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Biology 2014 semester 2 > Class Notes 5 - Evolution > Flashcards

Class Notes 5 - Evolution Flashcards

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1
Q

what is evolution in basic terms?

A

common concept of evolution is the formation of new species as a resultof accumulated changes over, generally, very long periods of time.

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2
Q

what is the working definition of evolution?

A

evolution is the change in allele frequency in a population over time. (which may or may not lead to new or different species being formed).

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3
Q

what is the definition of gene pool?

A

sum total of all alleles or genes within a specific

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4
Q

what is the definition of population?

A

all individuals of a particular species living within a defined geographic region

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5
Q

what is the definition of allele?

A

variation of a particular gene or different form of a particular gene

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6
Q

what is the definition of allele frequency?

A

the proportion (usually represented as a %) of a particular allele within a population.

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7
Q

what is the definition of deme?

A

populations that are in isolation from other populations (of the same species)

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8
Q

what is the definition of species?

A

individuals that share common traits and interbreed under natural conditions to produce fertile offspring

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9
Q

what is it important to note from the work sheets?

A

observe how allele frequency (as well as phenotypic frequency) changes over time.

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10
Q

what are mechanisms of evolution?

A

a mechanism is any process that ultimately causes a change in allele frequency.

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11
Q

list the three mechanisms of evolution discussed.

A

> natural selection
gene flow
genetic drift (which includes population bottlenecks and founder effect)
mutations

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12
Q

What is natural selection?

A

> natural selection is a case where nature ‘selects’ those organisms with traits that increase the likelihood of surviving and reproducing
As a result, these traits are passed on to some of their offspring.
natural selection is often thought of in terms of ‘survival of the fittest’.
which means these organisms with the most suitable traits (in their environment) are considered ‘more fit’ an hence are more likely to survive.

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13
Q

what is it important to note about natural selection?

A

natural selection is a non-random mechanism, and the only one that leads to adaptation.

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14
Q

what does fit or fitness relate to?

A

fit or fitness more accurately relates to an organism’s reproduction potential. the more ‘fit’ an organism, the more likely that organism will successfully reproduce.

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15
Q

what are the three types of natural selection?

A

directional selection
stabilising selection
disruptive selection

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16
Q

what is directional selection using an example?

A

in this example (refer to book) curve A represent the distribution of fur density of a mammel at a mean temp annually of 24 degrees C - X represents the mean fur density. Curve B shows a directional shift is mean fur density as a result in a decrease in mean annual temp.

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17
Q

What is a selection pressure in a directional selection cause?

A

it causes the mean to be shifted.

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18
Q

what is another example of directional selection?

A

the peppered moth is an example. Occurred in england during the industrial evolution. Black moths that lived near factories were being selected over peppered form as the pollution killed of the lichen. I.e., pollution is the selection pressure.

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19
Q

what is stabilising selection using an example?

A

the frequency of average birth weights.
> Refer to book
>babies born near the average birth weight are most likely to survive.
>babies born with low birth weights have a greater risk of dying due to the associated health issues. Mothers are more likely to die (from haemorraging) when giving birth to babies with high birth weights. Numbers of individuals in the extreme regions of the curve are reduced.

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20
Q

what is the selection pressure in birth weights of babies nd what does it do to the curve?

A

high mortality in babies who are underweight –> pushes curve towards centre.
high mortality in mothers and babies who are overweight —> pushes to curve towards the middle.

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21
Q

what is another example of stabilising selection?

A

the frequency of sickle cell trait in malarial regions.
> refer to book
> those with sickle cell trait are more likely to survive because 1) they have a greater resistance to malaria and
2) don’t actually suffer full effects of sickle cell disease.

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22
Q

what are the selection pressures in the frequency of sickle cell trait in malarial regions?

A

1) those without sickle cell trait have a high mortaility as they are less resistant to malaria
2) those who have sickle cell disease have a high mortaility because of the disease itself.

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23
Q

what is disruptive selection?

A

refer to graphs in book
>a selection pressure comes from above, thus splitting the population - creating two distinct mean values.
> if the selection pressure remains, it is possible that two distinct populations might be created from the original population.
> now if these two populations are subsequently exposed to different environmental conditions and remain reproductively isolated for long periods of time, then it is possible that populations A and B may evolve into different species.

