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AQA A Level Biology Essay Plans

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  • Course
  • A level Biology AQA (AQAALEVELBIOLOGY)
  • Institution
  • AQA

EVERY AQA ALEVEL BIOLOGY ESSAY PLAN IN FULL - includes all new specification titles as well as the majority of old specification titles - all in one PDF document - written by an A* student scored between 18&23 on final exam - includes importance’s for each paragraph - each paragraph writte...

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  • October 2, 2022
  • 73
  • 2022/2023
  • Other
  • Unknown

Subjects

  • aqa
  • alevel biology
  • aqa a level biology
  • aqa a level biology essay
  • aqa a level biology essay plans

Written for

  • A/AS Level
  • AQA
  • A Level Biology
  • A level Biology AQA (AQAALEVELBIOLOGY)
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2  reviews

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By: sudiptaroychoudhury • 1 month ago

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By: hcurrie294 • 8 months ago

amazing, detailed and understandable plans!!! this is making me a lot more confident for my paper 3 biology

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By: tassneemjmahdi • 8 months ago

Thank you for your review and best of luck with paper 3!

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è Biology Essay Plans AQA A LEVEL BIOLOGY:

(TAZM03)

1) The Importance of responses to changes in the internal and external environment of an

organism. (25)

PARA1: osmoregulation

- Osmoreceptors detect water potential too high in blood (eg: not enough mineral ions/salt in

diet or drank too much water).

- water enters osmosis receptors by osmosis in hypothalamus, causing these cells to swell.

- Stimulates hypothalamus to respond by reducing the amount of ADH produced.

- Hormone is transported and secreted at the posterior pituitary glands into capillaries and

blood. Travels in blood to target organ, the kidney.

- Normally ADH causes increased reabsorption of water into blood by imbedding more

aquaporins in walls of collecting duct at nephron, protein channels for water to diffuse/pass

through into interstitial space and diffuse into blood capillaries.

- Reducing amount of ADH menas less aquaporins and less water reabsorbed into blood.

- Collecting duct is less permeable to water, water stays inside nephron, more water is lost in

urine, urine more dilute to bring water potential of blood down back to normal

- Negative feedback mechanisms to restore deviations form a norm.

- IMPORTANCE: ensures body cells aren’t susceptible to cell lysis/damage by too much water

entering cell, this can lead to the cell losing its function eg: red blood cells loose

shape/rupture less transport of oxygen in haemoglobin present in red blood cells and so

insufficient oxygen transported for aerobic respiration and producing ATP for

metabolism/active transport/mitosis. Ensures not too much water is lost in hot climates for

example desert animals etc.

,PARA 2: plant tropisms (only choose 1 importance)


- auxins and growth factors can stimulate how plants respond to external stimuli

- IAA is a growth factor in plants, stimulate cell elongation in shoots in high concentrations

and inhibits cell elongation in cell roots when in high concentrations

- IAA produced in tips of shoots and diffuses throughout plant

- For example photo tropisms, responding to external stimuli of light

- Shoots: positive phototropism, bends towards light/stimulus. Light shone on one side of

light. IAA diffuses to shaded side of shoot. Stimulates cell elongation on shaded side causing

plant to bend more towards light.

IMPORTANCE: maximises light exposure and more light can be absorbed by chlorophyll

more electrons excited, more photolysis and LDR. For ETC ATP production and reduced

NADP for Calvin cycle essential to reduce GP to TP and use some TP for making hexose

sugars like glucose/sucrose needed for plant to use in creating plant cell walls and cellulose

polymer from Beta glucose.

- Negative phototropism: roots, bend away from light, IAA diffuses from lighter side of root to

shaded side of root, causes high concentration of IAA on bottom side of root, inhibiting cell

elongation. So cells on top side of root elongate more, root bends downwards away from

light and anchors plant into soil.

IMPORTANCE: plant needs to anchor deep in soil, access scarce ions in soil like phosphates

that are deeper in soil maximise water absorbance important for making phospholipid

bilayer, DNA/RNA ATP for metabolism, cell division. Using water in photosynthesis to

produce glucose etc.

,PARA 3: stomata opening and closing


- Stomata on bottom of leaf of plants

- How CO2 enters leaf cells by diffusion and release oxygen

- Surrounded by guard cells, control and regulate rate of transpiration by opening and closing

stomata

- Guard cells use osmotic pressure to open. Turgid, guard cell filled with water, guard cell

closes to reduce amount of water loss by transpiration, limits co2 and o2 as well.

- Flaccid, means stomata’s surrounding environment has a lower water potential, stomata

open allows more co2 in more water and o2 out

IMPORTANCE: regulating transpiration in response to humidity, light, temperature and wind

prevents excessive water loss of plant, needed as a reactant in photosynthesis and also

needed to have the ability to open and let CO2 for Calvin cycle in to produce glucose in

photosynthesis. This can then be used in respiration to produce ATP providing energy for

active transport, cell growth etc.


PARA 4: responding to internal stimuli, pathogen humoral response


- Pathogen has proteins on its surface, antigens

- Complimentary receptors on specific B lymphocytes/ white blood cells bind to antigen and

recognise as foreign/non self

- Helper T cells with specific complimentary receptors stimulate B lymphocytes to divide by

mitosis and clone

- Develop plasma cells that release large quantities of specific complimentary antibody to

antigen rapidly allowing for agglutination, attaching to many pathogen molecules, clumping

one large target of phagocytes to engulf ingest and destroy than many pathogens/targets

speeding up immune response

, - Some plasma cells develop into memory cells and circulate in blood for long term immunity

specific complimentary receptors to this antigen, ready for a greater more rapid immune

response upon a second infection

IMPORTANCE: destroying disease causing microorganisms, keeping tissues and cells healthy,

maintains their functions. More likely to survive reproduce and pass on alleles if able to

avert disease/infection more desirable mate. Better competitive position for food and

habitat if remain free of disease and harmful symptoms of disease.

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