Genetic Inheritance Flashcards
(210 cards)
1
Q
Define allele
A
A version of a gene. It produces a particular characteristic which can be different in different people e.g eye colour
2
Q
Why is haemophilia more common in males than females?
A
This genetic disease is caused by sex linked genes. Females have two X chromosomes whereas men have one X and one Y. The allele for haemophilia is recessive so two copies are needed in a female however only one copy is needed in males as they only have one X chromosome
3
Q
Define recessive
A
A variety of genetic code which does not create a phenotype if a dominant allele is present. Two copies needed
4
Q
Define dominant allele
A
A variation of a gene will produce a certain phenotype even in the presence of other alleles. Only one copy needed
5
Q
What can you use to prove there is a 50% chance of a couple having a boy?
A
Punnet square
6
Q
What happens during reproduction?
A
Two parents needed and their gametes fuse together (joining of nuclei/mixture of genetic information = fertilisation) as 23 chromosomes from the egg/ovum and 23 chromosomes from the sperm create a zygote with 46 chromosomes in 23 pairs. Offspring are genetically different and they divide by mitosis to produce a copy of itself, mitosis repeats many times to produce lots of new cells in an embryo which become differentiated as the embryo develops
7
Q
What are the sex cells in an animal?
A
Sperm, egg
8
Q
What are the sex cells in a plant?
A
Pollen and eggs
9
Q
Describe the 5 stages of meiosis
A
Cells in the reproductive organs divide by meiosis which halves the number of chromosomes in gametes because fertilisation produces the full set of chromosomes. The dna is replicated then lines up in the cell and is pulled apart by spindle fibres, identical daughter cells are produced as some of father’s chromosomes and some of mother’s chromosomes go into each new cell, the cell divides again so the cells are non identical daughter cells. Meiosis makes new gametes only with a single set of chromosomes each
10
Q
What are the differences between mitosis and meiosis?
A
4 cells produced in meiosis but only 2 in mitosis, there is variation in meiosis but not in mitosis, meiosis is sexual but mitosis is asexual, meiosis is involved with gametes and the reproductive system whereas mitosis is involved with all other cells, there are 2 divisions in meiosis but only one in mitosis
11
Q
What does DNA stand for and what is it?
A
Deoxyribonucleic acid, a chemical forming genetic material in the nucleus which carries the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses
12
Q
How is DNA arranged?
A
In a double helix (two chromosomes wrapped together)
13
Q
Define gene
A
Short strand of DNA which codes for a particular sequence of amino acids which build up to make a protein and produce a particular characteristic. Only 20 amino acids are used but they make up thousands of different proteins
14
Q
Define chromosome
A
Long strand of DNA which twists and spirals to form a double helix structure
15
Q
How many strands are DNA molecules made from?
A
2
16
Q
DNA is a polymer, what is meant by the term ‘polymer’?
A
A long molecule made up of repeating units
17
Q
Which bases pair together?
A
A (adenine) with T (thymine), C (cytosine) with G (guanine)
18
Q
What is the genome of an organism?
A
The entire genetic material of the organism
19
Q
What does DNA control?
A
Protein synthesis but the proteins are synthesised in the cytoplasm if the cell on the ribosomes
20
Q
What are the long strands of your DNA made up of?
A
Alternating sugar and phosphate sections which make the backbone of the molecule. Attached to each sugar is one of the bases
21
Q
What is the combination of a sugar, base and phosphate called?
A
Nucleotide
22
Q
What does the human genome have the ability to do?
A
Make many different proteins from the same gene by using it in different ways or switching part of a gene on and off
23
Q
What does the order of the bases control?
A
The order the amino acids are assembled to produce a particular protein for use in your body cells. Each gene coded for a particular combination of amino acids which make a specific protein.
24
Q
What is the key to the structure and functioning of the DNA molecule?
A
The way the four bases join up; they hold the structure of the DNA double helix together. It is also key in the way the information from the genes on the DNA is translated into proteins in the cell
25
What do genes produce for a protein?
A template for the protein which reflects the sequence of bases in the DNA but it is small enough to leave the nucleus through the pores of the nuclear membrane
26
What happens when the protein shape is complete in photosynthesis?
The molecule folds up to form a unique shape that will enable it to carry out its functions in the cell. For example if the protein is an enzyme if will fold to produce the active site. If it is a structural protein it will form fibrous structure such as collagen. If it is going to act as a hormone or clotting factor in the blood or a muscle or part of the structure of the cell membrane, the protein will fold so it can carry out its specific job in the cell. This is how DNA controls protein synthesis
27
What happens if a person has XXY chromosomes?
