Unit 4: AoS 2 EVOLUTION Flashcards
1
Q
What is evolution?
A
Changes that occur in the genetic makeup of a population over time.
2
Q
What is gene flow?
A
Gene flows is the movement of genes/alleles from one population to another as a result of reproduction between individuals from each of the populations.
3
Q
What is the gene pool?
A
The genetic information present in a population of organisms.
4
Q
What is genetic drift?
A
Genetic drift involves the unpredictable changes in allele frequencies in a population due to chance events.
5
Q
What results in evolution?
A
Mutation (spontaneous, random, very rare)
Gene flow
Genetic drift
Non-random mating
Natural selection (makes a population better adapted (more fit) to its environment)
6
Q
An explanation for stripes in Zebras by Lamarck VS Darwin?
A
Lamarck:
*A zebra is able to develop stripes for camouflage and survival against predation.
Darwin:
*There is pre-existing variation in zebras. Some zebras have prominent stripes, some don’t.
*Zebras with prominent stripes can camouflage well and SURVIVE, REPRODUCE AND PASS ON ALLELES TO THE NEXT GENERATION.
*Over time, more and more zebras will have prominent stripes.
7
Q
What are the steps involved in somatic cell nuclear transfer?
A
1) Isolate a somatic cell and transfer nucleus from that cell to an egg cell without a nucleus (enucleated egg cell)
2) The egg cell with the new nucleus acts like a zygote which develops into an embryo.
3) The embryo is then implanted into a surrogate mother and carried to term.
8
Q
What are stem cells?
A
Cells that have the ability to differentiate into many different specialized cells.
9
Q
What are the general steps involved in therapeutic cloning?
A
1) Isolate stem cells (from individual or embryo)
2) Program stem cells to become desired type of cell.
3) Reinsert programmed cell into patient.
10
Q
What is therapeutic cloning?
A
THe harvesting of stem cells to treat various diseases or replace damaged cells in the body by process of stem cell therapy.
11
Q
What is reproductive cloning?
A
The process of creating a genetically identical organism.
12
Q
What are the advantages of reproductive cloning?
A
- TO prevent extinction of species
- To clone livestock with high quality of meat
- TO clone animals with desirable characteristics
13
Q
Disadvantages of reproductive cloning?
A
- Decreased variation–> may affect survival of species
- Genetic disorder passed down from donor
- Ethical concerns (ie interfering with natural processes)
- Only accessible to the rich
14
Q
What is gene therapy?
A
- Adding functional alleles to replace defectivevalleles of certain genes, mainly targetting somatic cells.
- Can use microinjections and viruses to insert functional genes.
15
Q
What are the different stem cell types and examples?
A
Totipotent (all) eg fertilised egg and cells of a 2,4 or 8 cell embryo.
Pluripotent (most) eg cells from inner cell mass of an early embryo
Multipotent (many) eg adult/somatic cells such as bone marrow stem cells
16
Q
What is the definition of a species?
A
A group of organisms that can interbreed (mate) to produce viable, fertile offspring.
17
Q
What is speciation?
A
The formation of a new species.
18
Q
What is allopatric speciation?
A
Formation of a new species due to populations being affected by geographical isolation.
19
Q
What are the steps involved in the theory of allopatric speciation?
A
VISCAMN.
V-VARIATION. Pre-existing genetic variation must be present in a population.
I- ISOLATION. The population is separated by a physical barrier such as a permanent river or highway –> NO GENE FLOW.
S- SELECTION PRESSURES. No gene flow between groups (ie mating/interbreeding is restricted). Different selection pressures select for different traits.
CA– CHANGE IN ALLELE FREQUENCY. Changes in allele frequencies between the two groups (genetic variation)
M- MUTATION. A mutation may occur in one group which affects their ability to mate or reproduce.
N- NEW SPECIES. When reintroduced, individuals from different groups can no longer mate or reproduce to produce viable, fertile offspring–> New species has formed.
20
Q
Why would some species not be able to mater after speciation?
A
- Genetalia may not be structurally compatible.
- Different mating seasons.
- Different mating calls.
- Different mating rituals.
- Offspring may be infertile–> results in sterility (chromosomes are not able to be arranged in homologous pairs)
21
Q
What are homologous structures?
A
Structures that share basic similarities but may have different functions because they evolve in different ways due to different selection pressures.
22
Q
What are analogous structures?
