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Biology Flashcards

1
Q

What are the characteristics of living organisms?

A

They: move, reproduce, sense the surroundings, grow, respire, excrete waste, and need nutrition.

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2
Q

Describe some typical organelles of an animal cell.

A

The nucleus contains genetic material and controls the cell’s activities.
The cell membrane surrounds the cell and controls what goes in and out.
The cytoplasm is where most chemical reactions take place and contains enzymes.

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3
Q

Describe some typical organelles of a plant cell.

A

Chloroplasts carry our photosynthesis, and contain chlorophyll.
The cell wall supports the cell and strengthens it and is made of cellulose.
The vacuole contains ell sap and helps to support the cell.

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4
Q

What are tissues and what are organs?

A

Tissues are similar cells working together to carry out a particular function, for example muscle tissue.
Organs are groups of tissues working together to perform a function.

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5
Q

What makes a plant and what is an example?

A

Plants are multicellular, with features of a plant cell. They also store carbohydrates as sucrose or starch. Eg. Tomato plant.

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6
Q

What makes an animal, and what is an example?

A

They are multicellular, and don’t have chloroplasts or cell walls. Often store carbohydrates in the form of glycogen. Eg. cornetfish.

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7
Q

What makes a fungi and what is an example?

A

These can be single celled. They can have a body of mycelium made up of hyphae. Their cell walls are make of chitin. They have saprotrophic nutrition where they dissolve their food with enzymes and then absorb it. They can store carbohydrates as glycogen. Eg. Yeast.

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8
Q

What makes a protoctist and what is an example?

A

They are single celled, have a nucleus, and some have chloroplasts. Eg. Amoeba.

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9
Q

What makes bacteria and what is an example?

A

They are single celled and don’t have a nucleus. Some have chloroplasts. Eg. Thermus.

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10
Q

What makes a virus and what is an example?

A

They are parasites and depend on living organisms to reproduce. They have a protein coat around some genetic material. Eg. Rabies virus.

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11
Q

What organisms are pathogens and what diseases do they cause?

A

Protoctists can cause malaria. Bacteria can cause pneumonia, and viruses can cause rabies.

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12
Q

What does an enzyme do and what is it made of?

A

It is a catalyst, and speeds up useful chemical reactions in organisms. These reactions are called metabolic.
Enzymes are proteins.

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13
Q

What does an enzyme do in a reaction?

A

It usually breaks up or joins together chemicals, called substrates. The substrate goes into the active site of the specific enzyme and gets reacted.

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14
Q

How does temperature effect enzyme’s work?

A

The temperature changes the rate of the reaction. There is an optimum temp as it gets hotter the substrate particles have more energy and react faster, but after the optimum temperature the enzyme can denature so the active site changes shape and the enzymes don’t work.

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15
Q

Describe an experiment for how temperature affects enzymes.

A

Use drops of iodine in a spotting tile and every five seconds drop in a drop from a solution of starch and analyse. When the enzyme has worked the starch will no longer turn blue black. Control the temp by adjusting a water bath around the solution.

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16
Q

How does pH affect enzymes?

A

It changes the rate of reaction as it changes the shape of the active site and denatures the enzyme as you get further away from the optimum pH.

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17
Q

What is diffusion?

A

The movement of particles from an area where they are highly concentrated to where they are low concentrated.

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18
Q

What is osmosis?

A

The movement of water molecules through a partially permeable membrane from a region of higher water concentration to a lower one.

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19
Q

How are plant cells affected by water amount?

A

When they have lots of water they become turgid and strong. Without lots of water they become flaccid and the plant will wilt.

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20
Q

Describe an experiment for osmosis.

A

Get some visking tubing and fill it with salt solution. Attach a glass tube at the top. Put it in a beaker of pure water and after a day measure how much water has gone up the glass tube.

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21
Q

What is active transport? Where is it used?

A

The movement of particles from a low concentration to a high one (against a concentration gradient) using energy released during respiration. Eg. Plants take in minerals from the soil.

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22
Q

What affects the movement of substances?

A
  • Surface area to volume ratio: movement will happen faster with a large surface area compared to the volume.
  • Temperature - particles move faster the hotter it is.
  • Concentration gradient - if it’s large particles will move faster. Doesn’t affect active transport.
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23
Q

What is the structure of carbohydrates?

