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Genes, Evolution and Development > Evolution Mathew Cobb > Flashcards

Evolution Mathew Cobb Flashcards

1
Q

Define evolution

A

Evolution is defined as a change in the allele frequence in a population over time

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2
Q

Define natural selection

A

Natural selection is the mechanism by which evolution occurs. Natural selection occurs when a change in the environment causes certain traits/alleles to be advantageous, allowing certain individuals with those traits to survive, reproduce and pass on traits too offspring.

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3
Q

Explain the difference between evolution and natural selection

A

Evolution is the change in allele frequency, natural selection describe how that change takes place. NS is one out of many possible mechanisms for evolution (adaptive)

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4
Q

State the 3 pre-conditions required for natural selection

A
  • genetic variation in population
  • differential survival and reproductive success
  • hereditary (traits have a genetic basis and can be passed on )
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5
Q

What is a tik-taalik and why was its discovery significant

A

1) It is a fish
2) From late denovian period
3) But it had similiar features to the tetrapod.
4) discovery of the tik taalik sheds light on a pivotal point in the history of life on earth.

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6
Q

Explain why the tik taalik discovery was important

A

It was a fish that had legs. The existance of tetrapod features in tik taalik marks the earliest appearance of fish having legs in the fossil record. This is the moment when the 1st ever fish ventured from sea to land.

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7
Q

Explain what is meant by a vestige

A

This is an anatomical structure or organ of the body that is degenerate, having become functionless in the course of evolution.

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8
Q

Define gene flow

A

Gene flow is defined as the transfer of alleles from one population to another population due to migration of individuals.

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9
Q

Explain why there is restricted gene flow between the Galapagos islands and South america

A

because galapagos islands are separated from the south america coast by 1000km of deep ocean! thus there is georgaphical isolation between the birds on the galapagos islands and the birds on mainland south america

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10
Q

Explain how Natural selection can sometimes not lead to evolution.

A

If natural selection acts on traits that do not have a genetic basis. Ie If Kylie jenner reproduces because she has dank lips, this trait will not be passed on to stormy so natural selection has acted, but evolution has not taken place because stormy gets her pre-surg lips.

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11
Q

List the 4 mechanisms that can bring about evolution

A

Natural selection
Mutation
Migration
Genetic drift

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12
Q

Explain genetic drift

A

This is a mechanism of evolution and is defined as chance fluctuations in allele frequency in a population. Individuals that survive do not represent healthy/fitter organisms, but just the “lucky” ones.

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13
Q

Does genetic drift produce adapatations

A

No. It is variation in allele frequency due to chance fluctuations.

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14
Q

Define an endemic species and give some examples

A

Some animal species found on the galapagos islands are not found anywhere else on earth. Finches are examples of endemic birds.

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15
Q

How many endemic species of finch were found on the galapagos

A

13

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16
Q

Summarise the Grants’ findings on the Galapagos

A

Evolution occured quickly enough to observe within a few years.
A single weather event can cause evolution, if there are traits that result in differential survival and there is genetic variation in those traits.

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17
Q

Explain why the Grants were so succesful?

A

Finches were not used to human contact, so were easy to catch and measure.
The grants measurements of beak legnth were very careful. The change in beak legnth could not be physically observed by eye, as it was so small .
Meticulous measurements allowed them to see even a difference of 0.55mm was enough to make a difference between survival and death in a drought year.

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18
Q

State three examples of vestigial structures in humans

A

Plica semilunaris

Preauricular sinus

Left laryngeal nerve

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19
Q

What is the preauricular sinus in humans

A

An evolutionary remnant of fish gills, this is a small hole at the top of the ear.

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20
Q

What is the left laryngeal nerve in humans

A

Often cited as evidence for evolution. left laryngeal nerve loops under the aortic arch and moves in opposite direction from the nerve it stems from. Despite the function of the branchial arch changing, the left RLN maintained its position despite this.

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21
Q

What is the plica semi-lunaris in humans

A

This is a vestigial structure

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22
Q

What are trilobites

A

One of the earliest known groups of Arthopods, they are marine animals.

