Topic 6 Evolution and Variation Flashcards
what is variation?
all the differences in the characteristics of individuals of a population
whats the first cause of variation
allelles the individuals have inherited ,which are genetic variation
some variation is caused by what?
the environment
what are examples of variation being caused by the environment?
ph of soil changing the colour of flowers or language in humans
what are the 3 main causes of variation?
alleles , environment , genes
whats an example of the 3rd type of variation?
Some people having alleles which will make them grow taller but theyll require more calcium in their diet for bones to fully develop so their height will b a combo of genetics and environment
what are mutations
random changes to dna
when do mutations take place and what do they have no effect on?
all the time,,
the phenotype
VERY rarely, mutation can lead to a new what?
Phenotype, this can be beneficial if the environment changes
when do scientists believe life first developed on earth?
more than 3 billion years ago
all species of living things have evolved from what?
simple life forms (single cells)
what is the process called when species evolve from simple life forms?
evolution by natural selection
what is natural selection (rabbits example)
-every rabbit will have a different combo of alleles
-some may have alleles for thicker fur
-if environment gets colder, rabbits with alleles for thicker fur are more likely to survive, reproduce and pass allele onto children
-over generations the allele for thicker fut will become more common among population of rabbits
what is evolution definition
the change in the inherited characteristics of a population over time, through a process of natural selection
how can two rabbits become different species?
if they become so different in phenotype they can no longer produce fertile offspring
what are the 4 types of selective breeding using examples
-dogs being bred to have a more gentle nature
-food crops being bred to resist disease
-cows being bred to produce more milk/meat
-plants being bred to produce large/unusual flowers
how is selective breeding carried out (if you wanted to breed large cows for meat)
take a mixed population of cows & select the largest male and female , breed them together, select the largest male and female offspring and breed them together ,, continue this over many generations until all the offspring are large
whats a big biological problem with selective breeding?
if you breed closely related animals then you can get inbreeding,, this can cause some breeds to be prone to disease or inherited defects (eg dog breeds inheriting disorders like joint problems, heart disease or epilepsy)
what happens in genetic engineering?
genes from one organism are cut out and transferred to cells of a different organism (genome of second organism is modified and now includes gene from first organsism)
example of genetic engineering for diabetic people:
bacteria has been genetically modified to contain human insulin, these now produce human insulin gene which can be purified and used for type 1 diabetes
why do we love GM crops? x
they produce a larger yield & we can make them resistant to disease or insect attack or produce bigger/better fruits
why do farmers love GM crops
some GM crops are resistant to herbacides so farmer can spray their fields to kill weeds without harming the GM crops
what is gene therapy
genetic modification being explored as a way to treat inherited disorders in humans
why is gene therapy #scary?
the long term effects are unknown, eg if we modify a gene we don’t know the potential effects on other genes
what are the main steps in genetic engineering?
1- identify the gene we want to transfer
2-use enzymes to isolate the gene
3-transfer the gene into a small circle of DNA called a plasmid (we can use virus instead of plasmid)
4-the desired genes transferred into cells of target organism
why are plasmids v useful?
they originally come from DNA so are v good at transferring DNA from one organism to another
in genetic engineering, why do we always transfer the gene at an early stage in the organisms development?
to ensure that all cells receive the transferred cells so organism develops w the characteristic we want
whats the advantage with cloning plants?
as the clone is genetically identical tot he og, we know exactly what the clones characteristics will be (eg the colour of flowers)
how to clone a plant using cuttings?
a small piece of the plant is removed and the end is dipped in rooting powder containing plant hormones and encourages the plant to develop roots
when may cutting method not work the greatest
if we want 100s of clones of a plant
what happens in tissue culture?
we take a plant that we want to clone and divide the plant into hundreds of tiny pieces each containing a small n.o of cells,
these groups of cells are incubated with plant hormones ,, these stimulate the plants to grow and develop into fully grown clones
what condition must we use for tissue culture and why
sterile,, we do not want to introduce any microorganisms such as bacteria or fungi
where is tissue culture extremely useful?
commercial plant nurseries where 1000s of genetically identical plants need to be grown cheaply and quickly
what is tissue culture used for other than simply cloning
preserving rare species of plants
what are the stages of cloning by embryo transplants
start with sperm and egg cell from mammal w/ characteristics we desire
fertilisation produces fertilised egg
allow fertilised egg to develop into an early stage embryo
(cells must NOT have started to specialise)
use glass rod to split embryo into two
transplant 2 embryos into host mammal which will grow and develop into 2 identical offspring
what is the main issue with embryo transplants
