6.3 Genetics and evolution (Triple) Flashcards
Outline the theory of evolution by natural selection. (Triple)
Individuals of a species show a wide range of variation for a characteristic.
Those with the characteristic most suited to the environment will survive and breed most successfully.
The desirable characteristic that has enabled the individuals to survive our post onto their offspring.
Why was Darwin’s theory of evolution not accepted initially? (Triple)
● Most people believed in creationism
● Insufficient evidence to prove the theory
● The mechanism of variation and inheritance was not known as the time
What was Jean-Baptiste Lamarck’s theory of inheritance? (Triple)
That changes during the lifetime of an organism can be inherited
What is speciation? (Triple)
The formation of a new species, when two populations become so varied that they cannot interbreed to produce fertile offspring.
What is the definition of a species? (Triple)
A group of organisms with similar characteristics which are able to interbreed to produce fertile offspring
Outline the process of speciation through geographic isolation. (Triple)
- Two populations of the same species are separated geographically
- Geographic isolation prevents interbreeding and mixing of genes between the populations
- Due to different selection pressures, different mutations occur producing different phenotypes in each population
- Over time, the two populations may evolve so that they are not able to interbreed
Why is genetic variation important in speciation? (Triple)
Genetic variation produces phenotypic variation, some of which are better suited to the environment and are selected for.
How did Mendel study inheritance? (Triple)
By carrying out breeding experiments on plants and analyzing the ratio of characteristics in offspring
Why was Mendel’s work not recognized until after his death? (Triple)
He could not explain the mechanism of inheritance, as chromosomes were only discovered after his death.
It was not communicated well to other scientists and not published in a reputable scientific journal.
State two kinds of evidence used to show evolution
● Fossils
● Antibiotic resistance in bacteria
How are fossils formed?
Parts of organisms that have not indicated due to conditions needed for decay being absent
Parts of organisms that have been replaced by minerals as they decayed e.g. bones
Traces of organisms are preserved, covered in sediment and becoming rock
Why are there few traces of early life forms left behind?
Early life forms were mostly soft bodied
How the fossils act as evidence for evolution?
Scientists can identify the ages of the fossils and use them to show how organisms change over time
What do branches in evolutionary trees indicate?
Where speciation has occurred
What is extinction?
Where there are no individuals of a species still alive
