SB1, SB3, SB5 Biology (Paper 1) Flashcards
1
Q
monomer definition
A
building block
2
Q
asexual reproduction definition
A
reproduction that requires an organism to produce genetically identical offspring eg binary fission
3
Q
Sexual reproduction definition
A
Reproduction that requires a male and female parent to produce genetically different offspring eg humans
4
Q
Advantages of asexual reproduction
A
• Time and energy efficient
• Exploits different environments quickly
• Parents pass down desirable traits
5
Q
disadvantages of asexual reproduction
A
• No genetic variation
• Offspring are vulnerable to environmental changes (they’re unable to adapt)
• Diseases likely to affect whole population
6
Q
Cells produced in sexual reproduction
A
4 haploid genetically different gametes
7
Q
Advantages of sexual reproduction
A
• Genetic variation
• Has survival advantage as offspring can adapt to environment
• Less susceptible to disease
8
Q
Disadvantages of sexual reproduction
A
• Time consuming to find a mate and also to produce
• Difficult for those isolated
9
Q
Diploid definition
A
Gamete containing the full set of chromosomes
10
Q
haploid definition
A
Gamete containing half the number of chromosomes
11
Q
What is a nucleotide made up of?
A
• Phosphate
• Sugar
• Base
12
Q
Polymer definition
A
a long chain of molecules
13
Q
Genome definition
A
The entire set of the genetic material of an organism
14
Q
what are the complementary base pairs?
A
Adenine and Thymine, Cytosine
and Guanine
15
Q
What are complementary base pairs held together by?
A
Weak hydrogen bonds
16
Q
how many bonds do thymine and adenine have compared to guanine and cytosine?
A
2 compared to 3
17
Q
RNA meaning
A
ribonucleic acid
18
Q
examples of RNA molecules
A
mRNA and tRNA
19
Q
Mutation definition
A
A rare and random change in the sequence of DNA bases
20
Q
Gene definition
A
section of DNA that codes for a particular sequence of amino acids
21
Q
what base do RNA molecules have instead of Thymine?
A
Uracil
22
Q
What are the 2 processes in protein synthesis
A
Transcription and Translation
23
Q
Where does transcription take place?
A
in the nucleus
24
Q
Where does translation take place?
A
In the cytoplasm
25
What is the enzyme used in transcription?
RNA polymerase
26
What is RNA polymerase?
Enzyme that synthesises the mRNA strand by binding to the non coding section of DNA
27
what happens in transcription? (Takes place in nucleus)
• DNA’s double helix unzips (as weak hydrogen bonds break)
• Free mRNA nucleotides attach to complementary DNA bases
• mRNA strand is produced and it leaves the nucleus via nuclear pore (gap)
28
what takes place in translation? (Takes place in cytoplasm)
• mRNA attaches to ribosomes
• tRNA contains an amino acid binding site and also an anticodon to join to mRNA
• ribosome reads 2 codons at a time and every codon codes for one amino acid
• amino acids join through peptide bond
• polypeptide produced
29
What is a codon?
Triplet of bases
30
What codes for an amino acid?
a codon (triplet of bases)
31
What does salt do in DNA extraction?
sticks the DNA together
32
Why is ethanol used in DNA extraction?
Ethanol precipitates the DNA (makes it a visible)
33
Why is detergent added in DNA extraction?
Breaks down nuclear and cell membranes
34
Why is the fruit mashed?
(DNA extraction practical)
To make the DNA easier to extract
35
Why is the ethanol ice cold?
(DNA extraction practical)
DNA is insoluble in cold ethanol
36
Why is the mixture filtered in DNA extraction?
to remove any debris (insoluble parts) from the mixture
37
What would the DNA appear as during extraction?
A stringy white precipitate
38
Precipitate definition
To be made visible
39
Allele definition
Variations of the same gene
40
Phenotype definition
Observable characteristics that are expressed in an organism
41
Genotype definition
Combination of alleles that controls a characteristic
42
Dominant allele
Allele that is always expressed even with only one copy present
43
Recessive allele
Allele only expressed when 2 copies are present
44
Homozygous definition
2 of the same alleles in a gene
45
Heterozygous definition
When 2 alleles in a gene are different
46
Chromosome definition
Thread like structure of DNA that carry genes
47
What did Gregor Mendel study?
How characteristics were passed down between pea plant generations
48
What does a punnet square diagrams show?
