a4.1 evolution and speciation Flashcards
what allows different variations in a species
mutation of genes inside organisms over a period of time
theory of evolution
natural selection
evolution
cumulative change in the heritable characteristics of a population
what is not regarded as evolution
acquired characteristics that are not genetic in origin
eg. language
explanation for natural selection
- organisms with more favourable characteristics within the environment will survive
- higher chance to pass on their genes onto the next generation
what does “the fittest” mean
organisms that can adapt to the current environment
what happens if no organisms in a species can adapt to the new environment
become extinct
word for gaining species
speciation
steps for selective breeding [4]
- humans choose the individual animals or plants with the desired characteristics
- then they breed them together to produce offsprings
- then they choose the offsprings carrying the desired characteristics and have them breed with each other
- repeat these steps for several generations, eventually the desired characteristics will be present in more of the offsprings
analogous structures
same function but different evolutionary origins
homologous structures
might look different as the species evolved and perform different functions
eg for homologous structures
pentadactyl limbs
eg of corn
wild ancestor- teosinte (grass)
domesticated- maize (corn)
cons of artificial selection [3]
- reduce variations in the species
- may cause extinction if the environment changes
- selectively bred organisms may not survive in the wild without human support
how is dna base sequences used to support the theory of evolution
not just about gaining genes
also losing genes that are no longer fit for survival
what might mutations in dna do to a species
more adaptive to their environment
name for ‘dead gene’
pseudogene
what leads to divergent evolution
adaptive radiation
why are analogous structures not evidence for evolution
- did not come from the same origin
- species evolved and body parts served a similar function
what is analogous structure a product of
convergent evolution
how to promote speciation
reproductive isolation- their gene pools can no longer mix
eg for speciation
bonobos and chimpanzees
conditions of diff parts of the jungle
south (bonobos)- make friends, less likely to be eaten by predators and can mate
north- presence of gorillas so chimpanzees evolved to be violent and aggressive
differential selection
when theres a selection pressure on a certain type of mates
allopatric speciation
caused by geographical isolation
sympatric speciation
anything BUT geographical
temporal isolation
sympatric speciation
diff time of flowering or in heat
behavioural isolation
sympatric speciation
diff bird songs
adaptive radiation eg
galapagos finches
- adapted on diff islands based on diff food sources
- diff species meet again- diff songs and appearance stops them from mating
why are hybrids rare
zygotes often die during embryo development
are hybrids efficient
no
- genes are not passed onot the next generation
ways to prevent hybridisation [3]
- very specific courtship behaviour
- sterility of interspecific hybrids (odd number of chromosomes so cant be evenly divided and cant make gametes, meiosis cant happen)
- geographical isolation
result if hybrids can produce offsprings
abrupt speciation
factors that cause abrupt speciation [2]
- offspirngs of hybrids
- polyploidy
what is polyploidy
more than 2 sets of homologous chromosomes
why can polyploidy occur
- eg. meiosis did not occur after S phase and a diploid gamete fused with a haploid gamete
- can be due to error in meiosis or hybrid between 2 species
polyploid
cant reproduce with original species but if they can produce fertile offsprings, then u have a new species
4 sets of chromosomes
tetraploid
autotetraploid
4 sets of chromosomes that came from the same organism
why is polyploidy more common in plant cells
pluripotent (stem cells)
triploid
meiosis in an autotetraploid individual produces diploid cells
allotetraploid
- involved hybridisation
- can interbreed with other allotetraploids but not w either of the diploid parent species
how to create new species w polyploidy
2 homologous pairs w AB
- can do meiosis normally
