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General IGCSE Biology > Biology IGCSE > Flashcards

Biology IGCSE Flashcards

To help revise for the Edexcel Certificate in Biology

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1
Q

What is the placenta for?

A

Brings the mothers blood supply close to the blood supply of the foetus, allowing CO2, water and urea to diffuse from the baby to the mother and allowing glucose, amino acids and minerals to diffuse into the blood stream of the foetus

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2
Q

What is an experiment that determines the energy content in a food sample?

A

Measure the mass of the food. Place 20ml of water into a boiling tube. Measure initial temperature of the water. Spear food with a mounted needle and light it up with a Bunsen flame until it catches fire. Place burning food under tube of water. Keep relighting and doing the same until the food no longer burns. Measure the final temperature. Use the equation: Energy= 4.2 x Volume of water x Temperature change (divide by the change in mass of food as a comparative aid)

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3
Q

What does denitrifying bacteria do in the nitrogen cycle?

A

Reduce nitrates to nitrogen

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4
Q

What does the use of cloned transgenic animals have the potential for?

A

Allows mass production of useful chemicals (e.g. insulin, antibodies and even organs)

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5
Q

What causes mutations?

A

Inherited, exposure to ionising radiation, chemical mutagens

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6
Q

Why is it important for plant cells to be turgid?

A

It provides strength and support to the plant. Plants have a cell wall that stop them bursting when turgid. (When plant cells start to lose water they become flaccid, causing wilting. Flaccid cells can become plasmolysed when the cell membrane peels away from the cell wall, killing the cell)

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7
Q

What are the biological consequences of pollution of water?

A

eutrophication

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8
Q

How do vaccinations work?

A

They result in the manufacture of memory cells that enable future antibody production to occur sooner, faster and in greater quantity.

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9
Q

How are enzymes affected by pH?

A

After optimum pH, the active site of the enzyme changes shape (the enzyme is denatured) and stops being able to bind to the substrate.

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10
Q

What does nitrifying bacteria do in the nitrogen cycle?

A

Turn ammonium into nitrate (NO3)2-

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11
Q

Describe an experiment to investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator.

A

Place hydrogen-carbonate indicator in four test tubes, with a leaf in three of them (one without is the control). Place one in the light, one in dark and one in dim conditions. The hydrogen carbonate indicator stays orange in normal CO2 conditions, turns yellow in high CO2 and purple with less CO2.

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12
Q

What should a balanced diet include?

A

Appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre.

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13
Q

What is the role of the phloem?

A

To transport sucrose and amino acids between the leaves and other parts of the plant.

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14
Q

What is the role of the xylem?

A

To transport water and minerals from the roots to the leaves. The xylem consists of dead cells, and only move the water in one direction.

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15
Q

How is the bacteria Lactobacillus used in the production of yoghurt?

A

Lactobacillus uses lactose sugars in the milk to produce lactic acid by anaerobic respiration. The lactic acid affects the milk proteins, making the yoghurt curdle.

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16
Q

What does co-dominance mean?

A

Affect the phenotype equally in the presence of another co-dominant allele.

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17
Q

How does the eye focus on a far away object?

A

Incoming light is parallel so cilliary muscles relax and suspensory ligaments contract, the lens is pulled thin and light is refracted less.

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18
Q

Describe a simple experiment to demonstrate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms.

A

Hydrogen-carbonate indicator solution turns from orange to yellow in the presence of CO2. An organism is placed on a gauze platform above the solution in a boiling tube.

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19
Q

What are the four main stages in the water cycle?

A

Transpiration, evaporation, condensation, precipitation

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20
Q

What are platelets for?

A

Clotting the blood to prevent infection and blood loss.

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21
Q

What does nitrogen fixing bacteria do in the nitrogen cycle?

A

Turns N2 (nitrogen) into ammonium (NH4+)

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22
Q

What causes energy requirements to vary?