The possible combinations of alleles that could be produced in the offspring
49
Monohybrid inheritance
When a single gene controls the inheritance of characteristics
50
Female sex chromosome
XX
51
Male sex chromosome
XY
52
What is a family pedigree diagram?
Used to trace the pattern of inheritance of a certain characteristic through family generations
53
What can we learn from a family pedigree diagram?
The probability that someone will inherit a disease or disorder
54
Codominance definition
When both alleles in a gene are expressed
55
What blood group is recessive?
O
56
Sex linked inheritance definition
When alleles are found on the sex chromosome
57
Why are there usually alleles on only the X chromosomes during sex linked inheritance?
X chromosomes are much larger than Y chromosomes
58
Polygenic meaning
Characteristics controlled by more than one gene
59
Example of polygenic inheritance
Eye colour
60
Why are males more likely to have sex linked characteristics?
Males only have 1 X chromosome therefore the allele would always be expressed
61
Structure of DNA
A double helix formed by two complementary strands of nucleotides
62
Magnification of eyepiece lens
X10
63
Monomer of starch
Glucose
64
Function of protease in DNA extraction
It breaks down proteins in cell and nuclear membranes
65
What are the types of mutation?
Insertions, deletions and substitutions
66
Insertion mutation definition
When a new base is randomly inserted into the DNA sequence
67
Deletion mutation definition
When a base in the DNA sequence is randomly deleted
68
Substitution mutation definition
When a base in the DNA sequence is randomly replaced
69
Causes of mutation
Gamma rays, x rays, ultraviolet rays, chemicals such as tar in tobacco
70
What does a genetic variant affect in non coding DNA?
ability of RNA polymerase to bind
71
Effects of the inability of RNA polymerase to bind
less mRNA would be transcribed therefore less protein would be produced
72
Cause of genetic variants in coding DNA
mutation
73
Effect of the coding region of DNA being altered
The active site of an enzyme would change making it difficult for the substrate to bind
74
Why can mutations be advantageous to a species?
• New alleles are developed and this creates new phenotypes
• This can give an individual a survival advantage
(Eg being able to run faster)
75
What does a polypeptide do to form a protein?
It folds
76
Why is the solution heated up during the process of dna extraction?
To denature the enzymes and prevent the DNA from being digested
77
How is a gene represented in codominance?
I
78
How is an allele represented in codominance?
A B or O
79
What are the blood groups?
A B AB O
80
What are the 3 transport processes?
Osmosis, active transport and diffusion
81
What is the Human Genome Project?
A collaborative research effort to find out the human genome’s DNA sequence
82
What does the Human Genome Project help with?
• Prediction and prevention of diseases
• Testing and treatment
• Development of new medicines
83
How does the Human Genome Project help with prediction and prevention?
It helps doctors identify any faulty genes and give advice on diet to avoid/delay the disease
84
How does the Human Genome Project help with testing and treatment?
It allows doctors to identify faulty alleles quicker and provide treatment earlier
85
How does the Human Genome Project help with development of medicines?
Doctors are able to design personalised medicines to improve effectiveness and reduce side effects
86
Disadvantages of the HGP
• someone may suffer from increased and unnecessary stress or anxiety • could be pressured into not having children
87
Variation
Differences between individuals of the same species
88
Continuous variation
when differences for a characteristic falls within a range
89
Discontinuous variation
When differences for a characteristic belongs in a group
90
How is genetic variation caused?
Meiosis creates genetic variation between gametes produced by an individual
91
How is environmental variation caused?
Environmental factors eg climate, diet and culture
92
What is discontinuous variation caused by?
genetic variation alone
93
Examples of phenotypes caused by a combination of genetic and environmental variation
Height and Weight
94
Examples of genetic variation
Blood group, eye colour, gender
95
Examples of environmental variation
accent for a language, weight gain from eating too much, scar from an accident
96
2 ways variation can be grouped
Continuous and discontinuous variation
97
A combination of genetic and environmental causes contribute to
continuous variation
98
(SB5)
Definition of health
A state of complete physical, mental and social wellbeing and not merely the absence of disease (WHO)
99
What are the 3 types of well beings?
Physical, social and mental well being
100
Disease definition
A problem with a structure or process in the body that hasn’t occurred from an injury
101
What are communicable diseases caused by?