A

Contains C, H, and O. Starch and glycogen are long strings of simple sugars.

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24
Q

What is the structure of proteins?

A

Contains C, N, H, and O. It is made up of long chains of amino acids.

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25
Q

What is the structure of lipids?

A

Contains C, H, and O. Made up of fatty acids and glycerol.

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26
Q

What are the tests for different biological molecules?

A
  • Glucose is with Benedicts Reagent goes from blue to green, yellow, orange, and red depending on the amount when heated.
  • Iodine is for starch, goes from brown to blue black.
  • Protein is with Biurette’s solution, goes from blue to purple.
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27
Q

What are the functions of different nutrients?

A

Carbs and lipids provide energy. Protein is for growth and repair of tissue. Iron is needed to make haemoglobin. Fibre helps with the movement of food. Vitamin A is for vision, C for scurvy, D for calcium absorption.

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28
Q

How can you work out the amount of energy food contains?

A

Burn it under a boiling tube containing water and measure the temperature change. The amount of energy in joules is equal to the mass of water (g) x the temp change x 4.2

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29
Q

What do the different enzymes do tho different molecules?

A
  • Amylase converts starch to maltose.
  • Maltase converts maltose to glucose.
  • Protease converts proteins to amino acids.
    Lipase converts lipids to glycerol and fatty acids.
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30
Q

What does bile do?

A

It is produced in the liver and stored in the gall bladder, and in the small intestine it emulsifies fats into smaller drops with a larger surface area.

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31
Q

From the mouth to the pancreas, describe the journey of food.

A
  • Amylase in saliva start to break down food.
  • The oesophagus connects the mouth to the stomach
  • The stomach produces protease and hydrochloric acid (which gives the optimum pH for protease).
  • The pancreas produces protease, amylase, and lipase, which are released into the small intestine.
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32
Q

From the small intestine to the anus describe the journey of food.

A
  • The small intestine produces enzymes, and absorbs all the nutrients.
  • The large intestine absorbs excess water
  • The food moves along through peristalsis, where the muscles squeeze the food along.
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33
Q

What are the main stages of digestion?

A
  • Ingestion (eating/drinking)
  • digestion (breaking it down)
  • Absorption (moving molecules into the blood)
  • Assimilation (the molecules go into the body cells)
  • Egestion (getting rid of faeces)
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34
Q

How is the small intestine adapted?

A

It is very long, and has a large surface area with lots of villi. These have a single layer of cells for quick absorption.

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35
Q

What is the equation for photosynthesis?

A

6CO2 + 6H2O goes to C6H12O6 + 6O2

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36
Q

What are the different parts of a leaf?

A

Waxy cuticle on top, upper epidermis, palisade mesophyll layer, spongy mesophyll layer with air spaces, lower epidermis, and stoma with guard cells.

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37
Q

How are leaves adapted for photosynthesis?

A
  • There are lots of chloroplasts in the palisade layer.
  • The upper epidermis is transparent so light can pass through.
  • The waxy cuticle reduces water loss through evaporation.
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38
Q

What is the effect of light on photosynthesis?

A

Not enough light will slow down photosynthesis. Increasing light will increase the rate of photosynthesis only up to a certain point

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39
Q

What is the effect of CO2 of photosynthesis?

A

Not enough CO2 will slow down photosynthesis.

Increasing CO2 will increase the rate of photosynthesis only up to a certain point.

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40
Q

What is the effect of temperature on photosynthesis?

A

As temperature increases, photosynthesis increases, until it gets too hot and the enzymes start to denature.

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41
Q

How can you test a leaf for starch?

A
  • Kill it with boiling water.
  • Boil it in ethanol in a water bath to get rid of the chlorophyll.
  • Rinse the leaf in cold water and add some iodine.
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42
Q

How can you show that chlorophyll is needed for photosynthesis?

A

Test a variegated leaf for starch.

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43
Q

How can you show that CO2 is needed for photosynthesis?

A

Put a plant in a sealed bell jar with some soda lime that will absorb CO2, then after a while test for starch.

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44
Q

What’s an experiment to find out the rate of photosynthesis?

A

Put some pondweed in a test-tube with water, and attach it to a syringe to draw out the oxygen produced. Vary the experiment by moving a light source closer and further away from the plant.

