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GCSE Biology > Paper 2 Overview > Flashcards

Paper 2 Overview Flashcards

1
Q

SB6a - What is the equation for photosynthesis?

A

Carbon dioxide + Water → Glucose + Oxygen

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2
Q

SB6a - What is the equation for respiration?

A

Glucose + Oxygen → Carbon dioxide + Water

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3
Q

SB6a - What does photosynthesis do?

A

It traps energy from the sunlight and converts it to glucose

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4
Q

SB6a - Where does photosynthesis occur?

A

In the chloroplasts of the plant cell

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5
Q

SB6a - What type of reaction is photosynthesis?

A
  • Endothermic.
  • The products have more energy than the reactants.
  • This means they have taken in energy from the surroundings during the reactions
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6
Q

SB6a - Why is glucose necessary?

A
  • Glucose molecules are joined together to form a polymer of starch.
  • After photosynthesis stops, this is broken down to simple molecules which are used to form sucrose.
  • Sucrose is used to make:
    • Starch (In a storage organ such as a potato)
    • other molecules for the plant (cellulose, lipids etc.)
    • Glucose for respiration (to release energy)
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7
Q

SB6a - How are leaves adapted for their purpose?

A
  • They have a broad flat shape giving them a large surface area for photosynthesis
  • There are lots of palisade cells near the top which are packed with chloroplasts to absorb light
  • Stomata allow carbon dioxide to diffuse in for photosynthesis
  • When there is light (during day) water flows into guard cells making them rigid and when there is less light (nighttime) The water flows out making it loose its rigidity
  • When it is rigid, it is open so it is only open when there is light
  • This means it will only allow carbon dioxide to diffuse when there is also light to conduct photosynthesis
  • Leaves are thin meaning carbon dioxide doesn’t have far to diffuse
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8
Q

SB6a - Tomayto, tomahto?

A

Stomayto, stomatoh

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9
Q

SB6a - Why are the stomata an example of a gas exchange system?

A

They let carbon dioxide diffuse in and let oxygen diffuse out

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10
Q

SB6b - What are the three main limiting factors that affect photosynthesis?

A
  • Carbon dioxide concentration
  • Light Intensity
  • Temperature temperature
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11
Q

SB6b - Why are plants less likely to grow higher up on a mountain?

A

Higher up, the air pressure is lower meaning the carbon dioxide concentration is lower

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12
Q

SB6b - A graph showing how increasing rate of light intensity affects rate of photosynthesis eventually levels out. Why can’t it get any higher despite light intensity increasing?

A
  • As the graph curves, light intensity is the limiting factor.
  • Once it levels out, something else is the limiting factor.
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13
Q

SB6b - Once the rate of photosynthesis can’t increase anymore (due to light intensity in this case) how would you increase the rate of photosynthesis?

A
  • Something else is the limiting factor.
  • Increasing the CO2 concentration or increasing the temperature will allow the rate of photosynthesis to continue to increase.
  • Eventually it will level out again as something else has become the limiting factor.
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14
Q

SB6b - Why is it that even if temperature is the limiting factor, you’ll get to a point where increasing it won’t increase the rate of photosynthesis?

A
  • At a temperature that is too high, the enzymes in the plant become denatured.
  • They can no longer bind to their substrate and therefore processes can’t occur anymore
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15
Q

SB6b - What is the inverse square law, and where does it apply to?

A
  • The inverse square law is used to find out how light intensity chages ith distance from the source.
  • I: light intensity
  • d: distance

I(original) x d(original)² = I(new) x d(new)²

  • light intensity is inversely proportionate to the square of the distance
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16
Q

SB6b CP - Describe a method, using algae balls and hydrogen carbonate indicator, to investigate rates of photosynthesis at differing light intensities.

A
  • Add 20 algae balls and the same amount of indicator to as many glass bottles as you need
  • Compare the colour of the bottle at the start to a key to work out its starting pH (they should all be the same)
  • Place a tank of water between the light and the first glass to absorb the heat given off by the light
  • Cover one with foil so it is in the dark and place it next to the one closest to the lamp
  • Measure out the distances you place all of the bottles
  • Turn on the light and wait till you see noticable changes in the pH
  • Once you’ve decided to stop, work out the pH again by comparing to a key
  • Work out the change in pH/hour to be your rate of reaction
  • Plot a graph of rate of reaction vs distance from light
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17
Q

SB6c - Why do plants need to take in water?

A

To be used in/to:

  • Carrying dissolved mineral ions
  • Keeping cells rigid so plants don’t wilt (droop)
  • Cooling leaves (when it evapourates)
  • Photosynthesis
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18
Q

SB6c - How are roots adapted to absorb water?

A
  • Roots have root hair cells
  • The hairs make the surface area larger meaning there is more area for mineral ions to be quickly absorbed through water
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19
Q

SB6c - What is a concentration gradient and what can it cause to occur?

A

When two areas are connected in some way and having differing levels of concentration of a substance, they have a concentration gradient If this is in a fluid, diffusion can occur, where the substance moves from the area of higher to lower concentration

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20
Q

SB6c - What do root hair cells and root cells have between them and why?

A

They have a little tube allowing diffusion of fluids between cells

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21
Q

SB6c - How can some water enter the root hair cells if not through openings?

A

The root hair cells have a semi-permeable membrane meaning that osmosis can take place with the water moving down the concentration gradient into the cytoplasm of the cell

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22
Q

SB6c - How do plants take in mineral ions?