Pathogens entering the body changing how it works
102
What are microorganisms that cause diseases called?
Pathogens
103
Communicable disease meaning
A disease caused by pathogens which can be spread from person to person
104
Non-communicable disease meaning
A disease not caused by a pathogen and is unable to be passed on from person to person
105
Why can the presence of a disease lead to a higher susceptibility to other diseases?
• The immune system can be compromised
• Meaning that white blood cells are reduced making someone more vulnerable to infection
106
What are the 4 pathogens?
• Fungi • Bacteria • Viruses • Protists
107
Risk factors for obesity and malnutrition
A lack of exercise and a poor diet
108
Cause and Effect of obesity
Eating significantly more calories than we burn • Increases the risk of other non communicable diseases (Type 2 diabetes and atherosclerosis)
109
Cause and effect of malnutrition
Eating fewer calories than we burn (deficiency) • Causes brittle bones (low calcium levels)
110
BMI is an abbreviation for
Body Mass Index
111
Equation for BMI
Weight / Height²
112
Risk factor for liver diseases
High intake of alcohol for a long period of time
113
What are alcoholics more susceptible to?
Liver failure and cancer (uncontrollable cell division in DNA)
114
Risk factor for lung diseases
• Smoking
• Tar produces carbon monoxide which reduces the lungs surface area
• This decreases gas exchange and the oxygen transported
• Leads to less respiration
115
What diseases can smoking cause and why?
Pneumonia and lung cancer: • (Tar chemical causes lung cancer) • (Nicotine chemical causes atherosclerosis and high blood pressure)
116
Define atherosclerosis
Build up of fat in arteries restricting the flow of blood
117
Risk factors for cardiovascular disease
Smoking • Poor diet • Lack of exercise • High alcohol consumption
118
Effects of atherosclerosis
• The individual will suffer from high blood pressure
• Increases chances of blood clots and heart attacks/strokes (CVD diseases)
119
Definition of alveoli
Air sacks in the lungs with a large surface area to support gas exchange
120
Carcinogens meaning
Chemicals that lead to mutation
121
Risk factor meaning
Something an individual does to increase the likelihood of getting a disease
122
What is cardiovascular disease?
• Disease of the heart / circulatory system
• Sometimes as a result of high cholesterol levels
123
What does the immune system do?
Protects the body from infection
124
Ways of measuring obesity
BMI and waist:hip ratio
125
What chemical can cause atherosclerosis?
Nicotine
126
How can pathogens spread?
• **Air** (pathogens in the air through the wind or from sneezing)
• **Water** (pathogens that live in dirty water)
• **Oral transmission** (pathogens ingested through food/water)
• **Direct contact** (exchange of saliva, blood or semen)
• **Animal vectors** (Animals that carry pathogens)
127
What can the spread of pathogens lead to?
Diseases:
**Airborne:** Colds, influenza, Chalara ash dieback
**Waterborne:** Cholera
**Oral transmission:** Stomach ulcers
**Direct contact:** HIV, Chlamydia, Ebola
**Animal vectors:** Malaria
128
How can infections such as colds or chalara ash dieback be prevented?
(airborne diseases)
**Animals:** Avoiding crowded areas, good hygiene, having ventilation
**Plants:** Preventing the import of trees or cutting down trees known to carry the disease
129
How can infections such as cholera be prevented?
(waterborne diseases)
Avoiding poor quality water (eg by filtering or purifying tablets) and consuming clean water instead
130
How can infections such as stomach ulcers be prevented?
(orally transmitted diseases)
Ensuring food is cooked properly and by having good hygiene standards
131
How can infections such as Chlamydia and Ebola be prevented?
(Diseases through body fluids)
Wearing protection • screening after sex • Avoid sharing needles
132
How can infections such as malaria be prevented?
(Diseases carried by vectors)
• Mosquito nets
• Taking malaria tablets
• Preventing the vector from reproducing (removing stagnant (dirty) water)
133
Characteristics of bacteria
• Doesn’t always affect host cells
• Toxins it produces can damage cells
• It’s small and can reproduce very quickly
134
What diseases can bacteria cause?
Tuberculosis • Cholera • Stomach ulcers • Chlamydia
135
Tuberculosis and its effects
Bacteria is transmitted through the air • Caused by poor hygiene • Damages the lungs
136
Cholera and its effects
• Waterborne disease spread through bacteria • Can lead to diarrhoea and vomiting
137
Characteristics of protists
Diverse group of multi and unicellular organisms • Need a host to survive (parasite)
138
Parasite meaning
Organisms that need a host to survive (Protists and Viruses)
139
What disease can protists cause?
