lec 26- species and speciation Flashcards
who studied polar bear evolution in greenland (Denmark)?
Eline Lorenzen
how did polar bears come to be?
a northern population of brown bears became adapted to glacial conditions during an ice age, leading to new adaptations that resulted in the origin of the polar bears around 300,000 to 500,000 years ago
do grizzly bears explore northern ice habitats even today?
yes
what area has the highest density of brown bears in the world?
the ABC islands of Alaska
what is the closest relative to polar bears?
ABC bears, closer to polar bears that other brown bears
can polar bears undergo introgressive hybridization?
yes they can interbreed and make viable hybrids
what happened during pleistocene glaciation cycles?
during warm interglacial periods, forests expanded northwards, and some grizzlies also moved north and became isolated till the next glacial
what were the 4 steps to polar bear evolution and interbreeding?
- warm interglaciation with forests up north caused grizzly bears to move up north
- cooling climates as next glaciation approached caused strong selection pressures for grizzly population, resulting in alleles becoming fixated
- mutation in fur color to be white was favored
- interbreeding occurred
what is introgressive hybridization?
complex repeated movement of genes from one species into another species
what are the two types of polyploidy (multiple genome sets in offspring)?
- Autopolyploidy- chromosomes all come from the same species (e.g. 4n, 6n, 8n)
- Allopolyploidy- hybridization followed by genome duplication (multiple genome sets derived from two different species, common in plants)
what part of the human body is polyploidy?
tetraploid liver cells
does allopolyploidy allow for rapid speciation?
yes
what is an example of an allopolyploidy plant?
bread wheat, made up of chromosomes from 3 different species of wild grasses
what are the characteristics of polyploidy plants?
larger flowers and fruits than regular diploid plants
how does allopolyploidy occur?
the two species create hybrid daughter cells but if uneven number of chromosomes, they undergo a doubling event where duplication occurs and then the daughter cells are fertile
why are tetraploids reproductively isolated?
because they have an uneven number of chromosomes (3n) cause eggs and sperm to not be viable
what were the results when Georgi Karpechenko crossed the radish with the cabbage?
it caused a useless allopolyploidy hybrid to form, had the worst characteristics of both rather than the good leaves and roots
who created a tetraploid plant in 1932?
Arne Muntzinc
why are skipper butterflies a cryptic species?
they look alike when butterflies, but caterpillars are very diverse in color and food, there are at least 10 different species
what two domains contain the most cryptic species?
archaea and bacteria
what ancient gene was screened to reveal variation in archaea and bacteria?
16S rRNA
is horizontal gene transfer similar to introgression and allows for variability?
yes
how much DNA is shared between the three different strains of E coli?
only 6%, showing how much variability is in prokaryotes due to horizontal gene transfer
is it hard to classify bacteria?
yes, due to horizontal gene tranfer
If it is hard to define bacteria based off of genes, how do they define them?
by ecological adaptations (e.g. hot spring bacterial mats)
