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Biology > Selection and Evolution > Flashcards

Selection and Evolution Flashcards

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1
Q

describe the difference between continuous and discontinuous variation

A

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

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2
Q

describe genetic variation

A

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

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3
Q

describe mutation

A 
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
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4
Q

describe environmental variation

A

access to nutrition
exposure to pollutants
disease
horizontal gene flow

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5
Q

how does continuous variation occur

A

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

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6
Q

how does discontinuous variation occur

A

different genes have large effect on phenotype

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7
Q

definition of natural selection

A

fittest organisms has its alleles with advantages passed down to offsprings

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8
Q

examples of biotic factors

A

predation
infection
competition for food

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9
Q

examples of abiotic factors

A

humidity
overcrowding
light
temperature

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10
Q

definition of fitness

A

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

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11
Q

definition of selection pressure

A

increase/decrease chances of alleles being passed down

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12
Q

definition of negative/positive selection

A

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

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13
Q

definition of balancing selection

A

more than one variation that increases fitness

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14
Q

definition of sexual selection

A

traits passed down only for obtaining mate

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15
Q

how does resistance in mosquitoes arise?

A

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

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16
Q

definition of evolution

A

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

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17
Q

three types of selections

A

directional
stabilizing
disruptive

18
Q

describe directional selection

A

for on extreme trait

against other extreme

19
Q

describe stabilizing selection

A

for moderate traits

against both extreme

20
Q

describe disruptive selection

A

for both extremes

against moderate traits

21
Q

describe antibiotic resistance

A

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

22
Q

describe industrial melanism

A

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

23
Q

describe sickle cell anemia

A

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

24
Q

definition of genetic drift

A

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

25
Q

what is the hardy weinberg principle

A

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

26
Q

when does the hardy weinberg principle not apple

A 
mutation
migration
non-random mating occurs
population is small
selective pressure occurs against one of the alleles
asexual reproduction
organism is haploid
27
Q

why do unreleated species have similar characteristics

A

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

28
Q

describe selective breeding of animals/crops

A

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;

29
Q

effects of inbreeding and hybridisation in maize

A

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

30
Q

definition of darwin-wallace theory of evolution

A

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

31
Q

definition of species

A

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

32
Q

describe prezygotic isolation

A

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

33
Q

describe postzygotic isolation

A

failure of cell division

offspring that will soon die

34
Q

types of speciation

A

allopatric

sympatric

35
Q

describe allopatric speciation

A

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

36
Q

describe sympatric speciation

A

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

37
Q

types of reproductive isolation

A

prezygotic

postzygotic

38
Q

describe why new species arise from geographical isolation

A 
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
39
Q

what are the two ways of molecular comparisons between species

A

comparing amino acid sequences of proteins

comparing mtDNA

40
Q

describe comparing amino acid sequences of proteins

A

more similar = more closely related species are;

more similar = more recent common ancestor;

41
Q

describe using nucleotide sequences of mtDNA

A 
inherited from mother;
recombination doesn't occur;
mutations constantly occur;
mtDNA mutates faster;
many copies of mtDNA;
no histones;
analysis is quicker;
42
Q

what causes extinction

A

climate change
increased competition
habitat loss by humans
deforestation

Biology (19 decks)

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