B15:GeneticsAndEvolution Flashcards
what did Gregor Mendel do
carried out breeding experiments on plants
what were Gregors observations
the inheritance of each characteristic is determined by “units” that are passed on unchanged to their descendants
what was studied in the late 19th century
the behaviour of chromosomes during cell division
what was discovered in the early 20th century
the “units” now called genes were located on the chromosomes
what was discovered in the mid 20th century
the structure of DNA and the mechanism of gene function
what did this scientific work all lead to
the gene theory being developed
what did earlier theories of evolution suggest
changes that occur in an organism during its lifetime can be inherited but we now know in the vast majority of cases this can’t occur
who made a world expedition to propose his theory of evolution
Charles Darwin
what do the individual organisms in a particular species tend to show
a wide range of variation for each characteristic
what does reproduction always give
more than the environment can support
what is the name typically given to the organisms that have inherited the most suited characteristics for their environment
“the fittest”
what are the “fittest” more likely to be able to do
survive and breed successfully
when the “fittest” breed what do they pass on to the next generation
the characteristics that enabled them to survive
why was Charles Darwin’s theory only gradually accepted
conflict held with the belief that God created everything, insufficient evidence, no mechanism for explaining variation and inheritance
what is Alfred Russel Wallace best known for
warning colouration in animals and his theory of speciation
why do new species arise
isolation, genetic variation between the populations, natural selection which operates differently on the two populations, speciation
what is speciation
where the populations become so different that successful interbreeding is no longer possible
what are fossils the remains of
organisms from millions of years ago
in what form are fossils found
in ice, rocks and other places
how can fossils be formed
absence of decay, parts replaced by minerals as they decay and as preserved traces of organisms
what do fossils give us information on
organisms that lived millions of years ago
why is it difficult to determine how long ago life on earth began
very little evidence
what have many traces of early life been destroyed by
geological activity
why are there few traces of early life
as they were soft-bodied so didn’t leave much behind
