Evolution Flashcards
1
Q
What is the definition of evolution?
A
A change in biological entities over time (over generations)
2
Q
What was the belief before evolution?
A
the chain of being - ladder of increasing complexity
3
Q
who is Carolus Linnaeus?
A
- father of taxonomy (biological classification)
- promoted hierarchal, nested classification
(note that linnaues was a taxonomist, not an evolutionist, he did not believe natural selection)
4
Q
What are fossils?
A
-rocks of different age in the same location containing different species from differing
5
Q
What did Lamarck propose about fossils and evolution?
A
- observed progressions of similar species in the fossil record
- proposed new species arise by modification of existing species (A turns into B turns into C)
6
Q
What were Lamarck’s ideas about pattern of evolution?
A
He proposed the living world was made up of many separate lineages with independent origins and each lineage progressed for perfection/complexity (he was wrong)
7
Q
What were lamarcks ideas about the process of evolution?
A
the Use and Disuse of parts idea with inheritance of aquired characters. an individual will evolve and then pass those changes onto their offspring
8
Q
Were Lamarck’s ideas correct?
A
No!
9
Q
What did Darwin propose?
A
Natural selection
10
Q
What was Darwins idea on the pattern of evolution?
A
- Living things were united in one branching tree of relationships
- new lineages made by the splitting of existing lineages
11
Q
What does the splitting of a lineage have to do with relation?
A
An earlier split results in greater difference while a later split results in a more common ancestor which allows for there to be more similarities between species
12
Q
** note that after the splitting they share common ancestors (similar) but also are independent after the split
A
13
Q
What was Darwin’s idea on the process of evolution?
A
-Darwin proposed natural selection
14
Q
What are the aspects of natural selection?
A
1) Heritable variation
2) excess production
3) differential success
15
Q
What is heritable variation?
A
- Individuals in a population are born with traits
- Many traits can be passed on from parents to offspring
16
Q
What is excess production?
A
- In any population more offspring produced than needed to maintain it
- when resources are limited, offspring fail to survive
17
Q
What is differential success?
A
- due to differing traits some individuals are more likely to survive (fitness)
- these traits increase in frequency while unfavourable traits are less frequent (evolution)
18
Q
What is artificial selection?
A
Artificial selection on heritable variation present in existing species
- show plausibility of natural selection
19
Q
What is adaptation?
A
Natural selection over time creates organisms well suited to their environment
20
Q
What are some examples of natural selection in action
A
Drug resistance in pathogens, positive resistance, host switching insects, warfarin resistance, soapberry bug
21
Q
What is required for a good visual of natural selection?
A
strong selective pressure and short generation times
- this is so we can see the changes in a generation obviously and quickly rather than waiting for light changes over generation, like the neck length of giraffes
22
Q
Describe how warfarin resistance in rats demonstrates natural selection?
A
Rats that are exposed to warfarin have resistance increase rapidly in the population because they build resistance and the weak die. -
23
Q
Does natural selection create variations?
A
No! Natural selection only works on pre existing variations (rat mutation)
24
Q
Is natural selection beneficial in these rats?
A
Not necessarily. Natural selection does not always act to improve the rat, simply based on the environment. In the rat’s case, when they were no longer exposed to warfarin they were not able to create vitamin K as effectively, resulting in malnourishment
25
How does the soapberry bug represent natural selection?
Soapberry bugs switched from one flower to another, so the shorter beaks were more common and ling beak populations fell.
26
What selection is the soapberry bug representative of?
| What is it?
Directional selection
- This is a favoured phentoype causing the allele frequency to continuously shift in one direction
27
What are 3 examples of evidence of the tree of life model?
1) Homology
2) biogeography
3) fossil records
28
What is homology?
- A similarity resulting from common ancestry
29
What is an example of homology and why does it prove the tree of life?
one example is the structure of forelimbs of mammals. They are built very similarly, indicating that most humans have a common ancestor with this bone structure.
30
What are vestigial structures?
Structures with little to no functions, going back to common ancestors both would descend from an organism that has a functional use for that structure
31
What is molecular homology?
- homologies (similarities) at the biochemical level
32
What is an example of molecular homology?
The universal genetic code (the coding for nucleotide bases) is universal in all living organisms due to shared ancestry ie: genetic code codes for the same proteins
33
How can molecular homology describe relations between species?
Once relationships are identified based on similarities, the slight differences in gene sequence can differentiate between organisms
34
What is Biogeography?
