natural selection and speciation

Question 1

stabilising selection

Answer 1

• response to STABLE environment
• mode stays same, sd falls - population graph gets narrower and taller as selection against mutation takes place
• eg. birth weight

Question 2

bottleneck event

Answer 2

• when a population is reduced to a few breeding individuals ∴ much narrower gene pool
• drastic reduction in population

Question 3

directional selection

Answer 3

• response to CHANGE in environment
• eg. poison used and resistant individuals start to occur
• phenotypes shift in one direction and one aspect of a trait is emphasised (curve shifts right or left)

Question 4

disruptive/diversifying selection

Answer 4

• response to FLUCTUATING environment
• favours 2 extremes of a trait at expense of intermediate forms
• middle of curve is eliminated and 2 peaks form either side of it
• eg. rock pocket mouse

Question 5

prezygotic barrier

Answer 5

those which prevent fertilisation from happeneing

Question 6

postzygotic barrier

Answer 6

fertilisation may occur but any offspring are either not viable or are sterile

Question 7

eg. prezygotic barrier (3)

Answer 7

• seasonal isolation
• behavioural isolation
• mechanical incompatibility

Question 8

eg. postzygotic barrier (2)

Answer 8

• hybrid inviability

- hybrid sterility

Question 9

allopatric speciation

Answer 9

between 2 geographically isolated populations - gene pool physically separated ∴ separate populations evolve independently

Question 10

sympatric speciation

Answer 10

organisms in the same area become separated into 2+ reproductively isolated groups

Question 11

variation

Answer 11

difference in characteristics shown by organisms belonging to the same natural population or species

Question 12

discontinuous variation

Answer 12

when you have or haven’t got a feature - 2 options

eg. blood group

Question 13

continuous variation

Answer 13

characteristics on a gradient from one extreme to the other - influenced by polygenes and environmental factors

Question 14

causes of variation (4)

all lead too…

Answer 14

1) crossing over of alleles during mitosis
2) independent segregation of chromosomes (Meiosis I)
3) random fusion of gametes
4) mutations in DNA

… gene reshuffling ∴ variation

Question 15

selection

Answer 15

process by which organisms better adapted to the environment survive and reproduce and those not so well adapted fail to reproduce or die

Question 16

genetic drift

Answer 16

a change In the gene pool due to chance

Question 17

founder effect

Answer 17

new colony started by a few members of the original populations, reducing genetic variation ∴ may lead to speciation

Question 18

isolating mechanism

Answer 18

barrier preventing gene exchange

Question 19

point mutation

Answer 19

change in base sequence at a single base in the gene - single base deleted, substituted or inserted

Question 20

stem cells

Answer 20

unspecialised cells which can develop into other types of cell

Question 21

totipotent stem cells

Answer 21

can specialise into ANY body cell, including placenta

Question 22

pluripotent stem cells

Answer 22

can specialise into any body cell, but NOT placenta

Question 23

multipotent stem cells

Answer 23

present in adult mammals - able to specialise into a few different types of cell

Question 24

unipotent stem cells

Answer 24

present in adult mammals - able to specialise into only one type of cell

Question 25

how do stem cells become specialised?

Answer 25

during development they only transcribe and translate part of their DNA, depending on conditions they are in, causing some genes to be expressed and others not to be

Question 26

iPS cells

Answer 26

induced pluripotent cells

Question 27

how are iPS cells made

Answer 27

in lab - infecting cells with specially-modified virus which has genes coding for transcription factors within its DNA - genes are passed to the cell's DNA meaning that the cell can produce the transcription factors

Question 28

stem cell treatments (currently)

Answer 28

bone marrow transplant - to replace faulty bone marrow - treat leukaemia

Question 29

future stem cell therapies (5)

Answer 29

- spinal cord injuries - heart disease and damage caused by heart attacks - bladder conditions - respiratory diseases - organ transplants

Question 30

how can transcription factors reprogram cells to form iPS cells

Answer 30

- attach to promoter region of gene | - stimulate/prevent binding of RNA polymerase so that transcription does/doesnt occur

Question 31

transcription factors

Answer 31

proteins that control rate of protein synthesis by switching genes on and off

Question 32

transcription factors act as...

Answer 32

activators | repressors

Question 33

how to transcription factors work?

Answer 33

- factors binds to promoter region - rna polymerase is complimentary and therefore binds to region, activating it - gene then switched on - transcription can occur

Question 34

proto-oncogenes

Answer 34

regulate stages in mitosis - stimulate cell division/growth

Question 35

tumour supressor genes

Answer 35

prevent tumours

Question 36

mutation type in proto-oncogenes

Answer 36

gain of function mutation

Question 37

mutation type in tumour supressor genes

Answer 37

loss of function mutation

Question 38

metastisis

Answer 38

travel in bloodstream + affect other tissues and spreads

Question 39

why does genetic drift occur faster in smaller populations

Answer 39

as relatively few individuals = relatively small gene pool = less genetic diversity therefore any mutation will quickly affect members of population because frequency is relatively high (in large pops effect is diluted)

Question 40

competition

Answer 40

when 2+ individuals share any resource that is insufficient to supply all requirements fully

Question 41

infraspecific comp

Answer 41

between 2 members of the same species

Question 42

interspecific comp

Answer 42

between 2 members of different species

Question 43

competitive exclusion principle - overall message?

Answer 43

population of species with competitive advantage will gradually increase in size and the other one will diminish - if conditions remain the same, one species will be completely removed - no 2 species can occupy the same niche indefinitely when resources are limited

Question 44

genome

Answer 44

all genetic material (alleles) in an organism

Question 45

proteome

Answer 45

all the proteins produced by the genome (controlled by transcription factors)