Variation and inheritance Flashcards
what is the cause of variation and why is it important?
environmental variations and genetic variation (mutations)
important as leads to natural selection, and so, evolution
What is chlorosis?
conditions in plants preventing them from producing norm levels of chlorophyll = pale or yellow leaves
reduces plants ability to make food by photosynthesis
this change in phenotype is mainly caused by enviro mental actors
What environmental factors cause chlorosis?
lack of light- in absence of light plants turn off their chlorophyll production to conserve resources
Mineral deficiencies- eg. lack of iron or magnesium- iron needed as cofactor for enzymes that make chlorophyll, magnesium found in the heart of the chlorophyll molecule. If either are lacking in the soil, plant cannot make chlorophyll and leaves will gradually become yellow
virus infections- viruses interfere with metabolism of cells, symptom is yellowing in infected tissue as they can no longer support the synthesis of chlorophyll
What is variation of body mass a result of?
both environmental and genetic factors
extreme variations, such as obesity= more environmental
obesity can sometimes be genetic= eg. the obese mouse has mutation on chromosome 7, causes the pattern of fat deposition in body to be altered
How can genetic variation be created?
inheritance of different alleles from parents
combination determined by sexual reproduction, the random fusion of gametes at fertilisation and meiosis, will affect characteristics displayed
What are modifications?
any change the environment makes to a person’s phenotype
cannot be passed to offspring
What is continuous variation?
there are 2 extremes, with every degree of variation possible in between
many genes are normally involved (polygenes) and the environment can have great affect
EG. height and weight
What is discontinuous variation?
individuals fall into distinct groups
normally only one gene is involved and the environment has little, to no effect
EG. blood group