Malaria
140
Malaria and its effects
• Disease spread by mosquitoes • Causes damage to the blood and liver
141
Vector meaning
Carrier of a pathogen that causes a disease
142
Fungi characteristics
• More common in plants than animals
• Can be single or multi cellular
• Produces spores and can infect organisms through the air
143
Chalara Ash Dieback and it’s effects
• Airborne disease that affects ash trees • Causes dark patches, early leaf loss and bark lesions
144
Characteristics of viruses
• Not considered a living organism • Do no carry out the 7 life processes • Takes over a host cell in order to reproduce (parasite)
145
Ebola and its effects
• Virus transmitted through body fluids
• Causes headaches, rashes and haemorrhagic fever
146
HIV (Human Immunodeficiency Virus) and its effects
• Sexually transmitted disease
• Destroys white blood cells in immune system
• Weakens the immune system leading to the onset of AIDS
• Therefore the body is unable to destroy the specific pathogen it may get infected by
147
What disease can Fungi cause?
Chalara Ash Dieback
148
What diseases can viruses cause?
Ebola and HIV
149
Structure of viruses
• Have no cellular structure
• Have a protein coat (protects genetic material)
• Contain one type of nucleic acid (DNA or RNA)
150
2 pathways viruses use to reproduce
• Lytic pathway • Lysogenic pathway
151
Which pathway that viruses use is quickest?
The lytic pathway
152
Describe the process of the lytic pathway
• Virus infects host cell and injects its DNA into cytoplasm (to control the cell’s machinery)
• Virus uses the enzymes in host cell to produce new virus particles
• Cell bursts (lyses) releasing virus particles into the host to infect more cells
153
Describe the process of the lysogenic pathway
• Virus injects it’s DNA to the host cell and becomes incorporated into the host DNA
• As host cell replicates the viral DNA replicates
• No new viruses are made as the virus is dormant
• Changes in the environment causes the viral DNA to move to the lytic pathway to make new virus particles
154
Why aren’t antibiotics effective on viruses?
• Viruses have a different structure to bacteria and they don’t carry out the same life processes
• They also reproduce inside host cells while bacteria don’t
155
What type of defences do plants have to infections and infestations?
Chemical and physical defences
156
Chemical defences plants have to prevent infection from pathogens
• They release chemical poisons (to deter/kill insects)
• Can release antibacterial chemicals to kill bacteria
[• Mechanisms to attract other insects (eg colour) in order to remove pests]
157
Physical plants defences that help prevent infection
• Waxy cuticle acts as a barrier to microbes from entering
• Cellulose cell wall makes it difficult for pathogens to penetrate
• Thorns make it difficult for pests to access the plant tissue
158
How would you test the soil in order to identify and detect plant diseases?
Take a sample of the soil and send it to a lab to test for pH or nutrient levels (to identify if it’s due to an environmental factor)
159
How would you use drones to detect and identify plant diseases?
Use a drone to map out the distribution of symptoms to determine how the disease has spread (taking samples to test for pathogens)
160
How would you use knowledge from books to identify and detect plant diseases?
Examine the area around the plant and use books to compare with known plant diseases to identify any pathogens or also a pattern
161
Two examples of ways plant diseases can be identified
• DNA analysis (testing for pathogenic DNA)
• Monoclonal antibodies (identifying antigens from pathogens)
162
What forms the first line of defense
Physical and chemical barriers
163
Physical barriers in humans
• Skin (covers the body to prevent infection and forms a scab if it gets cut)
• Hairs and mucus in the nose (prevent pathogens from being inhaled)
• Mucus and cilia in lung airways (to trap pathogens and waft mucus to the back of throat)
164
Chemical barriers in humans
• Stomach acid (contains hydrochloric acid strong enough to kill pathogens)
• Lysozymes (enzymes produced in tears from the eye that kill bacteria)
• Sebum (oily substance on skin that kills bacteria & fungi)
165
What is the second line of defence?
The immune system
166
What are the two main types of white blood cells?
Phagocytes (carry out phagocytosis) and Lymphocytes (produces antibodies)
167
How do phagocytes protect the body from pathogens?
