Evolution Flashcards
1
Q
Pattern of evolution
A
- Speciation
- Morphological patterns
2
Q
Processes of evolution
A
Explain the patterns
- e.g. natural selection
3
Q
Unity and Diversity
A
- Organisms have many shared characteristics nit at the same time there is rich diversity
- Pre-dates Darwinism
- Darwins dezent with modification is sued to try and resolve this
4
Q
Plato (427-347 BC)
A
Species are immutable types - earthly forms were imperfect copies of a transcendental ideal
- Natural variation viewed as ‘noise’ to be filtered
- essentialism
5
Q
Aristotle (381-322 BC)
A
- First serious attempt to classify animals on the basis of anatomy
- Scala Naturae
- Adopted by the Christian Church
6
Q
Linnaeus (1707-78)
A
- Swedish Naturalist
- Devised the present system of naming species
- Latin binomial nomenclature
7
Q
Copernicus and Galileo
A
- Later Newton and Descartes
- Replaced the will of God by teleology (explanation based on purpose)
8
Q
Cuvier (1769-1832)
A
- Staunchly opposed the idea of evolution, he believed major changes in strata were results of catastrophes separating species
- Showed with modern Ibis birds were identical to ancient Egyptian birds showing “fixity” of species
- After mass extinction, the “creator” would make up new species
9
Q
James Hutton (1726-97)
A
- Proposed the Earths geologic features could be the result of cumulative results of gradual mechanisms
- e.g. formations of canyons by erosion
10
Q
Charles Lyell (1797-1875)
A
- Expanded on gradualism and suggested geologic events happening now are operating at the same rate as in the past
- Uniformitarianism
11
Q
Darwin
A
- Defined evolution as decent with modification
- Influenced by Hutton and Lyell
- The earth must be very ancient
- Very slow and subtle processes persisting over a long time can result in a dramatic change
- Influenced by Wallace who talked about how variation allows evolution
12
Q
Lamerck (1744-1829)
A
Developed Transformation, a theory arguing that organisms arise from inanimate matter and progress along the Scala Nature to greater complexity
- Path of evolution if guided by the government
- Evolution is changes in traits allowing organisms to be successful in an environment
13
Q
Malthus (1766-1834)
A
- Inspired Darwin to see a connection between natural selection and capacity to overproduce offspring
- The struggle for existence
14
Q
Principles of Darwin’s Theory
A
- Individuals within a population are variable in terms of their morphology, physiology and behaviour
- VARIATION - The variation among individuals are, in part at least, passed from parents to offspring
HERITABLE - In every generation some individuals are more successful are surviving and reproducing than others
DIFFERENTIAL REPRODUCTION - The survival and reproduction of individuals are not random, instead they are tied to variation among individuals i.e.individuals with the most favourable variation are selected
SELECTION
15
Q
The New Paradigm
A
- Darwin and Wallace’s concept of dynamic biology challenged the long unquestionable view of the static world i.e. change is the natural order
- Darwin showed that material causes are a sufficient explanation biological and physical phenomena
- Coupling undirected, purposeless variation to the process of natural selection, make teleological or metaphysical explanations
16
Q
Artificial Selection
A
- ## The process by which the animal/plant breeders select individuals would be represented in the next generation
17
Q
Artificial Selection in Drug selection
A
- Certain strains of bacteria are becoming resistant to antibiotics
- Doctors keep coming up with new more powerful antibiotics but the bacteria keep developing resistant strains
18
Q
Macroevolutionary evidence
A
- Homologous Structures
- Vestigial Structures
- The fossil record
- Biogeography
- Adaptation
19
Q
- Homologous Structures
A
- Related species can have characteristics that are similar with different functions
- Similarity resulting from a common ancestor
- e.g. underlying skeleton of arm, forelegs, flipper, and wing represent variation on a structural theme inherited from a common ancestor
20
Q
- Vestigial Structures
A
- Functionless or rudimentary version of a body part that has an important structure in a related species
- Structures which make no sense unless arising from evolution
- e.g. Flightless North Island Brown Kiwi is a flightless bird but still has a tiny wing
21
Q
- The fossil record
A
- Pattern of evolution, showing past organisms are different to current ones and shows how extinction is common
- Can shed light on new groups
- e.g comprising fossils of ankle bone (astragalus) shows that cetaceans are most closely related to even-toed angulates
22
Q
- Biogeography
A
- Darwin observed that islands have many endemic species closely related to species on the nearest island
- Darwin realised some of flora on Tristan de Cunha was African and South American
- Also explained why two islands with the same environment in different parts of the world were not populated by the same species
23
Q
- Adaptation
A
