Biology additional Flashcards
0
Q
What is the cytoplasm function
A
Most of the chemical reactions happen in there
It contains enzymes that control these chemical reactions
1
Q
What is the nucleus function
A
Contains genetic material
Controls the activities of the cell
2
Q
What is the function of the cell membrane
A
Holds the cell together
Controls what goes in and out of the cell
3
Q
What is the mitochondria’s function
A
These are where most of the reactions for respiration takes place
Respiration releases energy that the cell needs to work on
4
Q
What is the ribosomes function
A
These are where proteins are made in the cell
5
Q
What do human/animal cells contain
A
Nucleus Cytoplasm Mitochondria Cell membrane Ribosomes
6
Q
What does the plant cell contain
A
Cell wall Vacuole Chloroplasts Chlorophyll Nucleus Mitochondria Ribosomes Cytoplasm Cell membrane
7
Q
What is the function of the cell wall
A
It is made of cellulose and it supports the cell and strengthens it
8
Q
What is the function of chloroplasts
A
These are where photosynthesis takes place which makes food for the plant
And they also contain a green substance called chlorophyll
9
Q
What is the function of the vacuole
A
Contains cell sap which is a weak solution of sugar and salts
10
Q
What does the yeast cell have
A
Nucleus
Cytoplasm
Cell membrane
Cell wall
11
Q
Name two single celled microorganisms
A
Yeast cell
Bacteria cell
12
Q
What does a bacterial cell have
A
Cytoplasm
Cell membrane
cell wall
13
Q
What is diffusion
A
Diffusion is the spreading out of particles from an area of high concentration to an are of low concentration
14
Q
Why does diffusion happen in both solutions and gases
A
Because the particles in these substances are free to move about randomly
15
Q
The bigger the difference in concentration……..
A
The bigger the difference in concentration the faster the diffusion rate
16
Q
What small molecules can diffuse through cell membranes?
A
Oxygen
Glucose
Amino acids
Water
17
Q
What cant fit through the cell membrane
A
Starch
Proteins
18
Q
Name 4 specialized cells
A
Palisade leaf cells
Guard cells
Red blood cells
Sperm/egg cells
19
Q
What are the three functions of palisade leaf cells
A
1- packed with chloroplasts for photosynthesis ( more of them are at te top of the cell so its nearer to light )
2- tall shape means a lot of surface area exposed down the side for absorbing CO2 from the air in the leaf.
3-thin shape means you can pack loads of them in a top of a leaf
20
Q
What are the 5 functions of guard cells
A
1-kidney shape which opens and closes the stomata (pores) in a leaf
2-when plant has lots of water the guard cells fill with water and go plump and turgid (gezwollen) this makes the stomata open so gases can be exchanged for photosynthesis
3-when the plant is short of water the guard cells lose water and become flaccid making the stomata close, this helps stop too much water vapour escaping.
4-thin outer walls and thickened inner walls make opening and closing work
5-they are also sensitive to light and close at night to save water without losing out on photosynthesis
21
Q
what are guard cells adapted for
A
They are adapted to their function of allowing gas exchange and controlling water loss within the leaf
22
Q
What are the three functions of red bloodcells
A
1-concave (hol) shape gives big surface area for absorbing oxygen and it also helps them pass smoothly through capillaries(haarvaten) to reach body cells.
2-they are packed with haemoglobin the pigment that absorbs oxygen
3-they have no nucleus to leave even more room for haemoglobin
23
Q
What are the 4 functions of sperm/egg cells
A
1-(egg function) to carry the female DNA and nourish the developing embryo in early stages,the egg cell contains huge food reserves to feed the embryo.
2-when a sperm fuses with the egg the egg’s membrane changes its structure to stop anymore sperm getting in, this makes sure the offspring end up with right amount of DNA.
3-(sperm function) to get the make DNA to the female DNA it has a long tail and streamlined head to help swim to the egg and there is a lot of mitochondria in the cell to give the energy needed.
