AQA Biology Unit 2 Foundation Part 1

A bunch of revision cards for Biology AQA Unit 2 Foundation. Part 1 is Cells, Organs and Populations

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Bacterial Cell
- No Nucleus
- DNA floats in cytoplasm because of no nucleus
Bacterial Cell (

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- Only one cell

Only one cell (

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- Slow movement of particles from a place where there are lots of particles to places where there are fewer of them
- Diffusion is the spreading out of particles from an area of high concentratrion to an area of low concentration


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Cell Membranes

- Hold cell together.
- Also allow stuff in and out the cell
- Very small molecules like Oxygen, Glucose and Amino Acids can fit through cell membranes
- Big molecules like Starch and Proteins can't fit through
- Dissolved substances can move in and out the cell by diffusion
- Molecules move from high concentration (alot of them) to low concentation (Not alot of them)
- They move boths ways. May have net movement if there are too many molecules on one side 

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Specialised Cells

- Do a Specific Function
- For an example, Palisade leaf cells carry out Photosynthesis so it will need lots of Chlorplast

Differentiate to Specialised
            ( O )            -------------------->       ( oo OOO oo)
Unspecialised Cell   Differentiation   Specialised cell (new features)

- This is called Differentiation
- Occurs when multicellur organisms (Humans and plants) develops (grow)
- Specialised cells form tissues, which forms organs, which forms organ systems 

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- Group of specialised cells that have a similar structure and function to do a specific function/job
- e.g. Muscular tissues, Glandular tissues and Epithelial tissues


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- A group of different tissues that work together to perform a certain function
- A stomach organ is made up of these tissues:
  - Muscular tissue, Moves stomach wall to churn (mix) up the food
  - Glandular tissue, Makes diggestive juices to digest food
  - Epithelial tissue, Covers outside and inside the stomach 

Epithelial tissue - Less than 0.1mm
Stomach - About 10cm  

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Organ Systems

- Group of organs working together to perform a paticular function
- The body has several organ systems such as:
  - The nervous system
  - The respiratory system
  - The reproductive system
  - The digestive system 

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How plants use Glucose

- For Respiration

- Making Cell Walls (Cellulose)

- Making Proteins

- Stored in Seeds

- Stored for Starch 

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Distribution of Organism

- The distribution of an organism is where an organism is found
- Environment varies

- Environmental factors: Temperature, Amount of water, Amount of light, How much oxygen there is, How much Carbon Dioxide there is and if there is enough food around

- An organism might be more common in one area than another due to environmental factors. e.g. you will find more daisies on the open field than under tree's due to sunlight

- We use Quadrats or Transects to find the distrubution of organism 

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- These are used to see how common an organism is in two different areas (sample areas)

How to do it?

1) Place a 1m² Quadrat at a randon point within the first sample area
2) Count all the organisms within the Quadrat
3) Repeat step 1 and 2 as many times as you can
4) Work out the mean (average) number of organisms within the first sample area.
    Mean = Total number of organism / Number of Quadrats
    Median = The middle value when results are put in order of size
    Mode = Most common
6) Repeat step 1 and 4 in the 2nd sample area
7) Finally compare the 2 means 

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- Transects are another way of finding out the distribution of organism across an area. These use lines.

How to do it?
1) Mark out a ling in the area you want to study using a tape measure
2) Collect data along the line by:
    - Counting all the organisms that touch the line (Left side on the picture)
    - Using Quadrats placed along the line (Right side on the picture)

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Population Size

Population size = Mean number of organism per 1m² quadrat x Total area (in m²)

For an example, There are 7 daisies per m² in a 100cm² field. So the population size = 7 x 10 = 700 daises

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Collecting Environmental data


Are the results realiable?

Are your results repeatable and reproducible?

To make results more reliable you need to: take a large sample size (lots of quadrats) or/and use random samples (Different areas)


Must be reliable to be valid

To answer original question you need to control all variables.

Question: Whether a difference in distribution between sample areas is due to a difference in one environmental factor

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