A
  • Through the water they absorb.
  • However as there is a higher concentration of these in the plant than in the soil, they can’t absorb it through diffusion but rather through active transport which takes up energy
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23
Q

SB6d - Describe the process of transpiration

A
  • The flow of water into a root, up the stem and out the leaves
  • As water on the leaves’ surface evapourates, a concentration gradient is created
  • This prompts water to be drawn out from the inside of the leaves through the stomata through diffusion and osmosis
  • They travel through the xylem down the concentration gradient
  • This is aided by the cohesion between the H2O molecules due to hydrogen bonds and adhesion to the walls of the xylem cell
  • At the root hair cells, as water moves up the xylem, water is also taken in due to the concentration gradient
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24
Q

SB6d - Describe the process of translocation

A
  • The transport of sucrose around a plant
  • The source is the leaf where glucose is created by photosynthesis
  • Glucose monomers join together to from a sucrose polymer (as only polymers can be transported this way)
  • The sucrose is actively transported into the phloem through a companion cell
  • At the top of the phloem there is a low concentration of water. So water from the xylem diffuses through pores in the cells
  • This water then has a high pressure so moves down the phloem taking the sucrose with it
  • It will then be actively transported through a companion cell to whatever cell it is needed in
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25
Q

SB6d - Describe the adaptations of the xylem

A
  • Multiple pores to allow water and mineral ions to enter and leave
  • dead cells, no cytoplasm and no cell walls to allow flow of water through it
  • rings made of lignin and thick side walls to keep the water inside
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26
Q

SB6d - Describe the adaptations of the phloem

A
  • Holes in cell walls to allow liquids to flow
  • No nucleus or cytoplasm as they aren’t needed and would be a waste of energy
  • Companion cells to pump have many mitochondria so they have energy to actively transport sucrose
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27
Q

SB6d - Describe how you can investigate rates of transpiration

A
  • A potometer is used for this. It involves using a plant attached to a rubber stopper connected to a reservoir of water and a capillary tube.
  • The capillary tube should have at least one bubble in it and should have a scale .
  • As the plant uses up water it will draw water from the tube moving the air bubble.
  • The speed of the bubble will allow you to calculate the rate of transpiration
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28
Q

SB6e - How is the structure of a leaf adapted for photosynthesis and gas exchange?

A
  • Leaves are broad and flat which gives them a large surface area.
  • Palisade cells near the top of the leaf are packed with chloroplasts to allow large amounts of light absorption.
  • Spongy cells create air spaces so gasses can diffuse in and out.
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29
Q

SB6e - Why do some plant have needle shaped leaves?

A
  • Small leaves result in a reduced surface area so transpiration happens more slowly.
  • A thick cuticle protects them from infection.
  • The smaller leaves helps them to withstand strong winds and a lack of water
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30
Q

SB6e - How do plants reduce water loss?

A
  • Having stomata located inside small pits
  • By losing leaves in winter
  • By closing stomata at night
  • Having thinner leaves
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31
Q

SB6f - What are the names of three main plant hormones?

A
  • Auxins: promote growth
  • Gibberellins: cause germination
  • Ethene: cause fruit ripening
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32
Q

SB6f - What are positive and negative phototropism and gravitropism?

A
  • Positive = towards
  • Negative = away
  • Phototropism = a response to light
  • Gravitropism = a response to gravity
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33
Q

SB6f - How does phototropism occur?

A
  • Auxins a produced in the tip of the shoot
  • As the shoot is exposed to light, auxins move to the shaded side of the root (the side away from the sun)
  • Here they cause the cells to elongate causing the shoot to point towards the sun
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34
Q

SB6g - How are auxins used by plant growers?

A
  • Selective weedkillers contain artificial auxins to kill plants with broad leaves.
  • Auxins are also used in rooting powders which cause plant cuttings to grow roots rather quickly
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35
Q

SB6g - What are the uses of gibberellins?

A
  • Produce seedless fruits
  • Promote flowering
  • Increase fruit size
  • Germinate seeds
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36
Q

SB6g - How do farmers ripen fruits once they have been removed from a tree?

A

Use ethene gas

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37
Q

SB6d - Describe the factors that affect transpiration.

A
  • Light intensity: stomata opens wider allowing water in quicker
  • Temperature: More evapouration means a greater concentration gradient on the leaf surface
  • Wind speed: Less water on leaf surface steepens the concentration gradient
  • Fall in humidity: As the air becomes less saturated, water vapour evapourates more easily steepening the concentration gradient
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38
Q

SB6f - How does gravitropism occur?

A
  • Auxins in the root are pulled down by gravity.
  • They inhibit cell elongation here causing the root to grow downwards (positive gravitropism)
  • Auxins in the shoot are also pulled down by gravity but here they cause cell elongation making the shoot grow upwards (negative gravitropism)
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39
Q

SB6f - Describe Darwin’s experiments with auxin and what can be concluded from the results.

A
  • Three intact shoots exposed to light. One covered with a black cap, one with a transparent cap and one normal
  • The one with the black cap didn’t bend towards the light while the other two did
  • This shows that auxins are dependent on light to work
  • One where the tip was removed didn’t bend towards the light.
  • This showed that auxins are produced in the tip of the shoot
  • A tip was also placed on a permeable and and impermeable base (removed from the plant)
  • The one on the permeable base (agar block) bent towards the light but the other didn’t
  • This shows that auxins need to travel further down in the plant to work
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40
Q

SB7a - What are hormones?

A
  • Hormones are chemical messengers (carried in the blood stream).
  • They are used in the hormonal response system which is typically slow-acting and long-lasting compared to the nervous system
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41
Q

SB7a - Where are hormones released? (Give examples)

A

Endocrine glands e.g:

  • Pituitary gland
  • Thyroid gland
  • Adrenals
  • Ovaries
  • Testes
  • Pancreas
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42
Q

SB7a - Where do hormones go to? (Give examples)

A

Target organs e.g:

  • Digestive system
  • Kidneys
  • Liver
  • Endocrine glands for other hormones (e.g growth hormone)
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43
Q

SB7b - What is your metabolic rate?

A

The rate at which energy stored as food is transferred by all of the reactions that take place in your body

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44
Q

SB7b - How do you measure resting metabolic rate?

A
  • At a warm room
  • Body at rest
  • Long after the person has had a meal
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45
Q

SB7b - What is a negative feedback system?

A

A response to an increase in one condition by causing actions that will decrease it, or vice versa (e.g response to body being too hot is to sweat to cool it down)

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46
Q

SB7b - Define homeostasis

A

Maintaining constant conditions in the body, typically through negative feedback

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47
Q

SB7b - What is thyroxine?