4-sperm also carry enzymes in their heads to digest through the egg cell membrane.
24
What is the function of a specialized cell?
It carries out a particular function
25
What is differentiation
The process by which cells become specialized for a particular job
26
Order from small to big
| tissues organ system cell organ organism
```
Cells
Tissues
Organ
Organsystem
Organism
```
27
Whats a tissue
A tissue is a group of similar cells that work together to carry out a particular function
28
Whats the function of a muscular tissue
It contracts to move whatever its attached to
29
Whats the function of a glandular tissue
It makes and secretes chemicals like enzymes and hormones
30
whats the function of epithelial tissue
Covers some parts of the body
| Example ; inside of the gut
31
What is an organ
An organ is a group of different tissues that work together to perform a certain function
32
What tissues is the stomach made of
Muscular tissue - moves the stomach wall to churn up the food
Glandular tissue - makes the digestive juices to digest food.
Epithelial tissue - covers the outside and inside of the stomach
33
What is an organ system
A group of organs working together ti perform a particular function
Example; digestive system breaks down food.
34
What organs is the digestive system made up of
1-glands( pancreas,salivary glands) which produce digestive juices
2-stomach and small intestine which digest food.
3-liver which produces bile
4-small intestine absorbs soluble food molecules
5-large intestine which absorbs water from undigested food leaving faeces
35
What other molecule other than glucose that can diffuse into the cell
Oxygen
36
Photosynthesis equation
Carbon dioxide +water = (sunlight and chlorophyll) glucose +oxygen
37
What organs is the plant made of
Stems
Roots
Leaves
38
Function of mesophyll tissue
Where most of the photosynthesis in a plant occurs
39
Function Xylem and phloem
They transport water, mineral ions and sucrose around the plant
40
function of epidermal tissue
Covers the whole plant
41
Defenition of photosynthesis
It is the process that produces food in plants and algae , the food it produces is glucose
42
Where does photosynthesis happen
Inside chloroplasts
43
What do chloroplasts contain
A green substance called chlorophyll which absorbs sunlight and uses its energy to convert co2 and water into glucose
44
What is a by product in photosynthesis
Oxygen
45
What are the 4 raw materials needed for photosynthesis
1 sunlight on the leaf provides the energy for the process
2 chlorophyll contained in chloroplasts
3 water that reaches the cells via the xylem
4 co2 that diffuses into the leaf
46
What 3 factors could be a limiting factor for photosynthesis
1. At night , LIGHT is a limiting factor
2. in the winter its often the TEMPERATURE
3. if its warm enough and bright enough the amount of CO2 Is limiting.
47
How do we control the amount of co2 ?
We dissolve different amounts of sodium hydrogencarbone in the water which gives off co2
48
How can temperature be a limiting factor?
When temp is too low the enzymes needed for photosynthesis work more slowly
but if the temperature gets at 45 degrees or above the enzymes needed for photosynthesis and its other reactions will be damaged
49
What is the most common way to artificially create the ideal environment for plants to grow?
In a greenhouse
50
Whats the 4 function of greenhouses
1. They help to trap the suns heat
2. Make sure temperature doesn't become limiting
3. In the winter heaters are used to keep temperature at the ideal level.
4. In summer it could get too hot so they might use shades and ventilation to cool things down.
51
Why is artificial light used in greenhouses
light is always needed for photosynthesis so when the sun goes down it gives the plants more photosynthesis time.
52
How can carbon dioxide get increased in a greenhouse?
By using a paraffin heater, to heat the greenhouse, as the paraffin burns it makes co2 as a by-product
53
How do farmers keep the plants healthy and free from pests/diseases?
They keep them enclosed in a greenhouse and the farmer can add fertilizers to the soil to provide all the minerals needed for a healthy grow
54
What are the 5 ways that plants use glucose ?
