Macroevolution!

Question 1

what is macroevolution

Answer 1

evolution above the species level (more than one species)

Question 2

what is microeveolution

Answer 2

evolution at the species level (of allele frequencies within a species or population)

Question 3

what is neo-darwinism

Answer 3

evolutionary theory from 185 which is a unified theory of darwin and mendels theories of natural selection and genetics

Question 4

what is speciation

Answer 4

when populations of the same species become allopatrically or sympatrically separated and therefore cannot interbreed. over time the populations become different enough to be classed as separate species.

Question 5

what is extinction and what can cause it

Answer 5

when a species completely dies out.
caused by natural disaster, increased predation or competition, introduction of a new pathogen or other changes to the environment, speciation.

Question 6

define allopatric speciation

Answer 6

when populations become geographically separated by a physical barrier so that there is no interbreeding between isolated populations

Question 7

define sympatric speciation

Answer 7

when populations are in reproductive isolation but are not separated geographically. this can be due to incompatibility of reproductive systems or temporal separation-reproduce at different times of year

Question 8

define parapatric speciation

Answer 8

new habitat is entered adjacent to the existing habitat. there is partial geographic separation of populations so there is still gene flow between overlapping populations but it is limited, so speciation can occur.

Question 9

define peripatric speciation

Answer 9

there is reproductive separation like with allopatric speciation but instead of there being a physical barrier across the existing habitat, a population enters new habitat and forms an isolated peripheral population.

Question 10

what is cladogenesis

Answer 10

where the parent lineage speciates into two distinct species forming a new clade of a phylogenetic tree

Question 11

what is anagenesis

Answer 11

when there is evolution within a lineage.

Question 12

what is genetic drift

Answer 12

random changes in the allele frequencies in a population. can be due to a chance event

Question 13

what is selection

Answer 13

changes to allele frequencies in a population that is not due to chance but due to environmental pressures.

Question 14

what is adaptive radiation

Answer 14

rapid diversification of a lineage in response to opportunity, where different species have different adaptations eg. darwins finches or horses.

Question 15

who discovered that the evolution of horses was due to adaptive radiation rather than a linear process

Answer 15

George Gaylord Simpson - a major participant in the modern evolutionary synthesis

Question 16

describe the evolution of horses

Answer 16

it was an adaptive radiation event in north america but there is only one extant species present today (equus).

Question 17

which horse species was present in the early eocene and describe it in terms of toes, teeth and braincase. Where was it found.

Answer 17

hyracotherium - present in laurasia (main continent in northern hemisphere).
this is the earliest horse-like from which had 3 hind toes and four distinct front toes that were like dog pads.
its teeth were flattened for grinding indicating herbivory.
It had a small braincase.

Question 18

what led to the development of oligocene horses from early eocene horses

Answer 18

continental drift (laurasia in the northern hemisphere separated into north america and eurasia) causing allopatric speciation of hyracotherium.

Question 19

what horse was present in the oligocene and describe it in terms of toes, teeth, and braincase. where was it found.

Answer 19

miohippus- north america.
larger than hyracotherium.
has lost a digit so now it has three digits on the forefeet instead of four. the lateral digits also have reduced in length. the teeth are similar to hyracotherium-flattened for grinding suggesting herbivory. has a larger braincase

Question 20

how did the true horse line arise from the horses of the oligocene

Answer 20

there was several lineages that branched off from the oigocene to the miocene and also several lineages that formed during the miocene and one of these lineages gave rise to true horses. the other lineages are now extinct.

Question 21

what horses were found in the miocene. describe them in terms of toes, teeth, skull and size. what kind of habitat were they found in.

Answer 21

Merychippus- large open grassland
still had three toes on the forefeet like miohippus but the lateral digits were even shorter.
major teeth development to produce teeth similar to true horses: long and high crowned with ridges filled with cement. coincided with extensive development of grassland. grinding to grazing.
deeper skull to accommodate longer teeth)
larger bodied than miohippus to exploit larger habitat.

Question 22

what features of grass led to horses becoming grazers?

Answer 22

grasses developed with adaptations against herbivory such as high silica content making them tough and having their meristems close to the ground so that they can grow back easily when damaged from above the meristem.

Question 23

horses were found in large open spaces- what major adaptation did this lead to

Answer 23

the spring foot- for running

Question 24

what is the spring foot and why is it an advantage

Answer 24

strong elastic ligaments that connect the toes to the to the main leg bones. this suspensory ligament provides lift to the limb which makes running more efficient as otherwise muscle would have to be expending energy to provide this lift rather than utilising elastic potential. muscle is also heavier.