A
  • Thyroxine is a hormone that is released by the thyroid gland.
  • It’s target organs are many different types of cells of which it will increase the rate at which protein and carbohydrates are broken down.
  • This affects your metabolic rate
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48
Q

SB7b - How is thyroxine used as part of a negative feedback system?

A
  • If the concentration of thyroxine in the blood is low, the hypothalamus may release TRH
  • This will cause the pituitary gland to release TSH
  • This stimulates the thyroid gland to release thyroxine, increasing the concentration of thyroxine
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49
Q

SB7b - How does your body’s fight or flight system work?

A
  • Adrenaline is released from adrenal glands and is always in the bloodstream at a low level
  • A fight or flight situation will cause increased impulses from neurons which will trigger the release of large amounts of adrenaline into your blood
  • Adrenaline has many target organs:
    • Causes the breakdown of glycogen to glucose in the liver so that there is more for cellular respiration (more energy)
    • Heart contracts more rapidly and strongly increasing the heart rate and blood pressure. This moves glucose around the body quicker
    • Diameter of blood vessels leading to muscles or target organs are widened to allow more blood through while the rest are narrowed to allow more to be sent to the widened vessels
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50
Q

SB7g - What is thermoregulation?

A

The negative feedback system that ensures our body stays at around 37°C

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51
Q

SB7g - What is fever/hypothermia and why is it bad?

A
  • Fever is when your body is above 38°C
  • Hypothermia is when your body is below 36°C
  • These are bad because the enzymes that enact most of the processes in our body that keep us alive have an optimum temperature of 37°C
  • So straying too far from it will stop these processes from occurring (properly) as enzymes can become denatured/ineffective
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52
Q

SB7g - How does the brain detect the temperature of the body?

A
  • In the dermis of the skin, there are temperature receptors
  • These feed information to the receptors in the hypothalamus in the brain
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53
Q

SB7g - When the body is too cold, what will happen?

A
  • Shivering: Muscles rapidly contract and expand. Some of the energy released form cell respiration warms you up
  • Vasoconstriction: Nerve signals from the hypothalamus tell the blood vessels near the surface of the skin (in the dermis) will narrow. This reduces thermal energy lost to surroundings as blood flows past
  • Erector muscles contract: Erector muscles in the dermis of the skin contract causing hair to stand upright. While it may not work for humans, on other mammals it traps air next t the skin for insulation
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54
Q

SB7g - When the body is too warm, what will happen?

A
  • Sweating: Your body secretes a thin layer of sweat on the epidermis of your skin. When this evaporates, it transfers energy from the body to the surroundings
  • Vasodilation: Nerve signals from the hypothalamus tell the blood vessels in the dermis widen. As more blood flows near the surface of the skin, more energy is transferred to the surroundings
  • Erector muscles relax: Hair lies flat meaning no air can be trapped and reducing the insulation (again it doesn’t make a difference for humans)
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55
Q

SB7h - What is osmoregulation?

A
  • The negative feedback system involving the balance of water and minerals in the body.
  • The wrong balance will result in cells taking in the wrong amounts through osmosis and being damaged
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56
Q

SB7h - Describe how the urinary system works

A
  • The urinary system removes excess amounts of substances from the blood inc. water mineral salts and urea
  • Renal arteries carry blood from the body to the kidney.
  • Once it is ‘cleaned’ renal veins carry the blood to the rest of the body
  • The kidneys remove excess substances from the blood to form urine
  • Ureters carry urine to the bladder where it is stored
  • Once the muscle keeping the bladder closed is released, the urine passes through the urethra to outside the body
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57
Q

SB7h - What is kidney failure and why is it dangerous?

A
  • Kidney failure is when both of the kidneys stop working properly
  • This means that there will be high concentration of waste products in their blood which will need to be removed by dialysis
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58
Q

SB7h - What is urea?

A

Urea is produced from the breakdown of excess amino acids in the liver. This is passed into the blood

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59
Q

SB7e - Describe the travel of glucose through the bloodstream of a non-diabetic person?

A
  • Glucose is released from the small intestine after digestion. As it flows into the bloodstream, the concentration rises
  • The pancreas detects the high levels of blood glucose and releases insulin. Now the concentration of insulin also rises
  • The insulin causes the liver, muscle and other cells to take up the glucose and store it as glycogen. Thus the glucose and insulin concentration reduces
  • Once the glucose concentration is too low, the pancreas releases glucagon.
  • This causes all the cell that contain glycogen to convert this back into glucose which is released into the blood
  • This is a negative feedback system
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60
Q

SB7e - What is type 1 diabetes and how can it be dealt with?

A
  • Pancreatic cells don’t produce insulin as they have been destroyed by the body’s immune system
  • This means they cannot control blood glucose levels naturally
  • A type 1 diabetic would have to inject insulin into the fat layer below the skin to reduce blood glucose levels
  • (Typically non-genetic)
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61
Q

SB7f - What is type 2 diabetes?

A
  • Insulin releasing cells don’t produce enough insulin or target organs don’t respond to insulin
  • Can be genetic or due to lifestyle
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62
Q

SB7f - Why can being physically active help with type 2 diabetes?

A
  • Physical activity increases cellular respiration that takes place in your body
  • This takes up glucose form your blood reducing the need for insulin
  • this lowers your blood glucose level
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63
Q

`SB7f - What is the relationship between T2 diabetes and average body mass?

A
  • The higher your body mass, the higher the risk of T2 diabetes.
  • These factors are correlated
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64
Q

SB7f - How do you calculate BMI?

A

BMI = mass (kg) ÷ height (m²)

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65
Q

SB7f - How do you calculate waist:hip ratio?

A

waist measurement ÷ hip measurement

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66
Q

SB7f - Why is waist:hip ratio preferred to BMI sometimes?

A

While both have a correlation with risk of T2 diabetes, BMI doesn’t account for muscle mass.

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67
Q

SB7c - What is the menstrual cycle?