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45
Q

What are the main mineral ions needed for plant growth?

A

Nitrates, Phosphates, and Potassium, and Magnesium.

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46
Q

Why do multicellular organisms need transport systems?

A

Substances have to travel large distances to reach all the cells, and diffusion would be too slow.

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47
Q

What are the two main transport systems of plants?

A

Xylem tubes transport water and mineral salts from the roots to the leaves.
Phloem tubes transport sugars and amino acids from the leaves to other parts of the plant.

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48
Q

How are root hair cells adapted?

A

There are millions of them and they have a large surface area. They take water in by osmosis.s

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49
Q

How does transpiration work and what are it’s effects?

A

It is caused by the evaporation of water from the plant’s surface. It creates a shortage of water in the leaves, which draws water up through the xylem tubes.

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50
Q

What affects transpiration rate?

A
  • Light intensity makes the stomata open.
  • High temperatures makes the water evaporate faster.
  • Wind speed can change the rate of diffusion.
  • Humidity can change the rate of diffusion.
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51
Q

What is respiration and what is the formula?

A

It’s the process of releasing energy from glucose in the cells of an organism.
C6H12O6 + 6O2 goes to 6CO2 + 6H20 + ATP

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52
Q

What is the difference between aerobic respiration and anaerobic respiration?

A
  • Aerobic is uses oxygen.
  • Anaerobic only uses glucose to get lactic acid and ATP.
  • In plants, anaerobic makes ethanol C6H2O, and CO2 and ATP.
53
Q

How can you test for carbon dioxide with indicator?

A

Use hydrogen-carbonate solution. If there is lots of CO2 it will turn from orange to yellow. If there is not much it will turn purple.

54
Q

How do plants exchange gases?

A

The O2 diffuses out and the CO2 diffuses in. When it is daytime this is the case, but at night the plant only respires so the CO2 diffuses out and the O2 in.

55
Q

How are leaves adapted for gas exchange?

A
  • Leaves are thin so gases only have to travel a short distance.
  • There are air spaces inside the leaf so the gases can easily reach the cells.
  • The underside is covered in stomata to let gases enter and exit.
  • The stomata close at night time.
56
Q

Describe the path of air going into your lungs.

A

It goes down the oesophagus, through the trachea, and down one of the bronchus’s. Then it goes into a smaller bronchiole and into an alveolus.

57
Q

What happens when you breathe in and out?

A

In: Intercostal muscles and diaphragm contract, volume increases, and air is drawn in.
Out: Intercostal muscles and diaphragm relax, volume decreases, and air is forced out.

58
Q

How can you investigate the effect of exercise on breathing rate?

A

Do some exercise and count your breaths for a minute.

59
Q

How do alveoli work and how are they adapted?

A

They are covered in capillaries carrying deoxygenated blood. The CO2 diffuses out and O2 diffuses in.
They have a large surface area and walls only one cell thick. They also have a very large blood supply for a high concentration gradient.

60
Q

What do the different ingredients of tobacco cause?

A

Tar damages the cilia, which means that chest infections are more likely.
The carbon monoxide reduces the amount of oxygen red blood cells can carry. This increases the heart rate and blood pressure, and increases the risk of heart disease.

61
Q

What are the three main parts of blood and what do they do?

A

Plasma carries everything around your body, e.g. Cells, glucose, hormones, etc.
Platelets help blood clot.
Red blood cells carry oxygen with the haemoglobin. They don’t have a nucleus for extra space.

62
Q

What do phagocytes do?

A

They detect pathogens and engulf them.

63
Q

What do lymphocytes do?

A

They produce antibodies that mark pathogens and destroy them. Lymphocytes will stay in the blood afterwards to protect from future pathogens.

64
Q

What are the differences between veins and arteries?

A
  • Arteries have high pressure, so the walls are strong.
  • Arteries carry blood away from the heart.
  • Veins have lower blood pressure, and don’t need to be as thick.
  • Veins have valves to keep blood flow in the right direction.
  • Veins carry blood back to the heart.
65
Q

What are capillaries?

A

They are tiny blood vessels that connect arteries to veins. They have walls only one cell thick, and exchange substances with cells.

