Selection and Evolution

Question 1

describe the difference between continuous and discontinuous variation

Answer 1

continuous is phenotypic characteristics that change over a range of values (environmental/genetics)
discontinuous is distinct categories with no intermediates (genetics)

Question 2

describe genetic variation

Answer 2

independant assortment of chromosomes;
crossing over between between chromatids;
random mating between organisms in species;
random fertilisation of gametes;

Question 3

describe mutation

Answer 3

a random change in DNA sequence by
insertion/deletion/silent
stop codon gives shorten polypeptide
does not code for amino acid
mutation passed down if it is in ovaries/testes

Question 4

describe environmental variation

Answer 4

access to nutrition
exposure to pollutants
disease
horizontal gene flow

Question 5

how does continuous variation occur

Answer 5

different alleles at single gene locus have small effects on phenotype
polygenes needed for observable variation

Question 6

how does discontinuous variation occur

Answer 6

different genes have large effect on phenotype

Question 7

definition of natural selection

Answer 7

fittest organisms has its alleles with advantages passed down to offsprings

Question 8

examples of biotic factors

Answer 8

predation
infection
competition for food

Question 9

examples of abiotic factors

Answer 9

humidity
overcrowding
light
temperature

Question 10

definition of fitness

Answer 10

capacity of an organism to survive and transmit its genotype to its offspring

Question 11

definition of selection pressure

Answer 11

increase/decrease chances of alleles being passed down

Question 12

definition of negative/positive selection

Answer 12

variations reduce/increase fitness less/more likely to be passed on

Question 13

definition of balancing selection

Answer 13

more than one variation that increases fitness

Question 14

definition of sexual selection

Answer 14

traits passed down only for obtaining mate

Question 15

how does resistance in mosquitoes arise?

Answer 15

mutation;
selection pressure;
resistant mosquitoes have selective advantage;
survive + reproduce;
resistance alleles passed on;
increase in frequency of resistant allele;

Question 16

definition of evolution

Answer 16

changes in allele frequency in a population, due to natural selection it gives some alleles a better chance of survival

Question 17

three types of selections

Answer 17

directional
stabilizing
disruptive

Question 18

describe directional selection

Answer 18

for on extreme trait

against other extreme

Question 19

describe stabilizing selection

Answer 19

for moderate traits

against both extreme

Question 20

describe disruptive selection

Answer 20

for both extremes

against moderate traits

Question 21

describe antibiotic resistance

Answer 21

bacteria has allele resistant to pencillin
acts as selective advantage
reproduce and survive

Question 22

describe industrial melanism

Answer 22

changing environmental factors acts as selection pressure of moths
having black colour is selective advantage

Question 23

describe sickle cell anemia

Answer 23

genetic drift - heterozygous sickle cell anemia survive and reproduce - don’t suffer from malaria/sickle cel;

Question 24

definition of genetic drift

Answer 24

change in allele frequency that occurs by chance, because only some reproduce

Question 25

what is the hardy weinberg principle

Answer 25

frequency of genotype is its proportion of total population p^2 + 2pq + q^2 p + q = 1

Question 26

when does the hardy weinberg principle not apple

Answer 26

``` mutation migration non-random mating occurs population is small selective pressure occurs against one of the alleles asexual reproduction organism is haploid ```

Question 27

why do unreleated species have similar characteristics

Answer 27

had similar selection pressure; allow organisms to escape predators; allow organisms to find food;

Question 28

describe selective breeding of animals/crops

Answer 28

Humans select crops/animals with desirable characteristics to breed; Desirable characteristics (animals: higher product yield/more meat/ plants: higher yield, disease-resistant) Over several generations; Select offspring with desirable characteristics; Frequency of desirable allele increases;

Question 29

effects of inbreeding and hybridisation in maize

Answer 29

maize inbred had smaller + weaker generation = inbreeding depression outbreeding is better

Question 30

definition of darwin-wallace theory of evolution

Answer 30

organisms change over time due to atural selection of fittest organisms with selective advantages, which are able to survive and reproduce

Question 31

definition of species

Answer 31

a group of organism (similar physiological features) which can interbreed to produce fertile offspring and are productively isolated from other species

Question 32

describe prezygotic isolation

Answer 32

individuals not responding to mating behaviour animals physically unable to meet inability for gametes to fuse

Question 33

describe postzygotic isolation

Answer 33

failure of cell division | offspring that will soon die

Question 34

types of speciation

Answer 34

allopatric | sympatric

Question 35

describe allopatric speciation

Answer 35

geographical isolation causes barrier = same species don't mix - features become different cannot interbreed = new species

Question 36

describe sympatric speciation

Answer 36

polypoid organism has more than two complete sets of chromosomes in cells - meiosis goes wrong

Question 37

types of reproductive isolation

Answer 37

prezygotic | postzygotic

Question 38

describe why new species arise from geographical isolation

Answer 38

``` no gene flow; different selection pressures; different mutations; some mutation s make individuals better adapted; those individuals survive/reproduce; pass on advantageous alleles; many generations ```

Question 39

what are the two ways of molecular comparisons between species

Answer 39

comparing amino acid sequences of proteins | comparing mtDNA

Question 40

describe comparing amino acid sequences of proteins

Answer 40

more similar = more closely related species are; | more similar = more recent common ancestor;

Question 41

describe using nucleotide sequences of mtDNA

Answer 41

``` inherited from mother; recombination doesn't occur; mutations constantly occur; mtDNA mutates faster; many copies of mtDNA; no histones; analysis is quicker; ```

Question 42

what causes extinction

Answer 42

climate change increased competition habitat loss by humans deforestation