A
  • The cycle of changes that take place in a women’s reproductive system for about 28 days
  • Starts with puberty (around 12) and ends with menopause (around 50)
  • Prepares the body for the fertilisation of an egg and pregnancy
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68
Q

SB7c - Describe the stages of the menstrual cycle

A
  • Days 1-5ish: Menstruation is when the lining of the uterus breaks down and is lost with an unfertilised egg
  • Days 10-12ish: The uterus lining starts to thicken again
  • Days 13-15: The new egg is released from the ovary
  • Days 16-28: Uterus lining continues to thicken
  • Day 23ish: The egg cell travels along the oviduct to the uterus
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69
Q

SB7d - What is FSH?

A
  • (Follicle stimulating hormone) is involved in the maturing and growth of the egg follicle
  • It is released from the pituitary gland and is inhibited by higher level of progesterone (which is released after the follicle becomes a corpus luteum)
  • Highest levels around day 4 and 12
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70
Q

SB7d - What is LH?

A
  • (Luteinising hormone) is involved in causing the egg to be release
  • It is released from the pituitary gland and is inhibited by higher levels of progesterone but stimulated by higher levels of oestrogen
  • Highest levels around day 13 (with oestrogen)
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71
Q

SB7d - What are progesterone and oestrogen?

A
  • Oestrogen: Causes the uterus lining to thicken and stimulates releases of LH
    • Highest around day 13
  • Progesterone: Inhibits release of LH and FSH
  • Both reduce in concentration after the menstruation but stay constant if the egg is fertilised
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72
Q

SB7c - How do hormone based contraceptions work?

A
  • Release progesterone and oestrogen-like hormones to ‘trick’ the body into thinking the egg is fertilised (due to no drop in concentration after day 28) and stops ovulation
  • Thickens the mucus at the cervix making it harder for sperm to pass through
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73
Q

SB7c - What is contraception?

A

The prevention of fertilisation. e.g:

  • Condom
  • Diaphragm or cap
  • Hormonal pills / implants
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74
Q

SB7d - How can problems with conception be overcome?

A

Using ART (Assisted reproductive technology) (Inc. IVF)

Friggin art students, this is what they’re doing

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75
Q

SB7d - What is clomifene therapy?

A

Used on women who rarely or never release an egg, this uses a drug that increases levels of FSH and LH, this prepares the body for the egg by thickening the lining and stimulates the release of an egg

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76
Q

SB7d - What is IVF and how does it work?

A

In vitro fertilisation is when the egg is fertilised in a lab and the embryo is re-inserted into the women’s uterus:

  • Egg follicle maturation is stimulated by hormones
  • Eggs are released by many follicles and they are taken from the ovary
  • Sperm cells are taken from the man
  • The egg cells and sperm cells are allowed to combine in a petri dish for fertilisation
  • One or two healthy embryos are re-inserted into the uterus
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77
Q

SB7h - How does dialysis work?

A
  • Blood containing waste is taken form the vein and passed through a dialysis machine
  • Dialysis machine contains fluid which has the same glucose concentration as blood plasma
  • There is a semi-permeable membrane which allows the waste and excess substances to leave the blood through osmosis (due to conc. gradient)
  • The same level of glucose on either side of the membrane means there won’t be a net loss/gain
  • The ‘cleaned’ blood is sent back to the person’s veins
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78
Q

SB7h - What is organ donation and why doesn’t it always work?

A

Another person’s kidney is used to replace a faulty one. However:

  • This takes a lot of surgery and may not be suitable for weaker patients
  • Like all cells, the have antigens on them and the recipient’s immune system may attack it. This is called rejection
  • Even with a successful organ donation, the patient needs to be on lifelong medication to weaken their immune system making them more susceptible to other infections
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79
Q

SB7i - What is ADH and how does it do its job?

A
  • Anti diuretic hormone is used to control the water concentration of urine as it leaves the kidney
  • When the pituitary gland detects a low water concentration in the blood it releases ADH
  • ADH makes the collecting duct’s walls more permeable allowing more osmosis of water out through it and making the urine more concentrated with urea
  • A lack of ADH means the collecting duct’s walls are less permeable. Less water leaves through osmosis and so the urine is more dilute
80
Q

SB7i - What are nephrons?

A

Nephrons are tiny microscopic tubes in the kidney where urine is made

81
Q

SB7i - How is the nephron adapted for re-absorption of substances?

A
  • Protein pumps containing mitochondria providing energy for active transport
  • large surface area of contact between nephron and capillaries (convoluted tubes) and…
  • micorvilli on the first convoluted tube. These increase surface area:volume ratio increasing rate of osmosis
82
Q

SB7i - What is filtration in the kidney?

A
  • Blood flows through a network of capillaries (glomerulus) in the bowman’s capsule
  • Here, the smaller molecules (water urea glucose) move into the nephron while larger particles (protein blood cells) stay
  • This is filtration
83
Q

SB7i - What happens at the first convoluted tube of the kidney?

A
  • Selective re-absorption
  • At the first convoluted tube, glucose and some mineral ions are reabsorbed
  • However, if a person is diabetic, not all the glucose will be reabsorbed leaving some in the urine
84
Q

SB7i - What happens at the loop of henle in the kidney?

A
  • Selective re-absorption
  • Here, water is selectively reabsorbed depending on how much is needed in the bloodstream
  • Some mineral ions are also reabsorbed
85
Q

SB7i - What happens at the collecting duct of the kidney?

A
  • Selective re-absorption
  • Some water is reabsorbed depending on how much is needed (ADH dependent)
  • The collecting duct takes the filtered fluids along from the filtered fluids from the second convoluted tube to the ureter
  • Here it is urine and contains excess water, urea and other substances
86
Q

SB7i - What is selective re-absorption?

A

Using active transport to transfer substances back from the nephron into the bloodstream

87
Q

SB8a - What are all the chemical reactions in your body known as?

A

Your metabolism

88
Q

SB8a - What must happen to waste products in your body?

A

They must be excreted so that they don’t cause any problems

89
Q

SB8a - What are some examples of waste products in your body?

A
  • Urea
  • Carbon dioxide
90
Q

SB8a - What are some examples of substances that your body takes in?

A
  • Glucose
  • Amino Acids
  • Oxygen
91
Q

SB8a - Through what process do most substances move around the body?