A

activity levels, age and pregnancy

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23
Q

How do germinating seeds use food reserves until it can photosynthesise?

A

Seeds contain a small amount of carbohydrate and lipid which is used as a fuel to respire, providing the energy for growth. (The plant must grow leaves before the food store is used up)

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24
Q

How does the body carry out homoeostasis when it is hot?

A

Hairs on the skin lie flat (erector muscles relax), sweat, vasodilation (blood is diverted closer to the surface of the skin - arteriole opens)

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25
Q

When does respiration occur in plants?

A

All the time (day and night).

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26
Q

What are the conditions needed for seed germination?

A

Oxygen, water and correct temperature (warmth)

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27
Q

How does the eye respond to dim light?

A

Photoreceptors detect, radial muscles in the iris contract and ciliary muscles relax. The pupil diameter opens which allows more light to enter the eye.

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28
Q

How are developing embryo’s protected?

A

Amniotic fluid

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29
Q

What do decomposers do in the nitrogen cycle?

A

Turn nitrogen in protein into ammonium (NH4+)

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30
Q

What does the term ‘transgenic’ mean?

A

The transfer of genetic material from one species to a different species.

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31
Q

What does the net exchange of carbon dioxide and oxygen in plants depend on?

A

Intensity of light

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32
Q

Describe the process of eutrophication

A
  1. Excessive nutrients from fertilisers are washed into rivers or lakes.
  2. All of the plants in the ecosystem flourish.
  3. Algae blooms and depletes oxygen from pond. Sunlight is prevented from reaching other parts of the pond and plants die.
  4. Dead plants decomposed by bacteria, causing even more oxygen to be depleted.
  5. Death of ecosystem - not enough oxygen. Fish and all life in pond die.
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33
Q

What are the characteristics of living organisms?

A

Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition, Internal Control

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34
Q

What are the main groups of living organisms?

A

Plants, Animals, Fungi, Bacteria, Protoctists, Viruses

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35
Q

How do plants store carbohydrates?

A

As starch or sucrose

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36
Q

What is an example of a flowering plant?

A

Cereal (e.g. maize)

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37
Q

How do animals store carbohydrates?

A

As glycogen

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38
Q

Can fungi photosynthesise

A

No

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39
Q

Describe the body of a fungus

A

Chitin cell wall. Mycelium made of many thread-like hyphae, with many nuclei.

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40
Q

What is a fungus’ cell wall made of?

A

Chitin

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41
Q

How do fungi feed?

A

By extracellular secretion of enzymes by hyphae onto food, which is then absorbed. Saprotrophic nutrition.

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42
Q

How do fungi store carbohydrates?

A

As glycogen

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43
Q

Give two examples of fungi

A

Mucor, yeast

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44
Q

Are bacteria single-celled?

A

Yes

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45
Q

Do bacteria have a nucleus?

A

No

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46
Q

What do bacteria have instead of a nucleus?

A

Circular chromosome of DNA

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47
Q

How do bacteria feed?

A

Most feed off dead or living organisms. Some can photosynthesise.

48
Q

Give two examples of bacteria

A

Lactobacillus, E.Coli

49
Q

What are protocists?

A

Microscopic single celled oragnisms

50
Q

What are the two types of protocists?

A

Some have animal-like cells (e.g. Amoeba) and live in ponds. Others like Chlorella have chloroplasts.

51
Q

Give a pathogenic protocist?

A

Plasmodium, which causes malaria

52
Q

Are viruses bigger than bacteria?

A

No

53
Q

Where do viruses reproduce?

A

Inside living cells only

54
Q

Do viruses have a cellular structure?

A

No

55
Q

What do viruses have instead of a cellular structure?

A

A protein coat and a nucleic acid (either DNA or RNA)

56
Q

Are viruses parasitic?

A

Yes - they exploit living organisms to stay alive

57
Q

Give an example of a virus?

A

Human Immunodeficiency Virus (HIV)

58
Q

What does pathogen mean?