1. For respiration
2. making cell walls
3. making proteins
4. stored in seeds
5. stored as starch
55
How do plants use glucose in respiration
1. They keep glucose in their leaves
2. Then use some glucose for respiration
3. This releases energy which allows them to convert the rest of glucose into other substances which they can use to build new cells and grow.
4. to produce these substances they also need to to get a few minerals from soil
56
How do plants use glucose to make cell walls
glucose is converted into cellulose for making strong cell walls
57
How do plants use glucose for making proteins
Glucose is combined with nitrate ions to make amino acids which are then made into proteins
58
How do plants use glucose to store seeds
Glucose is turned into lipids for storing seeds.
59
How do plants use glucose to store starch
1. glucose is stored into starch and stored in roots,stems,leaves ready for use when photosynthesis isnt happening
2. starch is insoluble which makes it better for storing and a cell with lots of glucose would draw in loads of water and swell up.
3. potatoe and parnsip plants store a lot of starch underground over the winter so new plants can grow from them the following spring
60
What is a habitat
The place where an organism lives
61
What is the distribution of an organism
Where an organism is found
62
What are the 5 environmental factors?
1. Temperature
2. Availability of water
3. Availability of co2 and oxygen
4. Availability of nutrients
5. Amount of light
63
Where an organism is found is affected by environmental factors
Blabla
64
Why would an organism be more common in one area?
because there are differences in environmental factors between two areas
65
What are the two ways of studying the distribution of an organism?
1. Measure how common an organism is in two sample areas (using quadrats) and compare them
2. study how distribution changes across an area by placing quadrats along a transect
66
What are the 6 steps to compare how common an organism is in two sample areas?
1. Place 1m^2 quadrat on the ground at random point within the first sample area
2. count all the organisms within the quadrat
3. repeat steps 1 and 2 as many times.
4. Work out mean number of organisms per quadrat within sample area
5. Repeat steps 1-4 in the second sample area
6. Compare the two means
67
What is the mean in quadrats
Total number of organisms devided by number of quadrats
68
What is the mode in quadrats
Most common value
69
What is the median in quadrats?
It is the middle value when they are in order of size
70
What are the two steps to work out population size
1. work out the mean number of organism per m2
| 2. then multiply the mean by the total area (in m2) of the habitat
71
What are transects used for
To help find out how organisms are distributed across an area
72
What are the tree things you do when an organism becomes more or less as you move from a hedge towards the middle of the field?
1. Mark out a line in the area you want to study using a tape measure
2. Then collect data along the line
3. U can do this by just counting all the organisms you are interested in that touch the line
4. Or u can collect data by using quadrats and these can be placed next to Eachother along the line or at intervals. (for example every 2 m)
73
When collecting environmental data you need to think about two twings ;
1. Reliability
| 2. Validity
74
What do you need to do to make your results more reliable when collecting environmental data?
- take a large sample size
| - use random samples because results from one spot and everywhere else is different the results wont be reproducible.
75
How can you keep something valid
You need to control all variables
76
What are catalysts
A catalyst is a substance which increases the speed of a reaction, without being changed or used up in the reaction
77
What are enzymes
Enzymes are catalysts produced by living things.
78
What would happen if you rise the temp in a reaction
This would speed up the useful and unwanted reactions and there is a limit to how far you can rise the temp inside a living creature before its a start to get damaged
79
What do enzymes do
Enzymes reduce the need for high temperatures and we only have enzymes to speed up the useful chemical reactions in the body.
80
What are enzymes made of
Enzymes are all proteins and all proteins are made up of chains of amino acids
81
Why do ezymes have special shapes?
- chemical reactions usually involve things being split apart or joined together
- every enzymes has special shape that fits onto substances in reaction
- ezymes usually only catalyse one reaction
- for enzyme to work has to fit its special shape and if the substance doesnt match the enzymes shape then the reaction wont be catalysed
82
What happens when it gets too hot for enzymes
Some of the bonds holding the enzyme together break this destroys the enzymes shape and so it wont work anymore ( it denatures)
83
What temp do enzymes in the body work best?