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24
Q

learn the summary sheet in book

A

Its really good!

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25
Q

what is gene flow?

A

unlike natural selection, gene flow is a random process.
>gene flow is migration (e.g., immegration and wmigration), which means the movement of genes (or alleles) between two or more populations.
>gene flow tends to increase genetic diversity of a population
>Know diagram in book!!

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26
Q

What is genetic drift?

A

Genetic drift is a change in allele frequency resulting from random (often environmental) factors.
>We can say that there is ‘a drift in the allele frequency over time’.
>genetic drift has a greater impact on small populations
>genetic drift tends to decrease diversity of a population

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27
Q

describe the difference on population diversity between gene flow and genetic drift

A

gene flow tends to increase the population diversity over time.
genetic drift tends to decrease the diversity over time.

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28
Q

what is the bottleneck effect?

A

the bottleneck effect occurs when some environmental factor results in a dramatic decrease in the original population size, e.g., tsunami, brush fire, cyclone etc.
> the subsequent population that arises will, most probably, not accurately represent the allele frequencies of the orginial population.
> refer to diagram

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29
Q

what is the founder effect?

A

the founder effect is when a small number of individuals leaves the main population.
> the new ‘founder’ population will not, probably, accurately represent the allele frequencies of the main population.
>refer to book

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30
Q

what are mutations?

A

> ultimately, mutations are the source of all variation and ply a role in gene flow, genetic drift and in particular, natural selection.
mutations are often a result in errors made during DNA replication (or errors occurring during meiosis).

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31
Q

in terms of evolution, what are the four categories of mutations?

A

1) neutral mutations
2) disadvantageous mutations
3) lethal mutations
4) advantageous mutations.

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32
Q

What are neutral mutations?

A

represent the majority of mutations occurring in populations. these types of mutations do not affect the fitness of the organisms, e.g., variation in eye or hair colour.

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33
Q

What are disadvantageous mutations?

A

reduce the fitness of organisms. e.g., albinism in tropical areas.

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34
Q

What are lethal mutations?

A

are fatal to the organism - typically before they reach reproductive maturity, e.g., cystic fibrosis and haemophilia

35
Q

What are advantageous mutations?

A

in some way increase the fitness of the organism, e.g., DDT resistance in fruit flies and antibiotic resistance in bacteria.

36
Q

what is speciation and what are the to categories?

A

speciation is the formation of new species. there are two broad categories of speciation:

1) allopatric speciation
2) sympatric speciation

37
Q

what is a working definition for species?

A

organisms that share common features and are able to naturally ( in a natural setting) reproduce fertile offspring.

38
Q

what is allopatric speciation?

A

> allopatric speciation has to do with new species being formed when two populations become reproductively isolated from each other due to geographical boundries.
e.g., mountain ranges, valleys, canyons etc.
for isolated populations to evolve into separate species, it is necessary for each population to be exposed to different selection pressures, e.g., environmental conditions.

39
Q

What is sympatric speciation?

A

the formation of new species where geographical barriers do not occur. instead, other ‘barriers’ are imposed, e.g., seasonal, diurnal (daily) etc. It has been found that sympatric speciation is a process that readily occurs in plants.

40
Q

wha is an example and explanation of sympatric speciation?

A

example: distribution of pupil diameter in a population of predators.
>premise: a long term climate change results in drier conditions (i.e., prolonged drought). As a result, food sources become scares ( hence competition for food increases dramatically within this population of predators). originally, this population were diurnal hunters (hunted during the day).
>the original population is split into two - diurnal vs. nocturnal. Those individuals with larger than average pupil diameters are now more ‘fit’ in a nocturnal environment. if the two populations become reproductively isolated from each other, (e.g., population A mates during the day and population B mates at night), then these two populations may eventually evolve into different species.

41
Q

What are the ideas behind rates of evolution?

A

the fossil record leads to two broad interpretations regarding the rate of evolution: 1) gradualism and 2) punctuated equilibrium.

42
Q

what is gradualism?

