Transcript Key Idea #

Key Idea #16
All organisms have a life span and must
reproduce in order to continue the species.
Reproduction
allows the genetic material of living
things to be passed from generation to
generation.
 is required for the survival of a species.
 includes two types:

– sexual
– asexual
Asexual Reproduction
Advantages:
 only one parent is needed
 offspring are genetically identical to parent
 can produce large numbers of offspring
Disadvantages:
 no genetic variety because offspring are genetically
identical to the parent
 since organisms are identical, the species can’t adapt
to a changing environment
Types of asexual reproduction include:

runners
 bulbs
 tubers
 budding
 binary fission
 fragmentation
 regeneration
 cloning
FYI: Fragmentation and Regeneration

A type of asexual
reproduction found in
less evolved animals.
 When the parent body
breaks into pieces,
each piece can grow
into a new organism
that is identical to the
parent.
– starfish, planaria
http://images.google.com/imgres?imgurl=http://image.tutorvista.com/content/reproduction/planaria-regeneration.jpeg&imgrefurl=http://www.tutorvista.com/content/science/science-ii/reproduction/asexualreproduction.php&usg=__RTk4xJj77XukAzKY23f81XPmc1o=&h=371&w=415&sz=16&hl=en&start=28&um=1&itbs=1&tbnid=AO9LlKVsW0u0XM:&tbnh=112&tbnw=125&prev=/images%3Fq%3Dregeneration%2Band%2Bfragmentation%26ndsp%3D20%26hl%3Den%26sa%3DN%
26start%3D20%26um%3D1
http://web.mit.edu/neuro/planaria.html
Sexual Reproduction
Advantages:

Genetic variety
• offspring are genetically similar to their parents
• both parents contribute 50% of the offspring’s genetic
material.

Organisms have a greater chance of adapting to
environmental changes
learn.genetics.utah.edu
Sexual Reproduction
Disadvantages:



Two organisms must be involved.
Some genetic combinations can negatively affect the
survival of some species by passing on diseases
and genetic defects.
Genetic defect examples: (see book pages 120-123)
–
–
–
–
Cystic Fibrosis
Sickle-Cell Disease
Hemophilia
Down Syndrome
What
about fraternal and
identical twins?
FYI: Fraternal Twins

are produced when two separate sperm cells
fertilize two different egg cells by sexual
reproduction.
 are not identical because they have different
DNA (chromosomes and genes)
http://www.womenshealth.gov/pregnancy/you-are-pregnant/twins-multiples.cfm
FYI: Identical Twins

are produced after one sperm cell fertilizes an
egg cell by sexual reproduction and the
fertilized egg divides into two fertilized egg cells
by asexual reproduction.
 are identical because they have identical DNA
(chromosomes and genes).
http://www.womenshealth.gov/pregnancy/you-are-pregnant/twins-multiples.cfm
Some
organisms reproduce
in more than one way……
Bacteria reproduce
Asexually

genetic material is duplicated before the cell divides
resulting in two daughter cells that are genetically
identical to each other.
– Note: a disadvantage is antibiotics will kill all bacteria
Sexually

genetic material is transferred from one cell to
another cell forming one new bacteria cell that is
genetically different from the parent cells
– Note: An advantage is antibiotic resistance in offspring.
http://biology.about.com/od/bacteriology/a/aa080907a.htm
Plants reproduce

sexually through
pollination and
fertilization
 asexually through
production of runners,
tubers, regeneration,
bulbs, cloning, etc…
Life Cycle of the Flowering Plant