37 degrees
84
What other than temperature effects enzymes
If the ph is too high or low because the ph interferes with the bonds holding the enzyme together
85
Name 3 big molecules that are too big to pass through the walls of the digestive system
Starch , protein, fats
86
What optimum ph do enzymes work best at?
Its often neutral ph 7
Pepsin is enzyme that breaks down proteins in the stomach and it works best at ph 2 , it is well suited to the acidic conditions there
87
Name 4 smaller molecules that can pass easily through the walls of the digestive system
Sugars, amino acids, glycerol and fatty acids
88
What is the function of the digestive enzymes
They break down the big molecules into smaller ones
89
Whats the function of amylase
It converts starch into sugars
90
In what 3 places is amylase made
1. Salivary glands
2. Pancreas
3. Small intestine
91
What is the function of protease?
Protease converts proteins into amino acids
92
In what 3 places is protease made
1. stomach (called pepsin there)
2. Pancreas
3. Small intestine
93
What is the function of lipase
Lipase converts lipids into glycerol and fatty acids
94
In what two places is lipase made
Pancreas
| Small intestine
95
Where is bile produced
It is produced in the liver and its stored in the gall bladder before its released into the small intestine
96
What is the function of hydrochloric acid in the stomach
- It makes the PH too acidic for enzymes in small intestine to work properly
- bile is alkali it neutralizes the acid and makes conditions alkaline.
97
What is the function of bile
It emulsifies fats ( it breaks the fat into tiny droplets) and this gives a bigger surface area of fat for the enzyme lipase to work on , which makes digestion faster
98
Where are enzymes in the digestive system produced
They are produced by specialized cells in glands and in the gut lining
99
What does the salivary gland produce
Amylase enzyme in the saliva
100
What is the function of the stomach
It pummels the food with its muscular walls
It produces the protease enzyme =pepsin
And it produces hydrochloric acid for two reasons 1- kill bacteria
2- to give right ph for protease enzyme to work ph 2 (acidic)
101
What is the function of the liver
Bile is stored there before it is released into the small intestine
102
Function of large intestine
Where excess water is absorbed from food
103
Function of rectum
Where the faeces are stored before they leave the body from the anus
104
Function of the pancreas
Produces protease amylase and lipase enzymes and releases these into the small intestine
105
Function of small intestine
Produces protease amylase and lipase enzymes to complete digestion
This is also where the digested food is absorbed out of the digestive system into the blood
106
Definition of respiration
Respiration is the process of releasing energy from glucose which goes on in every cell
107
How do all living things release energy from their food?
They respire
108
What is aerobic respiration
It is respiration using oxygen
| Most efficient way to release energy from glucose .
109
What is anaerobic respiration? And what does it produce ?
This happens without oxygen and its doesnt release as much energy and it is the incomplete breakdown of glucose which produces lactic acid
110
Where does aerobic respiration happen?
Inside the mitochondria
111
Respiration equation
Glucose + oxygen = co2+water+energy
112
Plants and animals respire its how they release energy from food
Blabla info
113
What are the 4 examples of what energy released by aerobic respiration is used for?
1. To build up larger molecules from smaller ones (proteins from amino acids)
2. In animals to allow the muscles to contract.
3. In mammals and birds the energy is used to keep their body temp steady.
4. In plants to build sugars nitrates and other nutrients into amino acids which are then built up into proteins
114
What is cyanide and what does it do
Its a toxin that stops respiration by stopping enzymes involved in the process from working
115
When you exercise does the body quickly adapt ?
So that the muscles get more oxygen than glucose to supply energy
116
When there is an increase in muscle activity why does the blood have to flow at a faster rate?
Because when muscle activity increases more glucose and oxygen is required to be supplied to muscle cells and extra co2 is removed from muscle cell and for this to happen blood has to flow at a faster rate
117
What does physical activity do?
