Transcript genetically identical

Asexual vs. Sexual
Reproduction
Standard 9: Compare sexual reproduction (offspring inherit half of
their genes from each parent) with
asexual reproduction (offspring is an
identical copy of the parent’s cell).
Definition
Advantages/
Disadvantages
Sexual
Reproduction
Asexual
Reproduction
•Involves sex cells and
fertilization
•Does not involve sex
cells and fertilization
• DNA from 2 parents
•Only one parent
genetically
•Offspring are not
genetically identical to
one another
•Offspring have no
variation
•There is variation in
the offspring
•Offspring are
genetically identical to
one another
Asexual reproduction in Plants
Vegetative Propagation –
New plants develop from the roots, stems, or
leaves of the parent plant.
Examples:
-tubers
-bulbs
-runners
Tubers
Tubers are
thickened underground stems
created so plants
can survive
winter or dry
times
Examples:
potato,
artichoke, yam,
dahlia, water
chestnut,
arrowroot
Tubers
Food made by the new
plant is sent to make
new tubers, thereby
reproducing itself.
Tubers can be
separated (see
separated dahlia
tubers in picture)
and planted
individually
Dinnerplate dahlias
Bulbs
• Examples: daffodils, lilies, tulips
• Similar to tubers- can be separated
Runners
Runners are side shoots
which grow out from the
parent plant.
Buds form at points along
the runner and eventually
these buds form roots and
grow into new plants.
Examples: spider plant
(Anthericum), strawberry
(Fragaria x ananassa)
Artificial (man-made)
Propagation in Plants
• 2 methods used to cultivate plants
asexually
-taking cuttings
-grafting
Cuttings
Cuttings are small pieces of stem with some
leaves attached, the new plant grows from this.
They can be placed in moist
soil or water (and sometimes
dipped in rooting
powder).
Grafting
A cut stem of one plant (with good flower or
fruit growth) (the graft) is taken and firmly
attached to the rootstock of another plant
(which has a strong, established root system)
(the stock).
Examples- roses, fruit trees
Artificial Propagation
benefits
Artificial propagation has allowed us to
adapt and improve plants for our own
use.
Some of the benefits include:
•Quick production of large numbers of
genetically identical plants.
•Specific varieties, desired features or
consistent quality can be produced
especially in fruit, flowers.
Asexual Reproduction in
Animals/Fungi
• Parthenogenesis
• Regeneration
• Budding
Parthenogenesis
• Parthenogenesis is development of an egg
into an embryo without fertilization
• About 1% of animal species reproduce by
parthenogenesis
• an even smaller fraction switch between
sexual and asexual reproduction
• Parthenogenesis occurs most often in lowlevel species including some fish, amphibians
and reptiles
Why parthenogenesis?
• Many species reproduce by parthenogenesis in the absence of a wide pool of
potential mates (as alleged in the
movies "Jurassic Park")
• Some species switch to sexual
reproduction only in adverse conditions
for increasing the chance of survival.
WHY???
• Why would these organisms prefer
asexual reproduction in stable
conditions and sexual reproduction in
more uncertain or less favorable
conditions?
• Hint- think about genetic diversity
Regeneration
* This refers to the
ability of some
animals to re-grow
severed parts.
 Some of these
animals can also grow
whole new organisms
from the severed
pieces (some sea
stars and flatworms
shown to the right )
Why regeneration?
• These organisms can also reproduce
sexually
• They can use regeneration to escape a
predator or attack
• Sea star regeneration:
ehttp://longlist.org/play.php?videoId=d5
dOSyaKWTQ
• Gecko tail regeneration (go to 00:38)
http://longlist.org/play.php?videoId=d5d
OSyaKWTQ
Budding
• the parent cell or body gives out a
lateral outgrowth called the bud.
• The bud then falls off and germinates
into a new individual.
• Budding results in the formation of
daughter cells of unequal sizes that
later grow to adult size.
Budding
yeast
hydra
Asexual Reproduction in
Bacteria & Protists
• Binary Fission
• Copying DNA
then splitting into
2 equal-sized
cells
• Bacteria
• Unicellular
protists:
amoebas,
paramecia, etc.
Sexual Reproduction
• DNA comes from 2
sources
• Gametes: sex cells:
egg and sperm
• More genetic
diversity- helpful