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  • Created by: jawjeener
  • Created on: 22-03-16 10:43
What are the structures which produce spermatozoa?
Seminiferous tubules
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What are two structures which produce secretions that aid sperm mobility?
Seminal vesicle // Prostate gland
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Why is the middle piece of the sperm packed with mitochondria?
To provide ATP for movement
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What is the function of the Sertoli cells?
To nourish the spermatids and protect them from the immune system
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What is the function of the interstitial cells?
To secrete testosterone // The male hormone
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What is meant by the term 'fertilisation'?
The fusion of the sperm with the ovum
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What is the product of fertilisation?
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Why is internal fertilisation a necessary adaptation for life on land?
So that the organism becomes independent of water as the sperm is introduced directly into the female tract
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What is the function of the enzymes released after the rupture of the acrosome membrane?
To soften the layer of cells surrounding the oocyte to enable to sperm to penetrate the egg
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What is the function of the fertilisation membrane?
To prevent the entry of further sperm
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Why is urine used to test for pregnancy?
Urine of a pregnant female contains the hormone hCG
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What is one antigen?
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Why does a blue band appear in the large window when a sample of urine from a pregnant woman is tested?
The antibody hGC forms a blue bead complex with the first antibody // This complex binds to the antibody in the large window and prevents it diffusing any further
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What are three parts that make up a carpel?
Ovary // Style // Stigma
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What is the difference between self-pollination and cross-pollination?
Self - the transfer of pollen to the stigma of the same flower // Cross - the transfer to another flower on another plant of the same species
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Why do wind-pollinated flowers produce large quantities of pollen?
Due to chance, much of the pollen fails to reach the stigma of another flower and so it is wasted
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What is one way in which pollen grain is adapted for dispersal?
A tough wall to prevent drying out // sculptured // spiky surface to attach to insects
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What is the function of the pollen tube nucleus?
To control the growth of the pollen tube
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What assists the growth of the pollen tube?
The secretion of enzyme to digest a path // May provide nutrients for growth
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How is the triploid endosperm nucleus formed?
One of the male nuclei from the pollen tube fuses with both polar nulcei in the embryo sac
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What is the definition of a 'recessive allele'?
It expresses itself only in the presence of another identical allele // The effect of the allele is apparent in the phenotype of the diploid organism only
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What is meant by the phrase 'a gene is sex linked'?
A gene that is carried on either the X or the Y chromosome
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What percentage of recombinants would you expect from a cross of linked genes?
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Why do gene mutations rarely show up in the phenotype?
Most mutations are recessive and the recessive allele is not expressed in the genotype
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Why is bacteria used widely in mutation experiments?
Bacteria have a short life cycle and show a greater rate of mutation
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What is one mutagen?
Xrays // Gamma radiation // UV light
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What term is applied to a mutagen that causes cancer?
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What are the two forms of mutation?
Gene and chromosome
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What are the chances of two parents with sickle-cell trait having a child with sickle-cell anaemia?
1 in 4 // 25%
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During micropropagation of cauliflowers, the number of chromosomes in the cells of some of the plants produced is 36, not 18 as it is in the parent plant...
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How has the number of chromosomes doubled?
Breakdown of spindle fibres during cell division // Non - disjunction // Chromoatids don't separate
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Why are the cauliflower plants that have three of each chromosome type in each of their cells sterile?
Pairing of homologous chromosomes cannot take place // No meiosis // No gametes produced
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Which chemical in tobacco smoke contains carcinogens?
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Is the presence or absence of ear lobes an example of continuous or discontinuous variation?
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How might genetic variation be increased in asexually reproducing organisms?
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What are four sources of variation?
Mutation // Crossing over // Independent assortment // Alleles contributed from each parent
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What is meant by the term 'selection pressure'?
The environmental force altering the frequency of alleles in a population?
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Why do population numbers remain constant despite the production of large numbers of offspring?
Predation // Competition // Carrying capacity is reached
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What is meant by 'geographical isolation'?
When a physical barrier such as a mountain prevents two populations from interbreeding
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What is the term used to describe the mother that receives a transplanted embryo?
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Why would it be undesirable to produce all farm animals by cloning?
No variation
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What is one advantage of cloning animals?