• Phagocytes have a sensitive cell membrane to detect pathogenic chemicals • They engulf and digest the pathogens (phagocytosis) after identifying them
168
How do lymphocytes protect the body from pathogens?
• B-lymphocytes produce antibodies specific to the antigen on a pathogen to destroy it • Memory lymphocytes are produced to prepare for a secondary response
169
What are vaccines?
When weaker or dead versions of a pathogen are injected into the bloodstream to trigger an immune response
170
How does future infection affect immunity after vaccination?
Infection by the same pathogen will trigger a response much faster and larger than the initial (due to the memory lymphocytes in the bloodstream)
171
Reasons why people may not be immunised against a disease
• Side effect concerns • Lack of access to healthcare • Immunodeficiency
172
Herd immunity meaning
• When a large number of the population are vaccinated • This makes non - immunised people less likely to be infected
173
What are antibodies?
Y shaped proteins with a shape complementary to an antigen
174
What are antigens?
Molecules found on the surface of pathogens complementary to an antibody
175
Function of goblet cells
They produce mucus to trap pathogens in lung airways
176
2 types of medicines used to treat a disease
• Medicines that treat the cause (eg antibiotics) • Medicines that treat the symptoms (eg painkillers)
177
What are antibiotics?
Medicines that help cure bacterial diseases by killing infective bacteria (eg penicillin)
178
How do antibiotics work?
They inhibit processes in bacterial cells such as cell wall production or breaking down cell membranes (to prevent reproduction) • They only affect processes in bacteria so they aren’t harmful to host cells
179
How can bacteria become resistant to antibiotics?
• People do not finish their course of antibiotics • Some bacteria have mutations which leads to variation therefore natural selection occurs (where the more resistant bacteria can survive)
180
Evolution meaning
Gradual change in species over time
181
What did Alexander Fleming discover?
He discovered penicillin through finding out that mould releases a chemical that kills bacteria
182
What are new drugs tested for?
Toxicity (harmful side effects) • Efficacy (how well it works) • Dose (lowest dose that can make an impact)
183
What is preclinical testing?
Drug testing done in a lab using cells, tissues and live animals • Efficacy and toxicity are tested
184
What do clinical trials involve?
Drug testing on healthy volunteers at a low dose • Then tested on patients with the condition
185
What do double blind studies involve?
Patients are split into a group getting the active drug and another group getting a placebo • Neither the doctor or patient knows what is being given • The lowest effective dose is tested once it’s found to be safe
186
4 stages of drug development
• Preclinical testing • Clinical trials on healthy volunteers • Clinical trials on patients • Double blind study
187
Disadvantages of using other mammals for drug testing
• It could cause harm
• Could affect them differently from humans
188
Placebo meaning
An inactive substance given to someone instead of a medicine
189
Aseptic technique meaning
Method that prevents contamination by harmful microorganisms
190
Aseptic technique examples
• **Not putting sterile equipment down** (eg pipette - to prevent microorganisms being transferred)
• **Strongly heating the neck of the bottle of bacteria culture** (to kill any microorganisms and cause air to move away)
• **Lifting the Petri dish lid slightly** (to reduce the micro organisms contaminating the agar)
• **Placing the pipette in disinfectant** (kills any bacteria on it)
191
Why do we mark the bottoms of the Petri dish into different sections?
It helps us know which antibiotic disc went where
192
Why is a control disc placed in the Petri dish?
To ensure that the bacteria has grown and that any clear space is due to the antibiotics
193
Why is the lid taped onto the Petri dish at the end?
To seal the dish and reduce anaerobic pathogens growing
194
Why is the Petri dish turned upside down?
To prevent condensation onto the agar
195
What variable goes on the x axis?
Independent variable
196
What variable goes on the y axis?
Dependent variable
197
How is the bacteria culture spread onto the agar plate and why?
Using the forceps with a side to side motion as it ensures all the agar plate is evenly covered
198
Examples of CVD
• Coronary heart disease (disrupted blood flow to heart)
• Strokes (disruption of blood flow to brain)
• Aortic disease (type of blood vessel affected)
199
How does cholesterol increase the risk of CVD?
• It contributes to the build up of fatty plaques inside the coronary arteries
• This reduces the flow of blood therefore less oxygen is supplied
200
How do you calculate zone of inhibition?