A

gradualism is the idea that evolution occurs slowly and gradually, and thus gives rise to transitional fossils, e.g., a transition from reptile-like ancestors to birds. (refer to diagram)

43
Q

what is the problem with gradualism?

A

some scientists argue that there is not enough examples of transitional species in the fossil record to fully support gradualism. hence punctuated equilibrium is proposed as an alternative theory.

44
Q

what is punctuated equilibrium?

A

punctuated equilibrium is the idea that there are long periods of stability (i.e., equilibrium, which = no evolution) interspersed (i.e., punctuated ) with sudden evolutionary change - possibly brought on by drastic changes in the environment, e.g., massive volcanic eruptions or meteorite impacts. (see diagram)

45
Q

what are the four patterns of evolution?

A 
A) sequential evolution
B) divergent evolution
C) convergent evolution
d) parallel evolution.
SEE DIAGRAM
46
Q

what is an example of divergent evolution?

A

adaptive radiation:

finches and beaks

47
Q

what is adaptive radiation?

A

an example of divergent evolution where multiple branching occurs. In this case, 14 species of finches have evolved from a common ancestor from the south american mainland. the term ‘adaptive’ relates to the idea that new species of finches have evolved as a result of adapting to their environment through evolving different beak structures, which would allow them to exploit new food sources.

48
Q

what is another example of adaptive raditation?

A

the ratites - flightless birds (see diagram)

49
Q

what is parallel evolution?

A

parallel evolution is the evolution of geographically separated groups in such a way that they show physical resemblances

50
Q

what is an example of parallel evolution?

A

marsupial mammals and placental mammals, which separated from each other about 100 million years ago due to continental drift.

51
Q

know summary page

A

in book

52
Q

what is the evidence for evolution?

A

there is strong and convincing evidence to support evolution. the following is not a comprehensive list but highlights some of the more obvious evidence

1) the fossil record
2) DNA hybridisation (i.e., comparisons)
3) anatomical comparisons
4) vestigial organs

53
Q

what organisms have strong evidence in the fossil record to support evolution?

A 
SEE DIAGRAMS AND PHOTOS
>horses
>elephants
>whales
Birds from dinasaurs.
54
Q

what are the different types of fossils?

A

1) mold fossil
2) cast fossil
3) trace fossil
4) true form fossils
5) unaltered preservation fossils

55
Q

What are mold fossils?

A

a fossilised impression made in a substrate, i.e., a negative image of the organism (see diagram)

56
Q

What are cast fossils?

A

formed when a mold (fossil) is filled in

57
Q

What are trace fossils?

A

a geologic record of biological activity, e.g., fossilised nests, footprints, burrows, coprolites (faecal droppings) etc.

58
Q

What are true form fossils?

A

fossilised remains of actual animal or plant parts

59
Q

What are unaltered preservation fossils?

A

as seen when a small animal becomes trapped and encased in tree resin, which then hardens into amber.

60
Q

What are fossils and how are they formed?

A

> fossils are the remains of ancient organisms. AS a general rule, the remains must be at least 10,000 years old in order to qualify as a fossil.
there are a number of ways in which fossils can form, but the form you would be most familiar with is the process of permineralisation.

61
Q

what is permineralisation?

A

stated simply, permineralistation is where the bone tissue (or wood tissue) is replaced by minerals from the surrounding soil. in fact, when you look at fossilised bones/skeletons in museums, you are pretty much looking at rock.

62
Q

explain fossil formation

A

fossil formation is an extremely rare event. for fossils to form the animal must die in such an environment where its remains are prevented from being fully decayed.
>this would generally mean being buried under some type of sediment (e.g., sand, mud, silt, volcanic ash etc).
>the key is to remove oxygen from the environment.
>typically, only the hard parts (e.g., bones, teeth shells) of the animal survive the decay process long enough to become fossilised.

63
Q

why is there such large gaps in the fossil record?

A

> over 99% of organisms that die never become fossilised.
even for those rare occasions when fossils are formed, its then a matter of chance that these fossils will become exposed, due to uplift and erosional processes, and then discovered.

64
Q

give a brief outline of permineralisation process

A

bone tissue –> mineral particles replace bone material –> fossilised bone.

65
Q

how are fossils discovered?

