BIO 202 — Lesson 22

A

An island of nests, one bird to a nest. A bird with the helping allele helps its four neighbours raise more young, and raises fewer itself. Young settle near where they hatched. See when helping spreads.
Benefit, the blue arrow from the neighbours' helping; cost, the red arrow from helping; how close young settle, the arrow between a bird's helping gene and its neighbours'.

The islandThe island: 32 x 32 nests (the edges wrap round). Each square a nest; its shade, the bird's helping alleles: pale none, middle one, dark two; blank, a nest no young bird took this generation.Run 1, at the generation the plots have reached.

over timeThe 16 runs, each thin; their average thick.Helping allele: its share of the helping gene's alleles. Neighbours that share a parent: of the pairs of next-door birds, the share with a mother or father in common. Relatedness at the helping gene: how much a bird's neighbours' helping alleles go with its own, as a regression slope (lesson 13); blank when every bird is the same. Nests filled: the share of nests a young bird took.Neighbours with copies of one founding helping allele: every copy of the helping gene at the start (two a bird) is labelled, and its copies keep the label, as lessons 15, 16 and 20 traced copies back to where they meet. The share of next-door pairs carrying copies of one starting copy: what helping pays on is a copy of the same allele next door, not a family tie as such.

The change in the helping allele, taken apart since generation 0Each generation's change in the helping allele, added up since generation 0, taken apart as lesson 13 and lesson 21 took a change apart, averaged over the 16 runs.From its own helping: how a bird's own helping alleles go with the young it leaves (its cost). From its neighbours' helping: how its helping alleles go with its neighbours' helping, times what that helping does for its young. Together, who leaves more young. What the young keep: the young against their parents (meiosis's coin, and in C the broken copies).They add up exactly to the black line, the change in the helping allele since generation 0.

Genes, helping, youngHelping gene: two alleles, a helper and a non-helper; a bird with one helps half as much.Cost, the red arrow from helping: how many fewer young a full helper has (of about 2). Benefit, the blue arrow from the neighbours' helping: how many more young a bird has when all four of its neighbours are full helpers (a quarter for each).How close young settle, the arrow between a bird's helping gene and its neighbours': the young take a nest within that many nests of where they hatched, so the closer they settle, the more a bird's neighbours share its parents, and its alleles. It sets who the neighbours are, not what helping does.Grey arrows: fixed.

Target1,024 nests; at the start every nest full, half the helping alleles helpers (in C, all). Each bird's young take nests near where they hatched; a young bird whose nest is taken looks for an empty one around it; young with none left die. Go plays 100 generations (in C, 150), 16 times.The picture: what a hit looks like; the red box, where the thick line, the 16 runs' average, should end.

practice

To finish

Hit the three targets. 0 of 3

R code

B

The same island. Here, read how close young settle as what it does: it sets how often neighbours share a parent, and so how much a bird's helping alleles go with its neighbours'. Then find where helping neither spreads nor dies, its two parts cancelling.
The same three arrows.

The islandThe island: 32 x 32 nests (the edges wrap round). Each square a nest; its shade, the bird's helping alleles: pale none, middle one, dark two; blank, a nest no young bird took this generation.Run 1, at the generation the plots have reached.

over timeThe 16 runs, each thin; their average thick.Helping allele: its share of the helping gene's alleles. Neighbours that share a parent: of the pairs of next-door birds, the share with a mother or father in common. Relatedness at the helping gene: how much a bird's neighbours' helping alleles go with its own, as a regression slope (lesson 13); blank when every bird is the same. Nests filled: the share of nests a young bird took.Neighbours with copies of one founding helping allele: every copy of the helping gene at the start (two a bird) is labelled, and its copies keep the label, as lessons 15, 16 and 20 traced copies back to where they meet. The share of next-door pairs carrying copies of one starting copy: what helping pays on is a copy of the same allele next door, not a family tie as such.

The change in the helping allele, taken apart since generation 0Each generation's change in the helping allele, added up since generation 0, taken apart as lesson 13 and lesson 21 took a change apart, averaged over the 16 runs.From its own helping: how a bird's own helping alleles go with the young it leaves (its cost). From its neighbours' helping: how its helping alleles go with its neighbours' helping, times what that helping does for its young. Together, who leaves more young. What the young keep: the young against their parents (meiosis's coin, and in C the broken copies).They add up exactly to the black line, the change in the helping allele since generation 0.