They would technically be male as they have a Y chromosome present however they would appear female due to the two overpowering X chromosomes
28
Define genotype
The combination of alleles that you have e.g BB Bb or bb
29
Define phenotype
The characteristic expressed e.g blue eyes
30
Which is dominant: brown or blue eyes?
Brown
31
Define heterozygous
2 alleles present are different eg Bb
32
Define homozygous
Two alleles present are the same eg BB or bb
33
Identify two characteristics which are controlled by a single gene
Red green colour blindness in humans, fur colour in mice
34
What happens if you cross two homozygous plants?
All offspring would be the colour of the dominant allele in the F1 generation
35
What is polydactyl ?
Inherited genetic disorder giving you extra fingers or toes, caused by a dominant allele
36
What does a normal CFTR channel do?
Move chloride ions to the outside cell
37
What does a mutant CFTR channel caused by cystic fibrosis do?
Does not move chloride ions, causing sticky mucus to build up
38
How can two parents who are healthy have a child with cystic fibrosis?
If they have heterozygous alleles they are a carrier of the disease
39
Give 3 advantages of stem cells
Stem cells from an embryo can grow into any type of tissue, large numbers of stem cells can be grown in a laboratory, stem cells may be used in medical research or to treat human diseases
40
Give 3 disadvantages of stem cells
Collecting and growing stem cells is expensive, patients with stem cells need to take drugs for the rest of their life to prevent rejection, stem cells can grow out of control to form cancers
41
How could sexual reproduction form a new variety of onion?
Fusion of gametes occurs in sexual reproduction which causes a mixture of genetic information, one copy needed from each parent of each chromosome
42
How could a mutation in an enzyme cause it not to work?
If there is a change in the triplet code there is a change in amino acids which changes the protein, this changes the shape of the active site which means the substance will not fit and cans be broken down into glucose
43
Define codon
Triplet code which determines amino acids which build up to a protein which makes an allele to express a characteristic
44
Give 3 reasons why people support the screening of embryos for the cystic fibrosis allele
They can decide whether to continue or terminate the pregnancy, less people with cystic fibrosis if pregnancy is terminated, less money spent by the NHS/ lower healthcare costs if there are less people with CF
45
Give 4 reasons why people are against embryo screening for the cystic fibrosis allele
Pregnancy may be terminated but every embryo has a right to life, choice may go against people’s religions, could risk harming embryo or causing a miscarriage, costs a lot
46
Identify two methods of embryo screening
Pre-implantation genetic diagnosis, chorionic villus sampling
47
What does PGD involve?
In vitro fertilisation of a few eggs then a cell is taken from each embryo when it is 3 days old, the DNA can then be tested and an unaffected embryo is planted in the uterus
48
What are 3 negatives of CGD?
False positive result is around 1 in 6, the procedure costs avoid £6000, affected embryos would be discarded
49
Give 2 advantages of PGD
Unaffected embryos may be frozen and kept for later implantation or used in scientific research
50
What happens in CVS?
A sample of blood is taken from the placenta a few weeks into the pregnancy, DNA from white blood cells can then be tested, if an affected embryo is detected the parents have to decide whether to terminate the pregnancy
51
Identify 3 things which make CVS better than PGD?
Only 1 percent chance of giving an incorrect result, 0.9% chance of causing a miscarriage, only costs £600
52
What is variation?
Differences in the characteristics of individuals in a population, can be genetic or environmental variation
53
Identify 4 causes of variation
Genetics inherited from parents because differences in genotypes lead to differences in phenotype, environmental influences (amount of light a plant receives), combination of both. Originally caused by mutations (the gene is altered which produces a genetic invariant)
54
What is Darwin’s theory of evolution?
Individuals with characteristics that make them better suited/adapted to their environment are more likely to survive and reproduce because organisms have to compete for limited resources in an ecosystem, over time beneficial characteristics become more common in the population and it evolves
55
Define overproduction
Every species tends to produce more individuals that can survive
56
What is natural selection?
It is all about organisms with the best characteristics surviving to pass on their genes so that the whole species ends up adapted to its environment
57
Define speciation
The development of a new species because the phenotype of an organism has changed so much to become reproductively isolated (can't interbreed with each other to produce fertile offspring)
58
Define extinction
When no individuals of a species remain
59
Identify 5 reasons for extinction of a species
When the environment changes too quickly (destruction of habitats), new predator kills them (humans hunting), new disease killed them all, can’t compete with another new species for food, catastrophic event happens that kills them all (volcanic eruption or asteroid)
60
What is a mutation?