Production of single indentical genetic line of cells with desirable characteristics to maintain genetic stocks
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What is one medical application of tissue culture?
Skin graft // Organs for transplantation
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Why are sterile conditions necessary in micropropagation?
To prevent fungal growth
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What is the process by which totipotent cells develop into root and shoot cells?
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What are two advantages of micropropagation for large suppliers such as supermarkers?
Uniform crop // storage // transport
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What two phrases summarise the disadvantages of micropropagation?
Sterile conditions // Genetically unstable
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What events must take place once the replacement gene is inside the lung cell for the treatment to be successful?
Get into nucleus // Join the DNA of the cells // Protein synthesis // Reinserted into membrane
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The bacterium E.coli is widely distributed and capable of exchanging genetic material with other types of bacteria // Why do some scientists consider that the use of recombinant DNA could be dangerous?
A recombinant gene might pass from the organism it was placed in, into a completely different organism // A virus might transfer genes for herbicide resistance from a crop plant to a weed
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Genetically modified bacteria often have antibiotic resistance maker genes added // This antibiotic resistance could be transferred to harmful bacteria
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What is one advantage of the reverse transcriptase technique?
Contains only the gene required // not unwanted gene // Doesn't carry junk DNA or introns // Process doesn't produce a variety of other fragments which need to be screened out
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Why are gene markers necessary?
To show which bacterial cells have taken up the plasmid
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What is the main concern regarding the pollen of GM crops?
Pollen may be transferred to other plants // Introduce features such as herbicide resistance which could be detrimental if transferred to weed species
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What is the enzyme used to cut the DNA?
Restriction endonuclease
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What type of bond is broken when DNA strands are separated in the PCR?
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Why is it important that the fragments of DNA used in PCR are not contaminated with any other biological material?
Biological contaminants may contain DNA and this DNA would be copied
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Why do forensic scientists often use PCR when producing a genetic fingerprint?
To increase the quantity of DNA because the sample obtained from a crime scene might be very small
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What is meant by 'germ therapy'?
Replacing defective gene with a healthy gene in the fertilised egg
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Why do carnivores have a much higher secondary productivity than herbivores?
A protein rich diet is more readily and efficiently digested // No energy consuming symbionts in the digestive tract // faeces contain less undigested matter as there is no cellulose in the diet
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What is the main difference between primary and secondary succession?
Primary - the introduction of plants and animals into an area that has not previously supported a community // Secondary - the reintroduction of organisms into an area previously occupied but perhaps destroyed by fire
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What is the plant type found in a climax community?
Tree (e.g oak)
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How are some bacteria resistant to penicillin?
They produce the enzyme PENICILLINASE which makes penicillin ineffective
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What is the main disadvantage of interbreeding, in genetic terms?
Increases the chances of two harmful recessive genes combining
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What are three main reasons for the decline in numbers of large mammals such as gorillas and tigers?
Loss of habitat // Over-hunting by humans // Competition from introduced species
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Why does yield progressively decline if the same crops are grown in the same field year after year?
Mineral depletion // Increase in pests // Increase in disease
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What are three consequences of deforestation?
Climate change // Soil erosion // Destruction of natural habitats
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How does deforestation contribute to soil erosion?
Lack of roots binding soil together // Resulting in rainfall washing the soil away
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What is a crop used to manufacture biofuel?
Oil seed ****
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Which country is the world leader in the use of biofuels?
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What is the main technical problem associated with the production of biofuels?
Pre-treatment of cellulose prior to fermentation
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What are two measures that can be enforced to reduce overfishing?
QUOTAS // Restricting net mesh size // Limits to catches // Restricted times of year for fishing
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What are two substances added to fish stocks that can cause potential problems to the environment?
Antibiotics // Pesticides
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What are two reasons for the increase in carbon dioxide in the atmosphere?
Burning of fossil fuels // Deforestation
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What must farmers do to comply with regulations to reduce levels of nitrate in waterways?
Restrict the quantity of fertiliser added to soil // Only apply fertiliser when crops are growing // Leave 10 metre strop between land and waterway
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Other cards in this set

Card 2


What are two structures which produce secretions that aid sperm mobility?


Seminal vesicle // Prostate gland

Card 3


Why is the middle piece of the sperm packed with mitochondria?


Preview of the front of card 3

Card 4


What is the function of the Sertoli cells?


Preview of the front of card 4

Card 5


What is the function of the interstitial cells?


Preview of the front of card 5
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