Genes, helping, youngHelping gene: two alleles, a helper and a non-helper; a bird with one helps half as much.Cost, the red arrow from helping: how many fewer young a full helper has (of about 2). Benefit, the blue arrow from the neighbours' helping: how many more young a bird has when all four of its neighbours are full helpers (a quarter for each).How close young settle, the arrow between a bird's helping gene and its neighbours': the young take a nest within that many nests of where they hatched, so the closer they settle, the more a bird's neighbours share its parents, and its alleles. It sets who the neighbours are, not what helping does.Grey arrows: fixed.

Target1,024 nests; at the start every nest full, half the helping alleles helpers (in C, all). Each bird's young take nests near where they hatched; a young bird whose nest is taken looks for an empty one around it; young with none left die. Go plays 100 generations (in C, 150), 16 times.The picture: what a hit looks like; the red box, where the thick line, the 16 runs' average, should end.

practice

To finish

Hit the three targets. 0 of 3

R code

C

Every bird starts a helper. Each generation, 1 in 100 helping alleles passed on comes out broken: the young bird carries a non-helper there instead. Broken alleles are never mended. See when helping holds against the breaks, and when the breaks win.
The same three arrows; the breaks are fixed.

The islandThe island: 32 x 32 nests (the edges wrap round). Each square a nest; its shade, the bird's helping alleles: pale none, middle one, dark two; blank, a nest no young bird took this generation.Run 1, at the generation the plots have reached.

over timeThe 16 runs, each thin; their average thick.Helping allele: its share of the helping gene's alleles. Neighbours that share a parent: of the pairs of next-door birds, the share with a mother or father in common. Relatedness at the helping gene: how much a bird's neighbours' helping alleles go with its own, as a regression slope (lesson 13); blank when every bird is the same. Nests filled: the share of nests a young bird took.Neighbours with copies of one founding helping allele: every copy of the helping gene at the start (two a bird) is labelled, and its copies keep the label, as lessons 15, 16 and 20 traced copies back to where they meet. The share of next-door pairs carrying copies of one starting copy: what helping pays on is a copy of the same allele next door, not a family tie as such.

The change in the helping allele, taken apart since generation 0Each generation's change in the helping allele, added up since generation 0, taken apart as lesson 13 and lesson 21 took a change apart, averaged over the 16 runs.From its own helping: how a bird's own helping alleles go with the young it leaves (its cost). From its neighbours' helping: how its helping alleles go with its neighbours' helping, times what that helping does for its young. Together, who leaves more young. What the young keep: the young against their parents (meiosis's coin, and in C the broken copies).They add up exactly to the black line, the change in the helping allele since generation 0.

Genes, helping, youngHelping gene: two alleles, a helper and a non-helper; a bird with one helps half as much.Cost, the red arrow from helping: how many fewer young a full helper has (of about 2). Benefit, the blue arrow from the neighbours' helping: how many more young a bird has when all four of its neighbours are full helpers (a quarter for each).How close young settle, the arrow between a bird's helping gene and its neighbours': the young take a nest within that many nests of where they hatched, so the closer they settle, the more a bird's neighbours share its parents, and its alleles. It sets who the neighbours are, not what helping does.Grey arrows: fixed.

Target1,024 nests; at the start every nest full, half the helping alleles helpers (in C, all). Each bird's young take nests near where they hatched; a young bird whose nest is taken looks for an empty one around it; young with none left die. Go plays 100 generations (in C, 150), 16 times.The picture: what a hit looks like; the red box, where the thick line, the 16 runs' average, should end.

practice

To finish

Hit the two targets. 0 of 2

R code

D

A helper now reaches the birds within 2 nests of its own, and young settle within 4 nests of where they hatched. Each young bird copies its father's call, or makes up a call of its own. See when helping that follows the call spreads, and how often its help reaches family.
Checks the call, the arrow onto the help: the help goes only to birds that call like the helper. Young that copy it, the arrow from the father's call.
In the last target, every bird starts a helper, and 1 in 10 helping alleles checks the call.

The islandThe island: 32 x 32 nests (the edges wrap round). Each square a nest; its shade, the bird's helping alleles (in the last target, its helping alleles that check the call): pale none, middle one, dark two; blank, a nest no young bird took.A line between two nests: the birds there call differently. No line: they call alike.Run 1, at the generation the plots have reached.

over timeThe 16 runs, each thin; their average thick.Help that reaches birds sharing a parent with the helper: of all the help given in a generation, the share that went to a bird with a mother or father in common with the helper. Birds sharing a parent, within reach, that call alike: of the pairs of birds within 2 nests that share a parent, the share that call alike (the rest the call misses). Birds within reach that call alike: of all pairs within 2 nests.Help that reaches a copy of the helper's own helping allele: every helping allele at the start is labelled, and its copies keep the label (A-C's labels); the share of the help that went to a bird carrying a copy of one of the helper's.Helping alleles that check the call: of all the helping alleles, the share that check it.