A rare, random change in an organisms DNA which produces a genetic variant (different form of gene)
61
Define genetic engineering
Changing/ modifying the characteristics of an organism by manipulating its DNA. Transferring a gene responsible for a desirable characteristic from one organisms genome into another organism so it has the desired characteristic
62
What was Lamarch’s theory?
He didn’t disagree with the theory that god created the world, he said the more you use a feature and the more you want it to develop, the more it will develop and you will pass this onto offspring
63
What happens in genetic engineering? 3 steps
A useful gene is isolated (cut) from one organisms genome using enzymes and is inserted into a vector (virus or bacterial plasmid), when the vector is introduced to the target organism the useful gene is inserted into its cells, in some cases the transfer of the gene is carried out when the organism receiving the gene is at an early stage of development which means that the organism develops with the characteristic coded for by the gene
64
What are four uses of genetic engineering?
Bacteria have been genetically modified to produce human insulin that can be used to treat diabetes, generically modified crops have had genes modified to improve size or quality of fruit or make them resistant to pests, sheep have been genetically engineered to produce substances like drugs in their milk that can be used to treat human diseases, scientists are researching genetic modification treatments for inherited diseases caused by faulty genes e.g by inserting working genes into people with the disease (called gene therapy)
65
Why didn’t people know whether to believe Lamarck or Darwin’s theory?
There was no proof of either, we now know about genes. Relevant scientific knowledge was not available so Darwin couldn't give a good explanation why new characteristics appeared or how exactly individual organisms passed on beneficial adaptations to their offspring
66
Identify 5 advantages of GM crops
Almost any genes can be put into crops, enables farmers to reduce their dependence on chemical pesticides and herbicide sprays, the population goes up by 1/4 million every day and genetic engineering plays a part in feeding them, crop yield can increase, people in developing countries lack nutrition in their diets so GM crops could be modified to contain the nutrient that is missing
67
How have cabbages been engineered?
They contain scorpion venom which reduces use of pesticides, less pests eating cabbages which has economic benefits
68
Identify 7 arguments against GM crops
If GM crops pollinate non GM crops they could transfer foreign genes into the wild which makes non GM and organic crops more difficult to sell, adverse affects would be irreversible, could disrupt normal functions of genes in the crop, new proteins made could cause allergies, growing GM crops will affect the number of wild flowers and so the population of insects which reduces biodiversity, we do not fully understand the effects of GM crops on human health, transplanted genes may get out into the environment for example the herbicide resistance gene may be picked up by weeds and create a new super weed variety
69
What is selective breeding?
Involves two parents and mixing genetic information so the offspring is not a copy of the parent but has inherited features from both parents
70
How do farmers use selective breeding?
To produce stock that could produce products worthy of selling which could take several generations of breeding
71
What is true cloning?
Generates an identical copy of the animal you wish to clone in one generation
72
What are antibiotics derived from and what do they do?
Fungal toxins, they either slow or stop the growth of bacteria
73
What is the problem with antibiotics?
Certain bacteria are only sensitive to certain types of antibiotics. These medicines are not effective against viruses such as chicken pox and the common cold
74
Identify the 8 steps to antibiotics becoming resistant
You start taking an antibiotic, some bacteria are susceptible to (killed by) the antibiotic and others are resistant to it (some bacteria develop random mutations in their DNA like humans which leads to some antibiotic resistant strains), the susceptible bacteria are killed first, only resistant bacteria are left, they reproduce, the strong bacteria are now more common, you stop taking the antibiotic, if you take the antibiotic again it won’t work because all the bacteria are resistant
75
Define fossil
A trace of an organism in the earths crust from past geologic ages
76
Identify the 4 steps to fossil formation
Plants and animals die and fall to the earths surface, over time they are covered by layers of sediment which prevents scavengers eating them, more and more material is deposited on top and if the organism died in a place where bacteria can’t live a large part can be fossilised, the weight and pressure causes the deposits to from sedimentary rock
77
Give 3 reasons why an organism may not decompose
If it died in an area where bacteria cannot live, if it gets buried quickly, if they aren’t exposed to oxygen or moisture
78
How many kingdoms are all living things grouped into?
5
79
What are the 7 levels of classification?
Kingdom, phylum, class, order, family, genus, species
80
How do you test to see if two animals are in the same species?
If they can breed together to produce fertile offspring
81
How can you split animals into two groups?
Vertebrates and invertebrates
82
What are the five groups in vertebrates?
