B14 - Variation Flashcards
variation
differences in the characteristics of individuals in a population
variation due to
inherited
-environment
-or both
Natural selection
organisms are in competition with members of the same species
-ones that are at an advantage survive and breed
Variation within a species
genes are inherited
new variants
result of mutation
-Change in dna code
mutations when gametes are formed
affect phenotype
-new variants into genes
mutations rarely
produce an adaptation for the organism
theory of evolution by natural selection
all species have evolved from simple life forms
-produces a change in inherited characteristics
better adapted species
process of natural selection + evolution
- genetic variation within species
- better adapted individuals survive + breed
-alleles that are well adapted are passed on
when do two population split and become their own species
when they can no longer interbreed to produce fertile offspring
rapid change in species due to
a new phenotype which is better suited to the environment
selective breeding
speeds up natural selection by selecting animals or plants for breeding that have a required characteristic
Farmers eg of selective breeding
-select ones with desirable characteristics
-forms a breeding stock
Desirabl characteristics eg
-disease resistant crops
-animals that produce more meat/milk
-gentle nature dogs
-heavily scented flower
con of selective breeding
strange combination of genes that wouldn’t have occured naturally
- reduced variation
-inbreeding
pro of selective breeding
useful organisms have been produced
inbreeding causes
pront to disease + inherited defects
-lack of variation
lack of variation means
-reduces number of alleles
-if conditions are unstable and changes
-won’t be able to cope with change
-death of species