Concept
Statements |
Emphasis
in
your teaching
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General
importance
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| 1.
The life cycle of an organism begins with its appearance and ends with its death. |
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| 2.
The simplest of life cycles are asexual and
involve a process of fission, budding or fragmentation
such that
each offspring receives a complete copy of the genome plus
necessary cytoplasmic organelles, such as the chloroplasts
and mitochondria of eukaryotes. |
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| 3.
A
version of an asexual life cycle involves the formation
of alternative vegetative
state, such
as a spore.
Spores are passive (non-reproducing) but under appropriate
conditions can give rise to normally
dividing organisms. |
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| 4.
In an asexual organism, changes to the genome can occur
only through mutation or horizontal gene transfer. |
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| 5.
The process of sex involves genetic recombination between
two (or more) distinct organisms. In the most common
form, sex involves the fusion of gametes from two distinct
individuals. |
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| 6. Gametes are
haploid cells; typically gametes can fuse through the
process of syngamy/fertilization to form a diploid cell. |
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| 7.
In organisms with a haplontic
life cycle, the diploid
(sporophytic)
phase is transient and mitosis only
occurs
in the
haploid (gametophytic) phase. |
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| 8.
In organisms with a haplodiplontic
life cycle, mitosis can during either
the haploid or the diploid phase of the life cycle. |
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| 9.
Most animals are diplontic.
Mitosis occurs only in the diploid phase of the life
cycle and the haploid gametophytic phase is transient
ending in fertilization or death. |
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| 10.
The germ line of an organism gives rise to germ
cells,
which in turn produce the gametes and supporting cells. |
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| 11.
In many animals, the germ cells arise in one location
and migrate to the male (testes)
and female (ovary)
sexual organs. Testes produce sperm while
ovaries produce
eggs, both
of which produce haploid pronuclei which fuse to form
a diploid nucleus. |
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| 12.
Gametes can be similar in size (isogamous organisms)
or very different (anisogamous).
It is conventional to call the individual that produces
the larger gametes
(eggs) female and the smaller gametes (sperm) male. |
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| 13.
The egg contains the bulk of the cytoplasm present in
the new diploid organism formed upon fertilization. In
particular,
it is common that mitochondria are supplied only by the
egg. |
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| 14.
Eggs are typically non-motile, sperm motile. |
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| 15.
A number of different mechanism are used to insure that
an egg is fertilized by only a single sperm; fertilization
of an egg by multiple sperm generally leads to severe
developmental abnormalities. |
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