Transcript Sexual/Asexual Reproduction

 Sexual
Reproduction – type of reproduction in
which the genetic materials from two different
cells combine, producing an offspring
 Sperm
 Egg
– male sex cell
– female sex cell
 Fertilization
– joining of the sperm and egg cell
 The new cell that forms is called a zygote.

Organisms that reproduce sexually make 2
kinds of cells- body cells and sex cells
(gametes -sperm & egg)

Diploid cells – cells that have a pair of
chromosomes; divide by mitosis (full # of
chromosomes)


Different Organisms have different numbers
of chromosomes.


ex. body cells
Ex: Humans have 46 chromosomes.(23 pairs)
Homologous chromosomes – pairs of
chromosomes that have genes for the same
trait arranged in the same order
cells are Haploid – only have one
chromosome from each pair; divide by meiosis
(half the # of chromosomes)
 Sex

ex. sex cells (sperm and egg)
 Meiosis
– process by which one diploid cell
divides into four haploid cells; occurs in the
formation of sex cells
 Meiosis

It ensures the correct number of chromosomes in
offspring


is important because:
ex. sperm (23) + egg (23) = human (46)
creates more genetic diversity by producing haploid
cells.
Starts as diploid cell
 Body cells
 1 division of nucleus
 Produces 2 daughter
cells
 Diploid daughter cells
 Used for growth and
repair of cells

Starts as diploid cell
 Reproductive cells
 2 divisions of nucleus
 Produces 4 daughter
cells
 Haploid daughter cells
 Used to produce sex
cells

 Advantages

Genetic Variation



offspring inherit half their
DNA from each parent
helps with adaptations to
changing environments
Selective Breeding

breeding species with
desirable traits

ex. dog breeding, farming
 Disadvantages

Time and Energy



development of sex cells
finding a mate
Exposure to predators,
disease, or harsh
environmental conditions
 Asexual
reproduction – one parent organism
produces offspring without meiosis and
fertilization

offspring are genetically identical to parent (clones)
 Fission

simple cell division in
prokaryotic (bacteria)
cells
 Mitosis

simple cell division in
eukaryotic cells
 Budding

a new organism grows
by mitosis on the body
of its parent

ex: hydra

Animal Regeneration



Vegetative Reproduction


offspring grows from a piece of its parent
Many animals can regenerate damaged or
lost body parts. This is not reproduction; new
individuals are not produced.
offspring grow from a part of a parent plant
Cloning



A type of asexual reproduction developed by
scientists and performed in laboratories.
production of an identical individual from a
cell, or cluster of cells, taken from a
multicellular organism
The clone is a genetic copy of the parent
 Advantages


no mate required
Enables some
organisms to produce
a large # of offspring
 Disadvantages
little genetic variation which
can decrease an organism’s
chance of surviving if the
environment changes.
 more likely to suffer mutations