A

Diffusion

92
Q

SB8a - What do diffusion surfaces have to be like?

A
  • Thin: So particles don’t have to diffuse far
  • Large surface area: More room to allow particles to diffuse through
93
Q

SB8a - Why does blood need to continue flowing for substances to continue moving?

A
  • Oxygen and glucose diffuses out and carbon dioxide diffuses in at a certain point
  • The blood then continues to flow
  • This means that concentration gradient at the diffusion point is maintained
  • This allows diffusion to continue happening
94
Q

SB8a - Why do multi-cellular organisms need transport systems?

A

Transport systems are needed to take substances towards the centre of the body as diffusion from the outside to the centre of the body would take too long

95
Q

SB8a - What is the circulatory system made of?

A
  • The heart
  • Veins
  • Arteries
  • A network of fine capillaries
96
Q

SB8a - How do you calculate surface area : Volume ratio?

A

Surface area ÷ Volume

97
Q

SB8a - Why does SA:V ratio affect rate of diffusion?

A

A higher surface area means more area through which particles can diffuse, but a larger volume takes longer to be filled up

98
Q

SB8a - Why can’t cells be infinitely large?

A
  • As cells get bigger, their SA:V ratio gets smaller.
  • This means it will take longer and longer for substances to enter the cell
99
Q

SB8a - What adaptation do the lungs have?

A
  • The lungs have millions of aveoli which increase the surface area while maintaining the volume.
  • This increases the SA:V ratio increasing rate of gas exchange
100
Q

SB8a - What adaptations do alveoli have?

A
  • One cell thick wall allowing for easy diffusion
  • Large SA:V ratio due to its shape
101
Q

SB8b - What is 1dm3 equal to?

A

1000cm3

102
Q

SB8b - How do you calculate concentration?

A

Concentration (g/dm3)

=

mass of solute (g) / volume of solution (dm3)

103
Q

SB8b - How does concentration gradient affect rate of diffusion?

A

The steeper the concentration gradient (Greater the difference in concentration) the higher the rate of diffusion due to a larger net movement of particles in the same time

104
Q

SB8b - What is the relationship between concentration gradient and rate of diffusion?

A

They have a linear directly proportional relationship

rate of diffusion ∝ concentration difference

105
Q

SB8b - How does surface area affect rate of diffusion?

A
  • A higher surface area means that particles have more area to pass through.
  • This means that more particles can move through a membrane at one time.
  • This increases the overall rate of diffusion but doesn’t change the speed at which particles move
106
Q

SB8b - What is the relationship between surface area and rate of diffusion?

A

rate of diffusion ∝ surface area

107
Q

SB8b - How does the thickness of the membrane affect rate of diffusion?

A
  • A thicker membrane means that particles have a longer distance to travel.
  • This means that the rate of diffusion will be slower
108
Q

SB8b - What is the relationship between thickness of membrane and rate of diffusion?

A

rate of diffusion ∝-1 thickness of membrane

or

rate of diffusion ∝ 1 ÷ thickness of membrane

109
Q

SB8b - What is Fick’s law?

A

Fick’s law shows the relationship between the three factors that affect rate of diffusion.

110
Q

SB8c - What are the jobs of each of the components of the circulatory system?

A
  • Heart: Pumps blood around the body
  • Arteries: Take blood away from the heart
  • Capillaries: Fine networks taking blood to and through tissue
  • Veins: Takes blood back to the heart
111
Q

SB8c - What are the adaptations of arteries?

A
  • Narrow lumen (tube)
  • Thick elastic and muscle fibres
  • This helps it withstand high pressures
  • Recoil due to elasticity helps the blood continue to be pumped
112
Q

SB8c - What are the adaptations of capillaries?

A
  • Capillaries have very narrow lumen (tubes) as they are carrying very little blood
  • They have walls only 1 cell thick to allow for faster diffusion
113
Q

SB8c - What are the adaptations of veins?

A
  • Valves to ensure blood flows in one direction
  • Thin walls as pressure is low
  • Wide lumen (tube) to reduce pressure
114
Q

SB8c - Why are valves only necessary in veins?

A
  • Arteries have blood flowing at a high pressure and this ensures blood flows in the right direction
  • This is helped by the elasticity
  • Veins have blood flowing at a low pressure and so blood isn’t forced to travel in the right direction
  • Valves ensure blood flows in the correct direction
115
Q

SB8c - How do valves work?

A
  • Valves are like one way doors
  • Skeletal muscles help blood move along the veins
  • When blood is flowing in the correct direction, valves are open
  • When muscles are relaxed, blood can easily flow in the wrong direction
  • The moment any blood starts to flow in the wrong direction, the valves close, stopping blood from flowing this way
116
Q

SB8c - What is another word for red blood cells?

A

Erythrocytes

117
Q

SB8c - What are the components of blood?

A
  • Erythrocytes (RBC)
  • White blood cells
  • Platelets
  • Plasma
118
Q

SB8c - What do erythrocytes do?

A
  • Packed with haemoglobin which oxygen binds to allowing it to be transported
  • Biconcave shape to increase surface area for effective diffusion
  • No nucleus to make more space for haemoglobin and oxygen
  • Will turn a brighter shade of red when more oxygen is bound
119
Q

SB8c - What are the two types of white blood cells and what do they do?

A
  • Phagocytes: Surround and consume foreign cells
  • Lymphocytes: Release antibodies to attack foreign cells
120
Q

SB8c - What does plasma contain?

A
  • Water
  • Carbon dioxide
  • Glucose
  • Urea
  • Other dissolved minerals
121
Q

SB8c - What do platelets do?

A

Platelets are tiny fragments of cells that produce substances to allow the blood to clot when injured

122
Q

SB8d - What is a heart attack?

A
  • When blood stops flowing through the heart properly, it can damage the heart muscles.
  • This can cause a heart attack, also known as cardiac arrest.
  • If the heart stops working completely, an electric shock (i.e. a defibrillator) can get it to work again
123
Q

SB8d - What is the structure of the heart?