A

they must first be uncovered by uplift and erosional processes

66
Q

what type of rock is the only one here fossils are found?

A

sedimentary rock like limestone

67
Q

how are fossils dated?

A

only igneous rock can be dated, hence it is the igneous layers above and below the sedimentary layers that are dated. hence you get an age range for a particular fossil.

68
Q

what is DNA hybridisation?

A

an even stronger from of evidence for evolution is through DNA hybridisation. This process compares DNA from two different organisms. By doing such a comparison, it can be roughly determined when two organisms split off from a common ancestor.
> for instance, human and chimp DNA is 98% identical. it can be inferred that we had a common ancestor somewhere between 6 and 8 million years ago.

69
Q

what are anatomical comparisons?

A

> the pentadactyl limb (i.e., five part) limb found in mammals, reptiles, birds and amphibians is very strong evidence of a common ancestor.
The pentadactyl limb is an example of a homologous structure.

70
Q

what is a homologous structure?

A

a homologous structure is a feature that is shared by different species because it is inherited from a common ancestor.
>homologous structures may, however, vary in function, e.g., pentadactyl limb used for swimming in seals vs. pentadactyl limb used in primates for grasping etc.

71
Q

what type of evolution are homologous structures an example of?

A

divergent, i.e, common ancestor breaking off.

72
Q

what is an anatomical comparison that displays convergent evolution?

A

body shape between recently unrelated species. Note they have all evolved the streamlines body shape for more efficient movement through water.

73
Q

what is the case of convergent evolution with the examples of a shark, dolphin, penguin and icthyosaur?

A

in the case of the shark and the dolphin, they demonstrate analogous features with regards to the dolphin’s pectoral flippers (pentadactyl limb) and the shark’s pectoral fins (non-pentadactyl limb).

in the case of the reptile (icthyosaur), dolphin and penguin, all have pectoral fins/flippers/wings that have a similar shape and function too, which makes this feature analogous amongst those and the shark. But they are all homologous structures in that they are all pentadactyl limbs

74
Q

what are analogous features?

A

have similar shape in order to fufill a similar function in a similar environment BUT arise from different origins.

75
Q

what are vestigial organs?

A

vestigial organs (like our appendix) are organs that have lost their original function, though they may have evolved to have a secondary function. For example, the appendix is an active organ for digestion in other animals, e.g., rabbits, as it harbours bacteria that produce cellulase. In humans, the appendix has no digestive function, but it does play a minor role in our immune system.

76
Q

what are hominids?

A

is a term that relates to all modern and extinct great apes. ‘Great apes’ pertains to humans, chimpanzees, gorilla and orang-utans - PLUS all their immediate ancestors.

77
Q

what are hominins?

A

hominins are more specific and relates only to the group consisting of modern humans AND extinct human species an all our immediate ancestors. Thus ‘hominins’ pertain to all homo species.

78
Q

what is bipedalism?

A

one of the key features that distinguish humans is our bipedal nature, i.e., ability to walk on two legs.

79
Q

What came first, the large brain or bipedalism?

A

bipedalism, as shown from ‘lucy’ (Australopithecus afarensis)

80
Q

What are some of the lesser advantages to being bipedal?

A

> seeing over grass
carrying food
carrying offspring
hold tools and weapons

81
Q

what is the major advantage to being bipedal?

A

energy efficiency of travelling over extended distances. This need to travel over long distances was most likely driven by dramatic change in climate that resulted in the gradual change from rainforest to savanna grasslands.

82
Q

what are the anatomical features that have been evolved to allow for bipedalism?

A

1) lockable knee- make it possible to stand erect for long periods of time without leg muscles becoming fatigued.
2) curved spine - acts as a spring to absorb the shock of walking/running
3) aligned big toe - allows for more efficient transfer of energy when walking.
4) angled outwards thigh bone - more efficient re. load bearing when walking.

83
Q

what are the changes in human skull structure over time?

A 
>loss of sagittal crest
>reduction of canines
>increase in cranial size (brain case)
> Jaw less pronounced
>eyebrow ridges reduced
> prominent forehead appears
>prominent nose appears
>prominent chin appears
> no sloping forehead
> no prominent canines

Biology 2014 semester 2 (5 decks)

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