plant evolution

Question 1

how is a hybrid formed?

Answer 1

1. continuous population
2. barrier splits population
3. allopatric speciation
4. populations meet
5. populations breed and a hybrid is formed

Question 2

why are hybrids of two species not the same as their common ancestor?

Answer 2

1. new alleles arise in each lineage
2. hybrids possess new allele combinations that never existed before.

Question 3

F1 hybrid

Answer 3

first hybrid proceeded by two species.

Question 4

hybrid swarm

Answer 4

comes from F1 hybrids. it is a large population of hybrids.

Question 5

why can’t new mutations be caused in a hybrid swarm?

Answer 5

mutations happen because of your environment nt because of parent species.

any mutations caused will be the same as any other living in that environment.

Question 6

what are some long term evolutionary outcomes of second generation hybrids?

Answer 6

1. transfer of genes between species.
2. evolution of a new species.
3. extinction of one parent species
4. hybrid swarms persist

Question 7

what are the 6 pre-zygotic isolating mechanisms?

Answer 7

1. geographic separation (are they sympatric?)
2. habitat separation (do they grow together?)
3. temporal isolation (do they grow at the same time?)
4. pollinator isolation (do they share the same pollinator?)
5. pollen compatibility
6. pollen competition (conspecific and heterospecific pollen compete agains each other)

Question 8

how to overcome each pre-zygotic barrier

Answer 8

1. geographic isolation = human move things from one place to another.
2. habitat separation = create hybrid habitats or put the two habitats ext to each other.
3. temporal isolation = freak weather and extreme events.
4. pollinator isolation = pollinators can misbehave
5. pollen compatibility = cannot be overcome - barrier must be absent for hybridisation to occur.
6. pollen competition = remove conspecific pollen.

Question 9

post zygotic isolating mechanisms.

Answer 9

7. hybrid viability (will the genes/chromosomes work together?)
8. hybrid fitness (intrinsic) (can it compete with its parents?)
9. habitat-mediated fitness (can the hybrid cope with its habitat?)
10. hybrid fertility
11. hybrid breakdown (failure in F2 as a result of missing print alleles)
12. selection vs alien genes (will introgressed genes persist?)

Question 10

how to overcome each post-zygotic barrier

Answer 10

7. hybrid viability - cannot be overcome they must be viable
8. hybrid fitness - weak hybrid can survive if there is no competition
9. habitat-mediated fitness - intermediate habitat
10. hybrid fertility - at least one out of many sterile seeds will be fertile.
11. species must be closely related so there is a higher chance of allele gaps being filled by other parent alleles.

Question 11

transgressive segregation

Answer 11

hybrid swarm (F2 generation) receive different mixes of alleles and show transgressed phenotypes - further than that of the parent phenotypes.

Question 12

how does difference in genetics between F1 and F2 impact ecology?

Answer 12

1. F2 have many different phenotypes.
2. F2 colonise disturbed habitats because they can adapt to any environment with it (disturbed habitats are very variable)
3. selection for F2s adapted to disturbed habitat occurs.
4. speciation occurs.

Question 13

introgression

Answer 13

the transfer of DNA from one species to another by repeated backcrossing, diluting the material of one species into another.

Question 14

rhododendron ponticum story

Answer 14

alien species was altered in cultivation and most likely acquired cold tolerance, allowing it to become a more effective invader.

Question 15

polyploidy

Answer 15

chromosome doubling

Question 16

three key stages of polyploidisation

Answer 16

1. contact and hybridisation between parent species
2. formation of polyploid seed (chromosome doubling)
3. spread of new polyploid species (is there a habitat for it?)

Question 17

how does a polyploid species find a habitat?

Answer 17

1. displace parent species
2. occupy novel habitat (cold, cultivated, disturbed, crops)

Question 18

polyploid species are common in areas that are new. why is this?

Answer 18

polyploidisation gives plants a rapid means to exploit new environments. it is easier to find a niche in a new environment.

Question 19

how can detritivores go to being herbivores (arthropods)

Answer 19

plants die gradually, the do not go from dead to alive. the intermediate stages provide a pathway for arthropod adaptation.

Question 20

when did land animals evolve

Answer 20

500 mya

Question 21

when did land plants evolve

Answer 21

475 mya

Question 22

when did first land vertebrates evolve

Answer 22

395 mya

Question 23

when did first vertebrate herbivores evolve

Answer 23

300 mya

Question 24

how did large animals evolve?

Answer 24

once there is the first vertebrate herbivore, it diversifies and this results in a large variety of large animals eating plants.

Question 25

what are two possible reasons why flight evolved?

Answer 25

1. escaping predators 2. reaching food

Question 26

how did flight evolve?

Answer 26

1. plant stems were easy to climb but difficult to descend so they had to jump off. 2. in order to avoid landing on predators insects needed to grow bigger and better fling structures.

Question 27

what four ways can an animal get airborne?

Answer 27

1. ballooning 2. vertical takeoff 3. gliding from elevated height 4. horizontal take off high speed takeoff

Question 28

why might plants have encouraged insects to graze on material around their spores?

Answer 28

an insect eats the spores of one tree then goes to another and eats that ones spores. it poos and two spores of different trees are right next to each other and can easily fertilise to create new tree.

Question 29

why is grass so successful?

Answer 29

1. growing points are low to the ground so when top gets eaten it can continue growing. 2. silica in leaves and blades of grass is rough and wears down teeth of predators.

Question 30

how do mammals overcome effects of silica in teeth?

Answer 30

their teeth are long and never stop growing.

Question 31

what physiological innovation does grass have to increase the rate of photosynthesis in hot and dry places?

Answer 31

kranz anatomy to void photorespiration

Question 32

how can you tell from fossil records than animals switched from eating C3 to C4?

Answer 32

1. C3 has a strong bias against Carbon13. 2. can see a proportion of C13 in plant fossils. 3. can thus see carbon ratios in the teeth of animals and so can see from the date of the teeth at what point they stopped eating C3 plants.

Question 33

how did cheetahs evolve from C4 photosynthesis?

Answer 33

1. C4 photosynthesis enabled growing plants in hot places. 2. animals ate these. 3. cheetahs eat these animals.