πr²
201
Ways of treating CVD
• Surgical procedures
• Lifelong medication
• Lifestyle changes
202
What surgical procedures can treat CVD?
• Coronary bypass surgery
• Heart transplants
• Stents
203
How does coronary bypass surgery (surgical procedure) treat CVD?
• It involves replacing damaged vessels with healthy vessels from elsewhere in the body • This allows blocked sections of the heart to be bypassed/replaced • Supports uninterrupted blood flow
204
How do heart transplants (surgical procedure) treat CVD?
• It involves replacing a failing heart with a healthy heart from a dead donor
• It carries the risk of rejection and therefore the heart may not work at all
• Patients would need to be on medication permanently
205
How do stents (surgical procedure) treat CVD?
• A narrow tube is inserted into the blocked vessel so that the lumen widens • This increases the blood flow and therefore more oxygen is delivered • Balloon and tube are then removed
206
What is lumen?
The space inside a blood vessel
207
How does lifelong medication treat CVD?
• It involves the use of statins
(drugs used to reduce levels of cholesterol)
• They block an enzyme in the liver needed to make cholesterol
• This slows down the rate of fatty material building up in the blood
208
What drug reduces the levels of cholesterol in the blood?
Statin
209
How do lifestyle changes treat CVD?
• **Smoking prevention** reduces likelihood of atherosclerosis
• **Maintaining a balanced diet** eg:
- Low cholesterol (reduces atherosclerosis likelihood)
- Low salt (reduces high blood pressure risk)
• **Exercising** to maintain a healthy weight
210
What are monoclonal antibodies?
Identical copies of one type of antibody
211
Where is cholesterol synthesised?
In the liver
212
How are monoclonal antibodies formed?
• Isolate antigen from the pathogen
• Inject the antigens into a mouse to stimulate an immune response
• Lymphocytes will produce antibodies complementary to the antigen
• The lymphocytes are then removed from the mouse and fused with fast-dividing myeloma (tumour) cells
• This produces hybridoma cells that divide rapidly to produce millions of monoclonal antibodies specific to the original antigen
213
Scientific uses of monoclonal antibodies
• Pregnancy tests
• Cancer diagnosis (locate blood clots)
• Cancer treatment
214
How are monoclonal antibodies used in pregnancy testing?
• The pregnancy test detects a hormone (hCG) in urine
• The hormone binds to the antibody on the test as they’re complementary
• Antibody has a coloured bead attached to it
• A line appears because they’re immobile antibodies in the test window
215
Advantages of using monoclonal antibodies
• They only bind to molecules on a specific cell therefore no healthy cells are affected
• This causes fewer side effects
216
How are monoclonal antibodies used to treat diseases eg cancer?
• The monoclonal antibody is bound to a radioactive substance / drug
• It delivers the substance to the cancer cell and stops it from growing and dividing
• Other cells in the body are left unharmed
217
How are monoclonal antibodies used to locate blood clots?
• Radioactively labelled monoclonal antibodies bind to proteins in a blood clot
• A special camera creates an image of the radiation
• This locates the blood clot
218
Ways of visually detecting a plant disease
• Stunted growth
• Spots on leaves
• Discolouration
219
Reagent for protein
• Biuret solution (tests for peptide bonds)
• Changes from blue to purple in the presence of proteins
220
Reagent for reducing sugars
• Benedict’s solution
• Colour changes from blue to green/yellow (in low sugar amounts) or red (in high sugar amounts)
221
Describe the emultion test
• Add ethanol to food
• Mix them together
• If a white precipitate is formed, lipids are present
222
How many types of nucleotides are there?
4 (as there’s 4 bases)
223
Equipment used to measure rate of transcription
Potometer
224
What colour does hydrocarbon indicator turn during the lack of co2?
Turns from red to purple
225
Genetic variation meaning
Differences in the inherited genes of an individual due to variation from sexual reproduction
226
Environmental variation meaning
Differences in the conditions an organism develops in
227
Differences between light and electron microscopes
**Light microscopes:**
• Relatively cheap and easy to use
• Rely on light to magnify images
• Resolution limited to 0.2 um (micrometers)
**Electron microscopes:**
• Very expensive and hard to use
• Use electrons rather than light
• Max resolution 2000x better
• Can be used to study sub cellular structures
228
What is an um?
