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Developmental Biology. > Evolution. > Flashcards

Evolution. Flashcards

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1
Q

How old is the earth?

A

4.5 billion years old.

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2
Q

How long ago did the 1st cell nucleus appear?

A

Around 2.1 billion years ago.

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3
Q

When did animals first appear?

A

Around 590 million years ago.

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4
Q

How long ago did the first vertebrates appear?

A

Around 500 million years ago.

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5
Q

How long ago did the first mammals appear?

A

220 million years ago.

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6
Q

How long ago did human like mammals first appear?

A

2.5 million years ago.

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7
Q

When did modern humans first appear?

A

200,000 years ago.

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8
Q

Evolution is caused by what?

A

The mutations and changes that an organism will undergo as a response to changes in nature.

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9
Q

Very small changes in gene control can have what?

A

Huge phenotypic effects.

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10
Q

All modern animals are derived from what?

A

An urbilaterean ancestor

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11
Q

What has led to the changes and differentiations have led from the urbilaterean ancestor to the that animals we observe today?

A

Small genetic changes.

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12
Q

What are the 4 major mechanisms that have led to the changes in phenotype from the urbilaterian ancestor?

A

The genetic acquisition of new functions at birth.

Changes in growth rate.

Changes in timing.

Developmental constraints.

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13
Q

What about eye development can tell us that there was an urbilaterian ancestor?

A

The PAX-6 gene.

If there is no PAX-6 gene then no eyes develop.

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14
Q

Which genes give a species its identity for the anterior posterior axis?

A

The HOX genes.

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15
Q

How do HOX genes differentiate for a wing, arm or fins?

A

HOX genes are responsible for turning other genes on.

The genes that are turned on will then lead to an alteration in phenotype.

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16
Q

What accounts for the variation of anterior and posterior phenotypes in different organisms?

A

The expression of different HOX genes at different boundaries.

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17
Q

How has the different expression in HOX genes arisen?

A

By genetic mutations, such as gene duplications which have allowed new genes to come up with a new function.

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18
Q

How will the HOX genes in a different species be differentiate?

A

They will have a similar expression of HOX genes.

Whereas a different organism would have a very different expression.

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19
Q

Phenotypic differences in organisms that are due to HOX gene expression depend on what?

A

Changes in numbers of HOX genes.

Changes in spatial expression of HOX genes.

Changes in interaction between HOX genes.

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20
Q

When a chicken wing is developing, the AER will express what gene?

A

Distal-less.

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21
Q

What does distal-less do in the chicken wing?

A

Controls the growth of the wing.

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22
Q

What gene controls the growth of wing in insects?

A

Distal-less.

23
Q

Vertebrates have their spinal cord on what side of the body?

A

On the dorsal side.

24
Q

Vertebrates have their digestive and pulmonary

system on what side of the body?

A

On the ventral side.

25
Q

Arthropods have their digestive and pulmonary

system on what side of the body?

A

On the dorsal side.

26
Q

Arthropods have their spinal cord on what side of the body?

A

On the ventral side.

27
Q

How do vertebrates form their dorsal ventral axis?

A

Chordin will deactivate the BMP expression leading to dorsal appendages.

The places where BMP is still active will form ventral appendages.

28
Q

How do arthropods form their dorsal ventral axis?

A

SOG inhibits DPP.

SOG determines the ventral appendages and DPP the dorsal ones.

29
Q

What can we use to hypothesise what the urbilaterian ancestor looked like?

A

Gene expression.

30
Q

What would have defined the anterior/posterior axis in the urbilaterian ancestor?

A

HOX genes.

31
Q

What would have defined the dorsal/ventral axis in the urbilaterian ancestor?

A

Antagonistic gene pairs.

32
Q

What are 5 genes that we know would have existed in the urbilaterian ancestor and what did they do?

A

Pax-6 = Eyes.

Tinman/NKX genes = Heart.

Distal-less/DLX = Appendages.

OTD/OTX; EMS/EMX = Anterior brain.

HOM-C/HOX genes = Spinal/nerve cord.

33
Q

Why do we think that the urbilaterian ancestor expressed the same genes that we do?

A

Because so many organisms express these genes, that the common ancestor must have expressed them too.

34
Q

What did snakes evolve from?

A

Lizards.

35
Q

Ancient snakes had what that have gradually been lost through evolution?

A

Small back legs.

36
Q

Why do pythons have no forelimbs?

A

There is no boundary for the HOX-C6 gene.

In pythons, the HOX-C6 gene is expressed to the very end.

There is no anterior segment that allows for the formation of forelimbs.

37
Q

What do pythons have that leads us to believe that they could form hindlimbs?

A

Pythons develop a small limb bud and have a pelvic girdle.

38
Q

What stops pythons from developing limbs?

A

No AER forms.

This means there is no outgrowth of a limb.

39
Q

Why does the AER not develop in pythons?

A

SHH genes are responsible for maintaining the AER.

These genes are not present in the python due to a mutation in the SHH gene.

40
Q

What stops humans from having webbed hands?

A

They undergo apoptosis to develop fingers.

41
Q

What induces apoptosis in chicken feet?

A

BMP.

42
Q

What happens in ducks feet that does not happen in chickens that leads to webbed feet?

A

BMP is also expressed in ducks.

It is inhibited by the expression of a gene called GREMLIN.

Chickens do not express gremlin.

We can determine that GREMLIN will override BMP, causing no expression and therefore no apoptosis.

43
Q

If GREMLIN is implanted into a developing chicken foot, what will happen?

A

The webbed feet will stay.

44
Q

What inhibits apoptosis in bats wings?

A

FGF and gremlin.

45
Q

All vertebrates contain how many cervical vertebrae?

A

7.

46
Q

Why do all vertebrates have 7 cervical vertebrae?

A

When children develop an extra cervical rib, this generally leads to an increased risk of developing childhood cancer.

This means that reproduction is unlikely to occur and this genetic change will not be bred into offspring.

47
Q

What is allometry?

A

It is something that arises from local changes in growth rate during development.

48
Q

How does allometry affect mammalian limbs?

A

The way that mammals develop their limbs is down to the same process.

However changes in growth rate will alter the phenotype.

Bats have very long fingers, this is due to very quick growth.

49
Q

What did the 50 million year old ancestor of the horse have instead of a hoof?

A

4 digits.

50
Q

What happened to the ancestor of the horse 35 million years ago?

A

The horse has grown larger and started to lose 2 of its digits while the 3rd grew larger.

51
Q

What happened to the ancestor of the horse 15 million years ago?

A

The side fingers were almost gone and there was a large central finger.

52
Q

What happened to the ancestor of the horse 8 million years ago?

A

The side fingers are gone and a hoof is starting to develop.

53
Q

What happened to the ancestor of the horse 1 million years ago?

A

The horse developed.

54
Q

Why do Whales have a blow hole on the head and how does it differ from other mammals?

A

Whales have a blow hole at the top of their head due to a very long jaw.

The nasal bone is above the maxilla in mammals, however if the maxilla is extended, then the nasal bone is pushed to the top.

Developmental Biology. (21 decks)

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