- The geographic distribution of organisms
- some taxa are endemic (restricted to certain locations)
-Descent from a common ancestor that lived in that reason indicates tree of life because its not found anywhere else
35
How does the fossil record indicate the phylogenetic tree?
- Descent with modification predicts transitional forms
- order of appearance in the fossil record demonstrates transitional forms in which groups with major adaptation can reveal changes over time
36
What is an example of the fossil record indicating common ancestors?
Whales: A series of transitional forms links modern whales to land-dwelling sea animals
37
What is the definition of a population?
- A localized group of interbreeding and interacting individuals
- each species is made up of one too many populations
38
What are fixed alleles?
Whole population is homozygous at locus
39
What are polymorphic loci?
2+ alleles in a population, each present at some frequency
40
What are sources of genetic variation?
New alleles arise by mutation in existing alleles+ microevolution
41
What are the kinds of mutations and their description?
Neutral: Most mutations don't meaningfully affect fitness
Deleterious mutations: Reduce fitness, harmful alleles
Beneficial alleles : very few, can increase fitness
(alleles can be introduced through gene flow)
42
What is microevolution?
-Change in the frequency of alleles over generations
43
What is the Hardy Weinberg principle?
Describes the expected relationships between alleles and genotype frequencies when there is no evolution
44
** Review hardy Weinberg notes from class and in textbook. Since it's an equation it's important to practice.
45
What are the uses for the hardy Weinberg principle?
1) Estimating allele and genotype frequencies
ex: cystic fibrosis
2) Populations with genotype frequencies that conform to the equation are said to be in hard weinbverg equilibirum
46
What assumptions are made for the Hardy Weinberg principle?
1) No net mutations
2) Random mating
3) No natural selection
4) Very large population size
5) No migration
47
What occurs when the hardy Weinberg assumptions are violated?
This indicates evolution is occurring
48
What are the 3 causes of microevolution?
Genetic drift, gene flow, Natural selection
| NOTE: Natural selection is the only adaptive form of evolution
49
Which causes of evolution result in adaptive evolution?
only Natural selection
50
What effect does gene flow have on microevolution?
- Dispersal of gametes
- gene flow from population with different allele frequencies, changes in allele frequencies
- gene flow can introduce new alleles to a population
51
What is random genetic drift?
- 'sampling error' : random changes in allele frequencies over generations
- can lead to fixation of alleles
52
How is genetic drift affected by population size?
- rate of drift rated to population size, faster in small populations than large
- this is because smaller populations have less variation and, therefore, a lower ability to adapt to changing conditions.
53
What is a genetic bottleneck?
breeding population is very small for a time, genetic drift powerful, many alleles of extinct/change
- lower genetic diversity overall, rare alleles change in frequency
54
What is the founder effect?
Special case of the bottleneck, previously rare Allene's end up being much more common in new population
55
How can genetic diversity increase?
genetic diversity can be increased by adding individuals from other populations
56
What is the definition of a species? What are some ways to classify them?
- It is difficult to classify a species universally.
-morphological species is based on morphological similarities, historically the most commonly used concept
- Molecular sequences are also used
57
What is inter-fertility?
Populations that interbreed to produce fertile offspring
58
What is reproductive isolation?
Populations which do not normally interbreed in nature with other species (few hybrids)
59
Why is biological species concept not always applicable
It is difficult to use in concepts with fossils and asexual species
60
How are biological species classified in terms of similarity?
Species are not classified based on similarities rather on inter-fertility
ex: If similar looking birds do not breed between each other, they are classified as different species
61
What is speciation?
Splitting on the tree of life ie: species splits into different versions, becomes common ancestor
62
What can cause speciation?
Reproductive barriers,allopatric speciation, sympatric speciation
63
what are reproductive barriers?
Barriers inhibit gene flow between populations, allowing evolutionary divergence
64
What is a prezygotic barrier?
A form of reproductive barriers, acts before fertilization, prevents mating in the first place
- if the offspring is healthy as an adult, then the parents are of the same biological species
65
What is a post zygotic barrier?
Acts after fertilization
-if zygote is sterile, parents classified as different biological species
66
What are some examples of pre zygotic barriers?
- habitat isolation
- temporal isolation
- behavioural isolation
- mechanical isolation (reproductive organs don't fit)
-Gametic isolation (gametes don't recognize each other)
67
What are some examples of post zygotic barriers?
- Hybrid inviability
-hybrid infertility (mules are sterile due to only having 63/64 chromosomes)
-hybrid breakdown
68
How do reproductive barriers arise?