Question 25

what other development compliments the spring foot

Answer 25

hoofed feet rather than padded feet

Question 26

how many lineages developed from merychippus and what is this type of evolution called?

Answer 26

6. adaptive radiation

Question 27

which line out of the six formed by adaptive radiation led to the true horse (equus). how many toes did it have. when was it found and where.

Answer 27

pliohippus- late miocene north america connected to asia by bering land bridge so asia was invaded north america connected to south america so south america invaded europe also invaded. they had single toed feet.

Question 28

what is convergent evolution

Answer 28

despite not being closely related, the same features evolve independently usually due to the presence of similar selection pressures.

Question 29

what is the total number of predicted species and how many of those have been described

Answer 29

estimated 15million with only 2 million described

Question 30

give an example of a species that demonstrates persistence and explain why this type of species can educate us about evolution

Answer 30

coelacanth- has remained unchanged since the devonian/triassic millions of years ago. acts as a living fossil because it indicates a key step in tetrapod evolution with its lobed fins.

Question 31

give three examples of pleistocene megafauna that went extinct due to human influence

Answer 31

giant ground sloth, mammoth, sabre toothed cat (smilodon)

Question 32

when did life begin on earth and for how long did bacteria dominate

Answer 32

3.8 bya life began and bacteria dominated for the first 3.1by

Question 33

what did the primitive atmosphere mainly comprise of

Answer 33

nitrogen, carbon dioxide, hydrogen and water vapour

Question 34

what was the great oxygenation event and what was it caused by

Answer 34

2.6 bya cyanobacteria evolved. cyanobacteria can photosynthesise which made use of the large amounts of the co2 in the atmosphere. however, oxygen was released as a by-product. initially it was soaked up by iron in the oceans but after saturation it started to build up in the atmosphere (2.4 bya). this led to a global mass extinction event as it was toxic to most life.

Question 35

what is the main difference between bacteria and cyanobacteria

Answer 35

bacteria are anoxygenic photosynthetic and cyanobacteria are oxygenic photosynthetic which means they produce oxygen

Question 36

what organelle did the great oxygenation event lead to the development of

Answer 36

mitochondria

Question 37

what event describes a rapid increase in diversity

Answer 37

the cambrian explosion

Question 38

what is the K-T event

Answer 38

the extinction of the dinosaurs and other groups of animals around during the cretaceous/tertiary period (65 mya). likely due to a meteorite impact that led to volcanic eruption and other natural disasters.

Question 39

what impact does volcanic eruptions have on the climate- especially during K-T event

Answer 39

long term barrier to solar radiation, short term acid rain,

Question 40

how did the K-T event impact the types of life found on the planet

Answer 40

early mammals were able to survive and since there was little competition and many new niches available to be filled without the presence of the animals that had previously dominated, there was a radiation of mammals.

Question 41

how is a mass extinction event characterised

Answer 41

when more than 3/4 of species on earth go extinct

Question 42

what is the 6th mass extinction event

Answer 42

the holocene extinction- mass extinction event coinciding with and being caused as a result of human activity

Question 43

what are three major causes of extinction

Answer 43

climate change, introduction of new pathogens, invasive species

Question 44

who came up with the idea of continental drift and why

Answer 44

alfred wegener 1912 due to unexpected distributions of species and fossils around the globe

Question 45

what is the wallace line and why is this seen

Answer 45

by alfred russell wallace West of the line bird fauna is more similar to those of asia. this is because asia, indonesia and malaysia were part of one continent called laurasia. East of the line, bird fauna is more similar to that of australia. This is because Australasia was previously part of gondwanaland which was also a continent. pangea split into laurasia and gondwanaland

Question 46

how many ice ages have there been

Answer 46

5

Question 47

what was the last glacial maximum

Answer 47

the pleistocene glaciation

Question 49

what are the two main impacts of glaciation on populations

Answer 49

extinctions of species that cannot rapidly adapt to changes in conditions formation of barriers to movement which leads to speciation (populations exist in refugia)

Question 50

what is southern richness and northern purity?

Answer 50

as it gets warmer after a glacial maximum, the species that have survived in the southern refugia start to migrate north and these subpopulations will become more bottlenecked, losing genetic diversity as they move away from the refugia. DNA can be used to look at similarity between current fauna to identify the refugia they emerged from and their subsequent migration.

