ReproductionReproduction1. Hand in your Allele Frequency

Activity to the inbox.

2. You will take a five-question quiz on variation to begin the class, study up on yesterday’s

material now.

1. Hand in your Allele Frequency Activity to the inbox.

2. You will take a five-question quiz on variation to begin the class, study up on yesterday’s

material now.

HomeworkHomework

Objectives TodayObjectives Today

Be able to explain: How much reproduction occurs What the result of that is

Reproduction rates. When I was growing up, there were these barn swallows under the eve of our house, and their babies built nests of their own when they grew up…

Be able to explain: How much reproduction occurs What the result of that is

Reproduction rates. When I was growing up, there were these barn swallows under the eve of our house, and their babies built nests of their own when they grew up…

Reproduction RatesReproduction Rates

Barn swallows lay two clutches each year, an average of 5 nestlings in each clutch. Nestlings take only one year to grow up, so they start laying their own nests the very next year.

The barn swallows first arrived at my house in the summer of 1983. I want us to graph their reproduction up through 2005, when I last saw them.

Make a table with two columns, year and # of barn swallows. And I’d like a volunteer up front, please.

Barn swallows lay two clutches each year, an average of 5 nestlings in each clutch. Nestlings take only one year to grow up, so they start laying their own nests the very next year.

The barn swallows first arrived at my house in the summer of 1983. I want us to graph their reproduction up through 2005, when I last saw them.

Make a table with two columns, year and # of barn swallows. And I’d like a volunteer up front, please.

Year # of Barn Swallows

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993…

Reproduction RatesReproduction Rates

Why wasn’t I buried in barn swallows? All those corn kernels came from just one pair of them! And in 1983, there were millions of pairs in the U.S.! Why aren’t we all swimming in barn swallows?

And it’s not just barn swallows. With your partner, make tables like we just did to solve these problems on a fresh sheet of paper: P.S. You will need to recall scientific notation for these.

Why wasn’t I buried in barn swallows? All those corn kernels came from just one pair of them! And in 1983, there were millions of pairs in the U.S.! Why aren’t we all swimming in barn swallows?

And it’s not just barn swallows. With your partner, make tables like we just did to solve these problems on a fresh sheet of paper: P.S. You will need to recall scientific notation for these.

1. The bacteria Escherichia coli or E. coli live on your skin. They split in half, called binary fission, to reproduce asexually. They do this every 15 minutes. An E. coli individual finds a patch of your skin that’s miraculously unoccupied so far, and there’s enough space for a whopping 100,000 E. coli! How long will it be before the E. coli’s descendents have out-reproduced the space available?

2. A pair of 1-year-old striped bass are dumped into a fishless bay. These fish produce an average of 250,000 eggs a year. Five years later, if nothing has happened to stop them, how many striped bass would be in this bay? (Remember, every two bass will make 250,000 eggs, so it’s simpler to calculate it as 125,000 eggs per one bass. 125,000 = 1.25 x 105)

1. The bacteria Escherichia coli or E. coli live on your skin. They split in half, called binary fission, to reproduce asexually. They do this every 15 minutes. An E. coli individual finds a patch of your skin that’s miraculously unoccupied so far, and there’s enough space for a whopping 100,000 E. coli! How long will it be before the E. coli’s descendents have out-reproduced the space available?

2. A pair of 1-year-old striped bass are dumped into a fishless bay. These fish produce an average of 250,000 eggs a year. Five years later, if nothing has happened to stop them, how many striped bass would be in this bay? (Remember, every two bass will make 250,000 eggs, so it’s simpler to calculate it as 125,000 eggs per one bass. 125,000 = 1.25 x 105)

More examplesMore examples

A bacterium that divides even more slowly than E. coli, every 20 minutes, would have 40,000,000,000,000,000,000,000 offspring by the end of the day, with a mass of 3.2 million kilograms. After just two days of reproduction, the entire planet Earth would be covered in a layer of the bacterium’s descendents that’s two meters thick.

A female housefly lays about 120 eggs every two months. At that rate, a single female would produce more than 5 trillion flies in a year.

A bacterium that divides even more slowly than E. coli, every 20 minutes, would have 40,000,000,000,000,000,000,000 offspring by the end of the day, with a mass of 3.2 million kilograms. After just two days of reproduction, the entire planet Earth would be covered in a layer of the bacterium’s descendents that’s two meters thick.

A female housefly lays about 120 eggs every two months. At that rate, a single female would produce more than 5 trillion flies in a year.

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QuickTime™ and a decompressor

are needed to see this picture.

More examplesMore examples

Fruit flies lay and fertilize 200 eggs every three weeks. At that rate, their descendents after one year would exceed the mass of the Earth.

Geese live for about 10 years, and lay a brood of 8 eggs on average each year. A single pair of geese would produce tens of millions of birds in a decade’s time.

The Elephant is one of the slowest breeders among animals. Elephants start to breed when they’re near 30 years old, and have an average of 6 babies over the next 60 years. On that schedule, one pair of elephants would become 19,000,000 elephants in 750 years. Compare that to the number of elephants alive on the whole planet today: 700,000.