A
Structures that have similar functions in organisms that are distantly related (unrelated). They are a result of adaptation to similar selection pressures.
23
Q
What is the bottleneck effect?
A
Definition VCAA: A severe reduction in genetic diversity due to a chance event (catastrophe) that may change allele frequencies.
A bottleneck effect results from the reduction in size of a population, typically by a natural disaster, such that the surviving population is no longer representative of the original population.
24
Q
What is the founder effect?
A
The founder effect is an example of genetic drift caused by the colonisation of an area by a limited number of individuals from a parent population, not representative of the original population.
25
What is an adaptation?
Structural, biochemical or behavioural characteristic that assists an organism to survive and reproduce in its environment.
26
What does Charles Darwin's theory of evolution state?
1) individuals in a population possess different genotypes and therefore different phenotypes
2) the struggle for survival occurs in populations due to selective pressures
3) the best suited phenotypes produce more offspring. Variations are inherited and therefore each new generation will contain proportionally more of the favourable phenotype.
4) over time, the new variations are so distinctive from the original population that a new species has evolved.
27
What is divergent evolution?
The process by which an interbreeding population or species separates into two ore more descendant species, resulting in once similar or related species becoming more and more dissimilar due to different selection pressures.
28
What is convergent evolution?
Convergent evolution is when two species, which do not share a recent common ancestor, independently develop similar features due to similar selection pressures.
29
Describe the process of binary fission.
Bacteria reproduce asexually by binary fission. The single, circular chromosome that is attached to the cell membrane in bacteria is copied and then the cell membrane and cell wall expand separating the chromosomes. The cell membrane and cell wall then grow down between the two chromosomes creating two genetically identical daughter cells.
30
What is mitosis?
Mitosis is the nuclear division of one cell into two genetically identical daughter cells i.e. each daughter cell contains the same number of chromosomes as the original parent cell.
31
What is the purpose of mitosis?
It ensures that cells maintain a large surface area to volume ratio and allows for:
- growth of an organism
- replacement of cells which have died or been damaged
32
What is meiosis?
Meiosis is a reduction division involving one diploid parent cell dividing to produce four haploid daughter cells that are genetically varied, i.e. each daughter cell has half the number of chromosomes of the parent cell
33
What is independent assortment of chromosomes in meiosis and at what stage of meiosis does it occur in?
Maternal and paternal chromosomes of each homologous pair line up independently of all other homologous pairs along the equator of cell during metaphase I of meiosis. This is an important source of genetic variation within a species.
34
What is crossing over in meiosis and at what stage of meiosis does it occur in?
During prophase I, homologous chromosomes pair up and often make contact with one other, becoming intertwined. During this time, a section of the genetic material on a maternal chromatid can be swapped for the corresponding genetic material on the homologous paternal chromatid. The point of crossing over is called the chiasma and can lead to new combinations of genetic material on a chromosome, referred to as recombination.
35
When does non- dis-junction occur and what is/are the result of it?
Failure of chromosome pairs to separate during Anaphase I or Anaphase II
* If single chromosomes fails to separate (Down Syndrome, Kleinefelter's, Turner's) the event is anueploidy (older mother= greater chance of aneuploidy)
* If a complete set of chromosomes fails to separate, event is polyploidy (not viable in humans but viable in plants)
36
What is natural selection?
Selection that results in "survival of the fittest". A fit organism is one that is better adapted to the environment.
37
Key points to remember in natural selection questions?
```
VESIG.
Variation- pre-exisiting variation (what type of variation is present in the population?)
Environment (What is the environment like? How does this contribute to selection pressures?)
Selection pressures (Selective agent/ selective advantage)
Inheritance (variation must be inherited; that is, individuals survive, reproduce and pass on alleles to the next generation
Generations (What do you expect to happen to the frequency of the alleles over generations?)
```
38
What are the evidences in support of Darwinian evolution?
BADFEW.
Biochemical similarities exist between organisms of recent common ancestry.
Anatomy (structural) similarities exist between organisms of recent common ancestry
Distribution (biogeography) of present day organisms reveals many cases of common ancestors, once separated, evolving into different species (e.g. under influence of continental drift)
Fossil records reveal gradual changes in organisms from ancestral forms over time e.g. transitional fossils
Embryology comparisons
Witness of the process of change in living organisms, via natural selection or artificial selection.
39
What is a vestigial structure?
* Organs that are have no particular function or are reduced in nature.