Birds, mammals, reptiles, amphibians, fish
83
Give 5 characteristics of birds
Wings, claws, feathers, beaks, hollow bones
84
Give 3 characteristics of mammals
Warm blooded, produce milk, feed offspring
85
Give 2 characteristics of reptiles
Cold blooded, scales
86
Give 4 characteristics of amphibians
Gills, lungs, moist skin, cold blooded
87
Give 3 characteristics of fish
fins, gills, scales
88
What does the binomial system of naming species involve?
It uses Latin words. Each name has a genus and species part
89
Which genus and species do humans belong to?
Homo sapien
90
What is the three domain system?
Until 1977 scientists divided all life into two domains (eukaryotes and prokaryotes) but the updated system by Woese divides organisms into archea (primitive bacteria in extreme environments), bacteria (true bacteria), eukaryota (Protists, fungi, animals, plants)
91
What do evolutionary trees show?
The further up the tree, the more recently evolved. The more recent the common ancestor, the more closely related and the more characteristics they are likely to share
92
What can fossil evidence help identify?
Evolutionary relationships
93
What do arrows in food chains represent?
Energy being passed on so they must go to the next trophic level
94
What are the four trophic levels?
Producer > Primary Consumer > Secondary Consumer > Tertiary Consumer
95
What are food webs?
Inherited food chains
96
What does a food web show?
Interdependence of organisms. If we remove a population of primary consumers, the producers population would increase but the secondary consumers and tertiary’s population would decrease. ‘Lag pattern’
97
Define species
A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding
98
Define population
The number of living things that live together in the same place
99
Define community
An interacting group of various species in a common location
100
Define ecosystem
Biological community of interacting organisms and their physical environment
101
Define biosphere
Regions of the surface and atmosphere of the earth or another planet occupied by living organisms
102
Define predator
Animal that naturally preys on others
103
Define prey
Animal that is hunted and killed by another for food
104
Define habitat
The natural home or environment of an animal, plant or other organism
105
Define biotic factor
Relating to or resulting from living organisms
106
Define abiotic factor
Physical rather than biological; not derived from living organisms
107
Identify the five steps to producing organisms
Ecosystem > Biosphere > Community > Population > Individual
108
What are three adaptations of a camel?
Stores fat in hump to provide energy, has thick padded feet with a large surface area to withstand extreme hot or cold temperatures of sand, thin layer of fat and a large surface area to volume ratio to help them lose heat
109
Identify 3 adaptations of a polar bear
Claws help it rip apart prey and grip onto ice, white fur allows it to camoflauge (same as an arctic fox), black skin allows it to retain heat
110
Identify two adaptations of a cactus
Large fleshy stem allows it to retain water, spikes with low surface area minimise transpiration and fight off predators
111
What is the group of leaves, beetles, mice and owls in a habitat called?
Community
112
What are 5 abiotic factors which can affect the food chain?
Light intensity, wind direction, carbon dioxide level, mineral content of soil, temperature
113
Why do tiny plants near the surface of the sea?
Receive more light for photosynthesis
114
What could be an explanation for a large increase in the number of lion fish in the Atlantic Ocean? 3 ideas
More plants for lion fish to eat as there are less native Atlantic fish which they can also eat. No or few predators of the lion fish. No diseases
115
Give 4 factors animals may compete for
Food warmth, mates, statues
116
Identify a biotic factor which could affect the distribution of animals
Number of predators
117
Identity abiotic factor which could affect distribution of animals
Light intensity
118
How could people collect data about distribution of animals?
Use a quadrat (square frame enclosing a known area e.g 1m^2) To compare how common an organism is in different sample areas you place this on the floor at a random point within the first sample area then count all the organisms within the quadrat. Work out mean number of organisms per quadrat in the first sample area after repeating the method as many times as you could
119
Why do heavier animals need more energy?
They are harder to move as they have more inertia
120
What is the difference between Annelids (worms) and Anthropods (caterpillars of moths)?
Anthropods have legs but annelids do not
121
How do trees increase biodiversity?
A lot of life forms depend on them. Tree leaves and oak are producers in the food chain so they support all of the trophic levels because the more producers there are, the more food there is to support primary consumers which supports secondary consumers who live off primary
122
How do trees reduce pollution?