Fruit flies lay and fertilize 200 eggs every three weeks. At that rate, their descendents after one year would exceed the mass of the Earth.

Geese live for about 10 years, and lay a brood of 8 eggs on average each year. A single pair of geese would produce tens of millions of birds in a decade’s time.

The Elephant is one of the slowest breeders among animals. Elephants start to breed when they’re near 30 years old, and have an average of 6 babies over the next 60 years. On that schedule, one pair of elephants would become 19,000,000 elephants in 750 years. Compare that to the number of elephants alive on the whole planet today: 700,000.

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are needed to see this picture.QuickTime™ and a

decompressorare needed to see this picture.

QuickTime™ and a decompressor

are needed to see this picture.

Reproduction RatesReproduction Rates

The actual barn swallow population at the house? The same two parents kept coming back to their nest, and between 1983 and 2005, only two of their babies made nests of their own. So… four.

All organisms overreproduce, meaning that hey make more offspring than can possibly survive. All living things - bacteria, plants, animal, everything - reproduce at unsustainably high rates. The things that keep all those offspring from surviving are called “limiting factors,” and there are a lot of them.

Brainstorm, what are some specific things that would prevent all of an organism’s offspring from surviving?

The actual barn swallow population at the house? The same two parents kept coming back to their nest, and between 1983 and 2005, only two of their babies made nests of their own. So… four.

All organisms overreproduce, meaning that hey make more offspring than can possibly survive. All living things - bacteria, plants, animal, everything - reproduce at unsustainably high rates. The things that keep all those offspring from surviving are called “limiting factors,” and there are a lot of them.

Brainstorm, what are some specific things that would prevent all of an organism’s offspring from surviving?

Reproduction RatesReproduction Rates Limiting factors like…

Not enough vitamins and minerals to go around Not enough oxygen, nitrogen, or other elements to go around

Not enough water to go around Not enough food to go around Disease Parasites Predators Weather and the elements Fires and disasters Pollution and radiation Not enough physical space to go around

Limiting factors like… Not enough vitamins and minerals to go around Not enough oxygen, nitrogen, or other elements to go around

Not enough water to go around Not enough food to go around Disease Parasites Predators Weather and the elements Fires and disasters Pollution and radiation Not enough physical space to go around

Reproduction RatesReproduction Rates

If you have a limited amount of a resource, and a thousand times more individuals who need it than can have it, what happens?

If you have a limited amount of a resource, and a thousand times more individuals who need it than can have it, what happens?

Reproduction RatesReproduction Rates

If you have a limited amount of a resource, and a thousand times more individuals who need it than can have it, what happens?

Competition is the inevitable result for all living things. (Very fierce competition, at that…) Let me know if it doesn’t make sense why competition happens because there are too many babies, I’d be happy to clarify this important point!

If you have a limited amount of a resource, and a thousand times more individuals who need it than can have it, what happens?

Competition is the inevitable result for all living things. (Very fierce competition, at that…) Let me know if it doesn’t make sense why competition happens because there are too many babies, I’d be happy to clarify this important point!

FlowchartFlowchart

Organisms produce many offspring.

Organisms produce many offspring.

FlowchartFlowchart

Resources to support offspring are limited.

Resources to support offspring are limited.

FlowchartFlowchart

There is competition for survival and reproduction.

There is competition for survival and reproduction.

ConclusionConclusion

Organisms reproduce more than can possibly survive.

Competition is the inevitable result.

If any of the conclusions from yesterday or today do not make complete sense, please ask me to be clearer! Not understanding today and yesterday and then going forward will be like trying to go master dihybrid crosses if you don’t know what an allele or a trait are. It won’t work.

Organisms reproduce more than can possibly survive.

Competition is the inevitable result.

If any of the conclusions from yesterday or today do not make complete sense, please ask me to be clearer! Not understanding today and yesterday and then going forward will be like trying to go master dihybrid crosses if you don’t know what an allele or a trait are. It won’t work.

All Conclusions So FarAll Conclusions So Far

Variation Individuals and groups vary.

Genetic variation can be expressed as “allele frequency” = how often an allele occurs in a gene pool.

New phenotypes can arise from rare, random, regular events: Crossing-over gives you new combinations of alleles. Mutation gives you brand new alleles.

Inheritance Phenotypic variations come from genotypic variations.

So, these variations are inherited.

Struggle For Life Organisms reproduce more than can possibly survive. Competition is the inevitable result.

Variation Individuals and groups vary.

Genetic variation can be expressed as “allele frequency” = how often an allele occurs in a gene pool.

New phenotypes can arise from rare, random, regular events: Crossing-over gives you new combinations of alleles. Mutation gives you brand new alleles.

Inheritance Phenotypic variations come from genotypic variations.

So, these variations are inherited.

Struggle For Life Organisms reproduce more than can possibly survive. Competition is the inevitable result.