* They indicate that a role previously existed for functional forms of these organs in the ancestors of the present day organism
40
What are the different types of chromosomal (block) mutations?
* Deletion
* Inversion
* Translocation
* Duplication
41
What causes extinction?
* Predators
* Competition for food
* Lack of shelter/habitat destruction
* Disease
* Natural disaster
* Hunting/poaching
* global warming
42
What are the different types of selection pressures?
Physical agents e.g. climate change or food shortage
Biological agents e.g. infectious disease or predation
Chemical agents e.g. a pollutant in soil or water
43
What are the environmental conditions that increase fossilization probability?
* Sap
* Rapid burial
* Anoxic conditions (low oxygen levels)
* Lack of decomposers
* Alkaline soil
* Dry climate
* Cold climate
* Lack of scavengers (animals that feed off dead organisms e.g. vultures)
* Layers of rock--> pressure
* Soft surface allows for imprints
* Plentiful time
44
What is a transitional fossil?
Fossils that show the intermediate form between two groups of species.
45
What is an index/indicator fosssil?
A fossil that is found in the rock layers of ONLY ONE TIME PERIOD that is used to define and identify geologic time periods and is abundant.
*Used to establish age of rock layers
• an index fossil must be distinctive and easily recognisable
• an index fossil should be abundant
• an index fossil lived a short range through time
• an index fossil lived in a wide geographic distribution.
46
What is a fossil?
A fossil is a remnant, cast, impression, trace or actual remain of an animal or plant of a PAST GEOLOGICAL AGE that has been PRESERVED.
47
What is radiometricc dating?
A method used to determine the absolute age of fossils.
*The half life of a radioactive element, either in the fossil itself, or in the surrounding rock, is used to date the fossil.
48
What is the half life of a radioactive element?
The time taken for the half of the radioactive element to decay and form a different element.
49
What is the half life of Carbon -14?
Carbon-14--> Nitrogen-14 ~5, 730 years
50
Half life of Potassium 40?
Potassium-40 --> Argon-40 ~ 1300 million years
51
Half life of Uranium-238?
Uranium-238 --> Lead-206 ~4500 million years
52
Define extinction?
The loss of a species from the Earth's biodiversity
53
How does comparative embryology provide evidence for evolution?
The developmental stages of related organisms are similar.
* If new species have evolved from a common ancestor, it would be expected that they would have similar stages in their development.
* eg all chordates (fish, amphibians, mammals) have gill slits at some stage in their life cycle
54
How do transitional forms provide evidence for evolution?
If new species have evolved from a common ancestor, then the fossil record should include fossils that have characteristics that are intermediate between the ancestral form and the new form. eg Archaeopteryx fossil is the intermediate between birds and reptiles
55
How does biogeography provide evidence for evolution?
Biogeography is the study of distribution of organisms. A long time ago, continents were joined together and organisms were able to move across the continents. As a result of continental drift, the different land masses separated and with different selection pressures and no gene flow, the organisms in each region developed their characteristics (evolved). The example is in your notes. Eg Baobab trees pg 237.
If new species have evolved from a common ancestor, then species found in isolated areas will be more similar to species that live in distant areas with the same environment today.
56
What is relative dating?
Determining the age of a fossil or a rock based on stratigraphy. (least precise method)
57
How does DNA hybridisation provide evolutionary evidence?
The amount of hybrid DNA and the strength of the DNA bonds depends on the similarity between different species' DNA.
*greater the amount of hybridisation, the higher the temperature required to separate the strands, the greater the genetic similarity between the two species and the closer the two species are related.
58
How does amino acid sequencing provide evolutionary evidence?
If new species have evolved from ancestral species, then their proteins and DNA will be similar.
59
Why is mitochondrial DNA studied for evolutionary relationships?
* Changes in mitochondrial DNA are due to mutations only and not recombination during meiosis.
* High number of mtDNA in cells
* The non-coding regions of mtDNA evolves more regularly than non coding regions of nuclear DNA so it is used in comparisons between organisms that have diverged within the last 20 million years.
* Maternally inherited
60
What is the purpose of a phylogenic tree?
A phylogenetic tree can depict the approximate time of emergence of new species from the common ancestor/ original species and it is used to determine which of the depicted organisms are more closely related.