- provided evidence of selective forces in the environment and the imperfections of adaptations which suggested the historical constraints on evolutionary change
24
Q
Darwin on the Galapagos Islands
A
- HMS beagle
- Mocking birds and tortoises varied for island to island
- Finches beak size changed depending on food source on each island
25
Modern Synthesis/Neo-Darwinism
1. Ample genetic variation arises and is contained in populations via random mutation and recombination/chromosomal changes
2. Evolution in populations is influenced by natural selection and is characterised by changes in gene frequencies
3. Adaptive genetic variation produces small stepwise changes in phenotype which accumulate gradually
4. Divergence of geographically isolated populations leads to speciation
5. Continued gradual accumulation of genetic differences results in new genera and families (macroevolution)
26
Harvy-Weinburg Equations
p2 + 2pq + q2 = 1
p +q = 1
27
Harvy-Weinburg Conditions
1. No mutation
2. Mating is random
3. No selection i.e. all offspring are as likely to survive
4. Population is large enough so chance alone will not alter gene frequencies
5. No gene flow
28
Microevolution
- Accumulated changes in the composition of the gene pool
29
Blending Inheritance
- Theory that genetic material contributed by each parent mixes
- This could not be true as would "average" traits not create variation
30
Sickle Cell Anaemia
- Example of mutation being a genetic disorder
- Substitution of a singe AA in the haemoglobin protein (RBC)
- When O2 content is too low in the blood the sickle cell haemoglobin protein aggregates into long fibres and deforms the RBC
31
Maintenance of genetic variation
- Variability is preserved by diploidy, which shelters rare, recessive alleles
- Recessive refuge
- Inbreeding causes loss of variation and increased homozygosity
- Outbreeding increases variability
-
32
Genetic Drift
- Significant in small populations and can cause allele frequencies to change at random
- Certain alleles increase or decrease in frequencies in a result of a change of events
- Can lead to loss of variation
- Can cause harmful alleles to become fixed
33
Founder Effect
- Example of genetic drift
- Small group of a population move to a new "area", may not have a represent sample of the alleles of original population
- Move towards natural selection
34
Bottleneck Effect
- Example of genetic drift
- Some natural disaster greatly reducing numbers of a population
- Survivors may not have a representative same of alleles present in original population
- Move towards natural selection
35
Gene Flow
- Movement of alleles in or out of the population
| - Tends to restore genetic variation to a population and move away from natural selection
36
Fitness
- Natural selection occurs when genotypes differ in fitness
| - Darwinian fitness is the ability to survive and reproduce
37
Absolute Fitness
W
- is a measure of the total number of offspring an individual produces
38
Relative Fitness
w
- the contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals
- Relative fitness is the absolute fitness of an individual relative to the absolute fitness of the fittest individual in the population
- Can range from 0 - 1
= fitness of individuals genes/W
39
Major types of selection
1. Stabilising Selection
- Extreme phenotypes are eliminated
2. Disruptive Selection
- Extreme phenotypes are selected at the expense of intermediate forms
3. Directional Selection
- One of the extremes is favoured, driving the population in a particular direction
- Common when an environment changes, or when individuals move into a new environment
40
Sexual Selection
- Result of the commotion for mates
| - Responsible for the elaborate mating displays and secondary sexual characteristics
41
Intra-sexual Selection
Individuals of the same sex competing directly
| - Thought to occur in males of many species
42
Intersexual Selection
Mate choice i.e. females selecting mates
43
Heterozygote Advantage
- Heterozygote phenotype has a higher relative fitness of either homozygous phenotypes
- e.g. Sickle Cell anemia protects against Malaria in heterozygotes but can be dangerous in homozygotes
44
Frequency Dependant selection
Fitness of phenotype decreases as it becomes more common in the population and increases as it becomes less common
e.g. Scale eating fish attacking from left or right and fitness between phenotypes rotates
45
Exaptations
- Traits that have been enlisted for a new use i.e. evolved for one purpose but sued for another
- Traits function does not always explain its origin
- Birds feathers in flightless bird used for thermal protection in the past now instrumental in birds flight
46
Why natural selection cannot fashion perfect organisms
- Selection can only act on existing variation, new advantageous alleles do no arise on demand
- Events such as genetic drift and gene flow may counterbalance the forces of selection
- Potential for evolutionary change is constrained by the structure and development of the individual organisms and the extent of variation in the gene pool
