Download Reproduction

Reproduction
1. Hand in your Allele Frequency
Activity to the inbox.
2. Study your notes from
yesterday in preparation for a
short quiz…
Homework
 Paper due 4/2
Recall Quiz
 Answer these questions on a piece of paper.
 1. Complete this sentence from yesterday’s
objective: “Individuals and ______ vary.”
 2. Define “allele frequency.”
 3. Complete this sentence: “Phenotypic
variations come from _______ variations.”
 4. Name the two big sources of new
phenotypes.
 5. True or false, variations can be inherited.
Recall Quiz
 1. Complete this sentence from yesterday’s
objective: “Individuals and groups vary.”
 2. Allele frequency is how often an allele occurs
in a gene pool. (Acceptable alternatives are okay,
check them with me)
 3. Complete this sentence: “Phenotypic variations
come from genotypic variations.”
 4. Name the two big sources of new phenotypes:
Crossing-over and mutation.
 5. True or false, variations can be inherited.
Conclusions from Yesterday
 Individuals and groups vary.
 Genetic variation can be expressed as “allele
frequency” = how often an allele occurs in a gene
pool.
 Phenotypic variations come from genotypic
variations.
 So, these variations are inherited.
 New phenotypes can arise from rare, random,
regular events:
 Crossing-over gives you new combinations of alleles.
Mutation gives you brand new alleles.
Objectives 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…
Reproduction 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.
Year
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993…
# of Barn
Swallows
Reproduction 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 them 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 (this
is for a grade):
 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 outreproduced the space available?
 2. A pair of 1-year-old striped bass are dumped into
a fishless bay. These fish have a lifespan of 40
years, and 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.)
Answers
 1. E. coli question. Answer = 4 hours.
 (At 3:45, they had 65,536 bacteria. At 4:00, they
have 131,072 bacteria.)
 2. Striped bass question. Answer = 6.104 x
1025, or 6,104,000,000,000,000,000,000,000
bass in 5 years.
 Starting with a population of two. For year one, 2
+ (2 x 125000) = 250002. Year two, 250002 +
(250002 x 125000) = 31250500002. Year three,
31250500002 + (31250500002 x 125000) = 3.906
x 1015. Year four, 3.906 x 1015 + (3.906 x 1015 x
125000) = 4.883 x 1020. Year five, 4.883 x 1020 +
(4.883 x 1020) = 6.104 x 1025.
Reproduction 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 make more offspring than can
possibly survive. 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 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
Reproduction 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?
Reproduction 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!
Flowchart
 Organisms
produce many
offspring.
Flowchart
 Resources to
support offspring
are limited.
Flowchart
 There is
competition for
survival and
reproduction.
Conclusion
 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
Punnett Squares if you don’t know what a gene or
a trait are. It won’t work.
All 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.
Remainder
 There will be another short quiz tomorrow, be
prepared.
 For the remainder of the period,
congratulations on getting through the full
lesson! You have the rest of the hour as a
study hall.
 You may either work on homework for another
class, or read from my “science library.”
 Study hall, not social hour. If you’re chatting, you
must also be working diligently.