A

Harmful agent of disease; can be bacterial, viral, fungal or protocist.

59
Q

How are alveoli adapted to gas exchange?

A

One cell thick, Huge SA, alveoli wall is moist, Breathing maintains high concentration gradient, short diffusion distances.

60
Q

Why do multicellular organisms require gas exchange organs?

A

The SA to Volume ratio is very small so they cannot complete gas exchange directly through their skin.

61
Q

How are ions absorbed by root hair cells?

A

Active transport

62
Q

What is transpiration?

A

Water loss by evaporation from the surface of plants

63
Q

What affects rate of transpiration?

A

Temperature, humidity, wind speed, light intensity

64
Q

What is blood made of?

A

Red blood cells, White blood cells (lymphocytes and phagocytes), Platelets, Plasma.

65
Q

How are red blood cells adapted for transporting oxygen?

A

Biconcave shape gives higher SA:volume ratio. No nucleus means more space.

66
Q

What do phagocytes do?

A

Detect foreign bodies and engulf them

67
Q

What do lymphocytes do?

A

Produce antibody proteins which stick to foreign bodies. This stops pathogen from spreading.

68
Q

What are the two main roles of the kidney?

A

Osmoregulation and excretion

69
Q

Where is water reabsorbed into the blood?

A

In the Collecting ducts

70
Q

What happens when blood water levels are too low?

A

Pituitary gland releases more ADH - reabsorbs water from collecting ducts.

71
Q

What does urine contain?

A

Water, urea, salts

72
Q

What is selectively reabsorbed at the proximal convoluted tubule?

A

Glucose

73
Q

What is homeostasis?

A

Maintenance of a constant internal environment

74
Q

What does the CNS consist of?

A

brain and spinal cord

75
Q

What hormone stimulates egg production?

A

FSH

76
Q

What hormone stimulates egg release?

A

LH

77
Q

What hormone stimulates the ovaries to release oestrogen?

A

FSH

78
Q

What hormone stops FSH being produced?

A

Oestrogen

79
Q

What hormone stimulates the pituitary gland to release more LH?

A

Oestrogen

80
Q

What is diffusion?

A

The net movement of particles from an area of high concentration to an area of lower concentration

81
Q

What is osmosis?

A

The movement of particles in a liquid from an area of high concentration to an area of lower concentration across a partially permeable membrane.

82
Q

What is active transport?

A

The movement of substances against a concentration gradient, which requires energy.

83
Q

Give a balanced symbol equation for photosynthesis.

A

6CO2 + 6H2O –> C6H12O6 + 6O2

84
Q

Give the list of bodily structures from organelles to the body.

A

Organelles; cells; tissue; organ; organ systems; body

85
Q

Describe the cellular structure of a bacterium.

A

Bacteria have a cell wall, a cell membrane, a cytoplasm containing a circular chromosome of DNA and plasmids (both of which contain the cell’s genetic material), and occasionally a flagellum.

86
Q

Describe the process of absorption.

A

Products of digestion are absorbed into bloodstream by villi in small intestine.

87
Q

Describe the process of assimilation.

A

The digested food products are absorbed into cells by diffusion. Energy is used to build up into chemicals needed by the cell.

88
Q

How is blood pumped around the body by the heart?

A

Systemic circulation

89
Q

When is the heart in systole?

A

When the chambers contract and force blood out of the heart.

90
Q

When is the heart in diastole?

A

When the chambers relax and the heart fills with blood.

91
Q

What controls the heartbeat rate?

A

The pacemaker region. The heart beats at 70 bpm.

92
Q

What do different parts of the brain control?

A

The cerebrum controls conscious thought; the cerebellum controls coordination; the medulla controls bodily functions; the hypothalamus and pituitary gland control hormonal responses.

93
Q

What do greenhouses and polythene tunnels do to crops?