They absorb carbon dioxide from the air. Carbon dioxide contributes to the greenhouse effect. Trees reduce noise pollution as they absorb and block noise
123
Protein synthesis: what do proteins do after leaving the nucleus? 5 steps
It binds to the surface of a ribosome, cytoplasm contains carrier molecules (each attached to a specific amino acid) which attach themselves to the template in the order given by the DNA, amino acids join together to make a specific protein, carrier molecules keep bringing specific amino acids to add to the growing protein chain in the correct order until the template is completed, protein detaches from the carrier molecules and the carrier molecules detach from the template and return to the cytoplasm to pick up more amino acids
124
What can a change of mutation in a single group of bases cause?
could change or disrupt the whole protein structure and the way it works
125
How can you make sample results as valid as possible when using a quadrat? 2 ways
Use the same size each time, sample as many areas as possible
126
Why should sample areas be chosen at random?
To ensure ur results reflect the true distribution of the organisms, to make sure the conclusions u make are valid
127
How could you decide where to drop your quadrat? 2 ways
Person holding the quadrat closes their eyes, spins around, opens their eyes, walks 10 paces and drops the quadrat. More scientific way is a random number generator
128
What is quantative sampling?
Taking several readings then finding the mean number (of organisms eg)
129
What can you use quantative sampling for? 3 things
To compare the distribution of the same organism in different habitats or to compare the variety of organisms in several different habitats or to measure changes in the distribution of organisms over time
130
How do you use a transect?
Stretch a line of tape between two points when you suspect a change is linked to a particular abiotic factor, then sample the organisms along the line at regular intervals using a quadrat which shows you how distribution of organisms changes along the line. You can measure some of the physical factors like light levels and soil pH which may affect growth of plants along the transect
131
Photosynthesis produces carbon containing compounds called what?
Minerals
132
Why do bladderwrack grow quicker than saw wrack?
Bladderwrack have bladders filled with air so its fronds float to the top of the water. They receive more light than saw wrack which can be used by chlorophyll to make food for the plant and also it uses carbon dioxide, water and nutrients. The food helps the plant to grow
133
Define niche
Role of one organism in an ecosystem
134
Why is the water cycle important? 3 reasons
Trees and plants need water for photosynthesis, plants provide food for animals, habitats need hydration
135
Describe the 7 processes of the water cycle
Water falls as precipitation in upland areas, surface run off occurs and enters rivers, some water infiltrates into soil and flows through ground by percolation, some water is intercepted by trees and is later lost through the pores of the stomata in transpiration, energy from sun makes water evaporate from the land turning it into water vapour, warm water vapour is carried upwards and cools and condenses to form clouds
136
Describe how elements are cycled back to the start of the food chain by decay
Living things are made up of materials they take from the world around them, these get passed up the food chain, they are returned to the environment in waste products or when animals die and decay, decay puts the stuff that plants need to grow (e.g mineral ions) back into soil
137
Why do materials decay?
Because they are broken down (digested) by microorganisms which happens faster in warm, moist, aerobic (oxygen rich) conditions as microorganisms are more active here
138
Describe the 7 processes of the carbon cycle
Co2 removed from atmosphere by green plants and algae in photosynthesis, carbon used to make glucose which can be converted to carbohydrates, fats, proteins which make up bodies of green plants and algae, some CO2 returned when green plants and algae respire, some carbon becomes part of fats and proteins in animals bodies who eat green plants and algae, some carbon returned when animals respire, when detritus feeders and microorganisms who feed on dead plants and animals respire some co2 is returned, combustion of wood and fossil fuels releases co2
139
Define biodiversity
Variety of different species of organisms on Earth or within an ecosystem
140
Why is high biodiversity important? 2 reasons
Makes sure ecosystems are stable because different species depend on each other for different things like shelter and food. Different species can help to maintain the right physical environment for each other (e.g acidity of soil)
141
Why is the human population increasing?
Mostly due to modern medicine and farming methods which have reduced the number of people dying from disease and hunger
142
How does global warming occur?
The sun emits short wave UV radiation most of which is absorbed by the earth's atmosphere and warms it however some is reflected by it or scattered by clouds, as the earth cools it emits long wave IR radiation which stimulates the bonds in greenhouse gases causing them to bend and vibrate more vigorously, the gases trap IR radiation and act like an insulating layer to the earth by absorbing most energy that would normally be radiated out into space and re-radiating it back in all directions including back towards earth which increases energy in the atmosphere.
143
What is the temperature of the earth a balance between?
The energy it gets from the sun and the energy it radiates back out into space
144
How do the gases in Earth's atmosphere act like an insulating layer?
They absorb most of the energy that would normally be radiated out into space and re radiate it in all directions including back towards the earth which increases the temperature of the planet
145
What is scientific consensus about global warming based upon? Give an advantage and a disadvantage of this
Systematic reviews of thousands of peer reviewd publications. D:Limited amount of experimental data to show dangers A:Range of data included so a consensus agreement can be reached
146
How are humans putting pressure on the environment?
