Transcript Reproductive Strategies

Reproductive Strategies
Life Science #1 and #2
Vocabulary
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Asexual Reproduction
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Recessive Trait
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Dominant Trait
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Sexual Reproduction
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Gene
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Variation
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Heredity
What Do You Think?
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All plants and animals have traits, or
characteristics, that pass from one
generation on to the next.
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If individuals survive, the species survives.
What Do You Think?
When a bacterium reproduces, the
offspring are exact copies of the parent
bacterium and each other. Under what
conditions do you think this strategy
would help a species continue on to the
future.
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What Do You Think?
When rabbits reproduce, the offspring are
slightly different from the parents and
each other. Under what conditions do you
think this strategy would help a species
continue into the future?
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Heredity
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Heredity refers to the passing of traits
from parent to offspring.
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Tiny molecules called genes control the
traits that appear in those offspring.
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Each gene is a small piece of DNA,
arranged into chromosomes.
Sexual Reproduction
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The offspring of sexual reproduction have
two parents.
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Reproduction occurs when two gametes
(one from each parent) fuse together.
– Gametes have ½ of the normal amount of
chromosomes.
– The normal amount is 46, gametes have 23.
– This is how you get traits from both parents.
Sexual Reproduction
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An organism with 8 chromosomes reproduces sexually.
The diagram shows two gametes joining.
Complete the diagram to show the process of
fertilization.
Sexual Reproduction
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A species that reproduces sexually
typically shows a lot of variation among its
members.
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This is because different combinations of
genes leads to different combinations of
traits.
Sexual Reproduction
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The new combinations of traits that result
from sexual reproduction can increase or
decrease an individual’s chances for
survival.
– A cardinal with strong wings and a weak beak
mates with a cardinal with weak wings and a
strong beak. Which combination of traits
would be the most beneficial to the survival of
their offspring?
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Asexual Reproduction
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In asexual reproduction, the offspring has
one parent that multiplies without using
seeds, gametes or fertilization.
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The offspring of asexual reproduction are
almost always exact genetic copies of the
single adult parent.
– Name one organism that reproduces
asexually.
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Asexual Reproduction
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Many single-celled organisms reproduce
by binary fission.
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This is where a cell duplicated its
chromosomes, then divides into two cells.
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Each new cell is an exact copy of its
parent.
Asexual Reproduction
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An organism with 8 chromosomes reproduces by binary
fission.
Complete the diagram to show how the chromosomes
are distributed.
Asexual Reproduction
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Some offspring of asexual reproduction
have mutations.
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This means that they have some trait that
their parent does not have.
– This trait can be helpful or harmful, increasing
or decreasing its chance for survival.
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Mutations are rare, and most are harmful.
Asexual Reproduction
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An advantage of asexual reproduction is
that it limits the spread of harmful traits in
a species.
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It also leads to genetic continuity in a
species.
– This means that many generations may all
have the same genetic makeup.
Asexual Reproduction
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If many generations have the same
genetic makeup, this can be helpful or
harmful to the species.
– If there are not any changes in the
environment, the species does not need
genetic diversity.
– However, if there is a permanent
environmental change, and one individual is
unable to survive, then the whole species will
be wiped out.