biology flashcards

where are chromosomes found in the cell?
the genetic material in the nucleus is arranged into chromosomes- there are 24 pairs of chromosomes.
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true or false-- in humans, chromosomes are found in pairs of four?
false. they are found in pairs of two.
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what, exactly, are alleles?
different versions of the same gene are called alleles.
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is a person's weight determined by genes, the environment or both?
both. if you eat doughnuts all the time your going to be fat, no amount of genes or a high metabolic rate is going to save you.
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how do genes control our characteristics?
genes exist in different versions- each version gives a different form of characteristic. characteristics are often controlled by several different genes working together.
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what do "genotype" and "phenotype" mean?
a genotype is all the genes that an organism has, whereas a phenotype is the characteristics that an organism displays.
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name the two types of sex cell?
egg. sperm.
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how many chromosomes are found in the sex cells?
half of that found in an average cell- this is because when the sperm and egg fuse together it creates the normal twenty-three pairs.
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why do we all look like our parents?
we get some of our alleles from both our parents, which is why we look a bit bit like both, but identical to neither.
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what's the difference between homozygous and heterozygous?
homozygous: two of the same alleles for a trait. heterozygous: two different alleles for a trait.
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describe two ways that micro-organisms can cause the symptoms of an infectious disease?
1) they produce toxins that poison the cell, causing symptoms like fever. 2) the micro-organisms multiply within a cells walls, the cell eventually bursts under the excess pressure and strain.
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explain why bacteria multiply quickly inside the human body.
because humans have the correct temperature, as well as warm, moist conditions in places like the intestines and the gut.
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If you start with one bacterium that reproduces after every forty minutes, how many bacteria do you have after six hours?
six hours= three hundred and sixty minutes, divide this by forty to get the reproduction periods. three hundred and sixty divided by forty is nine. so two to the power of nine is five hundred and twelve.
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what is the role of the immune system?
to deal with infectious micro-organisms that enter the body.
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give three ways that antibodies help to get rid of infection?
1) mark- they mark the micro-organisms so that other white blood cells recognise that it needs to be ingested. 2) they kill it outright. 3) they neutralise the toxins the micro-organism produces.
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why are you immune to most of the diseases that you've already had?
after an infection a few white blood cells are always left over, these are memory cells, and if you get the same infection again they can reproduce quickly and halt the infection before you feel the symptoms.
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how does vaccination give you immunity in the future?
injecting dead or inactive pathogens into your body creates antibodies, these kill of the invading micro-organisms. if you get the illness again, the memory cells quickly recognise and kill it.
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how does some people getting vaccinated help the people that don't?
the disease cannot be spread easily through a small population, so the risk of being infected is decreased.
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why do people react to vaccinations differently?
because their genes mean that there can be side effects of the vaccination, like swelling or flu.
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what is an antimicrobial?
antimicrobials kill or inhibit bacteria, fungi and viruses.
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explain why someone with the flu would not be given antibiotics?
because the flu is a viral infection, so antibiotics won't help because they're meant for bacterial infections.
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how are some micro-organisms resistant to antimicrobials?
sometimes a gene on a micro-organism can mutate, this makes it resistant to antimicrobials. because of this it has a survival edge over other micro-organisms, so it will reproduce and thrive.
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why do you always have to finish a course of antibiotics?
because if you don't the naturally more resistant bacteria will continue to reproduce, and a mutation could mean that it becomes an incurable super bug.
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how are drugs tested before they are given to humans?
on animals, and on human cells.
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why are drugs tested on healthy people first, not the people with the illness?
to ensure there are no harmful side effects, people with an illness are more vulnerable to side effects.
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what is a placebo?
a fake drug given in place of an effective one.
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what is a double blind clinical trial?
when neither the patient nor the doctor knows whether they have been using a placebo instead of a drug.
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explain the importance of a long term clinical drug trial....
you can see the effects a drug has after a long period of time; you can check any side effects that a drug might have long term.
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the heart is a double pump- what does this mean?
the right side pumps de-oxygenated blood, the left side pumps oxygenated blood around the body.