61
Main processes in Interphase of Mitosis
* Chromosomes appear as long thin threads--> chromatin
| * Chromosomes replicate
62
Main processes in Prophase of Mitosis
* Nuclear membrane disintegrates
* Chromosomes condense, thicken and become visible
* Centrioles move to opposite poles
* Spindle fibres begin to develop/form
63
Main processes in Metaphase of Mitosis
* Spindle fibres become more prominent
* Chromosomes align at the centre of the cell in a single file
* Centromeres attach to the spindle fibres
64
Main processes in Anaphase of Mitosis
* Chromosomes separate and chromatids are pulled apart towards the poles by spindle fibres
* Spindle fibres conract
65
Main processes in telophase of Mitosis
* Spindle fibres break down
* Nuclear membranes form around chromosomes
* Chromosomes uncoil and lengthen
66
What is cytokinesis?
Division of the cytoplasm.
* In animals- burrow forms
* In plants- cell plate forms in between
67
How are fossils formed?
When decomposition of dead body tissue is very slow or does not occur at all.
68
What is a species?
Members of a population that can interbreed successfully to produce fertile and viable offspring.
69
What is the fossil record?
the record of the occurrence and evolution of living organisms through geological time as inferred from fossils.
70
What does DNA hybridisation involve?
DNA hybridisation involves the dissociation of different samples of DNA and their reassociation, providing a measure of similarity.
1) obtain DNA from different sources
2) heat DNA --> DNA strands separate (hydrogen bonds broken)
3) mix the single stranded DNA from both species to form hybrid DNA.
4) heat the hybrid DNA and measure the melting temperature (temp at which hybrid DNA separates)
5) greater the melting temperature, (Tm) the more similar the DNA sequence--> more closely related.
71
What is the difference between natural selection and artificial selection?
Artificial selection involves human intervention and humans can choose to breed desirable traits e.g. Farmers select crops with desirable traits to breed.
Natural selection is the survival of the fittest in terms of the ability to survive and reproduce viable fertile offspring. Fittest phenotypes best suited to environment have greater chance of surviving and reproducing.
72
What are the disadvantages/limitations of using stratigraphy to date fossils?
* Less precise than absolute dating
* Erosion
* There could be buckling of layers
73
How might the genetic makeup of a founder group differ from that of an original population?
* Genetic variation may decrease and
* There may be a SIGNIFICANT change in allele frequencies in the founding population compared to the original population.
74
Why is carbon-14 not useful to date fossils that are millions of years old?
Carbon-14 has a short half life of ~5730 years and there would be too little carbon left in the fossils as it can only be used to date fossils less than 50,000 years old.
75
Steps involved in DNA replication?
* Helicase enzyme helps to separate the DNA strands. (Single stranded binding proteins helps to keep them separated)
* RNA primase synthesises an RNA primer to which DNA polymerase adds DNA nucleotides to.
* DNA polymerase always synthesises DNA from 5' to 3'direction.
* Leading strand is synthesised in a continuous direction.
* Lagging strand is synthesised in Okazaki fragments.
* RNA primers are removed and replaced with DNA by another DNA polymerase.
* DNA ligase joins all the DNA pieces together.
76
Explain why low genetic diversity in a population threatens the survival of the population?
If individuals in a population are genetically similar and If one individual is disadvantaged due to an environmental selection pressure e.g. Disease or predator, then all individuals are likely to be disadvantaged and the population will become extinct.
Exchange of genetic material from another population of the same species that is more generically diverse, would increase genetic variation in endangered population and reduce chance of disappearance since some individuals will then have characteristics that allow them to survive and reproduce better under the selection pressure.
77
What is an examples of an index fossil?
Trilobites that were common during the Paleozoic Era (540-245 mya)
78
What is the order of emergence of organisms through geological time?
* Simple bacteria, invertebrates and vertebrates, fish, amphibians, reptiles, PANGEA, dinosaurs, mammals and birds, dinosaurs extinct and continent breakup, mammal domination, primates, ardi, modern Homo sapiens.
* Unicellular organisms, multicellular organisms, marine invertebrates, primitive plants (corals, fishes, seaweed and fungi), first vascular plants and jawed fish, amphibians, winged insects, reptiles, dinosaurs, mammals and birds, first primitive primates, hominids, humans
79
Advantages of phylogenetic trees?
They can assist with breeding programs
Help to find desired 'genes'/'alleles' in closely related species that are useful
To help identify antivenins for poisonous snakes.
Disease research and potential cures.
80
Key processes in Prophase I of meiosis?
* Nuclear membrane disintegrates
* Chromosomes condense, thicken and become visible.
