B14- variation and evolution Flashcards
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
- enzymes are used to isolate and cut out the required gene from an organism
- gene is inserted into a vector (bacterial plasmid or virus) using more enzymes
- vector then inserts gene into required cell which may be bacteria, animal, fungi or plants
- 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
expensive
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
- nucleus is removed from an unfertilised egg cell
- nucleus is taken from an adult body cell of an individual of the same species
- nucleus from adult cell is inserted into empty egg cell
- new egg cell is electric shocked which stimulates dividing to form embryo cells which contain the same genetic information as the original adult
- embryo is inserted into a womb to continue development