Speciation and natural selection Flashcards
what is a species?
group of organisms that can reproduce to produce fertile offspring
what are hybrid plants?
the plant produced when two different species of plant interbreed
What are the 2 types of speciation?
allopatric speciation-
physical barrier has appeared separating species into 2 sep areas = diff selection pressures = dif alleles favoured = speciation if they have changed so much that they can no longer interbreed to produce fertile offspring
sympatric speciation-
same habitat, same selection pressures, but mating preferences or disruptive selection happening
= new species to arise in same habitat
usually happens in animals - either due to mating preferences or 2 diff extreme phenotypes, meaning mating they cant physically recognise each other as same species, could also be mating behaviours arent recognised
reproductive barriers- barriers to successful interbreeding can be prezygotic (prevent fertilisation and formation of zygote), or postzygotic (result of hybridisation, reduce viability or reproductive ability of offspring)
What is speciation?
formation of a new species through the process of evolution
what is the wild type allele?
populations are usually polymorphic (display more than one distinct phenotype) for most characteristics
the allele coding for the most common, or normal, characteristic = the wild type allele
other forms of that allele, resulting from mutations = mutants
What is artificial selection and selective breeding?
fundamentally same as natural selection except for nature of selection pressure applied
instead of environmental changes leading to survival of fittest, it is the selection for breeding of plants, or animals with desirable characteristics by farmers or breeders
done by farmers
What is inbreeding?
breeding of closely related individuals
What problems are caused by inbreeding?
small gene pool, low genetic diversity, low chances of the population being able to adapt to changes in their environment
many genetic diseases are caused by recessive alleles (cystic fibrosis results in excess mucus in digestive system and lungs). organisms that are related are genetically similar = likely to have same recessive alleles = greater chance of offspring being homozygous for these recessive alleles = m more affected by these disorders, resulting in these organisms not being able to survive and reproduce
What are ethics of pedigree dogs and artificial selection?
canines began as the wild species - grey wolf
began to hang around with humans due to food being more available, became increasingly friendly,, becoming integrated into human groups, eventually used to help hunt and as guard dogs
hunter-gatherers made settlements, began farming, dogs had to herd animals
different traits were selected for depending on what they were used for- hunting, fighting, herding, for status
dogs with diff characteristics evolved
characteristics exaggerated by continuous selective breeding
selective breeding based off looks
health issues- skull of charles spaniel= too small for brain = pain
what are gene banks?
store biological samples, other than seeds, like sperm or eggs
they ae usually frozen
What are seed banks?
keep samples of seeds from both wild type and domesticated variations
How can alleles from gene banks increase genetic diversity?
outbreeding
reduces occurrence of homozygous recessive, increasing potential to adapt to environmental change