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23
Q

Why are trilobites important

A
  • Disappeared arond 250 million years ago
  • Lived around 280 million years.
  • Show clear signs of evolutionary change in v short time.
  • Evidence for microevolution
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24
Q

Why is there limited gene flow between the birds of south america and birds of the galapagos

A

Because birds rarely move between the south american mainland and the islands, due to geographical isolation.

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25
Explain why there are so many marsupial species in Australia
Because Australis was isolated from the rest of the world for a long time. The isolation of Australia allowed radiation of marsupial species in the absence of placental mammals.
26
Patterns of lactose intolerence in humans are examples of what?
not sure, got this wrong in minitest 1
27
The bill shapes of the finches on the Galapagos islands have been subject to natural selection. The best explanation of this process is:
not sure!! got this wrong in minitest 1
28
The conditions necessary for evolution by natural selection to occur are:
inherited characters that vary and differential survival of individuals. Evolution by natural selection requires both heritable variation and differential survival.
29
Molecular phylogenies are....
Many molecular phylogenies are based on differences in the amino-acid sequences of proteins i.e. non-synonymous substitutions.
30
A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats. That the actual forelimbs of these mammals do not seem to be optimally arranged is because:
natural selection is generally limited to modifying structures that were present in previous generations and in previous species. Even with very long time periods natural selection may not arrive at the optimal structure because of constraints imposed by the development of the organism. Natural selection is a tinkerer, not a designer
31
Explain what is meant by biogeography
This is the study of the geographical distribution of organisms across the planet.
32
Explain the significance of the biogeography of the oceanic islands
Oceanic islands are very far away from the coast, so you tend to find very specific, local species of plants, birds and arthopods with specific adaptations.
33
Do you find placental mammals in australia
No! There were no native placental mammals like humans in australia, due to australia's geographic isolation.
34
Define convergent evolution
This occurs when two geographically isolated species in two different locations evolve to have similiar appearance due to similiar environmental conditions.
35
Define divergent evolution
This is effectively speciation. Occurs when two groups of the same species evolve and look different due to different environmental conditions.
36
Define the molecular clock
This is a tecnhique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged.
37
Explain how the molecular clock works.
take two different species, say humans and mice, and compare them for the same protein (hb for example). Any observed differences in the protein sequence are correlated with divergence from fossil data. This means we can trace back to a point in time when two species diverged, based on differences in the coding sequences.
38
Explain what is meant by neutral theory
A large fraction of new mutations do not have an effect on the evolutionary fitness of an individual, so they would not be favoured or disfavoured by natural selection.
39
State which type of mutations can be described as being selectively neutral
Mutations found in non coding DNA. These do not code for protien, so do not change phenotype of organisms. Such mutations are not selected and hence evolve randomly.
40
Which part of the DNA provides the best moleculra clocks
Non coding region
41
What does lactase persistence show strong evidence of?
Lactase persistence shows strong evidence of natural selection.
42
State the first stage in the evolution of the eye
Single photoreceptor cell is the first stage in the evolution of the eye.
43
State the 4 stages in evolution of the eye
1) single photoreceptor cell allows non directional photoreception 2) Screening pigment allows organisms to detect where light comes from. 3) Compound/cup shaped eyes with more receptors produce crude images of objects 4) Evolved sensory structures including lenses, corneas and irises.
44
State the types of eyes in the west indian fuzzy chiton
This is a marine mollusk that has hundreds of tiny eyes in its shell plates. Each tiny eye has its own lens, retina and pigment layer.
45
What are the lenses made up of in the west indian fuzzy chiton
Lenses are not protein! The lens is made of aragonite and minerals made from calcium and carbonate molecules.
46
What is significant about non coding sequences and evolution
mutations in non coding regions are not selected for, thus evolve randomly and produce the best molecular clock as their mutation rate can be assumed to be constant?
47
When did the earth form? When was the RNA world present
4. 5 billion years ago. | 3. 8 billion years ago was RNA world