66
Q

Describe the structure of the left side of the heart and how blood flows through it.

A

Oxygenated blood comes in through the pulmonary vein, through the left atrium, out the valve, and into the left ventricle. This has a thick muscle and high pressure to pump blood out the aorta to the body.

67
Q

Describe the structure of the right side of the heart and how blood flows through it.

A

Deoxygenated blood comes in through the vena cava, and into the right atrium. It goes through the valve and into the right ventricle where it is pumped through the pulmonary artery to the lungs.

68
Q

Why does exercise increase heart rate?

A

You need more energy, so you respire more. Therefore, there is a greater need for gas exchange, and so your blood needs to be pumped faster.

69
Q

How can hormones control heart rate?

A

Adrenal glands release adrenaline which increases heart rate.

70
Q

Define:
Pulmonary
Hepatic
Renal

A

Lungs, liver, and kidneys.

71
Q

What happens during ultrafiltration?

A

Blood flows through the glomerulus, and water, urea, salts, and glucose are filtered out into the bowman’s capsule.

72
Q

What happens during reabsorption?

A

The filtrate moves through the proximal convoluted tubule, the loop of henle, and the distal convoluted tubule. All glucose is is absorbed, and sufficient salt. The filtrate moves to the collecting duct, and sufficient water is absorbed.

73
Q

What do you call the control of water entering and exiting the body?

A

Osmoregulation.

74
Q

Describe the body’s reaction is the body is dehydrated.

A

The brain detects water loss, and the pituitary gland releases more ADH. This makes the collecting duct more permeable, and the kidney reabsorbs more water.

75
Q

Describe three ways that the carbon in a plant makes it’s way back to the plant.

A

Animals eat the plant and respire.
Dead plants decompose.
We burn things, making Co2.
The Co2 in the air is absorbed by the plant.

76
Q

What are three ways that energy is lost along a food chain?

A

Not all of the food gets eaten.
Energy is lost as heat.
Energy is used for staying alive.

77
Q

What way do the arrows go on a food web?

A

They show the transfer of energy.

78
Q

How can bacteria become anti-biotic resistant?

A

They develop a mutation which lets them survive an antibiotic.
The bacteria reproduces and the gene is passed on.
Now the antibiotic does not work on that bacteria.

79
Q

What is natural selection?

A

Living things have variation.
Individuals compete to survive.
Better adapted individuals survive to pass on genes.

80
Q

How do you use a punnett square?

A

Put the two alleles at the top and two on the side and work out the combinations.

81
Q

How many chromosomes do we have? What do they contain?

A

23 pairs. DNA.

82
Q

What is the difference between DNA and genes?

A

DNA is a string of genes that give the instructions for making an organism.
Genes are a chemical instruction that codes for making one particular protein.

83
Q

Describe the structure of DNA.

A

It is a double helix, Adenine to Thymine and Cytosine to Guanine.

84
Q

What size of organism can cool down quicker?

A

Smaller organisms, because they have a bigger surface area to volume ratio to loose heat.

85
Q

What is homeostasis?

A

It is the maintenance of a constant internal environment.

86
Q

What do you call animals preying on other species and on their own species?

A

Interspecific predation.

Intra specific predation.

87
Q

Describe how fermentation of beer occurs.

A

Starch from barley is broken down into glucose. Yeast uses the glucose to anaerobically respirate, producing CO2 and ethanol.

88
Q

What is active transport and what is needed for it?

A

It is the movement of particles against a concentration gradient. It uses energy from respiration.

89
Q

What is the central nervous system and how does it create responses to stimuli?

A

It is the brain and spinal cord and it transmits information using high speed electrical impulses.

90
Q

What is a reflex?

A

It is an automatic response to a stimulus.

91
Q

Describe a reflex arc in detail.

A

Receptor neurones pick up stimuli.
Sensory neurones send the info to the CNS.
The relay neurone then receives the info across a synapse.
The motor neurone receives the info a cross a synapse. The motor neurone tells the effector what to do.

92
Q

What is the job and location of the following?

  • Conjunctiva
  • Cornea
  • Iris
  • Lens
  • Optic nerve
A
  • This is the very front layer, and lubricates and protects.
  • This refracts light into the eye (under the conjunctiva)
  • This controls the diameter of the pupil.
  • This focuses the light onto the retina (shaped like a ball)
  • This carries impulses to the brain.
93
Q

What are hormones and where are they produced?