A

You don’t need to know everythign on this diagram ,and a couple of stuff (e.g. the septum) is missing. But you need to have a general idea of what it looks like

124
Q

SB8d - How does blood move around the heart?

A
  • Firstly, blood from the upper body enters the heart through the superior vena cava; while blood from the lower body enters through the inferior vena cava
  • This travels into the right atrium and through the ventricle
  • The blood leaves through the pulmonary artery into the lungs where it becomes oxygenated
  • It then re-enters the heart through the pulmonary veins
  • Here it travels through the valves and left ventricle before leaving through the aorta
125
Q

SB8d - What is important to remember when looking at diagrams of a heart?

A

You are looking at the diagram as if you are looking at a person (left on right and v/v)

126
Q

SB8d - Why does the left side of the heart have thicker muscle?

A

It has to pump blood to all around the body rather than just to the lungs and so requires more strength

127
Q

SB8d - What is stroke volume?

A

The volume of blood pushed into the aorta per beat

128
Q

SB8d - What is the formula for cardiac output?

A

Cardiac output (litres/min)

=

Stroke volume (litres/beat) x heart rate (beats/min)

129
Q

SB8e - What does your body require a constant supply of energy for?

A
  • Moving
  • Keeping warm
  • Production and breaking down substances
130
Q

SB8e - What is cellular respiration?

A
  • A series of reactions that uses glucose to provide energy for the body.
  • It is exothermic
131
Q

SB8e - Where in the cell does respiration occur?

A

In the mitochondria

132
Q

SB8e - Describe the process of cellular respiration from breathing in to cell to breathing out

A
  • Breathing in adds oxygen into the blood flow
  • As the blood passes the small intestine, it absorbs glucose from digested food
  • When the blood reaches a cell, the cell takes in the glucose and oxygen in exchange for carbon dioxide and water
  • The blood takes this carbon dioxide back to the lungs where it is breathed out
133
Q

SB8e - What is the word equation for respiration?

A

Glucose + Oxygen → Carbon dixoide + Water (+ energy)

134
Q

SB8e - Why is respiration exothermic?

A

It releases energy to its surroundings and the products have less energy than the reactants

135
Q

SB8e - Why do you breathe faster when exercising?

A
  • Faster breathing allows more oxygen to be breathed in and diffused into the blood
  • This provides more oxygen for cells to respire more effectively
  • It also gets rid of more carbon dioxide
136
Q

SB8e - What is the word equation for anaerobic respiration?

A

Glucose → Lactic acid (+energy)

137
Q

SB8e - Why may anaerobic respiration occur?

A
  • Anaerobic respiration occurs in a deficit of oxygen
  • During strenuous exercise, your cells may need more oxygen than can be provided leading to anaerobic respiration occuring
138
Q

SB8e - What are the problems with anaerobic respiration?

A
  • It produces less energy than aerobic respiration
  • Lactic acid building up in muscles can cause cramps and damage
  • Muscles can tire quickly
139
Q

SB8e - Why may anaerobic respiration be important for a prey suddenly escaping its predator?

A

Anaerobic respiration can provide short sharp bursts of energy without needing a sudden increase in oxygen supply

140
Q

SB8e - Why may heart/breathing rates remain high after exercise?

A
  • Extra oxygen is needed to replace what has been lost
  • Extra oxygen is required to provide energy to get rid of lactic acid
141
Q

SB8e CP - Describe how you would investigate rates of respiration in small organisms

A
  • Set up the test tube with a bung attacthed to it so that:
    • A CO2 absorber (e.g soda lime) is at the bottom
    • Cotton wool is on top
    • The organism(s) are on this
    • The blob of coloured liquid is right at the start
    • The 0cm mark of the ruler is lined up with the liquid
  • This is called a simple respirometer
  • You measure how far along the capilary tube the blob moves every so often
  • Distance moved ÷ time = rate of respiration
  • Alter the temperature to see how this affects the rate of respiration
  • This is your independant variable, so ensure you keep everythign else the same as they are your control variables
  • To set up a control experiment for this, you would have the same set-up with no organisms
142
Q

SB9a - Define an Ecosystem

A

An ecosystem is all the organisms and the habitat in which they live

143
Q

SB9a - Define a Community

A

All the organisms that live and interact in an ecosystem

144
Q

SB9a - Define a population

A

The total amount of one species in a population

145
Q

SB9a - Define Interdependence

A

When organisms depend on each other for resources within an ecosystem.

146
Q

SB9a - How do you estimate population size using quadrat experiments?

A

Population size

=

(total size of area where organism lives ÷ total area of quadrats) x

number of organisms in all quadrats

147
Q

SB9b - Once a plant has taken in energy from the sun, where does the energy get transferred to?

A

Much is transferred to plant biomass. The rest is transferred to the environment by heating during the life processes.

148
Q

SB9b - Why isn’t energy transferred to surroundings by heating useful?

A

Other organisms can’t use it.

149
Q

SB9b - Why does a secondary consumer need to eat more then a primary consumer?

A
  • Only some of the energy from the PC’s diet is converted to biomass and the rest is wasted by transferring to heat in the surroundings.
  • Therefore to get the same amount of energy, the SC will need to eat more.
  • This is why there is a limit to the size of a food chain.
150
Q

SB9b - What happens to the biomass at each trophic level (on a pyramid of biomass)

A

It reduces significantly.

151
Q

SB9b - Why is a pyramid of biomass usually bottom heavy?

A

At each level more energy is being wasted so at each level there is less energy to be used and less biomass can be produced.

152
Q

SB9b - Why is there a maximum limit to how many trophic levels a food chain can have?

A

Since there is less biomass at each level, after a certain level, the amount of the lower species you’d have to consume would be too high.

153
Q

SB9c - What is the distribution of organisms?

A

Where organisms can be found in a food chain

154
Q

SB9c - What is an abiotic factor?

A

A non-living factor that affects organisms

155
Q

SB9c - Name some abiotic factors.

A
  • Abundance of Water
  • Light intensity
  • Temperature
  • Wind
  • Pollutants
156
Q

SB9c - What about an organisms may mean that they are affected by abiotic factors.

