B15 - genetics and evolution fact test Flashcards
what did gregor mendel do
- carried out breeding experiments on pea plants
- one of his observations was that the inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged
why wasn’t mendel’s work appreciated until after his death
- he didn’t publish his work in a scientific journal
- people weren’t aware of genes, DNA or chromosomes
what was lamarck’s theory of evolution
changes that occur in an organism during its lifetime will be inherited
what was darwin’s theory of evolution
evolution by natural selection
published his ideas in On the Origin of Species based on observations he made on a round the world expedition
what was the theory of evolution by natural selection
- individual organisms within a particular species show a wide range of variation for characteristic
- individuals with characteristics most suited to their environment are more likely to survive and breed successfully
- the characteristics that have enabled these individuals to survive are then passed on to the next generation
why were darwin’s ideas gradually accepted
- challenged the idea that God made all the animals and plants on earth
- there was insufficient evidence at the time the theory was published to convince many scientists
- the mechanism of inheritance and variation was not known until 50 years after the theory was published
why are darwin’s theories accepted today
- we now know how genes work
- there is more evidence from the fossil record
- there is knowledge of how resistance to antibiotics evolves in bacteria
when are two new species formed (speciation)
if 2 populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring
what are the steps of speciation
- 2 ancestral populations of a species are separated by a geographical barrier
- there is genetic variation in each population due to random mutations
- each population is under different environmental conditions
- natural selection occurs - better adapted individuals are more likely to survive and reproduce
- so favourable alleles are passed onto offspring
- over many generations, the populations become so different that they can no longer successfully interbreed to produce fertile offspring
what did wallace do
independently proposed the theory of evolution by natural selection
best known for his work on warning colouration in animals and his theory of speciation
what are fossils
the remains of organisms from millions of years ago, which are found in rocks
how may fossils be formed
- from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
- when parts of the organism are replaced by minerals as they decay
- as preserved traces of organisms, such as footprints, burrows and rootlet traces
what are conditions needed for decay
warm, moist with oxygen (aerobic conditions)
why can’t scientists be certain about how life began on earth
- many early forms of life were soft bodied which meant that they left few traces behind
- what traces there were have been mainly destroyed by geological activity
what is extinction
extinction occurs when there are no more remaining individuals of a species still alive
