cause change in DNA base sequance eg by base substition, addition, deletion.



SiAnY

- Describe what further evidence is required to show that this 'new species' is a different species from the dom. camels. [3]
-If the new species cannot breed with the original species to produce fertile offspring
-If the 'new species' can intra breed (within the 'new species') to produce fertile offspring.


SiAnY

- Suggest two physiological adaptatiojns that would allow some camels to survive when their only source of water is salty. [2]
-Long loop of Henle (is the main one we need to know)
- and a second general suggestion - eg adapted gut to absorb less salt.
THANKS EVERYONE!! I'm gonna print this out! :biggrin: I am actually worried again. I have Thursday evening, Friday, Saturday and Sunday to learn everything properly.

endeavour

I'll type out the mark scheme - probably the best way!

-rods/cones/retina/photoreceptors, detect light
-taste buds/olfactory cells/chemorepcetors detect chemicals
-Pacinian corpuscle detects pressure/touch
-..Ruffini's endings in skin/thermoreceptors detect temp changes;
-Proprioreceptors/stretch receptors in muscle, detect mechanical displacement
-hair cells in semicircular canals detect movement
-baroreceptors detect blood pressure changes
-osmoreceptors detect changes in blood water potential

Never heard of any of them except osmoreceptors. :redface: