Variation and Speciation

Question 1

what does variation mean?

Answer 1

-the differences in physical characteristics between organisms within the same species

Question 2

what type of genotype allows for variation?

Answer 2

-heterozygotes

Question 3

what are the 3 ways that genetic variation can be maintained?

Answer 3

-genetic and environmental factors
-meiosis
-gene mutations

Question 4

what are the 2 types of variation and what are2 examples of each?

Answer 4

-discontinuous= being male or female, or having or not having ear lobes
-continuous= height, weight

Question 5

what 2 things that affect continuous variation?

Answer 5

-genetic and environmental factors

Question 6

what are the 3 ways that meiosis leads to genetic variation?

Answer 6

-independent assortment along the equator at metaphase one
-random fertilisation to produce a random zygote
-crossing over of genes/ chisamata formation where one gene is switched with the corresponding gene on the other chromosome

Question 7

what can crossing over of chromosomes result in?

Answer 7

-an entirely new allele combination that were not present in the paternal chromosomes

Question 8

what is another process that can result in spontaneous variation?

Answer 8

-chromosome and gene mutations

Question 9

what is the definition of a mutation?

Answer 9

-a permanent change to the DNA in an organism

Question 10

what causes a gene mutation?

Answer 10

-a change in the sequence of bases in the DNA

Question 11

what is the consequence of a single base mutation in terms of the codon and protein produced?

Answer 11

-if one base changes then the codon changes which codes for a different amino acid, therefore a different polypeptide and eventually a different protein

Question 12

what are the three types of gene mutations?

Answer 12

-base substitution
-base deletion
-base insertion

Question 13

what is base substitution? what is the result of this and what is the term to describe the effects of this mutuation?

Answer 13

-when once base replaces another
-this will change is limited to one amino acid
-neutral mutation

Question 14

what is base deletion/ insertion? what does this cause to happen and what is the term to describe this?

Answer 14

-when a base is removed or added
-it changes the base triplet as well as the rest of the gene
-frame shift

Question 15

what do chromosome mutations involve?

Answer 15

-changes to large sections of DNA containing several genes

Question 16

what are the two type of chromosome mutations?

Answer 16

-aneuploidy
-polyploidy

Question 17

what is an aneuploidy chromosome mutation involve? how many chromosomes will a zygote therefore contain? what is an example of a condition caused by this?

Answer 17

-when one chromosome fails to separate at anaphase 1
-47
-Downs Syndrome

Question 18

what is polyploidy chromosome mutations? what organism are they common in?

Answer 18

-mutations where whole sets of chromosomes fail to separate
-plants

Question 19

what is one environmental factor that can encourage these mutations?

Answer 19

-UV exposure

Question 20

what does selection pressure mean?

Answer 20

-external agents that affect an organisms ability to survive and they can be positive or negative

Question 21

what is survival of the fittest?

Answer 21

-the better adapted organism to the environment will be the one who survives and outcompetes the less adapted

Question 22

who came up with the theory for natural selection?

Answer 22

-Darwin

Question 23

how does the genetic makeup of a population change over time?

Answer 23

-due to particular alleles increasing in frequency while other reduce due to not surviving in a certain environment

Question 24

what is the term to describe how selection is influenced by the environment?

Answer 24

-environmentally dependent

Question 25

what type of variation must occur to result in a change in a population or a species?

Answer 25

-both genetic and environmental

Question 26

what does fitness mean in terms of selection?

Answer 26

-how well an organism is adapted for its environment -selection favours the fitter organisms against those who are less fit

Question 27

what does differential reproductive success mean?

Answer 27

-if the better adapted individuals survive then they will produce offspring which are also better adapted -the less adapted are killed and so the frequency of their alleles decrease as they are outcompeted

Question 28

what are the 2 types of selection and what do they involve?

Answer 28

-stabilising selection -directional selection

Question 29

what does stabilising selection mean and what individual is best adapted? what type of environment does this occur in?

Answer 29

-it shows normal distribution -the average phenotypes are best suited whereas the extremes of individuals are less well adapted -occurs in unchanging environments

Question 30

what happens as consequence of the average individuals surviving during stabilising selection?

Answer 30

-they pass their genes onto their offspring

Question 31

look at graph of stabilising selection

Answer 31

-fsf

Question 32

why does stabilising selection not cause evolutionary change?

Answer 32

-because in highly adapted populations in stable ecosystems it will appear that selection is not occurring because there is not obvious changes in the phenotype over time

Question 33

what are the best adapted individuals in directional selection?

Answer 33

-those whose phenotypes lie closer to the extremes of variation

Question 34

where are the two places where directional selection is most likely to take place?

Answer 34

-changing environment -population colonies in a new habitat

Question 35

how is pesticide resistance in insects an example of directional selection?

Answer 35

-this resistance is caused by mutation -if insects subjected to pesticides this mutation offers subjective adaptive advantages -these will survive and pass their resistant genes onto their offspring -resulting in the frequency of this allele increasing and eventually the entire population will become resistant

Question 36

what is the selectional pressure which causes antibiotic resistance?

Answer 36

-the over use of bacteria

Question 37

does directional selection cause evolutionary change?

Answer 37

-yes

Question 38

what does polymorphic mean?

Answer 38

-population where there is more than one alternative for a particular trait -there are two or more genotypes that produce the same phenotype

Question 39

what are three examples polymorphisms in organisms?

Answer 39

-human blood groups -eye colour -banding in snails

Question 40

what is definition of species?

Answer 40

-a group of individuals of common ancestry that are normally capable of interbreeding to produce fertile offspring

Question 41

what is the definition of speciation?

Answer 41

-the formation of new species that are reproductively isolated from other species

Question 42

what must occur in order for animals to create a new species?

Answer 42

-reproductive isolation

Question 43

what are the 3 factors that cause reproductive isolation? what does each of these mean?

Answer 43

-geographical separation= population of same species live in different parts of the world -habitat isolation= same species lives in different parts of the same habitat -temporal isolation= same species live in same habitat but are reproductively active at different times

Question 44

what are the two types of speciation?

Answer 44

-allopatric speciation= geographical -sympatric speciation= reproductive

Question 45

what is the process of allopatric speciation?

Answer 45

-starts with an interbreeding population of one species -population becomes divided by a physical barrier e.g. geography changes like an earthquake, or due to migration -if the two new environments are different then the two species will evolve differently due to different selectional pressures -even if the barrier is removed the two populations are now so different they can no longer interbreed -they are now reproductively isolated

Question 46

what is a consequence to the original species if it is well adapted to its original environment if it is separated by allopatric speciation?

Answer 46

-if the environment changes the the species must adapt or die -this could result in the original species becoming extinct

Question 47

what is sympatric speciation? what are the 2 causes of this speciation?

Answer 47

-when a population is reproductively isolated within the same environment which is caused by reproductive seasons being different or living in different areas (niches)