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The Green Planet > Hybridization > Flashcards

Hybridization Flashcards

1
Q

What are the steps to form a hybrid in a plant species?

A
  1. continuous population
  2. barrier forms, splitting population
  3. speciation eg allopatric or sympatric
  4. populations meet
  5. hybrid is formed
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2
Q

What are possible consequences of a hybrid swarm?

A
  1. gene transfer between species
  2. new species evolves
  3. rare species extinct
  4. none of the above happen and hybrid swarm persists
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3
Q

What are the 6 pre-zygotic barriers to hybridization?

A
  1. geographical isolation
  2. habitat separation
  3. temporal isolation
  4. pollinator isolation
  5. pollen compatibility
  6. pollen competition
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4
Q

What are the 6 post-zygotic barriers to hybridization?

A
  1. hybrid viability
  2. hybrid fitness (intrinsic)
  3. habitat mediated fitness
  4. hybrid fertility
  5. hybrid breakdown
  6. selection vs alien genes
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5
Q

Which barriers, if present, are not able to be overcome?

A
  1. pollen compatibility - stigma controls which pollen can germinate
  2. hybrid viability: - if genomes are too different, zygote will not develop
    - if two proteins made by two different alleles come together in a hybrid it may be fatal
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6
Q

Which barriers can be overcome by human interference?

A
  1. geographical isolation
  2. habitat separation
  3. temporal isolation - occasional flowering out of season caused by freak weather can overcome this barrier but climate change has accentuated this
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7
Q

Comment on hybrid fertility.

A

hybrids are rarely 100% sterile, common to be nearly 100% sterile
but as plants make lots of seeds this is easy to overcome

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8
Q

What is a gene complex?

A

a collection of genes that all need to be present for each one to work

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9
Q

Why do F2 generations tend to have dramatically reduced fitness?

A

important genes more likely to go missing
recessive traits more likely to show
gene complexes become non-functional

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10
Q

What is an example of a situation in which an F2 hybrid can perform well?

A

F2 generation may gain alleles where it performs best in a habitat not similar to either parents, known as extreme segragation

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11
Q

What are complex hybrids?

A

hybrids after the F2 generation
shown in experiments to take 6 generations for complex hybrids to take on alleles allowing them to thrive in new habitats
through this method a species can evolve

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12
Q

What is introgression?

A

when an F1 hybrid offspring continuously backcrosses with parent
kind of like natural GM
1/2 of other parental genome is lost each time offspring backcrosses

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13
Q

What are examples of human induced selection?

A

habitat alteration
habitat creation
introduction which leads to competition
climate change

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14
Q

How can polyploidy occur?

A

if hybrid chromosomes dont pair v well (not v closely related), meiosis more likely to not proceed correctly and chromosomes double

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15
Q

What is meant by unreduced and reduced gametophytes?

A

unreduced = 2n
reduced = n

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16
Q

Where do polyploids commonly occur and what do these areas have in common?

A
  1. colder climates (high latitudes)
  2. cultivated land (as weeds)
  3. crops

all are recent in geological terms
polyploids give rapid adaptation to new habitats

17
Q

What is autopolyploidy?

A

polyploidy which occurs in error in meiosis without hybridization

18
Q

What is permaculture?

A

a method of farming that uses aspects of conventional farming (useful species, human design and control) as well as a virgin forest (functioning ecosystem, minimal maintenance needed)

19
Q

How much of the wolds global emissions could be offset by permaculture?

A

1/3

20
Q

Why is a hybrid different from the common ancestor of the parent species?

A

Alleles from common ancestor are lost and new ones selected
Once the new species cross, new never seen before combinations appear

21
Q

What is a hybrid swarm?

A

A large population of hybrids all descending from F1 hybrid

22
Q

How do gene complexes cause problems in F2 hybrids?

A

In the F2 generation chromosomes from the parent species have actually touched for the first time during meiosis.
The chromosomes cross over and some parent genes are missing (whereas there is at least one copy of each parent gene in an F1 hybrid)
This means that certain components of gene complexes are missing and so they break :(

23
Q

What is transgressive segregation?

A

Phenotypes are unpredictable in F2
Mixing of traits can give phenotypes not found in parents or F1

24
Q

Why are lots of F2 hybrids found in disturbed habitats?

A

Disturbed habitat gives brand new conditions.
Minority of hybrids with correct allele combinations can thrive in the new habitat

25
Q

What is the difference between F2 and complex hybrids further down the lineage?

A

While they both have a random allele assortment from the parent species
Natural selection has had time to remove or promote alleles in the complex hybrids
ie complex hybrids are refined F2

26
Q

How does a species form from hybridisation?

A

F1 and F2 hybrids are not new species
Natural selection and speciation must take place
Hybrid speciation in 1 gen occurs through polyploidisation

27
Q

How can introgression have a lasting effect?

A

If transferred genes are deleterious - selected out

If habitat has remained the same - transferred genes not needed and selected out

Though if a change in the habitat has occurred, or alien species has arrived in a new environment, then introgression is likely to make a lasting effect.

28
Q

What sort of genes can flow freely between inter fertile species?

A

Neutral traits
Traits necessary to both species

29
Q

What are 3 types of selection?

A

Natural
Artificial (dog breeding)
Human induced (not deliberate, indirect)

30
Q

What is human induced selection?

A

Changes in environment such as:
Habitat alteration/creation
Climate change
Introduction of competition

Imposes new selective pressures

The Green Planet (8 decks)

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