Topic 7: Evidence of Population Flashcards
1
Q
define macroevolution
A
- evolutionary change at or above the species level (phenotypic variations)
2
Q
what is a population?
A
- group of individuals of the same species that live in the same area and interbreed, producing viable, fertile offspring
- smallest unit of evolutionary change
3
Q
what is the smallest unit of evolutionary change?
A
populations
4
Q
what is the one “thing” that evolves under the pressure of natural selection?
A
populations
5
Q
define microevolution.
A
- evolutionary change at or below the species level
- change in allele frequencies in a population over generations
6
Q
what does microevolution account for?
A
accounts for evolutionary changes of both phenotypes and genotypes
7
Q
define chromosome.
A
cellular structure carrying genetic material
8
Q
define gene.
A
discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses)
9
Q
define allele
A
alternative versions of a gene that correspond to different combination of nucleotides in each version
10
Q
what is meant by the term homologous chromosome
A
the one chromosome that each sexually reproducing parent gives to their offspring
11
Q
true or false: each chromosome has one set of alleles
A
true
12
Q
define gene pool
A
aggregate of all copies of every type of allele at all loci in every individual in a population
13
Q
if interbreeding is not possible in geographically separated population of the same species what may occur?
A
distinct gene pool
14
Q
how do individuals within a population share alleles? what happens throughout this process of sharing?
A
- by interbreeding and producing viable off spring
- frequencies of alleles in the gene pool are changed
15
Q
what is a key prerequisite for evolution?
A
variations in heritable traits provide materials for natural selection
16
Q
what is genotypic variation?
A
- variability in genotypes within a population
- one of the main components of biodiversity
17
Q
can all phenotypes be inherited?
A
no
18
Q
are all phenotypes subjected to natural selection?
A
no
19
Q
brief explanation of genotypic variation in regards to microevolution
A
- interbreeding of individuals with different genotypes
- increase in different genetic make-up (alleles) in gene pool
20
Q
how do phenotypic variations arise?
A
- due to alternation of genetic make-up
21
Q
what can natural selection act on?
A
- only acts on variations with a genetic component
22
Q
what are the sources of genotypic variation? (sources of new genes and alleles)
A
- mutation
- gene duplication
- gene recombination
23
Q
what is meant by the term mutations?
A
- random changes in the nucleotide sequence of an organism’s genetic make-up
24
Q
what are the key characteristics of mutations?
A
- occur only randomly
- can be beneficial, neutral, or deleterious
- create new alleles
- only mutations in gamete-producing cells are heritable in sexually reproducing taxa
25
what are the two key types of mutations?
- small scale
- large structural changes
26
what are the types of small scale mutations? give brief definition for each type.
- point mutations (single change in nucleotide base)
- insertions/deletions (addition or removal of one or small number of nucleotide bases
27
what are large structural mutations?
major alterations (usually damages) in structure of DNA
28
what is the product of mutations?
- creation of new alleles
29
what is the result of an accumulation of mutations?
- evolutionary changes in both genotypes and phenotypes
30
how often do mutations occur?
- rates overall low in animals and plants
- higher rates in prokaryotes than eukaryotes
31
what is gene duplication?
copies of nucleotide sequence of an organism's genetic make up
32
what are the types of gene duplication?
- small segments
- gene duplication
- whole-genome duplication
33
what is small segment gene duplication?
duplication of DNA segments that affects multiple genes
34
what is gene duplication?
copy of entire gene
35
what is whole-genome duplication?
- doubling of the entire genome
- supply of new materials for evolution and for increased genome complexity
36
what is gene recombination?
shuffling of exsiting alleles into new combinations during sexual reproduction
37
what are the types of gene recombination?
- during meiosis
- random fertilization
38
what are the types of gene recombination during meiosis? and brief explanation of each.
- cross-over (reciprocal exchange of homologous genetic material)
- independent assortment (different genes are independently separate from one another)
39
what is random fertilization?
combination of gamete with different versions of chromosomes
40
what is meiosis?
type of cell division in sexually reproducing organisms to produce gamete that contains half the chromosomes as the original cells
41
what are factors that influence allele frequencies?
- natural selection
- genetic drift
- gene flow
42
true or false: natural selection leads to adaptive evolution?
true
43
what does the term "adaptation" mean?
- inherited characteristics of an organisms that enhances its survival and reproduction in a specific environment
44
what does the term "relative fitness" mean?
- contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in the population
45
true or false: genetic drift and gene flow are non-adaptive processes? why?
- true
- changes in allele frequency that do not increase the populations capacity to adapt to its environment
46
true or false: only natural selection can lead to adaptation?
true
47
does natural selection act on existing variations or create adapted traits?
act on existing variations
48
true or false: better adapted individuals can generally produce more offsprings and contribute their alleles to the gene pool in greater portions?
true
49
what are the types of natural selection?
- directional selection
- disruptive/diversifying selection
- stablishing selection
50
what is directional selection?
natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals
51
what is directional selection response to?
consistent selection pressure
52
what happens under directional selection?
- genotypic variations lead to new phenotype with higher relative fitness
- frequency distribution of phenotypic variations shift towards adapted traits
- theoretically genotypic variations in a population would be reduced
53
what is disruptive/diversifying selection?
natural selection in which individuals at both ends of the phenotypic range survive or reproduce more successfully than do other individuals
54
true or false: intermediate phenotypic traits are less adapted than either one of the extremes
true
55
what happens under disruptive selection?