Question 51

what are the southern refugia in europe from the pleistocene ice age

Answer 51

iberian peninsula apennine peninsula -italy balkan peninsula -greece

Question 52

what is symbiosis

Answer 52

long term interaction between species that benefits at least one party. includes mutualism, commensalism and parasitism

Question 53

what is parasitism

Answer 53

when there is one species benefited and one species harmed in a symbiotic relationship. there is two way selection resulting in coadaptation such as an 'arms race'

Question 54

what is commensalism

Answer 54

where there is one species benefitted and one species neutrally effected in a symbiotic relationship. there is less likely to be coevolution in this case as it is only one way selection.

Question 55

what is mutualism

Answer 55

when both species benefit from a symbiotic relationship. there is two way selection resulting in coadaptation 'marriage'

Question 56

describe the symbiotic relationship between sloths, moths and algae.

Answer 56

sloths have algae growing in their fur which can harvest to supplement their diet. moths also colonise the fur and bring nutrients such as nitrogen for algal growth. the moths lay their eggs in sloth faeces when three toed sloths come down from the trees to defecate. therefore, the behaviour of coming down from the trees to defecate leads to better algal growth in their fur. this can be seen when comparing three toed sloths to two toed slots which don't come down from the trees to defecate and also have less moths and less algal growth.

Question 57

describe the obligate mutualism between yucca flowers and yucca moths

Answer 57

yucca moths pollinate the yucca flowers and then lay their eggs in the flower ovary. this is obligate mutualism because they rely heavily on the other for survival.

Question 58

describe the obligate mutualism between figs and wasps

Answer 58

female wasp enters the fig which rips off her wings so she cant escape. she lays her eggs which hatch and mate inside the fig. the males burrow holes in the fig so that the females can fly out but this rips off their wings so the males are trapped inside (the fig releases digestive enzymes to break down the wasps left inside). the females fly away to another fig which gives off an odour when ready for pollination. they lay their eggs in the fig and pollinate it in the process (fig flowers are on the inside).

Question 59

describe the relationship between bees and angiosperms

Answer 59

bees and angiosperms evolved alongside one another because if it wasn't for the diversification of angiosperms, bees wouldn't have evolved and would have remained wasps (which are more generalist). bees are important pollinators of angiosperms

Question 60

why have there not been many cases of co-speciation between bees and angiosperms?

Answer 60

1.this is not an obligate relationship (there are very few flowering plants that rely on one pollinator species). 2.there are many drivers for angiosperm diversification such as environmental conditions and herbivory

Question 61

what is phylogenetic congruence and what is it used to suggest

Answer 61

when the number of host species is approximately equal to the the symbiont number, with mostly one-to-one interactions between one host and one symbiont species. this is used to suggest obligate mutualism and co-evolution

Question 62

what is co-speciation/co-cladogenesis and when is this more likely to occur

Answer 62

when the host speciates so does its specialist mutualist or parasite (phylogenetic congruence). the closer the relationship between host and symbiont, the more likely this is to occur

Question 63

what reasons are there for phylogenetic incongruence?

Answer 63

- the host speciates but the parasite doesn't speciate. 1.the parasite can survive on both of the new hosts. 2. the parasite survives on only one of the daughter hosts (it either switches to the new host and goes extinct on the original host, or doesn't switch onto the new host and remains only on the original host)

Question 64

what are homeotic genes

Answer 64

regulatory genes which are involved in embryogenesis. in bilateral animals they are called the Hox genes and they control differentiation along the sagittal plane. they are the master control genes which activate builder genes in certain regions of the embryo to construct the appropriate structures. they are highly conserved even across kingdoms.

Question 65

what would a mutation in a homeotic gene cause

Answer 65

structures to be formed in the wrong places, eg a leg in place of an antenna. these would be highly maladaptive and selected against.

Question 66

give two examples of a highly conserved homeotic gene

Answer 66

the gene controlling eye development in flies and humans are theoretically interchangeable. the gene controlling heart development in insects and humans is identical.

Question 67

what is an advantage and limitation of homeotic genes

Answer 67

adv- gives flexibility for development of different new body plans and organs which leads to high levels of diversity, despite high conservation of genes. disadv- there are limitations to the body plans possible eg no 8 legged insects and no 6 legged vertebrates.