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explain the structure of an artery...
thick walls and elastic, strong walls- this is because arteries are under high pressure.
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explain the structure of a vein...
thin walls because it is under less than the arteries, they have valves to keep the blood flowing in the right direction,
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explain the structure of a capillary...
they're one cell thick, permeable walls so that blood can diffuse across, small lumen.
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how can you take someone's heart rate by measuring their pulse?
the pulsation of an artery is caused by blood being pumped by the heart, so they're equal.
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what is a blood pressure measurement?
reading the pressure of the blood against the walls an artery.
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how does high blood pressure increase the risk of heart disease?
high blood pressure can ruin the smooth wall of an artery, these can cause the build up of fatty deposits and restrict blood flow.
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how can epidemiological help to identify the risk factors for heart disease?
it can find patterns in diseases and identify the factors that caused them.
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what is homeostatis?
maintaining a constant internal environment.
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name the three main components of the body's automatic control systems...
1) brain. 2) nerve endings. 3) _______?
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give two ways that water is gained by the body:
1) drinking, 2) respiration, 3) food.
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what factors affect the concentration of urine produced by the kidneys?
fluids and salts, exercise and external temperature.
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which gland releases ADH?
the pituitary gland.
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if there is a lot of water in the blood will more or less ADH be released?
increase the amount of ADH, this way the kidneys will absorb more water.
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what affect does alcohol have the production of urine?
alcohol suppresses ADH production, this means that a larger amount of more dilute urine is produced.
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what is a species?
a group of organisms that can breed to create fertile offspring.
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what has a greater effect on species- mutations in the sex cells or in normal cells?
mutations in sex cells.
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how does elective breeding differ from natural selection?
selective breeding choosing specific features that you want to emulate through the offspring of an organism, whereas natural selection is a completely random mutation.
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how long ago did life on earth begin?
three thousand five hundred million years ago.
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how does evolution lead to the formation of new species?
the random mutations cause new features, if these are of benefit they are passed onto the offspring of the organism, environmental changes also play a part- a species will adapt to be more suitable for its environment.
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how do scientists use DNA to show evolution?
any similarities in a species DNA suggests they have all evolved from the same simple life forms, similarities and differences in DNA show how life has evolved.
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how do scientists use fossil records to show evolution?
fossil records show organisms getting more and more complex as time goes on.
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why lamarck's theory of evolution rejected in favour of darwin's?
because lamarck said that anything that was developed on an organism was immediately passed onto its offspring- like, if i was really, really muscley then all my kids' would be as well.
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what is biodiversity?
the number of different species on earth, the range of different types of organism, the genetic variation between organisms of the same species.
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give one likely cause for the increase in species extinction
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why do scientists classify animals?
it shows us evolutionary relationships between animals, and it can extend to fossilised organisms.
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give one factor that scientists use when they classify organisms?
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how do scientists use classification to show evolutionary relationships?
organisms that are in similar classification groups will share a lot of genetic and structural characteristics, so its likely they evolved from the same ancestors.
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what four things do plants need to live?
light- for photosynthesis, food- for growth and energy, carbon dioxide- for photosynthesis, water- for growth.
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why do organisms compete for resources?
if any essential factor in a habitat is in short supply then all the species that need it will compete for it, some organisms won't survive. this limits the size of the populations in that particular habitat.
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why is a whole food chain effected if one thing dies out?
because there is interdependence between species, this means that any change can have far reaching effects.
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what are the three main reasons for a species going extinct?
environmental changes, new species introduced, change in the food web.
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what is the source of all the energy in a typical ecosystem?
the sun.
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explain how energy is transferred through a food web?
energy is transferred when an organism eats another organism, some of this energy is lost through waste, heat and movement- this means that energy is lost at each stage.