48
When did the first DNA/protein life form
3.6 billion years ago.
49
Summarise the key role of the cell in how life came to be
All DNA life can be traced back to a last common universal ancestor (LUCA) DNA was highly fragile and needed protection in the form of the cell.
50
Outline the key events in geological time
• Universe is 14 billion years old • The Earth is 4.5 billion years old • Life is 3.8 billion years old • Life required cool temperatures, gravity, water and protection from radiation. As soon as the conditions for life were ready on earth, it appeared. • Eukaryotes formed 2 billion years ago. Prokaryotes formed 3.5 billion years ago
51
When did Eukaryotes form
2 billion years ago
52
When did prokaryotes form
3.5 billion years ago
53
Name the first prokaryotes
Methanogens - methane producing bacteria.
54
Briefly describe the process of Eukaryogenesis
Occured 2 billion years ago. | Archaebacteria englufed heterotrophic eubacteria and formed a mitochondria.
55
When was the Cambrian period/explosion
540 - 515 million years ago
56
Why is the Cambrian explosion important
It marks the time when most of the major animal groups first appeared in the fossil record! Represents a rapid explosion of growth of life and represents a period of time over which the first life forms appeared.
57
List the types of organisms formed in the cambrian explosion
Arthopods, chordates and wormds
58
List the potential causes/hypotheses of the cambrian explosion
1) interaction of abiotic and biotic factors 2) steep rise in oxygen concentration sparked change 3) rise in sea levels 4) increase in nutrients 5) biomineralization, increase in habitable volume of ocean.
59
When did the Edicaran period occur
570 million years ago, before the cambrian.
60
Which types of organisms formed during the edicaran period
1) Big animals but they were slow and immobile. 2) Dickinsonia, Rangeomorphs 3) Erniettomorphs
61
What was notable about edicaran organisms
relatively simple, lacked evidence of legs, eyes and many other anatomical structures.
62
Is formation of eukaryotes due to natural selection ?
No!!!! Formation of eukaryotes is not the product of natural selection. Eukaryogenesis was a chance event that took place. There were numerous encounters between archaea and bacteria in 3.6 billion years but engulfment only happened once by chance!
63
How did Eukaryotes form?
• Archaebacteria engulfed a heterotrophic eubacteria and formed a mitochondria Mitochondria and energy they provide allow for a large complex life.
64
How did plants form?
There is a 2nd event for plants; autotrophic eubacterium engulfed by eukaryotic plant ancestors.
65
During Eukaryogenesis, which type of gene flow took place?
Horizontal gene flow.
66
Define Species according to the Biological species concept
A population of reproducing organisms that are isolated from other populations
67
List the limitations of the biological species concept
- Definition cannot be easily applied to prokaryotes - Does not apply to plants that do not reproduce sexually - Does not apply to extinct organisms - Does not apply to bacteria and Archaea that showed horizontal gene transfer.
68
Define allopatric speciation
takes place when two populations of same species become geographically isolated from one another.
69
Define sympatric speciation
Occurs due to reproductive isolation. This type of speciation most commonly occurs through polyploidy, in which an organism or group of offspring will have twice the no. of chromosomes.
70
Explain what is meant by polyploidy.
polyploidy is where offspring or group of offspring will be produced with twice the normal number of chromosomes.
71
What do polyploidy individuals often lead to
Reproductive isolation, resulting in sympatric speciation
72
Define and explain genetic drift
This is the variation in frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce.
73
Give examples of different forms of genetic drift
Founder effect and Bottleneck effect
74
Explain the founders effect
If a small group of individuals break away from the popuation and start a new population, the gene pool is smaller and les diverse than the original gene pool.
75
Explain the Bottleneck effect
Occurs due to natural disasters, when a population is wiped out , leaving only a few alleles.
76
Explain what is meant by allopolyploid
When organisms contain 2 or more sets of chromosomes that are from different species.
77
Explain how Allopolyploid speciation occurs
Allopolyploid offspring have the genetic makeup from two different species, which makes it a hybrid, so a different species from the parent species, hence speciation has occured.
78
Explain the mechanism for how allopolyploid speciation occurs in plants
1) There is failiure of plant cell division after chromosome duplication, this creates tetraploid tissue. 2) gametes produced are diploid, not haploid. 3) tetraploid offspring produced may be viable and fertile, but this can only happen in plants as they have greater physiological and developmental flexibility.
79
Define polyploidy
