evolution in plants

Question 1

geographical isolation: redbud (allopatric)

Answer 1

best understood mechanism for speciation is geographical isolation…

two species: western redbud and eastern redbud…
Allopatric speciation…
eastern redbud: weather is rainy year round
western: weather is drier, hotter, grows along streams

no crossover range of geogrpahical location… cant plant one or the other on either side of the country, due to weather.

Question 2

vicariance

Answer 2

something that splits a population into two that allows allopatric speciation… gene flow is cut off which leads to natural selection and other changes in the gene pool. Now are two separate species because dont breed

Question 3

ecological isolation : serpentine soils (sympatric speciation)

Answer 3

soil has high Mg content… which is slightly toxic.
This causes a lot of plants not being able to grow, except for some small subsets… (serpentine arnica and heart-leaf arnica).

Become isolated from other species that cant live on that soil. become isolated

Question 4

temporal isolation: dutchmen’s breeches vs squirrel corn (allopatric)

Answer 4

dutchmens breeches: common in eastern north american forests.

In the east, squirrel corn looks very similar to dutchman breech… flower in a different season. one of these plants mutated to create the other species.

Question 5

Mechanical isolation: catasetum orchids

Answer 5

pollinium must be inserted very specifically for pollination to occur.
Different flower configurations prevent cross pollination.
Can pollinate catasetum by hand, but in nature it must be an insect.
In nature, all 4 are pollinated by same bee specieis, but one attaches pollium to head, anotehr to back, anotehr to abdomen and fourth to left front leg.

Question 6

physiological isolation: S-locus

Answer 6

stigma of one blocks germination of pollen from another species.
Can block the pollens growth, because flower must provide nutrients wont provide the energy for a foreign pollen grain.

Question 7

Hybridization: introgression

Answer 7

two separate species that can hybridize a little bit.
Ex: wild sunflower

Question 8

hybridization : polyploidy

Answer 8

nondisjunction of chromosomes, leads to double the number of chromo.
Gamete is reproductively isolated
over 40% may be polyploids
ex: domestic rose and fireweed

Question 9

asexual reproduction

Answer 9

some sterile specifies can still propogate themselves…
ex: dandelion and blackberry
(apomixis)

Question 10

apomixis

Answer 10

not mixing chromosomes