- Some may rise accidentally as a result of evolution in isolation
- May evolve through natural selection in order to reduce interspecies mating that lowers reproductive success
69
What forms of speciation lead to evolutionary change?
Allopatric speciation and sympatric speciation
70
What is allopatric speciation?
Geographic barrier blocks gene flow between population
71
What is sympatric speciation?
New species arise within range of parent population
72
What is polygenic inheritance?
Phenotypes influence by several genes (alleles at several loci)
-the inheritance of a trait governed by more than one gene
73
NOTE: the curve changed based on where the curve faces the most selection pressure (directional pressure)
74
What are the modes of selection?
1) Directional selection
2) stabilizing selection
3) Disruptive selection
75
What is directional selection?
One end of distribution selected against : classic response to changing environment
76
What is stabilizing selection?
Extreme phenotypes selected against, often due to different opposing forces
ie:intermediate selection
77
What is disruptive selection?
Intermediate phenotypes selected against, plays a role in some speciation events
78
What is sexual selection?
- a special case of natural selection, competition for mating opportunities results in adaptations that increase mating success (sometimes may reduce survival)
79
What are the forms of sexual selection?
Intrasexual selection and intersexual selection
80
What is intrasexual selection?
Competition within one sex (usually males) fighting for opportunities
81
What is intersexual selection?
One sex (usually female) chooses mate from competing members of other sex
82
What is sexual dimorphism?
- adaptations benefit only one sex, so it is common to see only one sex receives the adaptations that both sexes have the gene for
- sexual selection: increases chances of survival
- natural selection: differences occur from simple natural selection for other fitness reasons
| Can occur from sexual or natural selection
83
How can sexual dimorphism evolve?
From both sexual selection or natural selection.
Sexual selection (male peacocks) for mating purposes
Natural selection (larger female raptors) for survival purposes
84
How can rare alleles be preserved?
Diploidy (two alleles) 'hides' recessive alleles from selection when rare (consider a single alleles in a population, difficult to remove because its masked and not common)
| diploidy: the presence of 2 alleles = one can mask another
85
What is reinforcement?
this is when natural selection imposes reproductive barriers in order to reduce interspecies mating that Lowes reproductive success
86
What may occur when two allopatric populations reestablish contact?
1) complete reproductive barriers evolve: Populations are biological species
2) partial reproductive barriers evolved = formation of hybrids
87
What types of hybridization are there?
Fusion, reinforcement, and lon-lasting hybrid zone
88
What is fusion?
Hybrids form readily, have high fitness, the species merge into one again
89
What is reinforcement?
Hybrids have low fitness, natural selection barriers strengthen, hybridization ends resulting in two biological species
90
What is long-lasting hybrid zone?
Hybrids between species have variable fitnesses
91
What is allopolyploid speciation?
One example of polyploid speciation, and hybrid speciation first hybrid is infertile, however potential mitotic or meiotic errors occur form a viable fertile hybrid
92
What is one exception to the 'tree of life' model?
allopolyploid speciation (rare hybrids form fertile hybrid)
93
What occurs after species separation?
Natural selection to different environments, genetic drift
94
In what populations is genetic drift more significant?
Smaller populations experience genetic drift greater, because the changes can be expanded faster
95
What are systematics?
- the study of the diversity of life
-Two components: taxonomy and phylogenetics
96
What is taxonomy?
Naming and identification of taxa (species and groups of species)
97
What are phylogenetics?
Estimation of evolutionary trees (phylogenies)
98
What are the 3 important hierarchies to know in taxonomy?
Family, Genus, Species
99
How does taxonomy and the tree of life relate?
Hierarchal taxonomy is consistent with the tree of life (recall that Linnaeus' model corroborated Darwin's model)
100
What should taxonomy reflect ideally?
Taxonomy should reflect phylogeny, specifically taxa should be monophyletic groups where possible
101
Describe the 3 aspects of the phylogenetic tree?
tips = species
branch points ie: internal nodes = recent ancestors
branches = connecting these
102
What are sister taxa?
Species which are closest in ancestry
103
How many ways can a phylogenetic tree be drawn?
As many ways so long as the branches are not 'broken'
104
What is a cladogram?
An evolutionary tree whose branch lengths have no meaning
105
What is a phylogram?
an evolutionary tree whose branch lengths represent evolutionary change
106
What are the different types of groups to be found on a phylogenetic tree?
1) monophyletic
2) paraphyletic
3) polyphyletic
107
What are monophyletic groups?
Called clades
an ancestor and all of it's descendants
108
What are paraphyletic groups?
an ancestor and some, but not all, of it's descendants
109
What are polyphyletic groups?