• Where an organism contains more than 2 sets of homologous chromosomes. Can be tripod, tetrapod etc. Polyploids are widespread in plants, in major crops like cotton, rapeseed and wheat.
80
Give examples of polyploidy plants
Cotton, rapeseed and wheat.
81
List three pre-zygotic barriers that result in reproductive isolation
- Habitat isolation - Temporal isolation - Behavioural isolation
82
Reproductive isolating mechanisms
xxx
83
If the relative fitness of genotypes MM, MN, and NN are 0.8, 1.0, and 0.2 respectively, what do you expect to happen to the frequency of the N allele?
It will be maintained in the population because the heterozygote has the highest fitness
84
Genetic drift leads to....
Genetic drift tends to reduce genetic variation within a population because alleles are either fixed or lost by chance
85
Define hybrid infertility
This is a failure of the hybrid to contribute to future generations
86
Give some examples of pre-zygotic barriers
``` Habitat isolation Temporal isolation Behavioural isolation Mechanical isolation Gametic isolation ```
87
Define prezygotic barriers
Anything that prevents mating and fertilization is a pre-zygotic isolating mechanism
88
Give some examples of post zygotic barriers
- Reduced hybrid viability - Reduced hybrid fertility - Reduced hybrid breakdown - Hybrid zones
89
Define and explain hybrid breakdown
The f1 generation hybrids are viable and fertile, but the later generations are sterile, not viable or both.
90
Define and explain hybrid zones
A hybrid zone is a geographic region where allopatric populations happen to come back in contact with one another. There are three potential outcomes for the hybrid zone over time.
91
State the potential outcomes that can arise for the hybrid zone
- Re-inforcment - Fusion or reconnection - Stability
92
Define and explain re-inforcement after speciation
This takes place when two hybrids in the hybrid zone mate, but the offspring is less fit than parents, so over time, the two species continue too diverge until hybrids can no longer form.
93
Define and explain fusion/re-connection after speciation
Where the hybrid fitness is equal to or greater than that of the parents, so hybrids continue to reproduce until the original species is restored.
94
Define and explain stability after speciation
Where two separate species continue to reproduce and occasionally produce hybrids, but still remain distinct. There is no net change to the hybrid zone. For a hybrid zone to remain stable, the offspring produced by the hybrids have to be less fit than members of the parents species.
95
If the hybrids produced by two separate species are less fit than parents, predict what will happen to their population and explain why
Hybrids tend to be less fit so reproduction to produce hybrids will diminish over time. This nudges the two species to diverge completely in a process called re-inforcement.
96
State the mechanisms which alter the allele frequency in the population (decrease genetic variation)
``` Genetic drift (founders and bottleneck effect) Gene flow (migration of individuals or transfer of gametes across populations, hence transferring alleles) Non random mating (positive assortative mating and negative assortative mating) Natural selection ```
97
State the types of non random mating
Positive assortative mating | negative assortative mating
98
State the mechanisms which preserve genetic/ allelic variation?
``` Diploid factors of organisms Balancing factors (heterozygote advantage and frequency dependent selection) Neutral alleles (synonomous and non synonomous mutations) Clinial variation (different selection pressures in different geographical environments) ```
99
Whales are most closely related to which organism?
Hippos
100
Give an example of natural selection that has not yet shown evolution
Lizards from hurricane Irma. Natural disaster caused many lizards to die. Lizards with certain trait (shorter legs) were able to survie better than those with long legs. (Differential survival) Evolution has not yet occured because this population has not yet reproduced.
101
Why do lizards in a hurricane show natural selection but not yet evolution
Because they have not yet reproduced.
102
Whales used to live on the land. What happened to their sense of smell? What happened to the smell receptor proteins in whales
68 percent of olfactory receptor genes in whales are pseudogenes. This means they have lost their function over time, as whales no longer need to smell now that they live in water and not land.
103
State features of trilobites
Compound eyes Spines for sexual selection Provide evidence for microevolution as fossil record shows an increase in the number of ribs over time.
104
Are whales mammals
Yes whales are mammals. Whales used to live on the land first,
105
State the closest living relative to a whale
A hippo. Hippo lives in water and has 4 legs.
106
What is the evidence for the closest living relative of a whale being a hippo
Whales show fossil evidencee of old legs.
107
State the only driving force for evolution
Natural selection is the only mechanism that produces adaptions!!

Genes, Evolution and Development (14 decks)

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