We take resources from the environment that we need to survive. People around the world are demanding a higher standard of living (so demand luxuries like cars, computers) so we use raw materials and more energy for manufacturing processes. Many raw materials are being used up quicker than they are being replaced
147
How do increased amounts of waste cause water pollution? 2 ways
Sewage and toxic chemicals from industry can pollute rivers/lakes/oceans, chemicals used on land (fertilisers/pesticides/herbicides) washed into water
148
How do increased amounts of waste cause land pollution? 3 ways
We use toxic chemicals like herbicides for farming, we bury nuclear waste underground, a lot of household waste is dumped in landfill sites
149
How do increased amounts of waste cause air pollution?
Landfill and waste from agriculture release carbon dioxide and methane when they decompose, smoke and acidic gases which enter the air can cause acid rain
150
What is eutrophication?
Caused by water pollution, a body of water becomes overly enriched with minerals and nutrients which induce excessive growth of plants and algae and can cause oxygen depletion (dissolved oxygen becomes reduced in a concentration to a point where it becomes detrimental to aquatic organisms.)
151
How does eutrophication reduce biodiversity? 2 ways
Results in increased incidences of fish kills and dead benthic animals as they may need high levels of oxygen to survive. Hypoxic conditions promote the growth of bacteria that produce toxins which are deadly to birds and animals
152
How does land pollution reduce biodiversity?
Chemicals pollute soil and alter its pH. plants have optimum pHs for growth so if this were to change the plants would be unable to carry out photosynthesis
153
How does global warming (consequence of air pollution) reduce biodiversity? 4 ways
Arctic ice melts which reduces habitats of polar bears, sea levels rise due to thermal expansion which can cause flooding and destroy habitats on coastlines, changes in rainfall and increased drought can affect availability of food and water, some species are unable to survive a change in climate
154
How could global warming lead to changes in the distribution of animals?
Species may become more widely distributed-those that need warmer temperatures may be spread over a larger area as the conditions they thrive in exist over a wider area, other species may become less widely distributed because the conditions they thrive in exist over a smaller area
155
How could global warming cause changes in migration patterns?
Some birds may migrate further north as more northern areas are getting warmer
156
What do trees, peat bogs and fossil fuels all do with carbon?
Trap it and lock it up
157
Identify 4 things humans use land for?
Building, quarrying, farming, dumping waste
158
What are bogs?
Areas of land which are acidic and waterlogged
159
Why do plants living in bogs not decay fully?
Not enough oxygen so partly-rotted plants build up gradually to form peat
160
Why does the destruction of peat bogs cause air pollution?
Bog plants absorb CO2 from the air as they grow then when they die the carbon is locked away in organic chemicals in soaking peat for thousands of years. When peat is dug up for compost or fuel, or drained and ploughed for farming, organic carbon stored inside is converted to CO2 gas. Rotting vegetation in peat bogs gives off methane
161
How does the destruction of peat bogs reduce biodiversity?
Destroys or reduces area of habitats of some animals, plants and microorganisms that live there
162
What 3 things is peat used for?
Peat bogs often drained so the area can be used for farmland, peat cut up and dried for fuel, sold to gardeners as compost. Peat is being used faster than it forms
163
How is global food demand reducing biodiversity? 4 ways
Agriculture is the most dominant land use on the planet so takes up a lot of space which destroys habitats, deforestation has to occur to clear land for agriculture which causes global warming, rice and cow farming contribute to global warming, global food demand may be rising quicker than the population of cows/pigs which could cause them to become extinct
164
Give a fact which shows how rapidly the population is rising
Could swell to 9.9 billion by 2050
165
How does light intensity affect distribution of green algae?
Where there is more light, growth occurs more slowly because they are adapted to grow in low light intensity
166
How do you prevent the spread of a bacteria which is only resistant to one antibiotic? 4 ways
Only give the antibiotic to people who are affected by the bacteria - not to viral infections - and see how the body's immune system responds to their illness first to prevent antibiotic resistance, keep bacteria infected patients separate from others, wash hands with antibacterial soap after visiting patients who are affected to prevent spread by contact, take the full prescribed course of antibiotics otherwise some bacteria will mutate then multiply and become resistant
167
Identify the 4 steps of selective breeding
Choose plants with desirable characteristics from your existing stock, breed these plants, choose from offspring those with the best characteristics, breed again over several generations so the desirable trait gets stronger and all the offspring eventually have it
168
How could a genetic mutation cause a different colour in carp?
A different protein would be made
169
Why can't triploid oysters reproduce?