A group that does not contain the ancestor itself
110
What group are reptiles considered to be?
A paraphyletic group ( to be monophyletic birds would need to be included)
111
How do we infer phylogenies?
Character states, morphological features, distribution of character states among organisms
112
What is an out group?
Present to distinguish between ancestral and derived states
- choose an animal that is not like the others
113
What does a 0 indicate in relation to the outgroup?
If an organism has traits that the our group also has, this means this trait is ancestral and therefore a 0 it placed. We can observe which animals on the tree have changes or no based on these inferences.
114
What causes character state distributions to be inconsistent on the same tree?
due to convergent evolution or reversal (the loss of a derived state)
115
How can we determine which phylogenetic tree is the best ?
The simplest tree, with the least amount of changes. This can be determined from looking at the trees and determining the minimum number of changes required for a characteristic and adding them up
- the tree with the fewest changes ( ie: parsimonious) is the best
116
What is the 1st 'rule' of checking phylograms?
are the organisms that share a derived state a clade?
If yes, they both have traits from one common ancestor
117
What is the 2nd 'rule' of phylograms?
If only one species has a derived state can always explain its lineage (1 change)
118
What is reversal?
This is a potential change on the tree that can reverse the derived state back into ancestral state
119
What is molecular sequence data?
- phylogenies of living taxa are usually estimated by comparing molecular sequences
- a site in DNA sequences is a character
120
What are phylogenies of genes?
- we can trace history of gene duplication or transfer between genomes
121
What is lateral/horizontal gene transfer?
- transfer of genes between species
- quite common in unicellular organisms
122
What are fossils?
- preserved remnant of past life
123
What kind of materials can fossils be found in?
- mineral components, petrified organic material;. casts, trace fossils 9footprints, etc)
124
What can fossils reveal?
Can provide information on past ecosystems and dating of geological record
125
What rock are fossils most likely to be found in?
Sedimentary rock -layers upon layers, eventually revealed due to geological formation/weathering exposes the bottom
126
What are Index Fossils?
Common widespread fossils characteristic of earth's history
- crucial for relative dating in geological record, reveals information about the earth at the time!
127
What is the geological record?
The timeline of the earth
- earth is ~4.6 billion years old,
- microbial life arose 3.5 billion years ago
128
What are the last 3 eras of the earth called?
Phanerozoic eon - divided into 3 eras, each era subdivided into several periods
129
What percentage of fossils exist from the past?
we have roughly fossils from the last 15% of the timeline
130
What are mass extinctions?
Many species go extinct in a very short period of time
131
How many mass extinctions have there been?
5 'big ones', marking end of eras/periods
132
What are the causes of mass extinctions?
large environmental changes (eg: massive volcanic activity, asteroid/comet)
133
What is the most devastating extinction?
The end permian mass extinction
- 550 million yeas ago, extinction of ~90% of species on earth, many families went extinct
134
What is the end cretaceous mass extinction?
- 65 millions years ago, most recent big mass extinction
- caused extinction of ~50% of species, notably dinosaurs (apart from birds) went extinct
135
What are adaptive radiations?
- rapid speciation and evolutionary changes in underexploited habitats
- increase in species with common ancestor because many changes occur to a species as they adapt to a new environment
136
What are the two forms of adaptive radiations?
- regional : colonization of new islands
- world-wide - following mass extinction species, only surviving lineages can radiate, replacement in fossil record
137
What did Darwin's theories propose about how complex adaptations evolve?
Darwinian evolution proposes that evolution occurs through many small steps, and every step should improve fitness
138
What are the mechanisms for the evolution of complex adaptations?
1) functioning intermediates
2) modification of existing structures (exaptation)
3) evolution of developmental regulation
139
What are functioning intermediates?
- Simple forms pf complex structure are functioning
- evidence: organs of different complexity in related species
- step wise evolution plausible (each is better than the last)
140
What is the modification of existing structures that leads to complex adaptations?
exaptation: structures adapted for one function are coincidentally useful for another function
141
What is exaptation?
when structures adapted for one function are useful for another. one example is dinosaurs feathers, which were originally simple structures used for warmth or other functions, and over time increased in complexity to form wings and flight
-a feature that performs a function but that was not produced by natural selection for its current use
142
What is developmental regulation?
- mutations affecting genes that control development
- small genetic changes can result in large, calculated changes in phenotypes
143
What are homoeotic genes and what do they prove?
- Hoxgenes control identity of segments along the developing animal body, mutations in fruit fly created new pair of wings
- Homeotic genes are master regulator genes that direct the development of particular body segments or structures.