The change in the helping allele, taken apart since generation 0Each generation's change, added up since generation 0, taken apart as in A-C, averaged over the 16 runs.From its own helping: how a bird's own helping alleles go with the young it leaves. From the help it receives: how its helping alleles go with the help it gets, times what that help does for its young. What the young keep: the young against their parents.In the last target, the change in the helping alleles that check the call: who leaves more young, and what the young keep (where the 1 in 200 that turn into the other kind show).They add up exactly to the black line.

Genes, calls, youngHelping: as in A-C, but a helper's help is split among the birds within 2 nests of its own (24 nests), not its 4 neighbours. Cost, benefit and how close young settle are held.Checks the call, the arrow onto the help: from a helping allele that checks, the help is split only among the birds within reach that call like the helper; with none, that help is not given and costs nothing. Dashed: the help goes to every bird within reach.Young that copy it, the arrow from the father's call: the share of young that copy their father's call; the rest each make up a new one. At the start every bird has a call of its own.In the last target: two kinds of helping allele, one that checks the call and one that does not; a copy keeps its kind, but 1 in 200 copies passed on turns into the other kind. Grey arrows: fixed.

Target1,024 nests, every one full at the start; half the helping alleles helpers (in the last target, all). Go plays 100 generations in the first target, 200 in the next two, 300 in the last, 16 times.The picture: what a hit looks like; the red box, where the thick line, the 16 runs' average, should end.

practice

To finish

Hit the four targets. 0 of 4

R code

E

No helping now. A new gene: in a bird with one driving allele and one fair one, the driver goes into more than half of the bird's eggs and sperm. Birds carrying it raise fewer young. See when it spreads, and what it does to the island.
Drive, the blue arrow: the driver's share of a carrier's eggs and sperm. Cost, the red arrow.

The islandThe island: 32 x 32 nests (the edges wrap round). Each square a nest; its shade, the bird's driving alleles: pale none, middle one, dark two; blank, a nest no young bird took.Run 1, at the generation the plots have reached.

over timeThe 16 runs, each thin; their average thick.Driving allele: its share at the driving gene. Nests filled: the share of nests a young bird took. Young a bird leaves: those that took a nest, half to each parent.

The change in the driving allele, taken apart since generation 0Each generation's change in the driving allele, added up since generation 0, averaged over the 16 runs.Who leaves more young: the young's parents against the birds there were. What the young keep: the young against their parents, where the driver's unfair share shows.They add up exactly to the black line.

Genes, helping, youngDriving gene: a driver and a fair allele. In a bird with one of each, the driver goes into a share of its eggs and sperm set by the drive (half is fair).Cost, the red arrow: how many fewer young a bird with two drivers has (half as many fewer with one).No helping in this stage. Grey arrows: fixed.

Target1,024 nests, every one full at the start; 1 in 20 alleles at the driving gene is the driver. Go plays 100 generations, 16 times.The picture: what a hit looks like; the red box, where the thick line should end.

practice

To finish

Hit the two targets. 0 of 2

R code

A

The islandThe island: 32 x 32 nests (the edges wrap round). Each square a nest; its shade, the bird's helping alleles: pale none, middle one, dark two; blank, a nest no young bird took this generation.Run 1, at the generation the plots have reached.

To finish

B

The islandThe island: 32 x 32 nests (the edges wrap round). Each square a nest; its shade, the bird's helping alleles: pale none, middle one, dark two; blank, a nest no young bird took this generation.Run 1, at the generation the plots have reached.

To finish

C

The islandThe island: 32 x 32 nests (the edges wrap round). Each square a nest; its shade, the bird's helping alleles: pale none, middle one, dark two; blank, a nest no young bird took this generation.Run 1, at the generation the plots have reached.

To finish

D

To finish

E

The islandThe island: 32 x 32 nests (the edges wrap round). Each square a nest; its shade, the bird's driving alleles: pale none, middle one, dark two; blank, a nest no young bird took.Run 1, at the generation the plots have reached.

Target1,024 nests, every one full at the start; 1 in 20 alleles at the driving gene is the driver. Go plays 100 generations, 16 times.The picture: what a hit looks like; the red box, where the thick line should end.

To finish

Good job!