Increases the speed at which the heart pumps
Increases your breathing rate and makes you breathe more deeply to want extra oxygen
118
Some glucose from food is stored as glycogen
Blabla info
119
Where is glycogen mainly stored?
In the liver but each muscle also has its own store
120
During a healthy exercise muscles use glucose rapidly so some of the stored glycogen us converted back to glucose to provide more energy
Blabla info
121
When do you use anaerobic respiration ?
When you do a healthy exercise and your body cant supply enough oxygen to your muscles.
122
Anaerobic respiration equation
Glucose ---> energy + lactic acid
123
Why is anaerobic resporation not the best way to convert glucose into energy?
Because lactic acid builds up in the muscles which gets painful
and it also causes muscle fatigue so the muscles get tired and they stop contracting efficiently
124
What is the advantage of anaerobic respiration?
That at least you can keep on using your muscles for a while longer
125
What happens after anaerobic respiration?
When you stop exercising you will have an oxygen debt
126
What is an oxygen debt and how can you get rid of it ?
1. You have to repay the oxygen that you didn't get to your muscles in time because your lungs heart and blood couldn't keep up with the demand earlier on
2. So you will have to breathe harder for a while after you stop to get more oxygen into your blood
3. blood flows through your muscles to remove the lactic acid by oxidizing it to harmless co2 and water
127
While high levels of co2 and lactic acid are detected in the blood by the brain the pulse and breathing rate stay high to try and correct the situation
IN OXYGEN DEBT
Bla bla info
128
What does yeast produce instead of lactic acid?
They produce ethanol and co2 as they also respire anaerobically
(But only yeast does this if humans would produce ethanol we would all be drunk after a healthy exercise )
129
In what two things are enzymes used
Biological detergents
| Change foods
130
What enzymes are used in biological detergents?
Mainly protein-digesting enzymes (proteases) and fat-digesting enzymes (lipases)
131
why are they good for being washing powders?
Because the enzymes break down animal and plant matter they are perfect for removing stains like food or blood.
132
What temp does biological detergent work best?
More effective at low temperature (30 degrees)
133
Why is it easier for the baby to digest the proteins in some baby foods
Because they are pre-digested ysing protein digesting enzymes (proteases)
134
Why is glucose syrup turned into fructose syrup and how?
Glucose syrup can be turned into fructose syrup using an isomerase enzyme.
Fructose is sweeter so we can use less of it and it is good for slimming foods and drinks
135
Why are enzymes useful in the industry? Give 4 advantages
1➡️they are specific so they only catalyse the reaction you want them too
2➡️using lower temp and pressures means lower cost as it saves energy
3➡enzymes work for a long time so after the initial cost of buying them you can continually use them
4➡️they are biodegradable and therefore cause less environmental pollution
136
What are the 4 disadvantages of enzymes in the industry?
1➡️some people can be allergic to the enzymes (eg in washing powders)
2➡️enzymes can be denatured by even a small increase of temperature and they are also likely to be harmed by poisons and changes in PH, so conditions in which they work must be tightly controlled.
3➡️enzymes can be expensive to produce
4➡️contamination of the enzyme with other substances can affect the reaction.
137
What are chromosomes ?
Chromosomes are really long molecules of DNA
138
What does DNA stand for ?
Deoxyribose nucleic acid
139
Where is DNA found?
It is found in the nucleus of animal and plant cells in really long molecules called chromosomes.
140
What is the order from big to small
| single chromosomes DNA nucleus
Nucleus, single chromosomes , DNA
141
What is a gene and what is its function
A gene is a section of DNA and it contains the instructions to make a specific protein (simply tells in what order to put amino acids together)
142
How do cells make proteins?
By stringing amino acids together in a particular order
143
How many amino acids are used to make proteins?
20 amino acids are used but they make up thousands of different proteins
144
What does the DNA also cause ?