144
How are new genes formed?
gene duplication and horizontal gene transfer
145
How does gene duplication work?
1) part of chromosome
2) gene duplication
3) over time, independent evolutionary change occurs
146
What is subfunctionlaization?
An example of gene formation, when a gene initially has 2 functions, and then eventually these functions are split onto two different genes for specifically one function
147
What are paralogs?
Two related genes in one genome
- genes historically duplicates of one another in the same gene
- they are homologs but different versions of the same gene
148
Are paralogs homologous?
They are homologous because they are still derived from one common ancestor, however the creation happened from an initial duplication
149
What is a common example of paralogs?
hemoglobin and myoglobin began as one carrying unit
150
What is another form of gene duplication?
lateral/horizontal gene transfer
-the acquisition of genetic material from another organism without being its offspring
151
What are the three major lineages of life?
the 3 domains: bacteria, eukarya, archaea
- note: bacteria and archaea are both forms of prokaryotes
152
Why are prokaryotes important?
- on earth for ~3.5 billions years, responsible for most biological activity in ecosystems (ocean, soil) cause many diseases/infections, more [orkryotes than cells, useful for biotechnology
153
Describe bacteria?
Includes most well known prokaryotes, all known disease causing
154
What is the bacterial cell envelope like?
usually two bounding membranes - plasma membrane and outer membrane
- peptidoglycan wall between the membranes (complex polymer of sugar and amino acids)
155
What are the two membranes that form the bacterial cell envelope?
plasma membrane and outer membrane
156
What lipid is found in the bacterial cell envelope?
peptidoglycan - complex of sugars and amino acids
157
What are the important bacterias to note ?
1) spirachetes
2) gram positive bacteria- no outer membrane , cause many diseases/infections
3) cyanobacteria- photoautotrophs (oxygenic photosynthesis - produces oxygen)
4) protobacteria - very diverse ex: E.Coli
158
What are Archaea?
- a form of prokaryotes, many are extremophiles
- many are menathogens -produce methane as waste
159
What is the archaean membrane like?
- no outer membrane, no peptidoglycan
cell membrane lipids are chemically different from bacteria and eukaryotes
- note the lipids have branches (hydrocarbon branches)
160
Which of the 3 domains are more closely related?
archaea are most closely related to eukaryotes than to bacteria
161
What are the steps to the origin of eukaryotic cells?
put this in later lol
162
What are some similarities between prokaryotes and mitochondria/plastids ?
- divided by binary fission, have prokaryotic like ribosomes, have their own genomes- encode some rans and some proteins are translated on organelle ribosomes
163
What are protists?
eukaryotes Responsible for most of eukaryotic diversity, abundant in ecosystems, important photosynthesizes, major predator of prokaryotes
-parasites cause some major diseases (malaria)
164
What are the origins of animals and fungi?
- phylogenies of molecular show that animals and fungi closely related, but individually evolved from single celled protists
-Plants evolved from photosynthetic green algae protists
165
What are are the things of the eon?
- Phanerozoic eon
- Paleozoic era, mesozoic era, cenozoic era
- the end permian was in the paleozoic era
- end cretaceous was in the mesozoic era
166
What are nucleosomes comparable to?
Beads on a string
167
Describe (In more detail) the Hershey chase experiment
Radioactive bacteria: radioactive phosphorus and sulfur used (sulfur not used in DNA, Phosphate is)
168
When does DNA become transcriptionally inactive?
When the DNA wraps around histones (wraps tightly around that prevents access to DNA polymerase, which would normally align the nucleotides)
169
Which is bigger, a sister chromatid or metaphase chromosome?
Metaphase chromosomes are larger because they are homologous
170
What are Mendel's law?
1. Segregation of alleles:
Two alleles for a heritable character segregate
(separate from each other) during gamete
formation and end up in different gametes.
2. independant assortiment of genes
During gamete formation,
a pair of alleles for one gene
will segregate independently of
a pair of alleles for another gene.
171
What is the magic ratio for genotypic ratios?
1:2:1
- 3:1 ratio for phenotype
172
What are the names of the discovery of DNA components?
Miescher- isolation of the nuclein
Griffith - transformation of DNA
Avery - purification of DNA
Hershey-chase - Radioactive DNA (viruses composed of only DNA/RNA and protein)
Rosalin franklin X-ray diffraction
Watson and crick - DNA model
Meselson and stahl - semi conservative model
Arthur kornberg- molecular components of DNA replication