The chromosomes cannot be halved evenly to produce a full set of chromosomes in fertilisation
170
Why do triploid oysters grow quicker than diploid?
Triploid oysters do not reproduce therefore do not use energy for this so more energy is left for protein synthesis
171
Identify 4 positives of growing triploid oysters
Taste good all year round so have become more popular, cheaper to produce so more food for larger population, grow faster so more economic profit, can be harvested all year so more sustainable
172
Identify 6 negatives of growing triploid oysters
Expensive to buy seeds which they need to be grown from, risk of causing cancer in humans because the chemical used (Cytochalasin B) causes it in mice, may outcompete diploid oysters which would upset the population balance, people may not buy them due to the carcinogen which would lead to economic losses, should not be eaten until we know the effects on human health ad the environment
173
What does DNA determine?
The proteins a cell produces and therefore the type of cell it is
174
Define genome
Entire set of genetic material in an organism
175
Why is understanding the human genome important for science and medicine? 2 reasons
Allow scientists to identify genes which are linked to different types of disease which helps them understand the diseases better and develop effective treatments, scientists look at genomes to trace migration of certain populations of people around the world (all humans are descended from a common ancestor in Africa but now humans live all over the world) because the human genome is mostly identical in all individuals but as people migrated away from Africa they gradually developed tiny differences in their genomes so scientists investigate differences I order to work out when populations split off in a different direction and what route they took
176
What does the mixture of genetic information in fertilisation cause? 2 things
Variation in offspring, offspring inherits features from both parents
177
Why is each of the gametes genetically different in meiosis?
Chromosomes all get shuffled up in meiosis and each gamete gets only half of them, at random
178
How do the 23 pairs of chromosomes in each body cell do?
22 are matched pairs which control characteristics but the third pair are labelled XX or XY which decides your sex
179
What happens with chromosomes when sperm and eggs are made?
The X and Y chromosomes are drawn apart so there is a 50% chance a sperm gets an X chromosome and a 50% chance it gets a Y. A similar thing happens when making eggs but the original cell has two X chromosomes so all the eggs have one X chromosome
180
What is a monohybrid cross?
When you cross two parents in a punnet square to look at just one characteristic
181
How can you tell from a family tree if the allele for an illness is recessive?
If a lot of people in the family carry the disease but are not sufferers. For a child to be able to get the disease, both its parents must be carriers or sufferers
182
What is cystic fibrosis?
Genetic disorder of the cell membrane caused by a mutation that changes the protein which controls movement of salt and water in and out of cells which causes the body to produce a lot of thick mucus in the air passages and in the pancreas which can make it difficult to breathe and digest food, caused by a recessive allele, carried by about 1 in 25 people
183
Give 3 arguments for embryo screening
Helps people to stop suffering, laws to stop it going too far (at the moment parents cannot even select the sex of their baby), treating disorders costs the government and tax payers a lot of money
184
Give 3 arguments against embryo screening
Increases prejudice against people with genetic problems as they are presented as undesirable, may come a point when everyone wants to screen embryos to choose the most desirable one (e.g blue eyed or blonde haired), expensive process
185
Give an example of when an invariant causes only a small change to the organism's phenotype
Eye colour and some other characteristics are controlled by more than one gene so a mutation in one of the genes may change eye colour slightly but not cause a huge difference
186
How was Darwin's theory later backed up? 3 ways
Discovery of genetics provided an explanation of how individuals born with beneficial characteristics can pass them on and showed that it is genetic variants that give rise to phenotypes that are suited to the environment, by looking at fossils of different ages (the fossil record) you can see how changes in organisms developed slowly over time, discovery of how bacteria are able to evolve and become resistant to antibiotics
187
How does selective breeding reduce the gene pool? 3 points
The gene pool is the number of different allelles in a population so this is reduced as the farmer keeps breeding from the 'best' animals or plants which are all closely related which is known as inbreeding. Inbreeding causes health problems as there is more chance of organisms inheriting harmful genetic defects when the gene pool is limited , there can be serious problems if a new disease appears when they are all closely related because if one is going to be killed by a new disease all the others are likely to succumb to it
188
Identify 3 ways fossils form
Gradual replacement by minerals, casts and impressions, preservation in places where no decay happens
189
Describe fossil formation from gradual replacement by minerals
Things like teeth/shells/bones last a long time when buried as they don't decay easily, they're eventually replaced by minerals as they decay which forms 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 is dug up
190
Describe fossil formation from casts and minerals
Fossils can be formed when an organism is buried in a soft material like clay which later hardens and the organism decays leaving a cast of itself, an animals burrow or plant's roots can be preserved as casts or footprints can be pressed into soft materials which leave an imprint when it hardens
191
Describe fossil formation from preservation in places where no decay happens
In amber (a clear yellow stone made from fossilised resin) and tar pits there is no oxygen or moisture so decay microbes can't survive, in glaciers it is too cold for decay microbes to work, peat bogs are too acidic for decay microbes
192
Why can't hypotheses of how life began be supported?