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why is it unusual to find a food chain with more than five stages?
because energy is lost at each stage of the food chain by the fifth stage there is barely any energy left- this means there's not enough to support an organism.
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how is carbon dioxide turned into carbon compounds?
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how is carbon passed between animals in the ecosystem?
eating passes carbon compounds along the chain.
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give four ways that carbon returns to the atmosphere
combustion, plant and animal respiration, decomposition.
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what role to decomposers play in the nitrogen cycle?
decomposers break down proteins in dead plants and animals, and urea in excreted animal waste, into ammonia.
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which micro-organisms turn ammonia into nitrates?
nitrifying bacteria that are found in the soil.
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what important role do nitrogen fixing bacteria play in the nitrogen cycle?
they turn nitrogen in the air into nitrogen compounds which plants can use.
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give three non-living indicators that can be used to measure environmental changes.
temperature, nitrate levels, carbon dioxide levels.
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give three living indicators that can be used to measure environmental changes.
lichen- very sensitive to levels of sulphur dioxide, mayfly nymphs- very sensitive to levels of oxygen, phytoplankton- like high levels of nitrates and phosphates.
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explain how mayfly nymphs can be used to measure environmental change
mayfly nymphs are very sensitive to levels of pollution in water, if you find lots of mayfly nymphs in a river it probably means that the river is very clean.
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define sustainability.
meeting the needs of today's population without effecting future generations, and allowing them to meet their own needs.
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what is monoculture?
growing only one type of crop, it doesn't help maintain biodiversities, as it only supports a few species.
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explain two ways that packaging could be more sustainable
using renewable materials, using less energy.
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how is decreasing the amount f packaging the most effective solution?
making and transporting any packaging material uses energy, but a smaller amount of packaging means less energy is needed to ship and create it.
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what sex chromosomes do males have?
x and y.
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how does a gene on one of the human sex chromosomes cause embryos to develop into males?
the y chromosome causes the development of testes on an embryo.
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is the allele for cystic fibrosis dominant or recessive?
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what are the symptoms of cystic fibrosis?
coughing, thick mucus in the throat and lungs, difficulty digesting food.
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what are the symptoms of huntington's?
shakiness, confusion, clumsiness, poor concentration and mood changes.
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what is the chance of someone inheriting huntington's if their parent has one copy
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during IVF what is the process of testing embryos before they are implanted for genetic disorders?
pre-implantation genetic diagnosis- any embryos that do have a genetic disorder are destroyed before they can be implanted.
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other than testing embryos during IVF give one other use of genetic testing?
to check children and adults for faulty genes.
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describe three issues surrounding IVF...
potential harm to the mother, potential harm to the child, it's wrong to 'play god'
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what is the definition of the term clone?
clones are genetically identical organisms. they have the same genes, and the same alleles of those genes- any differences between clones are down to environmental factors.
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how can the following reproduce asexually- bacteria, some plants and some animals?
bacteria: bacteria divide, so any offspring are identically identical to the parent cell. some plants: some plants produce runners, these are identical to the parent plant. some animals: greenfly can reproduce asexually, but any offspring are female.
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how are identical twins formed?
when an egg is fertilised by a sperm it splits in half- each section has exactly the same genetic information, so they are clones.
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what are stem cells?
stem cells are unspecialised cells, they are usually taken from embryos but some are found in adult cells, like bone marrow.
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what is the difference between the two main types of stem cell?
embryonic stem cells can be grown into anything if given instruction, whereas adult stem cells can be grown into a wide range of different cells and tissues, but not everything.
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how can stem cells be used to treat illnesses?
because you can grow stem cells into anything, you can use them to replace dead or damaged cells- for example you can use them to grow insulin for people that have diabetes, or nerve cells for people with spinal injuries.
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Other cards in this set

Card 2


true or false-- in humans, chromosomes are found in pairs of four?


false. they are found in pairs of two.

Card 3


what, exactly, are alleles?


Preview of the front of card 3

Card 4


is a person's weight determined by genes, the environment or both?


Preview of the front of card 4

Card 5


how do genes control our characteristics?


Preview of the front of card 5
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