A

They are chemicals that send messages to particular cells. They are produced in glands. They are slow and long lasting.

94
Q

What is the source of and effect of the following hormones?

  • ADH
  • Adrenaline
  • Insulin
  • Testosterone
  • Progesterone
  • Oestrogen
A
  • Pituitary gland, increases the permeability of the collecting duct.
  • Adrenal glands, increases heart rate.
  • Pancreas, controls blood sugar level, by stimulating the liver to convert glucose to glycogen.
  • Testes, promotes secondary male characteristics.
  • Ovaries, maintains the lining of the uterus
  • Ovaries, promotes secondary female characteristics.
95
Q

What two things can plants sense?

A
  • They are phototrophic, to get maximum absorption.

- They are geotropic to grow in the right direction.

96
Q

What is the plant hormone, and what does it do in shoots and roots? How does it help with photo and geo tropism?

A

Auxin, which makes plant shoots grow faster, and roots grow slower. More auxin accumulates away from the light, so the shoot grows that direction.
More auxin accumulates under shoots, so it grows faster underneath and angles up.

97
Q

What does asexual reproduction involve?

A

It involves mitosis: an ordinary cell can make a new cell by dividing in two. Both new cells are genetically identical. It only has one parent, and there is no variation.

98
Q

How does mitosis work?

A
  • First, the chromosomes are duplicated, forming X shaped chromosomes.
  • The chromosomes line up, and the cell fibres pull them apart.
  • Membranes form around the sets of chromosomes, and the cytoplasm divides.
99
Q

What are three ways that plants are cloned?

A
  • Cuttings
  • Naturally, with runners or tubers.
  • Micropropagation: this is when plant shoots are taken, sterilised, and placed in a nutrient growing medium. Can be used to create many clones of one plant.
100
Q

How would you clone a mammal?

A
  • Take the nucleus out of any body cell.
  • Take the nucleus out of an egg cell to create an enucleated egg.
  • Put the nucleus into the enucleated egg.
  • Give it an electric shock so that it divides into an embryo.
  • Implant it into the uterus of a female.
101
Q

What are some advantages and disadvantages of GM plants?

A
  • They can be made resistant to pests.
  • They can be made resistant to herbicides.
    But
  • The genes could spread to other plants.
  • It could affect food chains.
102
Q

How do you genetically modify something?

A
  • Cut out the DNA you want to insert with a restriction enzyme.
  • Cut open a vector (e.g. a plasmid)
  • Use ligase enzymes to join together the pieces of DNA.
  • Insert the recombinant DNA into a cell.
103
Q 
What do the following mean:
Habitat
Population
Community
Ecosystem
A
  • The place where an organism lives
  • All the organisms of one species in a habitat
  • All the different species in a habitat
  • A community of organisms and their habitat together.
104
Q

What are two ways in which you can use a quadrat?

A
  • Use it to estimate population size, by placing it randomly, and counting the percentage.
  • Use it along a transect (line) to find out how the distribution of organisms change.
105
Q

Describe the structure of a food chain.

A

It starts with the producer, and then the primary, secondary, and tertiary consumers. These are trophic levels. The arrows show the transfer of energy.

106
Q

How do you draw a pyramid of numbers and biomass?

A

Draw the trophic levels in order, in proportion to the population, or the mass of living material.

107
Q

What are the causes and effects of acid rain?

A
  • They’re caused by burning fossil fuels. This creates sulphur dioxide. This mixes with clouds to form sulphuric acid.
  • It can make water systems more acidic and kill fish. It can also kill trees by damaging leaves.
108
Q

Where do the four greenhouse gases come from?

A
  • CO2 comes from burning fossil fuels and car exhausts.
  • Methane comes from cattle rearing and rotting plants.
  • Nitrous oxide comes form fertilised soil and vehicles.
  • CFCs come from aerosols.
109
Q

How does the greenhouse effect work?

A

Gases in the atmosphere absorb heat radiated out from earth, and radiate it back to earth.

110
Q

Why do we selectively breed, and what is the process?

A
  • Used to develop animals/plants with the best features.

- Organisms with the best characteristics are bred together. The best offspring are then bred together.