What proteins the cell produces ( haemoglobin,keratin) that in turn tells what type of cell it is ( red blood cell, skin cell)
145
How can DNA be used
To catch criminals or to identify someone
146
Everyone has a unique DNA except identical twins and clones
Blabla info
147
What is DNA fingerprinting (genetic fingerprinting)
It is a way of cutting up a persons DNA into small sections and then separating them
148
Every persons genetic fingerprint has a unique pattern what does this mean?
This means you can tell people apart by comparing samples of their DNA
149
What two methods is fingerprinting used in?
1 forensic science
2 paternity testing
150
What is forensic science
DNA from hair skin flakes blood semen taken from a crime scene is compared with a DNA sample taken from a suspect
151
What is paternity testing?
To see if a man is the father of a particular child
152
What 3 things are said about a genetic database of everyone in a country?
Some says that way DNA from a crime scene could be checked against everyone in the country to see whose it was
Others think it is a big invasion of privacy and they worry about how safe the data would be and what else it might be used for.
And there are also scientific problems/ false positives that can occur if errors are made in the procedure or if the data is misinterpreted
153
Why does mitosis make new cells
For growth and repair
154
How many copies do body cells have and of what?
They normally have two copies of each chromosome
| One from the mother and one from the father
155
What does a body cell do when it divides? And what is this type of cell division called
It needs to make new cells identical to the original cell with the same number of chromosomes
and this is called mitosis
156
When is mitosis used?
Its used when plants and animals want to grow or to replace cells that have been damaged
157
What is the definition of mitosis
Mitosis is when a cell reproduces itself by splitting to form two identical offspring.
158
describe mitosis process
1. In a cell thats not dividing the DNA is spread out in long strings
2.if the cell gets a signal to divide, it needs to duplicate its DNA
So there is one copy for each new cell.
The DNA is copied and forms Xshaped chromosomes each arm of the chromosomes is an exact duplicate of the other
3.the chromosomes then line up at the centre of the cell fibres pull them apart
So the two arms of each chromosome go to opposite ends of the cell.
4.membranes form around each of the sets of chromosomes these become the nuclei of the two new cells
5.lastly the cytoplasm divides
6. Now you have two cells containing the exact same DNA they are identical
159
Name an organism that uses asexual reproduction by mitosis
Strawberry plants that form runners which become new plants in this way
The offspring have exactly the same genes as the parent so there is no variation
160
Mitosis makes identical cells
| But there is another type of cell division which doesn't , what is that ?
Meiosis
161
What happens during sexual reproduction?
Two cells called gametes combine to form a new individual
162
What is special about embryonic stem cells?
They can turn into any type of cell
163
In most animal cells the ability to differentiate is lost at an early stage, but plants cells dont ever lose this ability
Blabla info
164
What are stem cells
Some undifferentiated cells that can develop into different types of cell depending on what instructions they are given.
165
Where are stem cells found
They are found in early human embryos
they are special for doctors because they can turn into any kind of cell
All different types of cell found in a human being have to come from those few cells in the early embryo
166
Where are adults stem cells found?
In bone marrow
| They aren't as adaptable as embryonic stem cells and they cant turn into any type of cell at all .. Only in certain ones
167
In what 4 ways can stem cells cure many diseases ?
1. Medicine already uses stem cells
People with blood diseases can be treated by bone marrow transplants because it contains stem cells that can turn into new blood cells to replace the faulty old ones.
2. Scientist can extract stem cells from early human embryos and grow them
3. These embryonic stem cels could be used to replace faulty cells in sick people ( u could make beating heart muscle cells for people with heart disease, insulin producing cells for people with diabetes , nerve cells for people paralyzed by spinal injuries)
4. To get cultures of one specific type of cell researches try to control the differentiation of stem cells by changing the environment they grow in , but it needs a lot more research.
168
What are the some reasons some people are against or for stem cell research?