A
  • An organisms adaptations.
  • If an adaptation is specific to a condition then an abiotic factor that affects that condition will mean that the organism is not longer adapted to their conditions
157
Q

SB9cCP - Quadrats and transects: Compare knowledge of SB9c to this CP.

A

Use CP book for revision

[Will add before real exam]

158
Q

SB9d - What are biotic factors?

A

The organisms in an ecosystem that affect each other.

159
Q

SB9d - What are the two main biotic factors?

A
  • Competition
  • Predation
160
Q

SB9d - Describe what a predator - prey cycle is.

A
  • When a predator eats their prey the population of prey decreases.
  • Now there isn’t enough food for the predator so their population decreases
  • Now that there is less predation, the prey’s population can increase again
  • Now there is more food for the predator so their population can increase again.
  • This goes on and so the predator is affected slightly after the prey
161
Q

SB9d - Explain why a predator - prey cycle may not be seen in larger ecosystems with more biodiversity.

A
  • In an ecosystem with more biodiversity, a predator doesn’t prey on one species and a prey isn’t predated by one species.
  • This means that it is unlikely that one species will ever cause another’s population to decrease and if so, this wouldn’t affect the other species.
162
Q

SB9d - How can adding just one new species to an ecosytem be benefical to the biodiversity?

A
  • New species provide more habitats and/or food for many species.
  • For example in yellowstone when wolves were (re)introduced, this decreased elk numbers increasing beavers and increasing the amount of dams which altogether promoted the biodiversity of the ecosystem
163
Q

SB9e - Name indicator species for levels of water pollution.

A
  • High levels of pollution:
    • Sludgeworm
    • Bloodworm
  • Low levels of pollution:
    • Stonefly nymph
    • Dragonfly nymph
164
Q

SB9e - Name indicator species for levels of air pollution in terms of sulfur dioxide concentration

A
  • Lower levels of sulfur:
    • Blackspot fungus on roses
  • Higher levels of sulfur:
    • Lichens such as Lecanora conizaeoides
165
Q

SB9d - Why is reforestation an effectivce way of preserving biodiversity?

A
  • Trees provide habitats and food for many species.
  • More trees is an effective way of making an ecosystem suitable for more species.
166
Q

SB9e - Why may indicator species not be effective?

A

They don’t give numerical/quantitative results and so aren’t fully accurate and comparable especially as both air and water pollution can be numerically measured.

167
Q

SB9f - What is a parasite?

A

An organism in a feeding relationship with another organism usually harmful to that other organism. e.g Lice and tapeworms

168
Q

SB9f - What is a mutualist (symbiote)

A

An organism in a realtionship with another organism which is beneficial to both as they each provide something to each other. (e.g. bees and flowers or oxpecker and zebras)

V̶e̶n̶o̶m̶ ̶i̶s̶ ̶a̶ ̶f̶i̶c̶t̶i̶o̶n̶a̶l̶ ̶c̶h̶a̶r̶a̶c̶t̶e̶r̶ ̶a̶p̶p̶e̶a̶r̶i̶n̶g̶ ̶i̶n̶ ̶A̶m̶e̶r̶i̶c̶a̶n̶ ̶c̶o̶m̶i̶c̶ ̶b̶o̶o̶k̶s̶ ̶p̶u̶b̶l̶i̶s̶h̶e̶d̶ ̶b̶y̶ ̶M̶a̶r̶v̶e̶l̶ ̶C̶o̶m̶i̶c̶s̶,̶ ̶c̶o̶m̶m̶o̶n̶l̶y̶ ̶i̶n̶ ̶a̶s̶s̶o̶c̶i̶a̶t̶i̶o̶n̶ ̶w̶i̶t̶h̶ ̶S̶p̶i̶d̶e̶r̶-̶M̶a̶n̶.̶ ̶T̶h̶e̶ ̶c̶h̶a̶r̶a̶c̶t̶e̶r̶ ̶i̶s̶ ̶a̶ ̶s̶e̶n̶t̶i̶e̶n̶t̶ ̶a̶l̶i̶e̶n̶ ̶S̶y̶m̶b̶i̶o̶t̶e̶ ̶w̶i̶t̶h̶ ̶a̶n̶ ̶a̶m̶o̶r̶p̶h̶o̶u̶s̶,̶ ̶l̶i̶q̶u̶i̶d̶-̶l̶i̶k̶e̶ ̶f̶o̶r̶m̶,̶ ̶w̶h̶o̶ ̶r̶e̶q̶u̶i̶r̶e̶s̶ ̶a̶ ̶h̶o̶s̶t̶,̶ ̶u̶s̶u̶a̶l̶l̶y̶ ̶h̶u̶m̶a̶n̶,̶ ̶t̶o̶ ̶b̶o̶n̶d̶ ̶w̶i̶t̶h̶ ̶f̶o̶r̶ ̶i̶t̶s̶ ̶s̶u̶r̶v̶i̶v̶a̶l̶.̶

169
Q

SB9g - Why is fish farming needed and what are the problems with it?

A
  • About 17% of the world’s protein consumption is fish based.
  • However overfishing leads to loss of certain fish species.
  • So the solution is to farm fish.
  • Since so many fish are kept in a small space, all their uneaten food and faeces sink to the bottom creating a harmful atmosphere alowing parasites and disease to spread easily throughout fish.
170
Q

SB9g - How may adding non-indigenous species to an ecosystem negatively effect biodiversity?

A
  • After humans have added new species to an ecosystem, these species may outcompete native species for resources meaning the native species reduce in numbers affecting the ecosystem.
171
Q

SB9g - Describe the process of eutrophication.

A
  • Fertiliser is added
  • Heavy rain washes fertilisers off dissolving nitrates and phosphates into soil water
  • If plants take up the nitrates and phosphates and there is still some remaining this gets washed into streams and rivers
  • The high concentration of fertilising substances encourages rapid growth of algae and plants on water surface
  • Surface plants block sunlight and so plants in the water die as they stop photosynthesising
  • The decomposing bacteria increases in numbers and consumes more oxygen
  • Oxygen concentration in water decreases
  • Aquatic animals die due to anoxic water
172
Q

SB9h - What are the benefits and limitations of keeping endagered species in captivity?

