B14- variation and evolution Flashcards Preview

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Flashcards in B14- variation and evolution Deck (14):

what is natural selection

organisms that adapt and gain an advantage are more likely to survive and breed


what are mutations

a change in the dna code that provides variation in an organism. most have no effect on the phenotype of an organsima but some can cause the organism to die or give them an advantage to survive


summarise the survival of the fittest theory

individual organims within a species may show a wide range of phenotype and genetic variation

individuals with characteristics most suited to the environment are more likely to survive to breed

the alleles that have enables this organism to survive are then passed on to the next generation


how do 2 populations of a species form 2 new species

when they become so different from each other due to natural selection that they can no longer interbreed and produce fertile offspring


what is selective breeding

selecting animals and plants from a mixed population that have useful or desirable characteristics


what features is selective breeding used for to select

disease resistance in food crops or garden plants
animals that produce more meat or milk
domestic dogs or farm animals with a gentle nature
large, unusual, brightly coloured or strongly scented flowers


what are limitations of selective breeding

reduces the number of alleles in a population as only organisms with certain alleles are selected
reduction in variation which can be a problem when environment changes as species can't adapt
inbreeding which results in diseases


what does genetic engineering involve

gene for a desirable characteristic is cut out of one organism and transferred to the genetic material in the cells of another organism


what is the process of genetic engineering

1. enzymes are used to isolate and cut out the required gene from an organism
2. gene is inserted into a vector (bacterial plasmid or virus) using more enzymes
3. vector then inserts gene into required cell which may be bacteria, animal, fungi or plants
4. genes are transferred to cells at an early stage of their development so it develops with the desired characteristics
(in plants genes are inserted into the meristem cells which then produce identical clones of the gm plants


what is tissue culture

allows you to make thousands of new plants from one tiny piece of plant tissue which is grown in agar with nutrients and plant hormones to form a big mass of tissues which results in many identical plantlets


how does cloning cattle embryos work

give a cow fertility hormones so she produces many eggs then fertilise the eggs inside the cow, gently wash out the embryos (can be done in a laboratory)
transfer embryos into host mothers who have been given hormones to prepeare for pregnancy


what are advantages of animal embryonic cloning

produces many identical organisms


what are disadvantages of animal embryonic cloning

same cow can produce embryos for 30 or more cows in a year as she doesn't have to carry them
skilled work


what is the process of animal cell cloning

1. nucleus is removed from an unfertilised egg cell
2. nucleus is taken from an adult body cell of an individual of the same species
3. nucleus from adult cell is inserted into empty egg cell
4. new egg cell is electric shocked which stimulates dividing to form embryo cells which contain the same genetic information as the original adult
5. embryo is inserted into a womb to continue development