111
Q

What are the advantages of glasshouses for growing plants?

A
  • They are warmer.
  • Pests are kept out.
  • Photosynthesis can be increased with artificial light.
112
Q

What are fertilisers made of and what do they do?

A
  • Nitrates, phosphates, and potassium.

- They replace the missing minerals in the soil or provide more of them to increase crop yield.

113
Q

What are two ways of controlling pests, and what are the advantages/disadvantages?

A
  • Pesticides kill pests, but are harmful to humans and other wildlife.
  • Biological control, eg. predators have longer lasting effects and are less harmful to wildlife, but can disrupt the ecosystem.
114
Q

What is eutrophication and how does it happen?

A
  • It occurs when water becomes full of nutrients. This can be from sewage or fertilisers.
  • The extra nutrients cause algae blooms, which block out the light. Microorganisms thrive in the algae, using up all the oxygen in the water. This causes fish to die.
115
Q

What are two effects of deforestation on the soil?

A
  • It allows nutrients to be washed away, leaving infertile soil.
  • The roots don’t hold the soil together, causing erosion.
116
Q

What controls the gender of baby genetically?

A
  • Males have XY and females have XX chromosomes.
117
Q

How can you work out your chances of having a genetic disease?

A
  • Work out which of your parents are carriers/normal/ill, and do a punnet square.
118
Q

What are alleles and what are the two types? What do you call people with two the same and two different?

A
  • Alleles are different versions of the same gene, controlling the same characteristic
  • Dominant alleles are alleles that will always control a phenotype
  • Recessive alleles are alleles that only affect a phenotype when there are two of them.
  • Heterozygous for Aa and homozygous for aa or AA
119
Q

What are the words used to describe a characteristic, and the alleles that cause the characteristic?

A

Phenotype, eg. healthy/normal/green eyes

Genotype, et. HH/Bb/gg

120
Q

Describe what physical changes occur during the different days of the menstrual cycle.

A
  • The uterus starts breaking down for four days.
  • From day 4 to 14 the uterus starts building up again.
  • On day 14 an ovum is released.
  • The wall is maintained until day 28, when it starts to break down again.
121
Q

What three hormones control the menstrual cycle and how?

A
  • Oestrogen causes the lining of the uterus to grow. It stimulates the production of LH, so it peaks between days 4 and 14.
  • LH is stimulated by oestrogen and it causes an egg to be released.
  • Progesterone maintains the lining of the uterus. When progesterone levels fall, the uterus breaks down.
122
Q

What is a way that plants can reproduce asexually?

A
  • Strawberry plants grow runners which turn into new cloned plants.
123
Q

What happens when a flower is fertilised?

A
  • The pollen grain lands on the stigma
  • A pollen tube grows through the style to the ovary.
  • The two nuclei fuse together to form a zygote, which turns into a seed.
124
Q

What are the differences between wind pollenated and insect pollenated flowers?

A 
Insect pollenated flowers have:
- Brightly coloured petals and nectar to attract insects
- Few large, sticky pollen grains
- A sticky stigma
Wind pollenated flowers have:
- Small, dull petals and no nectar
- Lots of small and light pollen grains
- Large and feathery stigma to catch pollen.
125
Q

Describe the male and female parts of a flower.

A

Male:
- The stamen is made up of the anther (which contains pollen grains) and the filament (like a stalk)
Female:
- The carpel is made up of the stigma at the top, the style (the rod), and the ovary, which contains female gametes.

126
Q

What is special about gametes, and what happens when they join?

A
  • They are haploid, and only contain 23 chromosomes.

- When they join, they form a zygote, and then divide through mitosis to form an embryo.

127
Q

How are gametes formed?

A
  • They are formed by meiosis
  • The chromosomes in a cell divide to form x shaped chromosomes and line up in the middle of the cell.
  • The PAIRS of chromosomes are pulled apart, so each new cell has two copies of the same chromosome.
  • The x chromosomes are pulled apart and you end up with four gametes.
128
Q

Why do larger organisms need transport systems?

A
  • Larger organisms have a smaller surface area to volume ratio.
  • Diffusion would be too slow and would not penetrate enough.
  • Transport systems help transport oxygen and nutrients.

IGCSE Revision (7 decks)

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