47
Allopatric Speciation
- Occurs in geographically isolated populations
- Most common form of speciation for Neo-Darwinism
- Occurs as a result of physical event and a group becoming isolated from the parent population
48
Sympatric Speciation
- Speciation occurs without geographic isolation
- Occurs principally in plants through polyploidy which is often coupled with hybridisation
- Can also take place via disruptive selection
49
Biological Species Concept
- A species is a group of populations who's members can interbreed with one another but cannot interbreed wither members of other species
- Defined by reproductive compatibility/isolation
- occurs as a result of biological factors which block gene flow - limited hybrid formation
50
Patterns of Speciation
1. Anagenesis
2. Cladogenesis
3. Adaptive Radiation
4. Extinction
51
1. Anagenesis
- Phyletic
| - Gradual change within a single lineage over time
52
2. Cladogenesis
- The evolutionary change produced by the branching o populations from each other to form new species
- Generally considered to be responsible for the diversity of species over evolutionary time
53
3. Adaptive Radiation
- Rapid formation of many species from a single ancestral group, characteristically to fill a new ecological zone
54
4. Extinction
- Extinction is the disappearance of a species from the earth
- The fossil record reveals a low steady rate of extinction interrupted periodically by mass extinction
- Two mass extinctions permian and Cretaceous receive the most attentions
- 5 main events in the past 500 million years
55
Punctuated Equilibrium
- New species appear in burst of rapid speciation among small peripheral populations
- the new species displace many of the exisiting species (which then become extinct)
- Persist for long periods of time with little change, and then in turn abruptly become extinct
56
Gradualism
- Species diverge slowly and steadily over time
57
Autopolyploidy
- Failure of gamete cell division in plants can double a cells chromosome number from the original 2n to a tetraploid 4n
- Animals cannot cope with this
58
Allopolyploidy
- Plant hybrid between two or more species (chromosome sets from different species)
- Most hybrids are sterile as chromosomes are not homologous and do not pair in meiosis
- May be able to reproduce asexually
- Mitotic or Meiotic non-disjunction can double the chromosome number and change a sterile hybrid into a fertile polyploid
- Allopolyploids are fertile when mating with each other but cannot mate with parental species
- Add diploid of parents to get diploid of allopolyploidy
59
Characters
- Heritable trait
- Can be morphological, molecular or behavioural
- Phylogenetic reconstructions are based on the analysis of the characters and changes in character states
60
Ancestral Characteristics
Those that are inherited with little or no change from remote ancestors
- Often are similarities
61
Derived Characteristics
Undergone recent changes and may be shared only by closely related species or taxa
62
Analogous Structures
Similarities between organisms due to convergence
63
Cladistic principles
- used to under phylogenetic relationships from homologous characteristics
- Clades are determined by shared derived characters and ignore overall similarity
64
Monophyletic
Includes ancestral species and all of its descendants
| - Taxon is a clade only if it is monophyletic
65
Paraphyletic
Includes ancestral species and some but not all of its descendants
66
Polyphyletic
Includes distantly related species but does not include the most recent common ancestor
67
Constructing a cladogram
Out-group is a species or a group of species that is known to have diverged before the lineage that includes the species to be studies (in-group)
- Sister taxa are closest related
- A lineage that evolved early and remains unbranched is a basal taxon
68
Principle of Parsimony
- Investigate the simplest explanation that is consistent with the facts i.e. fewest evolutionary events
69
Transposed Sequences
- Mobile sequences of DNA, very abundant in humans making up 44%
- Can insert themselves into many different locations of the genome
- Can cause mutations by direct insertions or by promoting DNA rearrangement such as chromosome deletions, duplications, inversions
- Retrotransposons (RNA to mediate)
- DNA transposons
70
DNA in Eukaryotes
- DNA sequences that code for proteins or produces tRNA or rRNA make up 1.5% of the human genome
- All coding and non-coding sequences make up 25% of the human genome
- Intergenic regions includes unique noncoding DNA such as gene fragments and pseudogenes (non functional vestigial genes)
71
Multigene Family
- genes whose sequences are very similar and that probably arose by duplication.
- Identical repeated DNA sequences
72
Neutral Theory
- Most mutations are not acted upon by natural selection
73
Phylogenies
Evolutionary tree
74
What does having more fixed gene loci in a population do?
- Lowers nucleotide variability and average heterozygosity
75
Macroevolution
- is evolutionary patterns above the species level