A

Pros:

  • Ensure they’re safe
  • Provide them with all needed resources meaning other organisms can’t outcompete them

Cons:

  • They may become habitualised
  • Inbreeding may be required causing many genetic problems
173
Q

SB9h - Why is it important to preserve biodiversity?

A
  • Many organisms are interdependant and all the organisms play an important role in each other’s survival
  • Areas with larger biodiversity have a greater chance of recovering form natural disasters as not every organism will be affected
  • As humans we require plants and animals for many thing (e.g medicine) and so it is important that we preserve all the species we can for when our needs change
174
Q

SB9h - Why is conservation crucial?

A

To ensure that species don’t become extinct

175
Q

SB9i - What is food security?

A

Having access to sufficient safe and healthy food at all times.

176
Q

SB9i - What is the difference in the trends of food consumption between first and third world countries.

A

Wealthier people tend to want:

  • More food
  • More meat and fish produce in their diet

Good thing I’m dirt poor I gueabhfdlbhsl vjl lnsk

177
Q

SB9i - Why is sustainability an issue in agriculture?

A
  • The amount of fertiliser used has increased as to increase the yield of crops.
  • However the process to create fertilisers release carbon dioxide.
  • Additionally, eutrophication can be a problem.
178
Q

SB9i - How can climate change promote the spread of new diseases?

A
  • Climate change can move pests and pathogens into new areas.
  • For example if there is a pest that is a vector for a disease but the pest can only survive in warm conditions, as climate change increases the global temperature, they can go to more places.
179
Q

SB9i - Why is meat an inefficient source of protien?

A

The amount of land and energy taken up to farm and produce meat as a food product is much more than crops. 15 times more protein is produced from soy bean than animals in the same amount of land.

180
Q

SB9i - What are the pros and cons of biofuel.

A

Pros:

  • Less CO2 emisison
  • Crops are easy to obtain

Cons:

  • Land could be used to grow food instead
  • May not be sustainable
181
Q

SB9j - Describe the process of the water cycle.

A
  • Water evapourates from lakes and oceans to form water vapour
  • As water vapour rises it cools, condenses and forms clouds
  • Once cloud droplets get too large precipitaiton occurs
  • Some water runs off the surface directly into the lakes and rivers
  • Other water is percolated
  • some of this moves through rocks and soils till it reaches lakes and rivers
  • the rest is taken up by plants through transpiration and is evapourated directly
182
Q

SB9j - Describe ways water may be made potable.

A
  • Solar stills
  • Nets
  • Distillation
  • Desalination in general. (obtaining pure water from salty water)
  • Treatment with chemicals and filteration
183
Q

SB9j - Describe the main features of the carbon cycle.

A
  • Plants respire and photsynthesise both releasing and taking in carbon
  • Animals feed off plants taking in carbon to their biomass and release it through respiration
  • When organisms die, their biomass is compressed into fossil fuels which release carbon through combustion
  • Soft tissue in the dead organism is eaten by decomposers which release carbon through respiration
184
Q

SB9j - What are the absorbed carbon molecules used for in plants?

A

They are made into carbon compounds like glucose. some may be used for growth as they are converted into biomass.

185
Q

SB9j - How does carbon travel through an animal?

A
  • The carbon is taken in as carbohydrates fats and protiens in another organism and excreted through faeces.
  • Some may be digested and used as biomass in tissue
186
Q

SB9k - Describe the main features of the nitrogen cycle.

A
  • Nitrogen in the air is taken into the soil by nitrgoen fixing bacteria and by lightning
  • Or the opposite way round by breakdown of soil bacteria.
  • Plants absorb nitrates in the soil through their roots or through nitrogen fixing bacteria in root nodules
  • Animals feed on plants takin gin nitrogen
  • Death and excretion of animals means decomposers such a soil bacteria break down the protien and urea to soil nitrates
187
Q

SB9k - Why is nitrogen so important for organisms?

A

Nitrogen is used to from protiens and DNA and this allows organisms to grow.

188
Q

SB9k - Why can’t plant absorb nitrogen form the air?

A

Plants absorb nitrogen through the soluble substances taken up by their root hair cells, thus nitrogen must be in a soluble form to be absorbed by plants.

189
Q

SB9k - Why are decomposers important to farmers?

A

They maintain soil fertility by breaking down substances into nitrogen.

190
Q

SB9k - How may farmers maintin soil fertility in their fields?

A
  • Spreading in manure around the field.The animal waste in this can be broken down to form nitrogen
  • Using fertilisers
  • Using plants that have root nodules and/or digging these roots in
191
Q

SB9k - What is the purpose of root-nodules?

A

They are parts of a plant that contain protected soil fixing bacteria which can produce soluble nitrogen compounds in the soil. (they are in a mutualistic relationship)

192
Q

SB9k - What is crop roation and what is its purpose?

A
  • Rotating which crops are planted when in a ceratin area.
  • This means that the root nodules of one plant rotation make the soil more fertile and useful for the next crop planted increasing the next crop’s yield.
193
Q

SB9m - What do methods of food preservation rely on and why?

A
  • Reducing oxygen and water content as water and oxygen are needed for decomposers to respire and grow
  • Reducing temperature as this reduces the rate of reaction of decomposers
  • Irradiation of food packing as it kills decomposers
194
Q

SB9m - What is compost and why is it used?

A
  • Well-decayed parts of waste garden material.
  • This is used to help crop fertility
195
Q

SB9m -What are the ideal conditions for a crop heap and why?

A
  • Covered top to stop too mcuh rain from entering and too stop moisture and heat from leaving
  • Sides have openings to let oxygen in
  • This is as decomposers require both oxygen and water to respire and grow and higher temperature will increase rate of reaction
  • Compost heaps are turned every so often to ensure even decomposition
196
Q

SB9m - How do you calculate rate of decay?

A

Loss of measure of decay ÷ the time taken

(e.g 6g lost in 3 days means 6 ÷ 3 = 2g/day)

GCSE Biology (11 decks)

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