1. Because some people feel that human embryos shouldnt be used to experiment with since each one is a potential human life
2. Some people think that The embryos used in research are the unwanted ones from fertility clinics that would probably just be destroyed if they weren't used for research
3. Some campaigners for the rights of embryos think that scientists should concentrate more on finding and developing other sources of stem cells so people could be helped without having to use embryos
4. In some countries stem cell research is already banned but its allowed in the UK as long as it follows strict guidelines
169
What do your chromosomes control?
Your chromosomes control whether youre a male or female
170
How many matched pairs of chromosomes is in every human body cell?
There are 22 matched pairs and the 23rd pair are labeled XX or XY
171
What are the men chromosomes and the women chromosomes?
All men have an X and a Y chromosome XY the Y chromosome causes the male characteristic
All women have two X chromosomes XX
The XX combination allows female characteristics to develop
172
When making sperm the X and Y chromosomes are drawn apart in the first division in....
Meiosis
173
How much chance is there each sperm cell gets an x or y chromosome?
50 precent each
174
What does the original cell have
Two X chromosomes for the original CELL
| so all the EGGS have one X chromosome
175
How can you work out the probability of offspring being male or female?
By using a genetic diagram
176
What do genetic diagrams show?
The possible combinations of gametes
177
In steps what do you do to make a genetic diagram
Put the possible gametes from one parent down the side and those from the other parent along the top.
Then in each middle square fill in the letters from the top and side that line up with that square. The pairs of letters in the middle show the possible combinations of the gametes
This is only the probability at each pregnancy
178
Who was the founder of genetics?
Gregor mendel
179
What did gregor mendel note
How characteristics in plants were passed on from one generation to the next
180
What are the three conclusions mendel reached about heredity plants (erfelijk)
1. Characteristics in plants are determined (decided) by hereditary units
2. Hereditary units are passed on from both parents, one unit from each parent
3. Hereditary units can be dominant or recessive - if an individual has both the dominant and recessive unit for a characteristic the dominant characteristic will be expressed.
181
Hereditary units are ofc genes
Blabla info
182
What do genetic diagrams show?
the possible genes if offspring
183
What are alleles
Different versions of the same gene
184
What is used in genetic diagrams to represent the alleles
Letters
185
When is an organism HOMOZYGOUS
When it had two alleles for a particular gene the same.
186
When is an organism HETEROZYGOUS?
If its two alleles for a particular gene are different
187
What is a dominant allele
The allele for the characteristic thats shown ( we use a capital letter for dominant alleles ) and recessive is the other one shown with ( a smaller letter)
188
For an organism to display a recessive characteristic what must it include
Both alleles must must be recessive
189
For an organism to display a dominant characteristic what must it include?
The organism can be either CC Or Cc because the dominant allele overrules the recessive one if the plant/animal/organism is heterozygous
190
What are the two disorders that can be inherited ?
Cystic fibrosis
| Polydactyly
191
What is cystic fibrosis
It is a genetic disorder of the cell membranes
It results in the body producing a lot of thick sticky mucus in the air passages and in the pancreas
192
What kind of allele causes cystic fibrosis
A recessive allele ( f )
| 1 out of 25 people have it
193
Because cystic fibrosis is recessive people with only one copy of the allele wont have the disorder
(If they did they were called carriers)
Blabla info
194
So for a child to have the disorder does one or two parents need to have cystic fibrosis?
They both need to be carriers or sufferers
195
What is the chance of having the disorder if both parents are carriers
1 in the 4 chance
196
What is polydactyly ?
It is a genetic disorder where a baby's born with extra fingers or toes
197
What is polydactyly causes by
It is caused by a dominant allele (D)
| And so can be inherited if one parent carries the defective allele
198
The parent that has the defective allele will be a sufferer from polydactyly too since the allele is dominant
Blabla info
199
How big is the chance of getting polydactyly
50 precent chance if one parent has the allele
200
What happens during In vitro fertilization?
Embryos are fertilised in a laboratory and then implanted into the mothers womb, more than one egg is fertilised so theres a better chance if the IVF being successful.
