Science - Biology 2a

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What is Diffusion?
Diffusion is the spreading out of particles from an area of high concentration to one of low concentration.
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Where does diffusion occur?
Solutions and Gases because the particles can move around freely
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Give one example of diffusion.
When gases diffuse through each other is a simple example. like when perfume diffuses through air in a room
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Can you give one sentence to describe Diffusion?
The bigger the difference in concentration, the faster the diffusion rate.
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What does a cell membrane do?
Hold the cell together but also let stuff in and out as well
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What type of molecules travel through the cell membrane?
Only small molecules can pass through the cell membrane. E.g. oxygen, glucose, amino acids and water.
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What specialised cells in a plant are adapted for Photosynthesis?
Palisade leaf cells
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What helps palisade cells photosynthesise and where are they found?
Packed with chloroplasts at the top of the cell closer to the light.
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Why are these cells shaped like rectangles?
The tall shape mean a larger surface area exposed to the air at the side of the leaf allowing more co2 to be absorbed
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Why are they thin in shape?
Allows for more to be fitted in along the top of the leaf
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Where are palisade leaf cells usually found?
Grouped together at the top of the leaf where most of the photosynthesis happens
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What are guard cells and what do they do?
Guard cells are special kidney shaped cells which open and closes the stomata (pores) of a plant
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What is a TURGID cell?
A plant cell which is fully inflated with water
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What is a PLASMOLYSED cell?
A plant cell that has lost water causing the cell membrane to pull away from the cell wall
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What is a FLACCID cell?
A plant cell that is limp through a reduction of pressure inside the cell
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What happens when a plant cell becomes TURGID?
The plant has lots of water so the guard cells fill and go plump, this opens the stomata so gases can be exchanged for photosynthesis
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What happens when a plant cell becomes FLACCID?
The plant is short of water, making the stomata close. This helps stop too much water vapour escaping.
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What helps the opening and closing of the stomata?
Thin outer walls and thickened inner walls
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How are guard cells adapted to their function?
They allow gas exchange and control water loss in a plant.
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How do Guards cells in a plant save water at night?
They are sensitive to light and close at night to save water without losing out on photosynthesis
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How are Red Blood cells adapted?
Concave shape gives a bigger surface area to absorb oxygen. Also helps them to pass smoothly through capillaries to reach body cells
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What is Haemoglobin?
The pigment that absorbs the oxygen
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What do red blood cells not have and why?
They have no nucleus, to leave more space for the haemoglobin
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What are specialised cells?
Cells which have a particular function in the body
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What is Differentiation?
The process by which cells become specialised for a particular job
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When does Differentiation occur?
During the development of a multicellular organism
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What is a Large Multicellular organism?
Humans or sqirrels are examples of this, which have different systems inside them for exchanging and transporting materials
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What is a Tissue?
A group of similar cells that work together to carry out a particular function
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Give three examples of Tissues?
Muscular tissue (contracts to move whatever its attached to),Glandular tissue (secretes chemicals like enzymes and hormones) and Epithelial tissue (lines the inside of the gut)
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What is the equation for Photosynthesis?
Carbon dioxide + water ---> glucose + oxygen
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What can effect the rate of Photosynthesis?
Light, temperature and amount of co2 are all limiting factors
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What five things do plants use glucose for?
Respiration, making cell walls, making proteins, stored in seeds and stored as starch
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How can you measure the distribution of organisms in a field?
By using a transect. Mark out a line in the are you want to study then collect your data along the line by counting the ones that touch the line.
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How can you make this more reliable?
Take a large sample size- use as many transects and quadrats as you can
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How can you make this more valid?
Use random samples. If your samples are all from one area everywhere else is different so the results would be different so wont be vaild.
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Give 5 environmental factors that can affect the distribution of organisms.
Temperature, Availability of water, Availability of oxygen and carbon dioxide, Availability of nutrients and amount of light.
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Other cards in this set

Card 2


Where does diffusion occur?


Solutions and Gases because the particles can move around freely

Card 3


Give one example of diffusion.


Preview of the front of card 3

Card 4


Can you give one sentence to describe Diffusion?


Preview of the front of card 4

Card 5


What does a cell membrane do?


Preview of the front of card 5
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