* Centrioles move to opposite poles of cell
* Spindle fibres form
* Homologous chromosome pairs begin to form
* Crossing over can take place
81
Key processes in Metaphase I of meiosis?
* Spindle fibre formation complete
* Homologous chromosomes line up in pairs independently of all other homologous pairs (important source of genetic variation)
82
Key processes in Anaphase I of meiosis?
* Homologous chromosomes separate and move to opposite poles of cell.
* NO splitting of centromere
* Spindle fibres disappear
* Non-disjunction could take place here
83
Key processes in Telophase I of meiosis and cytokinesis?
* Nuclear membrane forms around chromosomes(haploid but still consists of two chromatids) at each pole
* Cytokinesis: Cytoplasm cleaves into two daughter cells each with a haploid number of chromosomes
84
Key processes in Prophase II of meiosis?
* Nuclear membrane disintegrates
* Spindle fibres form
* Chromosomes become distinct
85
Key processes in Metaphase II of meiosis?
* Chromosomes arrange themselves along equator of cell in single file.
* Centromeres divide
86
Key processes in Anaphase II of meiosis?
* Sister chromatids separate and pulled to opposite poles of cell
* Non-disjunction may occur here
87
Key processes in Telophase II of meiosis and cytokinesis?
* Spindle fibres disappear
* Nuclear envelope forms around daughter chromosomes at each pole
* Cytokinesis: begins during telophase II; each cell pinches into two cells resulting in four haploid gametes (daughter cells)
88
Why is it difficult to classify discovered fossils into species?
Since it is not possible to experiment with interbreeding in regards to fossils, it is difficult to determine which fossils begin to which particular species.
89
Explain why populations with limited genetic variety due to inbreeding have a low reproduction rate and are more vulnerable to disease
* Where there is inbreeding, there is also increased chances of homozygous recessive disorders. In a closed community (where there is inbreeding), there is a higher chance of two heterozygous individuals (carriers) breeding and there is a high chance of producing homozygous recessive affected individuals which may not be able to survive long enough to reproduce.
* When there is less genetic variation, there is generally a higher chance that the species have a reduced chance of survival when exposed to a diseases (for eg, if most of the organisms are susceptible then it is likely that most of the popoulation may die- having variation such as resistant alleles in the population may increase the chance of survival of the species).
90
Examples of amphibians?
Frogs, toads
91
What features ensure that there is a static gene pool in a population?
Random mating, no natural selection, no gene flow and a large population size
92
What is electron spin resonance and what does it involve?
ESR is a method for absolute dating. The greater the accumulation of radiation in minerals, the older the fossil (5000 to 500000 years old)
93
What is thermoluminescence and what does it involve?
It is a method for absolute dating of a fossil. It is used to date pottery pots, the more light released, the more energy charged electrons that have accumulated and the older the fossil.
94
What is a selective agent?
An environmental factor which acts differentially on the various phenotypes in a population.
95
What are some remedies/solutions to prevent extinction of a species?
* Breeding in captivity
* Cloning
* Legislature to prevent hunting/poaching of species
96
What does Darwin's theory of natural selection state?
* There is pre existing variation in a particular species
* Those who will both survive and reproduce are the ones who are better suited for that particular environment
* There is a struggle for survival and the fitter organisms will stand a better chance of survival (survival of the fittest)
* Therefore subsequent generations will resemble the survivors rather than those who did not survive. This causes changes to the genetic composition of the population leading to evolution.
97
What is the diploid chromosome number?
The number of chromosomes found as homologous pairs in a cell (organism)
or
the number of chromosomes in a cell (organism) that have two copies of each chromosome.
103
What does it mean if DNA replication is semi conservative?
The new DNA produced contains one old DNA strand as well as one newly synthesised DNA strand and both of the strands act as template strands hence it is semi conservative.
104
How is biological fitness measured?
It's a measure of the relative proportion of offspring that an individual leaves to the next generation.
105
What are trace fossils?
Corprolites, burrows, footprints or other animal marks which are buried and then harden.
106
What is a cast fossil?
An organism is buried in rapidly hardening mud, decays completely and the space it occupied(the mould) is filled with material. This results in formation of a cast.
107
List possible outcomes of comparative genomics.
Using comparative genomics, it is possible to:
• identify genes that are conserved in different species
• make inferences about the evolutionary history of a species
• estimate the degree of evolutionary relationship between two species.