A

They increase the temperature and humidity, which increases rate of photosynthesis and hence crop yield

94
Q

What are magnesium ions used for in plants?

A

Magnesium ions produce chlorophyll which is used in photosynthesis.

95
Q

What is the function of nitrates in a plant?

A

To make amino acids, which are the building blocks of proteins

96
Q

What is the function of phosphates in a plant?

A

DNA’s skeletal backbone (not the bases) is made of phosphates

97
Q

What is a pesticide?

A

A chemical substance which kills pests but doesn’t damage the crop.

98
Q

What is a biological control?

A

Introducing a living organism which eats the pests but doesn’t harm the plants

99
Q

How do you make beer?

A

Barley seeds are allowed to germinate by soaking them in warm water (malting). They are then roasted and placed in a fermenter with yeast. The yeast feeds off the glucose in the barley (which was produced during germination), and anaerobically respires producing alcohol.

100
Q

What is selective breeding?

A

Making two organisms with characteristics desired by humans reproduce, so that their offspring’s phenotype will have both desired characteristics. This process is repeated over many generations.

101
Q

What is micropropagation?

A

Cells from leaves are collected. These are placed in Petri dishes with agar jelly, nutrients and auxins. The cells (cuttings) grow into individual plant organisms themselves (although cloned from the original plant). This process can be performed on a massive scale.

102
Q

How do you clone animals?

A

An egg cell is collected from a donor and enucleated. The nucleus from a cell from the animal to be cloned is inserted into the enucleated egg. This is then placed into the womb of a surrogate animal.

103
Q

How do you produce insulin?

A

The insulin-producing gene is removed from a human with a restriction enzyme. The bacteria’s genetic material is cut using a restriction enzyme, and then a ligase enzyme is used to join the insulin-producing gene to the bacteria’s genetic material. Then, the gene is re-inserted back into the bacterium via a vector.

104
Q

What is population?

A

The number of organisms of a certain species in the ecosystem.

105
Q

What is a community?

A

A group of different populations living in the same habitat.

106
Q

What is a habitat?

A

The physical, chemical and biological environment an organism lives in.

107
Q

What is an ecosystem?

A

A community of organisms and their habitat.

108
Q

What can you use to estimate the population of a certain area?

A

Using a quadrat.

109
Q

What do quadrats measure?

A

The distribution of organisms in their habitat.

110
Q

What are the four main processes in the carbon cycle?

A

Respiration; Photosynthesis; Combustion; Decomposition

111
Q

What are the effects of deforestation?

A

Leaching, soil erosion, disturbance of the water cycle, disturbance in atmospheric CO2 and O2 balance

112
Q

Describe an experiment to show how enzyme activity varies with different temperatures.

A

The enzyme catalase (found in potatoes) breaks down H2O2 into H2O and O2. The rate of reaction is proportional to the volume of oxygen produced. Changing the temperature will alter volumes of oxygen used.

113
Q

Describe an experiment showing diffusion.

A

Fill a Visking tube with starch solution, and put it into a boiling tube with iodine (which turns blue/black in presence of starch). The iodine will diffuse into the Visking tube and turn blue/black.

114
Q

Describe an experiment showing osmosis.

A

Place a piece of potato in a beaker with water, and another (of equal starting mass and volume) in a sugar solution. Leave the potato pieces for four hours. Potato in sugar will shrink, and potato in water will increase in size.

115
Q

Photosynthesis: Describe an experiment to show the evolution of O2 from a water plant.

A

Measure rate of photosynthesis by collecting the oxygen in a gas syringe and measuring its volume.

116
Q

Describe an experiment to show the role of environmental factors in determining the rate of transpiration from a leafy shoot.

A

Place a potometer in a sink. Cut the leafy shoot at an angle to make it easily enter the rubber tube. Use petroleum jelly to seal joints. A capillary tube is used to magnify uptake. Record the time taken for a bubble to move up the scale.

General IGCSE Biology (8 decks)

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