Before being implanted its possible to remove a cell from each embryo and analyze its genes
Embryos with good alleles would be implanted into the mother and bad ones would be destroyed
201
What are the 4 arguments against embryonic screening
1. There may come a point where everyone wants to screen their embryos so they can pick the most 'desirable' one.
2. The rejected embryos are destroyed.. they could have developed into humans
3. it implies that people with genetic problems are undesirable ... This could increase prejudice
4. screening is expensive
202
What are the 4 arguments for embryonic screening?
1. it will help to stop people from suffering
2. there are laws to stop going it too far and at the moment parents cannot even select the sex of their baby unless it is for health reasons
3. during IVF most of the embryos are destroyed anyway, screening just allows the selected one to be healthy
4. treating disorders costs the Government a lot of money
203
What is a genotype and a phenotype
Genotype is the letters
Phenotype is the way the genes are expressed (appearance of the individual) for example
Phenotype = purple flower white flower
Genotype= Pp or PP
204
What are fossils?
Fossils are the remains of organisms from many years ago which are found in rocks
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What do fossils show?
They provide the evidence that organisms lived ages ago
206
fossils from in rocks in one of the three ways;
From gradual replacement by minerals
From casts and impressions
From preservation in places where no decay happens
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What does gradual replacement by minerals include?
Things like teeth shells bones which don't decay easily can last a long time when buried
They're eventually replaced by minerals as they decay,forming a rock like substance shaped like the original hard part
The surrounding sediments also turn to rock , but the fossil stays distinct inside the rock and eventually someone digs it up.
208
What does casts and impressions include?
Sometimes fossils are formed when an organism is buried in a soft material like clay, the clay hardens around it and the organism decays leaving a cast of itself.
an animals burrow or a plants roots can be preserved as casts
Things like footprints can be pressed into these materials when soft, leaving an impression when it hardens
209
What does the it include when fossils are formed from preservation in places where no decay happens
In amber ( a clear yellow stone made from fossilized resin) and a tar pits theres no oxygen or moisture so decay microbes cant survive
In glaciers its too cold for the decay microbes to work
Peat bogs are too acidic for decay micbrobes
210
How can fossils help us ?
They can help us to work out how life on earth has evolved
211
What are a few hypotheses about life on earth?
Maybe the first life form came into existence under the sea here on earth
Maybe simple organic molecules were brought to earth on comets and these molecules could have become more complex organic molecules, and eventually very simple life forms
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Why cant hypotheses be supported or disproved?
Because there is a lack of valid and reliable evidence
And scientists believe many organisms were soft bodied and soft tissue tends to decay away completely so the fossil record is incomplete
Also have fossils that did form millions of years ago maybe been destroyed by geologic activity
( movement of tectonic plates may have crushed fossils already formed in the rock)
213
Name two animals that are extinct with only fossils to tell us they existed at all
Dinosaurs and mammoths
214
Give 6 reason why species become extinct
0. they cant evolve quickly enough
1. The environment changes too quickly
2. A new predator kills them all
3. A new disease kills them all
4. They cant compete with another species for food
5. A catastrophic event happens that kills then all
6. A new species develops
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What is a species
A group of similar organisms that can reproduce to give fertile offspring
215
What is speciation
It is the development of a new species
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When does speciation occur
When populations of the same species become so different they can no longer breed together to produce fertile offspring
217
What is isolation
Isolation is where populations of a species are separated
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What leads to speciation?
Isolation and natural selection
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How can isolation happen give examples
Due to a physical barrier ( floods , earthquakes can cause barriers that geographically isolate some individuals from the main population )
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Why could conditions on either side of a barrier be different?
They may have different climates and because the environment is different on each side ,
different characteristics will become more common in each population due to natural selection
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Individuals in each population with characteristics that make them better adapted to the environment have a better chance on survival and so are more likely to breed successfully so the alleles of the beneficial characteristics are passed on to the next generation
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