- genotypic variations lead to more than one new phenotypes with higher relative fitness
- frequency distribution of phenotypic variations shifts towards multiple adapted traits
- frequency of the intermediate trait decline over time
56
what is stablishing selection?
natural selection in which individuals at intermediate or common variants of the phenotypic range survive or reproduce more successfully than do other individuals
57
what happens under stablishing selection?
- conserve genotypic and phenotypic (often functional) traits and select against the extreme (often deleterious)
- the mean (average) of the trait stays the same but its variance (spread) is reduced
58
what is genetic drift?
random events that change allele frequencies in a population
59
what are the characteristics of genetic drift?
- non-adaptive factor
- allele frequency fluctuate over generations
- rare alleles may be lost, which could reduce the genotypic diversity
- genetic drift has greater impacts on smaller populations
60
what are the types of genetic drift?
- bottleneck effect
- founder effect
61
what is the bottleneck effect?
- population size suddenly decreases due to changes in environment
- alters the allele frequency in the gene pool
62
what are the characteristics of the bottleneck effect?
- events take place within the range of natural habitat
- caused by disastrous events
- initial result is the distinct reduction in population size
- allele frequency post bottleneck effect is not representative of the original population (if population remains small, genetic diversity may continue to decline under the effects of genetic drift)
63
what is the founder effect?
- selected few individuals of the populations become isolated and from a new population, whose gene pool also be distinct (these selected individuals are called founding individuals)
64
what are the key characteristics of the founder effect?
- events take place by forming a new population
- founding individuals carry a fraction of the total gene pool from the original population
- the alleles of the founding individuals become dominant in the gene pool of the new population
- the allele frequency in original population is unchanged
65
true or false: the absence of the founder effect can be detrimental to local ecosystems
true
66
after this group leaves do they maintain contact with the original group?
no they do not have contact
67
what are the key points of genetic drift? (name four)
- can alter the allele frequency in random fashion
- can lead to loss of genotypic diversity (trait becomes fixed or absent)
- larger impact on smaller populations
- can cause deleterious trait to be fixed in small population
68
what is gene flow?
transfer of alleles between populations
69
what are the characteristics of gene flow?
- events take place via movements of fertile individual or gametes (seed or pollens)
- can introduce new genotypic variation to receiving population (work against genetic drift and can slow down adaptation if selection pressure exists)
- gene flow reduced genetic variations between population over time (population become similar or homogenized over time)
70
true or false: gene flows can reduce the fitness of the receiving population (how well the population is adapting to the local environment). along with this what traits are introduced?
- true
- non-adaptive or deleterious traits are introduced
71
true or false: gene flows can increase the fitness of the receiving population. along with this what traits are introduced?
- true
- adaptive traits are introduced
72
what is meant by the term "local adaptation"?
populations become more adjusted to their local environment, often again adapted traits that are absent in population form other locations
73
what are factors that influence allele frequencies in population?
- natural selection (only factor that leads to adaptive traits)
- genetic drift and gene flow (non-adaptive)
74
what are factors that can introduce evolutionary changes?
- extinction
- extirpation
75
what does extinction mean?
last individuals of species is dead, or its survival cannot be considered beyond reasonable doubt
76
what does extirpation mean?
local extinction of species in certain area, but they have populations that can be found in other areas
77
what is natural variation?
genotypic variation that does not provide a selective advantages or disadvantages (they are not adaptive or deleterious)
78
natural variation maintained by a combination of what?
- gaining new alleles (mutation, duplication, recombination)
-stablishing selection
- gene flow
- balancing selection
79
what is balancing selection?
type of natural selection that maintains genetic diversity (stable allele frequencies) within a population (which cover a wide range of habitats, could promote balancing selection)
80
what are mechanisms for balancing selection?
- heterozygote adavantage
- frequency-dependant selection
81
what is heterozygote advantage?
individuals with two different alleles of a given gene (heterozygote(Aa)) are more adaptive to the environment compared to individuals with two identical copies of alleles (homozygote(AA or aa))
82
what are some key points of heterozygote advantage (name 2)
- natural selection tends to maintain heterozygotes
- both stablishing and directional selection can lead to heterozygote advantage
83
what is frequency-dependent selection?
selection is which the fitness of a phenotype depends on how common the phenotype is in the population (common to occur between species and between individuals in a population)
84
what are the two types of frequency-dependent selection?
- positive
- negative
85
what is negative frequency-dependant selection?
fitness of a phenotype decreases as it becomes more common in the population
86
what is positive frequency-dependant selection?
fitness of a phenotype increases as it becomes more common in the population
87
does the "perfect trait" exist?
no
88
what is the purpose of adaptation and genes?
to be continuously passed on
89
what is meant by "natural selection is not random, but it does not have a goal"?
individuals adapt to their environment as they struggle to survive without knowing how the environment may change in the future, so its just based on the now, but these traits may not be as beneficial in the future
90
true or false: natural selection can only act on existing variations, the genotypes and phenotypes that are subjected to natural selection arise randomly
true
91
do existing traits from prior adaptations have any effect on the range of natural selection?
yes, it limits the range that natural selection can operate