Many early forms of life were soft bodied and soft tissue tends to decay away completely so the fossil record is incomplete, fossils that did form millions of years ago may have been destroyed by geological activity (e.g the movement of tectonic plates could have crushed fossils already formed in the rock)
193
Identify 4 reasons antibiotic resistance is becoming more common
They are prescribed for non-serious illnesses and illnesses caused by viruses -this overuse provides a situation where naturally resistant bacteria have an advantage and so increase in numbers, some people do not take the full course of antibiotics so some bacteria are left which can mutate and develop into resistant strains, farmers give antibiotics to animals so they grow faster and don't become ill but this can lead to antibiotic resistant bacteria developing which are passed on to humans in meat preparation/consumption, the rate of drug development is slow so cannot keep up with the demand for new drugs as more bacteria become resistant and it is a very costly process
194
Identify 4 things plants need for survival
Water, light, space, mineral ions (nutrients) from soil
195
Identify 4 things animals need for survival
Mates, food, water, space (territory)
196
What are stable communities?
Communities where all the species and environmental factors are in balance so population sizes are roughly constant. Two examples are tropical rainforests and ancient oak woodlands
197
How are whales structurally adapted?
They wake up in cold places so have a thick layer of blubber and a low surface area to volume ratio
198
Identify a functional adaptation of desert animals
Conserve water by producing very little sweat and small amounts of concentrated urine
199
Identify a behavioural adaptation of bird species
Migrate to warmer climates during the Winter to avoid problems of living in cold conditions
200
Identify a functional adaptation of brown bears
Hibernate over Winter, they lower their metabolism which conserves energy so they don't have to hunt when there's not much food about
201
What is an extremophile?
Microorganisms adapted to living in very extreme conditions such as high temperatures or places with a high salt concentration or at high pressure or very acidic places
202
Describe the role of producers
Usually green plants or algae which make glucose by photosynthesis, some of this glucose is used to make other biological molecules in the plant (these biological molecules are the plants biomass, the mass of living material which can be thought of energy stored in a plant)
203
What are predator-prey cycles?
The population of any species is usually limited by the amount of food available, if the population of prey increases so will that of the predator but as the predator's population increases that of the prey decreases. Predator-prey cycles are usually out of phase with each other as it takes a while for one population to respond to changes in the other
204
Identify 4 conflicting pressures affecting how biodiversity is maintained
Costs of programmes and keeping a watch on whether these programmes are being followed, people who were employed in deforestation could be left unemployed which affects the local economy, certain organisms like locusts and foxes are killed by farmers to protect crops and livestock, land is sometimes in such high demand that previously untouched land with high biodiversity has to be built on
205
Identify 2 reasons deforestation occurs
Clear land for farming to produce more food, grow crops from which biofuels based on ethanol can be produced
206
Identify 3 consequences of deforestation
Amount of carbon dioxide removed from the air by photosynthesis is reduced and less is locked up in trees, carbon dioxide is released when trees are burnt to clear land and it is released as a waste product of respiration in microorganisms feeding on bits of dead wood, habitats like forests have high biodiversity so there is a danger of species becoming extinct when they are cut down
207
How do breeding programmes help protect ecosystems and biodiversity?
Animals are bred in captivity to make sure the species survives if it dies out in the wild, individuals are sometimes released out into the wild to re establish or boost a population
208
How does habitat protection help protect ecosystems and biodiversity?
Programmes to protect and regenerate rare habitats like mangroves/coral reefs/heathland helps protect the species that live there, programmes to reintroduce hedgerows/field margins around fields on farms where only one type of crop is grown -field margins are areas of fields where wild flowers and grasses are left to grow which provides a habitat for a wider variety of organisms than could survive in a single crop habitat
209
How does preventing global warming help protect ecosystems and biodiversity?
Regulations and programmes introduced by governments to reduce level of deforestation and amount of carbon dioxide being released into the sir by businesses
210
How does reducing waste help protect ecosystems and biodiversity?
Recycle more to reduce amount of waste dumped in landfill sites, this reduces the amount of land taken over for landfill which leaves ecosystems in place