A micrometer
229
Micrometer
10 ^ -6 metres
230
Nanometer
10 ^ -9 meters
231
Picometer
10 ^ -12 meters
232
Adaptations of sperm cell
• A long flexible tail allows it to swim
• Large number of mitochondria provides energy
• Head has an acrosome which contains enzymes and help it break through the membrane of the egg
233
Adaptations of egg cell
• Cell’s membrane changes after fertilisation to prevent more sperm entering
• Cytoplasm contains nutrients which will feed developing embryo
234
Adaptations of ciliated epithelial cells
• Cilia beat from side to side to sweep away mucus
• The mucus then traps bacteria and dust preventing damage to lungs
235
Resolution meaning
The ability to distinguish between points close together
236
What does amylase do?
Breaks down starch into simple sugars
237
What does protease do?
Breaks down proteins into amino acids
238
What does lipase do?
Breaks down lipids (fats) into fatty acids and glycerol
239
How is calorimetry carried out?
• Weigh food sample
• Fix food sample onto mounted needle
• Pour volume of water into test tube and record it
• Measure temperature of water at the start
• Set food on fire and hold it closely under tube
• Measure temperature at end and calculate increase
240
What is the theory of evolution by natural selection?
• Organisms in a species have variation (eg due to mutation)
• There would be selection pressures in environment
• Organisms best suited will survive
• Offspring inherit beneficial allele
• This is repeated over many generations
241
What theory did Wallace develop?
Theory of speciation
242
What is speciation?
The formation of new species
243
2 ways speciation can develop
• Isolation (difference in environment)
• Natural selection
244
What does GENIE mean?
• Genetic variation
• Environmental pressures
• Natural selection
• Inheritance
• Evolution
245
How do bacteria develop resistance to antibiotics?
• Variation in population
• Some bacteria develop a resistance through mutation
• Antibiotic treatment exerts selection pressure
• Bacteria resistant to antibiotics survive and reproduce
• Antibiotic resistance is inherited
• Overtime, antibiotic resistance in population increases
246
How does the use of antibiotics contribute to bacteria developing resistance?
• Not completing course of antibiotics
• Overuse of antibiotics
247
What are the three hominid fossils?
• Ardi
• Lucy
• Turkana boy
248
Ardi characteristics
• Female
• Ape-like big toe for climbing
• Short legs but long arms
• Brain same size as chimpanzee
249
Lucy characteristics
• Female
• Arched feet for walking and didn’t have ape like big toe
• Limbs size between ape and human
• Brain slightly larger than Ardi’s
250
Turkana boy characteristics
• Male
• Human like legs and arms, suggesting he walked more upright
• Brain size similar to human’s
251
3 ways to date stone tools
• Structural features (simpler tools are older)
• Rock layer location
• Carbon 14 dating
252
How may some of the tools have helped early humans to survive?
• Arrowhead to hunt for prey
• Making tools to help make fire
253
How do pentadacytl limbs provide evidence evolution?
• They have fairly similar bone structures
• Suggesting a common ancestor that also had this limb structure
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What is the 3 domain system?
• Archaea (bacteria usually in extreme environments)
• Bacteria (true)
• Eukaryota (protists, fungi, plants, animals)
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Sequence of classification of new system
• Domain
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species
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Why was the 3 domain class system proposed?
Genetic analysis showed that DNA of archea was more similar to eukaryotes
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Process of selectively breeding organisms
• Breed two organisms with desirable characteristics
• Select offspring that have desirable trait
• Repeat process over many generations
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Tissue culture definition
When very small pieces of organisms are grown using nutrient media
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Problems with selective breeding
• Can lead to inbreeding
• Reducing the gene pool
• Making organisms vulnerable to new diseases
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Tissue culture in plants
• Parent plant is chosen with desired traits
• Small amount of tissues is scraped from parent plant
• Under aseptic conditions, tissue pieces are transferred to sterile Petri dish (preventing growth of harmful pathogens)
• Auxins are added to encourage explant cell growth
• Plantlets are formed which can be transferred into compost and develop more
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Benefits of tissue culture
• Increases yield
• Cheap
• Quick
• Can be done at any time
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Animal tissue culture
• A sample of tissue is extracted from animal
• Enzymes separate the cells that make up tissue
• Cells are placed in culture vessel with growth medium
• Once grown it can be stored for future use
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Advantages of tissue culture
• Ensures prevalent diseases are not imported and spread
• Preserve rare plant species
